bigger wheels= power loss?

[ebbett21]

I recently went from aftermarket 18x8 235/40 R18 wheels to 19'' VX GTS 245/35 R19s How much power would have i lost if any?

[HEKYEH]

6.7345%

..................

Or otherwise probably not too much really...a few kws perhaps....

[ebbett21]

anyone experienced or tested before and after dyno with going a bigger wheel all round

[feistl]

There was a thread on the JC forums a while back... Direct back to back testing between an 18" and 20" wheel showed a 20rwkw difference. I think the car was making 290/270rwkw respectively.

Im not sure on the make/type/width/weight of each wheel, but was amazed at the results. Each wheel type had 3 runs spaced evenly apart and the numbers averaged out.

You'll also find the larger wheel offers less grip in the corners, has a harsher ride, uses more fuel (result of reducing the power levels), wear out faster (as a result of less grip), are more likely to crack/fail, cost more for rubber and reduce braking ability (due to more rotational mass).

On the upside they'll look better.

Personally, ill take the performance over looks :).

Each car will be different, but its possible you lost up to 10rwkw by going to a larger wheel. General rule of thumb for best performance is to go the smallest wheel that will clear your brakes.

[Wonky]

anyone experienced or tested before and after dyno with going a bigger wheel all round

Yep. I can't remember exact figures but I've seen people lose quite a bit when going bigger. Andy (HEKYEH) did you do runs with your 22s and then 20s?

[ebbett21]

There was a thread on the JC forums a while back... Direct back to back testing between an 18" and 20" wheel showed a 20rwkw difference. I think the car was making 290/270rwkw respectively.

Im not sure on the make/type/width/weight of each wheel, but was amazed at the results. Each wheel type had 3 runs spaced evenly apart and the numbers averaged out.

You'll also find the larger wheel offers less grip in the corners, has a harsher ride, uses more fuel (result of reducing the power levels), wear out faster (as a result of less grip), are more likely to crack/fail, cost more for rubber and reduce braking ability (due to more rotational mass).

On the upside they'll look better.

Personally, ill take the performance over looks :).

Each car will be different, but its possible you lost up to 10rwkw by going to a larger wheel. General rule of thumb for best performance is to go the smallest wheel that will clear your brakes.

Surely a inch bigger wheel like in my case isnt going to result in 20 rwkw loss if thats the case theyre coming off!! i have noticed a slight power loss all round

[HOTSV8]

I went the other way . I put 13's on my commodore and gained 376 rwkw .

[feistl]

Surely a inch bigger wheel like in my case isnt going to result in 20 rwkw loss if thats the case theyre coming off!! i have noticed a slight power loss all round

Its hard to say, back to back dyno testing doing multiple runs is the only real way to be sure.

Think about the difference of spinning a road push bike and motor bike wheel around... Extra weight in the driveline requires a fair amount of power to overcome the inertia. What is the weight difference between the wheels and is the width the same? (More surface area on the ground will result in more rolling resistance).

As seen in drag racing the smaller tyres can distort more giving the rubber more contact and smoother power delivery resulting in faster times/more grip.

Big brakes are the new bling :)

[ebbett21]

I can see only one solution and stick 18'' wheels back on ive decided to go with advanti phantics 18x8.

[ebbett21]

Its hard to say, back to back dyno testing doing multiple runs is the only real way to be sure.

Think about the difference of spinning a road push bike and motor bike wheel around... Extra weight in the driveline requires a fair amount of power to overcome the inertia. What is the weight difference between the wheels and is the width the same? (More surface area on the ground will result in more rolling resistance).

As seen in drag racing the smaller tyres can distort more giving the rubber more contact and smoother power delivery resulting in faster times/more grip.

Big brakes are the new bling :)

The 245/235 puts the spedo out alitle as opposed to 18'' 235/40, both rims 8'' wide, the 19'' wheel is actually a smoother quailty ride . Ive made up my mind going back to 18's

[HEKYEH]

I got 268rwkw with 22" wheels.

Then got 278rwkw with 20" wheels.

U will lose power with bigger wheels. Go with a smaller wheel. Much better performance all round.

[ebbett21]

I got 268rwkw with 22" wheels.

Then got 278rwkw with 20" wheels.

U will lose power with bigger wheels. Go with a smaller wheel. Much better performance all round.

Agree totally, im rather p@#ed off with myself for changing wheels. Im selling them atm even though they look mint. I prefer all out performance than looks, costly as i could have bought a new fuel system , spur of the moment purchase of the gts wheels

[macca33]

Just one of the reasons, contrary to the wishes of others, why I'm retaining the oem 18" wheels on my Senator 300. :idea:

cheers

[Black Diamond]

The extra unsprung weight and larger rolling diameter's are the killer here.
The difference between 20's and 22's was 14kw on my ute.

[duke5700]

Go to a dyno day with 17's, factory tyres and pump them up to the heavens.

[jimco]

Hi .
Simple maths to find out wheel diameter.

235/40x18 = 645.2mm diameter.
235/35x19 = 647.1mm "
245/35x19 = 654.1mm "

Based on rolling diameter the 235/35x19 would be the closest to your stock 18" rim/ tyre combo.

Regards.

[Bingo BIlly]

I know a ford guy who went from 18s to 19s and lost 17rwkw. Doesnt the bigger wheel retain more energy like a gearbox flywheel, harder to get rolling but also harder to pull up (poor braking performance)

I think cheap tyres also lose kw as more prone to slip on dyno

[VYSHSV8]

Hi .
Simple maths to find out wheel diameter.

235/40x18 = 645.2mm diameter.
235/35x19 = 647.1mm "
245/35x19 = 654.1mm "

Based on rolling diameter the 235/35x19 would be the closest to your stock 18" rim/ tyre combo.

Regards.

Its not just rolling diameter its rotational mass as well
the more alloy the more weight compared to tyres, Rubber weighs less than metal

[ebbett21]

Hi .
Simple maths to find out wheel diameter.

235/40x18 = 645.2mm diameter.
235/35x19 = 647.1mm "
245/35x19 = 654.1mm "

Based on rolling diameter the 235/35x19 would be the closest to your stock 18" rim/ tyre combo.

Regards.

the load rating on the 19'' wheels for 235/235 on a 1700 kg car mite not be suffice ? as a 245/235 The factory VT2 factory wheel is super heavy as opposed to the VX which is considerably lighter. The HSV engineers did there maths

VT2 GTS came out on 18'' 235/40 R18 and VX GTS 235/235 R19 both same power levels so yes the 235/235 is closest option

[jimco]

Its not just rolling diameter its rotational mass as well
the more alloy the more weight compared to tyres, Rubber weighs less than metal

Hi.
Granted,rotational mass plays some part as well.When I changed from stock 18" with 235/40x18 to 19" I chose the closest tyre spec's to match the 18's overall diameter. I did however notice a small lack of acceleration in the lower gears (rotational mass) running the stock 3.46:1 rear end.So I just changed to 3.91:1 gears and it was all academic after that.
Still the best mod you can do.

Regards.

[michaels1v8]

Sounds like at that size level there is very little difference in rolling diameter. I'd be weighing one of your new rims and tyres and comparing it to your old setup.

still have the old tyres in the boot weighing your car down? :stick:

Could just be a bad batch of fuel, hotter weather now than last time when you had old tyres, you were driving around with a quarter tank and now have a full one etc etc

[VYSHSV8]

will have to weigh 1 of nmy rears 1 day :):) 315/25/19 and they weigh a shitload more than the old 18's:lol:
Different rim manufacturers have different weights they can vary as much as 8-10kg a rim from Oz racing to other brands

[HSV Listy]

When I changed the wheels on the Avalanche from the stock 26kg 18s version to the Into KBRs there was a noticeable increase in take off speed, better road handling and more comfy ride. Even better with minor bumbs and better steering feel too (which is a good thing in a avalanche). I did the calculations and made sure the wheels were the same rotational diameter to the stock to avoid issues with the speedo and the AWD system

I went from 26kg per wheel 18s up to 19 but the 19s are full billet 3 piece and are about 10kg less per wheel including tyre what the stock avalanche wheels and tyres were
Fair amount of unsprung weight removal. I believe it is 1lb out of unsprung weight is 7 lb of chassis weight. That is around 120kg weight out. With a dyno, they read the torque/rotational force so that would equate to a power increase. In addition less load on the shocks, less rotional force required to turn the wheels etc etc. I suppose that is why the car seems faster and feels better on the road.

If you go the other way from light wheels and tyres to heavier wheels /tyres combination and then add in a larger rolling diameter wheels and tyres then that would work the opposite. Since you times each 1lb below the shock is added times that by 7lb in real weight. It is not surprising with bigger and heavier wheels the car will loose power and loose speed.

Happy to be corrected as there is allot of theory with unsprung weight verse speed, verse real weight and on and on. The 1lb to 7lb seems to be the one that race car people use to get some idea.

[The_Plague]

Interesting.
What about if you don't increase the diameter, just the width?

[feistl]

Interesting.
What about if you don't increase the diameter, just the width?

Its not the diameter thats the problem, its the weight of the wheel. Going a wider tyre is going to result in more weight, thus reducing rwkw.

If you can afford racing wheels (EG very light) then you can go faster with less engine power.

[The_Plague]

Its not the diameter thats the problem, its the weight of the wheel. Going a wider tyre is going to result in more weight, thus reducing rwkw.

If you can afford racing wheels (EG very light) then you can go faster with less engine power.

So technically if you can go a wheel an inch wider, that has the same weight as the wheel you are replacing, you will gain grip without loosing the KW?

[HSV Listy]

Its not the diameter thats the problem, its the weight of the wheel. Going a wider tyre is going to result in more weight, thus reducing rwkw.

If you can afford racing wheels (EG very light) then you can go faster with less engine power.

Kind off but wider and lighter will give more grip and potentially more power (tyres depending). I run 10 inch wide 295 on the back of the Avalanche yet they are way lighter than the 8 inch stock 245 wheels.

For the right money (or ebay bargains) you can get some touch big rims, light weight wheels and rubber without sacraficing power. Billet is the way to go for width without sacrificing weight or for real big money some race spec one piece custom jobies like dynamic racing, Braid racing etc. They will do what ever size, width or brake clearance you want for the right money.

[feistl]

So technically if you can go a wheel an inch wider, that has the same weight as the wheel you are replacing, you will gain grip without loosing the KW?

in simple terms, "Yes". You will add a little more rolling resistance but we are now talking very minor % difference. You might lose .5-1rwkw with a wider tyre... Its the weight thats the problem.

As Listy said, if you can afford proper racing wheels (very light weight) you'll reduce unsprung weight and driveline losses. Problem is cost...

But when your really pushing your engine, 10rwkw might cost you $10k more whereas reducing drivetrain losses with light weight wheels might only cost ya $4k....

[VYSLED]

A Rotating mass is what i'll be after The BBQ at the APS dyno day on the 4th december. :merry:

Sure the weight would play a small part , change the diff out to 4:11's and problem solved. :xmas:

When i was running my unopened 346ci rig, 18 inch tires with 4:11's and a bit of meth got me 310rwkw.


Gear change required every 100th of a second with 4:11's

[zorro]

anyone experienced or tested before and after dyno with going a bigger wheel all round

I watched an E39 M5 and also a 300zx do back to back dyno runs with different sized wheels. The M5 had no power difference, the 300zx had 4rwhp.

Im sure there are plenty of variables straps etc but watching it was interesting to see, especially with one bloke batting off that it will pull 20rwhp more

[The_Plague]

in simple terms, "Yes". You will add a little more rolling resistance but we are now talking very minor % difference. You might lose .5-1rwkw with a wider tyre... Its the weight thats the problem.

As Listy said, if you can afford proper racing wheels (very light weight) you'll reduce unsprung weight and driveline losses. Problem is cost...

But when your really pushing your engine, 10rwkw might cost you $10k more whereas reducing drivetrain losses with light weight wheels might only cost ya $4k....

Not worried about losing any RWKW, particularly a small amount, its more about being able to get a decent amount of grip.

[feistl]

But when your really pushing your engine, 10rwkw might cost you $10k more whereas reducing drivetrain losses with light weight wheels might only cost ya $4k....

I should clarify (before i get blasted), im talking about race cars where they have specific limits to what they can do in terms of capacity, induction type, exhaust size, head limitations etc. For a street/non competition car you'd throw a blower/turbo on and make a lot more than 10rwkw for $10k. But in a racing series where capacity is limited to 6000cc and N/A, it can be very expensive to get the last few kw from the engine. Reducing driveline losses makes the car easier to accelerate, brake and turn.

And yes, 1 or 2rwkw isnt really a big deal (especially if you cant put that power down), but in the case of going from say 18s to 20/22s, then the 20rwkw is very noticeable. I personally havnt seen it first hand, only going off what people have said (which may or may not be true?)

[Rhc 1]

for rotational mass wheel design would be a factor as well, wheels with less weight at their circumference would require less power to accelerate/decelerate than a wheel of the same diameter and weight that had proportionately more of its mass at its circumference. If some one was keen enough you could calculate fairly accurately how much power it would take to accelerate your different wheels over say a 1/4 mile run, calculating the rotating mass would be hardests as you would need to know comparatively how the weight was distributed in the wheel, if that was equal between the wheel sizes you were comparing it would be fairly straight forward. You would have to know your trap speed so you can work out how many rpm the wheel is doing at the end so it has a certain mass and you accelerate it from stationary to whatever rpm over how long the run takes. It shouldnt make a massive difference really, not like rotating flywheel mass for example which is accelerated very quickly - thousands of rpm in seconds. I think reducing unsprung weight is probably the real advantage with light wheels. I wonder if any of the drag racers have any info on the real world effect of wheel weight on acceleration?

[Millsy]

I lost 20rwkw going from 18s to 20s with NO other modifications at all done to the car, same dyno

However, since recently recently getting a head and cam combo installed, I've decided to stick with the 20s, traction is bad enough as it is with the power it makes, 18s would be stupid

[tomholzy]

wouldnt you have better traction with the 18's (assuming equal width) because they have a thicker sidewall?

[ATOMICSS]

Guys, the wheels on the car have no effect whatsoever on the power at the rear wheels. Doesnt matter if they're 13" wheels off a Mini Moke or those 22s off your favourite rapper's car.

Sure bigger (diameter) and heavier wheels will make the car accelerate slower (all else being equal), and the moke wheels would turn to smoke if you were silly enough to use them, but, the actual power at the wheels is exactly the same.

The inertia type "dynos" may show a lower reading, but they measure the rotational acceleration of the drum, and convert to a torque /power readout. Rather than measuring actual brake power directly.

[VYSHSV8]

power is measured by Torque:):)

It may only affect power by a smallish margin but it will affect it:):)

If you increase rotational weight/mass that will mean it needs more torque to turn it, but if nothing is changed it will make Torque suffer then it will affect Power....

This is when it will show on the dyno and I am pretty sure ramp rates are a multiplication of this

[ATOMICSS]

Gees I wish we were having this discussion at the pub rather on this forum. That way I could bet everyone a carton, actually make that 2 cartons each, that bigger wheels don't = power loss.

You guys weren't paying enough attentions in year 9 physics.

[BlueSS]

I lost 20rwkw going from 18s to 20s with NO other modifications at all done to the car, same dyno

However, since recently recently getting a head and cam combo installed, I've decided to stick with the 20s, traction is bad enough as it is with the power it makes, 18s would be stupid

would be supprised.. i put a set of 18's back on the back of mine for easternats a couple years back.. they actually gripped better than the 20's.. with exactly the same brand/type of tyre.. that's with 350rwkw..

[feistl]

Gees I wish we were having this discussion at the pub rather on this forum. That way I could bet everyone a carton, actually make that 2 cartons each, that bigger wheels don't = power loss.

You guys weren't paying enough attentions in year 9 physics.

"Inertia is the resistance of any physical object to a change in its state of motion or rest"

Yes, the engine will be making exactly the same power, but you will require more effort to accelerate the heavier wheels, thus leaving less energy to accelerate the car.

*Note how i said HEAVIER wheels... If you can find a set of ultra light weight 20"s they'll have less inertia than a smaller pair of heavy 18s. However in MOST (EG not all) cases the larger wheels are heavier than the smaller counterparts.

Once you are at cruising speed, there will be very little difference between the weight of wheels as the inertia will be keeping the wheel moving.

Also remember that if the dyno reading is showing 20rwkw difference on teh rear wheels, its effectively going to have the same effect at the front (EG the "loss" will be double)

Easiest way to see this is to try and spin up a mountain bike tyre and road racer tyre (EG the bike upside and you pedalling). If the gearing etc is identical, you'll feel how much extra effort is required to accelerate the heavier mountain bike wheel.

Once their both at speed, it will be about the same amount of effort to keep them at speed (Obviously things like air resistance/bearing resistance will take effect, but if you preformed the test in a vacuum with Mercury bearings it would be so similar).

[zorro]

I lost 20rwkw going from 18s to 20s with NO other modifications at all done to the car, same dyno

However, since recently recently getting a head and cam combo installed, I've decided to stick with the 20s, traction is bad enough as it is with the power it makes, 18s would be stupid

You might want to talk to drew, Im sure he has 300+ tires on the back of his VY. Id substitute bling for purpose anyday, although you have the HSV brakes 18" would be minimum you could go for clearance.

Find something that looks good with dish for the rear and get some good rubber

[ebbett21]

"Inertia is the resistance of any physical object to a change in its state of motion or rest"

Yes, the engine will be making exactly the same power, but you will require more effort to accelerate the heavier wheels, thus leaving less energy to accelerate the car.

*Note how i said HEAVIER wheels... If you can find a set of ultra light weight 20"s they'll have less inertia than a smaller pair of heavy 18s. However in MOST (EG not all) cases the larger wheels are heavier than the smaller counterparts.

Once you are at cruising speed, there will be very little difference between the weight of wheels as the inertia will be keeping the wheel moving.

Also remember that if the dyno reading is showing 20rwkw difference on teh rear wheels, its effectively going to have the same effect at the front (EG the "loss" will be double)

Easiest way to see this is to try and spin up a mountain bike tyre and road racer tyre (EG the bike upside and you pedalling). If the gearing etc is identical, you'll feel how much extra effort is required to accelerate the heavier mountain bike wheel.

Once their both at speed, it will be about the same amount of effort to keep them at speed (Obviously things like air resistance/bearing resistance will take effect, but if you preformed the test in a vacuum with Mercury bearings it would be so similar).

So really at the end of the day its all comes down to weight of the rim and tyre your running? For example the original GTS VT2 Wheels weigh a absolute tonne to pick one up. On the otherhand a VX GTS Wheels a alot lot lighter. Both the VX and the VT2 GTS had same power levels, so imguessing the HSV Engineers knew they had to make a lighter wheel for the VX GTS to be comparable to the VT2 GTS, which had heaver, yet smaller 18'' wheels. why would the VT2 leave the factory with such heavy wheels?

[feistl]

So really at the end of the day its all comes down to weight of the rim and tyre your running? For example the original GTS VT2 Wheels weigh a absolute tonne to pick one up. On the otherhand a VX GTS Wheels a alot lot lighter. Both the VX and the VT2 GTS had same power levels, so imguessing the HSV Engineers knew they had to make a lighter wheel for the VX GTS to be comparable to the VT2 GTS, which had heaver, yet smaller 18'' wheels. why would the VT2 leave the factory with such heavy wheels?

Remember the power level measured by HSV is ENGINE power (EG on an engine dyno), so the wheel weight would make no difference to this figure. It would have an effect on the 0-100 time though (how big is another question).

Not sure why there is so much difference between the wheels?

[steve_t]

It's for cycling but the principle is the same

http://www.analyticcycling.com/WheelsInertia_Page.html

[ATOMICSS]

"Inertia is the resistance of any physical object to a change in its state of motion or rest"

Yes, the engine will be making exactly the same power, but you will require more effort to accelerate the heavier wheels, thus leaving less energy to accelerate the car.

*Note how i said HEAVIER wheels... If you can find a set of ultra light weight 20"s they'll have less inertia than a smaller pair of heavy 18s. However in MOST (EG not all) cases the larger wheels are heavier than the smaller counterparts.

Once you are at cruising speed, there will be very little difference between the weight of wheels as the inertia will be keeping the wheel moving.

Also remember that if the dyno reading is showing 20rwkw difference on teh rear wheels, its effectively going to have the same effect at the front (EG the "loss" will be double)

Easiest way to see this is to try and spin up a mountain bike tyre and road racer tyre (EG the bike upside and you pedalling). If the gearing etc is identical, you'll feel how much extra effort is required to accelerate the heavier mountain bike wheel.

Once their both at speed, it will be about the same amount of effort to keep them at speed (Obviously things like air resistance/bearing resistance will take effect, but if you preformed the test in a vacuum with Mercury bearings it would be so similar).

Yes, with heavier wheels or bigger diameter the car will accelerate slower, I've acknowledged that and no one would argue that. It'll also accelerate slower if you put 15 slabs of XXXX in the boot, but thats not the point, there will still be exactly the same amount of power at the treads. If you somehow managed to bolt a pair of 150kg, 1 meter tall wheels from a B double road train to the back of your holden, it will still have the same power at the treads. Sure it'll accelerate slower than your grandads 173 automatic Belmont station wagon, but the power at the treads will be the same.

Please, no-one ask me to prove it with some simple equations, it'll make me look a bigger nerd than Kevin Rudd.

[STATIE]

F@#KEN dyno's.

[ebbett21]

Remember the power level measured by HSV is ENGINE power (EG on an engine dyno), so the wheel weight would make no difference to this figure. It would have an effect on the 0-100 time though (how big is another question).

Not sure why there is so much difference between the wheels?

So does anyone know what out of the factory a standard VX GTS does the quarter mile in compared to a standard VT2 GTS ? If they made the same times, obvious a 235/235 R19 tyre is what i require as both vehicles are same weight and suspension setups. One on a 235/40 18 tyre and other on a 235/235 tyre, Im running a 245/235 giving slightly more mass putting the spedo out by 2 kmph

[HSV Listy]

So does anyone know what out of the factory a standard VX GTS does the quarter mile in compared to a standard VT2 GTS ? If they made the same times, obvious a 235/235 R19 tyre is what i require as both vehicles are same weight and suspension setups. One on a 235/40 18 tyre and other on a 235/235 tyre, Im running a 245/235 giving slightly more mass putting the spedo out by 2 kmph

THe VX GTS did 5.1 0 to 100 in a number of mags. Can not remember the 1/4 but in the mid 13s from memory. It was always the fastest up until the a GTO reeled off a 4.99. I believe other than the W427 the best time for a regular HSV in the motor/wheels mags.
Suprising in 10 years the HSV are still in the 5.1 to 5.2 zero to 100 mark. (exception for the W427). Add weight everywhere including wheels and only very minor power increaces by a measly 17kw in 10 years it is not suprising. Maybe get some light wheels on there the same width and it will go quicker.
:)
THe very early VX GTS did have 18s too and the times were the same 5.1 seconds. THe VX GTS wheels with pirellie tyres weigh 25kg so interesting what the 18s weighed. I doubth it would be much difference but maybe a kg or two.

[VYSHSV8]

You might want to talk to drew, Im sure he has 300+ tires on the back of his VY. Id substitute bling for purpose anyday, although you have the HSV brakes 18" would be minimum you could go for clearance.

Find something that looks good with dish for the rear and get some good rubber

tell him/millsy he will get better traction with 18's than 20's:):)

I know what size rims I would want if i needed more traction and it aint 20's:):)
wider and better quality rubber :):)

[J_VZUTE]

Only reason I would stay away from such big wheels is extra weight and cost of tyres!! Tyres for 20's aren't cheap as many of you know! Unless I was building up a show car, I stay away from 20's for a daily ride..

[VYSHSV8]

Yes, with heavier wheels or bigger diameter the car will accelerate slower, I've acknowledged that and no one would argue that. It'll also accelerate slower if you put 15 slabs of XXXX in the boot, but thats not the point, there will still be exactly the same amount of power at the treads. If you somehow managed to bolt a pair of 150kg, 1 meter tall wheels from a B double road train to the back of your holden, it will still have the same power at the treads. Sure it'll accelerate slower than your grandads 173 automatic Belmont station wagon, but the power at the treads will be the same.

Please, no-one ask me to prove it with some simple equations, it'll make me look a bigger nerd than Kevin Rudd.

Yes I know it is only rotational mass and once it upto full revs it should read the same:):)

Thats why I said ramp rates on dynos can amd may affect this as it is calculated on a few things.....
but doesnt allow for tyre mass and thus show lower torque/power :):)

[VYSHSV8]

Only reason I would stay away from such big wheels is extra weight and cost of tyres!! Tyres for 20's aren't cheap as many of you know! Unless I was building up a show car, I stay away from 20's for a daily ride..
20's+ = show not much good fro traction really in any department :):)

[jimco]

Hi.
My way of thinking and I stand corrected is that larger diameter 20's are harder to spin than smaller diameter 18's that should = better traction and also rotate slightly slower than 18's at the same speed either in a straight line or especially in cornering that = better traction. The faster a wheel spin's the more likely it is to break traction.Just my thoughts.

Regards.

[ebbett21]

One thing ive noticed is the type of tyre plays a big part , at the moment on the 19 x 8 i have newish roadstone 245/35 N3000 Tyres all round and they are smooth and take the bumps extremely well, have good response.
On the otherhand the 18x8 predecessors, i had two rear brigestone pontenzas adrenlins and SO3 Bridgestones on the front 235/240 allround. Everyone who has been in the car for a spin has said the 19'' wheels are way more smoother and less harsh- so i find that surprisng after some said it would be the apposite.
Car is a SL Springs, FE2 Shocks 18'' wheels , harsh ride 19'' ride - Much much better...confusing to me as im thinking a touch up tune mite be the go instead of changing wheels

[jimco]

HI.
The reason 19's,20's or larger ride harsher is generally that they are lower profile tyres with less rubber to flex in the sidewalls and absorb bumps,they also require higher tyre pressures as well.As you decrease in tyre aspect ratio,40-35-30 as against the width sidewall depth reduces and therefore pressures must increase to reduce roll resistance and rim damage.

Regards.

[feistl]

Hi.
My way of thinking and I stand corrected is that larger diameter 20's are harder to spin than smaller diameter 18's that should = better traction and also rotate slightly slower than 18's at the same speed either in a straight line or especially in cornering that = better traction. The faster a wheel spin's the more likely it is to break traction.Just my thoughts.

Regards.

No because the overall diameter should stay the same (legally anyway). The larger the rim the "smaller" the rubber profile. As mentioned the smaller profile means the tyres are harder and have less "give". This means they cant distort properly to offer maximum traction.

By adding weight and a tyre with less "give" you end up with less traction and more resistance.

If bigger wheels were faster, how come all race cars run small wheels? (Rule of thumb is go the smallest wheel that will fit over your brakes).

Cheers

[MrHSV318]

So my 245 45 17's will be lighter tham my 245 35 19's? :confused: What is the difference in rolling diameter?

[Rhc 1]

Hey ebbett if you really want to test real world performance difference you could do it quite easily, as you have both sets of wheels with tyres on them. You need to have two land marks on the road (closed road of coarse or maybe travel back in time and go to Northern territory) anyway they need to be a good distance apart, you approach the first mark in say 3rd gear at a constant say 1500 rpm, then when beside the mark nail it and hold it flat till you reach the second mark at which point you make a mental note of the exact speed or rpm you are doing (if marks are right distance apart you will be doing near the top of the rev range still in 3rd) you could do a run the other way if youre really anal and average the two. Then change rims and repeat. this is the poor mans dyno.

[ebbett21]

Hey ebbett if you really want to test real world performance difference you could do it quite easily, as you have both sets of wheels with tyres on them. You need to have two land marks on the road (closed road of coarse or maybe travel back in time and go to Northern territory) anyway they need to be a good distance apart, you approach the first mark in say 3rd gear at a constant say 1500 rpm, then when beside the mark nail it and hold it flat till you reach the second mark at which point you make a mental note of the exact speed or rpm you are doing (if marks are right distance apart you will be doing near the top of the rev range still in 3rd) you could do a run the other way if youre really anal and average the two. Then change rims and repeat. this is the poor mans dyno.

I took the car for a two hour drive today to confirm The car drives smoother, less harsh, less in cabin noise than 18's but the throttle response in 4th and 5th gear up top isnt there like on 18'' wheels.

[Alex(AUS)]

The extra unsprung weight and larger rolling diameter's are the killer here.
The difference between 20's and 22's was 14kw on my ute.

What are the lightest wheels and tyres available (regardless of cost) you can fit over the HSV brakes. How much lighter are they? I can remember my rear wheel/tyre combo being over 32kg.

Alex

[Groboz]

What are the lightest wheels and tyres available (regardless of cost) you can fit over the HSV brakes. How much lighter are they? I can remember my rear wheel/tyre combo being over 32kg.

Alex

As money is no object, these Aussie wheels may interest you when they come on the market.:)

http://www.carsguide.com.au/site/news-and-reviews/car-news/carbon_fibre_wheels_keep_shelby_on_road

[jimco]

So my 245 45 17's will be lighter tham my 245 35 19's? :confused: What is the difference in rolling diameter?

HI.

245/45x17 = 652.3mm diameter.
245/35x19 = 654.1mm " .

Regards.

[flatlinerz]

Only reason I would stay away from such big wheels is extra weight and cost of tyres!! Tyres for 20's aren't cheap as many of you know! Unless I was building up a show car, I stay away from 20's for a daily ride..

yeah me too....pretty overpriced but if you had to grab some second hand ones

[Wonky]

Only reason I would stay away from such big wheels is extra weight and cost of tyres!! Tyres for 20's aren't cheap as many of you know! Unless I was building up a show car, I stay away from 20's for a daily ride..

Decent 20s are coming down in price all the time. I recently put 275/20 Kumho Ecsta Spt on the rear for well under $300 each and they are a good tyre!

[VTV691]

http://www.miata.net/garage/tirecalc.html

Sizing calculators aloowing you to comapre diametars and sidewalls of different size tyres and etc..

[afmss]

I know standard 18, 245 compared t,22, 295 is 10kw on a dyno

[HSVE-02]

well, i have 22' rims on my maloo and ive got cam n stuff and it feels the same as it was on 20's. my rims are forged tho, compared to the off the shelf rims which are heavy as anything lol...it just comes down to how the car feels to u on the street

[ebbett21]

well i had the VX GTS 19X9 245/35 wheels replaced today with new advanti 18x8 phantic wheels with goodyear eagle F1 GSD-1 235/40 ZR18 tyres.......and what a f@#ken difference im very happy:)

[HSV Listy]

well i had the VX GTS 19X9 245/35 wheels replaced today with new advanti 18x8 phantic wheels with goodyear eagle F1 GSD-1 235/40 ZR18 tyres.......and what a f@#ken difference im very happy:)

Yes avanti do make some light wheels. I used to run Avanti Racing in 18x8 and they were just below 10kg per wheel. With semi slicks which were pretty light it was about 19kg per corner. Dam near the Oz racing wheel weight

[xshore]

I don't think I saw it mentioned but you all might want to consider torque = force x distance

[IJ.]

Comes down to how most chassis dyno's read power, do ANYTHING to improve the acceleration on the ramp up section of the pull and you're going to see a higher end number, I cut 2.3Kg's from a crank and added an ATI damper on an I-6 a few years back so all up a 5Kg reduction in rotational mass, it resulted in a good power increase with NO other engine mods.

Conversly if you add a big/heavy set of wheels the Dyno is going to report a lower output, the engine is still making the same power as it always did.

[Martin_D]

Conversly if you add a big/heavy set of wheels the Dyno is going to report a lower output, the engine is still making the same power as it always did.

But you WILL have less power at the wheels....which is what the dyno reads. This is the reason behind competition cars having the lightest possible wheel and tyre combinations. The energy thats put into accelerating big heavy wheels cant be recovered without KERS or similar :)

[QldKev]

But when comparing numbers the rwkw is more important than the flywheel kw, as it takes into account all losses.


QldKev

[Martin_D]

Power and Torque at the road - where the tyre meets the black stuff - is what accelerates the car. The idea is to give away as little as you can on the way from the crank to the contact patch - hence lightest wheels and tyres are the go :)

[IJ.]

But you WILL have less power at the wheels....which is what the dyno reads. This is the reason behind competition cars having the lightest possible wheel and tyre combinations. The energy thats put into accelerating big heavy wheels cant be recovered without KERS or similar :)

Moral of the story is don't run big gay ass heavy wheels they're a fashion statement, that statement being "My car is slow" ;)

[ATOMICSS]

But you WILL have less power at the wheels....which is what the dyno reads. This is the reason behind competition cars having the lightest possible wheel and tyre combinations. The energy thats put into accelerating big heavy wheels cant be recovered without KERS or similar :)

Sorry, but no you WONT have any less power at the wheels. As per one of my previous posts it doesn't matter if you somehow manage to bolt some roadtrain wheels onto the thing, the power at the wheels will be exactly the same.
The inertia of the wheels, or any other part of the car will affect acceleration, but not the power available at the treads. Doesnt matter what an inertia type "dyno" (which by the way isn't really a Dyno) says. Put it on a brake type dyno and the truth will be revealed.

[Martin_D]

During acceleration the wheels absorb energy, during deceleration they release it - hence if the operator does a ramp up/down test the average power will remain the same. The acceleration of a heavy wheel car will be slower (power is being lost into accelerating the heavy wheel mass additional to the car) and the braking will be worse. At steady state it will be the same.

Moral of the story - heavy wheels are crap :)

[ICA747]

agreed lol

[ATOMIC MALOO R8]

wheel wight ASIDE if the gear ratio was modafide
for the larger wheel ve hsv 20" = hsv lower dif ratio in the ve all would relevent

[ebbett21]

During acceleration the wheels absorb energy, during deceleration they release it - hence if the operator does a ramp up/down test the average power will remain the same. The acceleration of a heavy wheel car will be slower (power is being lost into accelerating the heavy wheel mass additional to the car) and the braking will be worse. At steady state it will be the same.

Moral of the story - heavy wheels are crap :)

I agree: I have just gone from a 19'' to a 18'' wheel, advanti phantics, and i have noticed improvement in acceleration rite thru the rev range. I am pleasantly surprised.
My working out out is if: for example on a pushbike, it has two heavy wheels and tyres, the person cycling it uses more energy to accelerate off the mark and up thru the gears.
A lighter wheel requires less engery for the cyclist. This must be similar logic to racing cars alike.

[VYSHSV8]

During acceleration the wheels absorb energy, during deceleration they release it - hence if the operator does a ramp up/down test the average power will remain the same. The acceleration of a heavy wheel car will be slower (power is being lost into accelerating the heavy wheel mass additional to the car) and the braking will be worse. At steady state it will be the same.

Moral of the story - heavy wheels are crap :)

Basically exactly the same as I have been trying to explain all along :):) atleast we agree on the odd occasion Martin:lol:

[feistl]

Which is why an AWD power figure is more impressive... Ive been saying this for years.

If we assume traction, gearing, weight, aerodynamics etc are identical... a AWD car with 200awkw is more impressive than a RWD car with 200rwkw.

The AWD dyno run is spinning up all 4 wheels, so you have the power drain of 4 heavy wheels. In a RWD car, the front wheels dont spin so you cant calculate the loss.

Its also why im against the dynos that bolt directly to the hubs... The heavy weight of the wheels isnt considered.

The comments above saying how noticable going from larger to smaller wheels, imagine the difference without the front wheels.

[HSV Listy]

Which is why an AWD power figure is more impressive... Ive been saying this for years.

If we assume traction, gearing, weight, aerodynamics etc are identical... a AWD car with 200awkw is more impressive than a RWD car with 200rwkw.

The AWD dyno run is spinning up all 4 wheels, so you have the power drain of 4 heavy wheels. In a RWD car, the front wheels dont spin so you cant calculate the loss.

Its also why im against the dynos that bolt directly to the hubs... The heavy weight of the wheels isnt considered.

The comments above saying how noticable going from larger to smaller wheels, imagine the difference without the front wheels.

Never though about that. I actually wondered why more of these are not used due to people saying they loose power from slipping wheels etc. Guess I know now as even with the bolt on style and take the slip out of the equasion it still is not a true number due to the wheels missing.
Interesting but good to know

[ATOMIC MALOO R8]

would be good for dyno queens
some extra kw for free :rofl:

[Martin_D]

Never though about that. I actually wondered why more of these are not used due to people saying they loose power from slipping wheels etc. Guess I know now as even with the bolt on style and take the slip out of the equasion it still is not a true number due to the wheels missing.
Interesting but good to know

Listy at least with the wheels on at a sensible ramp rate on a dyno....this is the power and torque you will be accelerating down the front straightaway with, not a contrived 'wheel-less' figure.

Put some 30kg clunker rims on your GTS and giveaway around 1.0 - 1.2 second a lap around Hidden Valley...try it once, you wont do it again :cool:

[Alex(AUS)]

Listy at least with the wheels on at a sensible ramp rate on a dyno....this is the power and torque you will be accelerating down the front straightaway with, not a contrived 'wheel-less' figure.

Put some 30kg clunker rims on your GTS and giveaway around 1.0 - 1.2 second a lap around Hidden Valley...try it once, you wont do it again :cool:

I am pretty sure that the standard rear wheels of the VE GTS (and R8, Senator) weight around 32Kg (inc tyres).

What is the lightest available road legal rim/tyre combination for VE regardless of price?

Alex

[VYSHSV8]

I am pretty sure that the standard rear wheels of the VE GTS (and R8, Senator) weight around 32Kg (inc tyres).

What is the lightest available road legal rim/tyre combination for VE regardless of price?

Alex

Alex I think you will find out it is around the 20kg mark:)

[HSV Listy]

Alex I think you will find out it is around the 20kg mark:)

The billet into on the Avalance are very light but the wide 295 wheels do catch up a bit. Not too much though. I wished I weighed them before putting them on. Way light wheels. They allow for just about any brake package and would easly fit the VE GTS calipers. The room on this KBR wheel design for calipers is massive. Mine were originally desinged for a VE anyway but I got to them first.

[VYSHSV8]

The billet into on the Avalance are very light but the wide 295 wheels do catch up a bit. Not too much though. I wished I weighed them before putting them on. Way light wheels. They allow for just about any brake package and would easly fit the VE GTS calipers. The room on this KBR wheel design for calipers is massive. Mine were originally desinged for a VE anyway but I got to them first.

Hey Tony, ya got a spare set of brakes for my old girl;) 295 pffft get 315 on t6here:):)

Cheers
Drew

[sjhugh]

I am pretty sure that the standard rear wheels of the VE GTS (and R8, Senator) weight around 32Kg (inc tyres).

What is the lightest available road legal rim/tyre combination for VE regardless of price?

Alex

The 20” HRE rims on my AMG weigh 10kg without tyres.

http://i306.photobucket.com/albums/nn249/sjhugh/aIMG_1551.jpg


If you are interested in the weight of high end rims ranging from 18” to 20” and prepared to pay serious money, this is the thread for you. Many of these brands can be made to order to suit your application. The weights are in pounds.

http://www.m5board.com/vbulletin/m5-e39-group-buy-forum-sponsor-discussion-offerings/142394-wsto-wheel-weight-comparison.html

.

[BA_XR6_TURBO]

I have ROH Modena 3 piece wheels. In 19x8 they are 13.67 kg (wiuthout tyre) according to ROH, add a little more for the rear 9.5. Not a bad weight for a 19 I would think.

Wheel weight should definitely be a factor if you want go, not just show. I wonder how much your average chinese wheel weighs compared to the high end stuff.

[HSV Listy]

Hey Tony, ya got a spare set of brakes for my old girl;) 295 pffft get 315 on t6here:):)

Cheers
Drew

Next time I am in. They were a dam good price though for such a awesome tyre. Should of bidded.

[Alex(AUS)]

Alex I think you will find out it is around the 20kg mark:)

How about if the wheel was 2.76Kg?

http://www.carbonfibergear.com/wp-content/uploads/2008/08/weds-sport-carbon-fiber-wheel.jpg

Alex

[Speedy Gonzales]

The 20” HRE rims on my AMG weigh 10kg without tyres.


What did they weigh up with tyre and fully inflated?

[sjhugh]

What did they weigh up with tyre and fully inflated?


Fronts
20x8.5
245/20ZR20
20.8kg

Rears
20x10
285/25ZR20
22.6kg

Rim weight is very important but tyre weight is even more critical as tyres are further from the axis of rotation and therefore have a larger effect on steering, suspension movement, acceleration and braking.

Rim diameter and widths will play a big part in the cheaper cast types, not so much in the more expensive forged variety.

There are also big differences in the weights between tyre brands and styles and it comes down to, you get what you pay for.

If you want to get an idea of your tyre weight, this site will has them for the more common brands:

http://www.tirerack.com/tires/tire-brand.jsp

Click on your brand then style then click ‘specs’ then scroll down to your tyre size and it will give a wide range of info including tyre weight.

1pound = 0.453592kg

.