Bigger diameter wheels = slower acceleration

[kangavxss]

Now that i can get bigger wheels i have a question on acceleration. Read on the net some opinions that if you go bigger in wheel diameter that you will accelerate slower from standing start. I can understand this if your overall wheel/tyre diam increases but it shouldnt make any difference if you keep the same ratios as per standard ( ie: 17inch rim with 45 series tyres and 20inch rim with 30 series tyres should be almost the same! There is less than 1% difference with this example so dont think it will have any effect on take off speed. Anyone confirm please? Cheers

[ratter]

larger diameter rims are normally heavier than a smaller rim and the weight is further away from the centre line which makes it slower to accelerate

[kangavxss]

How much of an effect would that inertia have then on a typical ls1? Any professors here good with calcs.

[mattnsw]

Also rims weights change from manufacturer to manufacturer as do the weight of tyres. This can be significant is some cases. It’s a matter of you get what you pay for.

[kangavxss]

Thanks. So to keep my performance i maybe should only go up to 19 inch rims from the standard 17 inch unless i go for those expensive light weight items.

[awesome _vzss]

I can conform that 20in wheels Defently affect acceleration and performance as I used to swap them between my 18's a lot and Defently noticed a difference.

[mattnsw]

How much of an effect would that inertia have then on a typical ls1? Any professors here good with calcs.

There is plenty of info and reading on the internet regarding tyre weights per manufacturer and also for rims to help calculate the unsprung weight and effect on your vehicle.

There is no easy answer for you without knowing the details of what you are intending to purchase. Simply, if it’s cheap after market rims and tyres the weight will increase and slow takeoff. Otherwise your only alternative is to go smaller or spend the bigger dollars on track orientated rims and tyres.

[kangavxss]

I can conform that 20in wheels Defently affect acceleration and performance as I used to swap them between my 18's a lot and Defently noticed a difference.

That extra weight then is a big factor. When choosing rims manufacturers normally dont give you info on weight only size, offset etc.

[Evman]

*definitely

:)

[kangavxss]

Anyone recommend some wheel brands that arent too expensive but are fairly light weight?

[mattnsw]

That extra weight then is a big factor. When choosing rims manufacturers normally dont give you info on weight only size, offset etc.

Serious rim manufacturers will give you weights, you’ll have to go forged, not cast and possibly a 2 or 3 piece, though some monobloc type rims are also good for weight.

If you are looking at cheap mass produced rims you will be shocked at how heavy most are.

Start off by looking at BBS and work from there.

By the way, light and cheap don’t mix.

[ebbett21]

I went from 18'' to 19 '' and noticed a slight loss in acceleration on take off, but feel no loss mid range to top end , i went to 19'' PDW Vega on 235/235 tyres allround. Vegas are goodprice, same wheel on the V8 Brute ute series

[kangavxss]

Wonder if 19inch aftermarkets weight alot more than my stock 17 inch ss rims?

[6.2L.Club]

Aftermarket larger rim - more rolling mass and usually larger circumference depending on profile.
If your worried about looking such a small, barely noticeable loss in acceleration, just change your diff ratio to counteract the loss incurred.

[kangavxss]

Dont care if its point something of a second slower or so but dont want to lose a second or more.

[6.2L.Club]

You will be able to feel it, but it certainly won't turn it into a slug, l wouldn't stress about it.
If it were 22's on a stock 6 banger you might loose a second.

[kangavxss]

No worries. Cheers m8... Time to start lookin for rims, so many to choose from these days....

[VXSS346]

Interesting, :hmmm: another good reason for me to keep the stock 17's. :dance:

Everyone's different though.

[IJ.]

PMoI ;)...

[fishman88]

Definitely felt a difference when i changed from 17 inch VZ calais rims to 19 inch staggered aftermarket rims. Steering was heavier dats for sure probaly slight loss in acceleration. Try n lift a 15inch stock wheels n see how light it is.

[feistl]

The general rule of thumb is unsprung weight is worth about 7-8 times dead weight.

Now im not exactly sure what the weight is of each wheel, but here is something to think about.

If a standard 17" wheel weighs in at 10kg, and a 20" wheel weighs 15kg, thats 5kg extra per wheel.

So 4 wheels * 5kg = 20kg.

So 20kg of unsprung weight has the same effect as adding 140-160kg of lead into the boot (20*7).

I havnt done the testing myself, but apparently a VE doing back to back dyno runs with 18" and 20" saw a 20rwkw difference in favour of the smaller wheel. As this was on measured on the rear wheels, its effectively a 40rwkw difference (as you would lose another 20 fwkw (front wheel kw) at the front).

So yeah, changing rims can make a big difference.

Big wheels
Pros - Looks
Negs - higher Cost, less tyre life, less grip, less ride comfort, more unsprung weight, decreased fuel economy, increased brake wear, less braking ability, more fragile, higher chance of theft

So really, why would anyone run bigger wheels? (i only run 18s because 17s wont clear my brakes).

Cheers

[white lie]

Consistent 0.2 second difference in just changing my front rims from 20"s to 18"s on my car. Went from a fairly consistent 12.4/12.5 to 12.2/12.3, was always running 18" rears, only changed the front two rims between meets.

I'd go smaller all round but they won't clear my brakes. I couldn't tell you the 0-100 times but the loss in traction on street tyres overules it all anyway. ie you will lose more time in sheer acceleration on the street compared to running a slick or semi slick so I wouldn't worry about it.

[Timson]

The general rule of thumb is unsprung weight is worth about 7-8 times dead weight.

Now im not exactly sure what the weight is of each wheel, but here is something to think about.

If a standard 17" wheel weighs in at 10kg, and a 20" wheel weighs 15kg, thats 5kg extra per wheel.

So 4 wheels * 5kg = 20kg.

So 20kg of unsprung weight has the same effect as adding 140-160kg of lead into the boot (20*7).

I havnt done the testing myself, but apparently a VE doing back to back dyno runs with 18" and 20" saw a 20rwkw difference in favour of the smaller wheel. As this was on measured on the rear wheels, its effectively a 40rwkw difference (as you would lose another 20 fwkw (front wheel kw) at the front).

So yeah, changing rims can make a big difference.

Big wheels
Pros - Looks
Negs - higher Cost, less tyre life, less grip, less ride comfort, more unsprung weight, decreased fuel economy, increased brake wear, less braking ability, more fragile, higher chance of theft

So really, why would anyone run bigger wheels? (i only run 18s because 17s wont clear my brakes).

Cheers

I was talking to Matt Thomas from Joss today at the motor show and we got talking about unsprung weight. He said that for every kilo of unsprung weight it adds 4 times that onto the chassis. So it is very hard to get a firm rule of thumb for unsprung weight, everone has their own opinion on it. That is why he has gone carbon-ceramic brakes to try and reduce the unsprung weight further. The less unsprung weight, the less energy lost getting the car off the line. On a side note I asked him why he hadn't gone to carbon fibre rims and he said that of they get a knock like clipping a gutter the carbon can fracture but not break. With a proposed top speed of 360km/ph he said it is just not worh the risk.

[1BEAST2NV]

I reckon manufacturer plays a part, I recently got 20's fitted to my ve clubby and I can say my 19's with tyres feel heavier than my new 20's with tyres, both have new tread.

[kangavxss]

The general rule of thumb is unsprung weight is worth about 7-8 times dead weight.

Now im not exactly sure what the weight is of each wheel, but here is something to think about.

If a standard 17" wheel weighs in at 10kg, and a 20" wheel weighs 15kg, thats 5kg extra per wheel.

So 4 wheels * 5kg = 20kg.

So 20kg of unsprung weight has the same effect as adding 140-160kg of lead into the boot (20*7).

I havnt done the testing myself, but apparently a VE doing back to back dyno runs with 18" and 20" saw a 20rwkw difference in favour of the smaller wheel. As this was on measured on the rear wheels, its effectively a 40rwkw difference (as you would lose another 20 fwkw (front wheel kw) at the front).

So yeah, changing rims can make a big difference.

Big wheels
Pros - Looks
Negs - higher Cost, less tyre life, less grip, less ride comfort, more unsprung weight, decreased fuel economy, increased brake wear, less braking ability, more fragile, higher chance of theft

So really, why would anyone run bigger wheels? (i only run 18s because 17s wont clear my brakes).

Cheers

Thanks for the informative insight. Negs certainly outweigh the pros. Food for thought... Cheers

[kangavxss]

I reckon manufacturer plays a part, I recently got 20's fitted to my ve clubby and I can say my 19's with tyres feel heavier than my new 20's with tyres, both have new tread.

What brand/name rims did u fit? Light weight items?

[kangavxss]

I reckon manufacturer plays a part, I recently got 20's fitted to my ve clubby and I can say my 19's with tyres feel heavier than my new 20's with tyres, both have new tread.

You got power to burn with your ride....Cheers

[73.RSR]

performancealloys.com have a huge range of lightweight rims, UK based but they are that cheap that you can get 4 rims for under $1k (plus shipping).
I just switched from factory rims on my Golf (18x7.5) to Lightweight (9.1kg) 18x8 rims and the difference is a lot more noticeable than I expected, steering and acceleration are greatly improved.
http://i106.photobucket.com/albums/m252/CV8005/VW/june2011029.jpg

[Wonky]

The only potential problem with that is proving they meet Australian requirements else you may run into problems with insurance in the event of a claim (unlikely but worth taking into account).

[kangavxss]

performancealloys.com have a huge range of lightweight rims, UK based but they are that cheap that you can get 4 rims for under $1k (plus shipping).
I just switched from factory rims on my Golf (18x7.5) to Lightweight (9.1kg) 18x8 rims and the difference is a lot more noticeable than I expected, steering and acceleration are greatly improved.
http://i106.photobucket.com/albums/m252/CV8005/VW/june2011029.jpg

Cheers. The koya 19 inch x 8.5 rims I was after weigh about 10.8kg so thats not much heavier than yours and they were about $300each and they comply
with standards. Thanks for the link info anyway, will have a look.

[Popeye1]

Unles your runing in a comp that one tenth you wont notice, its hard to gues unles your on atrack and timed.

[sszkid]

What Koya's are they mate out of interest? I am looking at the Koya CR Teks myself in 18inch.

[CunningStunter]

The general rule of thumb is unsprung weight is worth about 7-8 times dead weight.

Now im not exactly sure what the weight is of each wheel, but here is something to think about.

If a standard 17" wheel weighs in at 10kg, and a 20" wheel weighs 15kg, thats 5kg extra per wheel.

So 4 wheels * 5kg = 20kg.

So 20kg of unsprung weight has the same effect as adding 140-160kg of lead into the boot (20*7).

I havnt done the testing myself, but apparently a VE doing back to back dyno runs with 18" and 20" saw a 20rwkw difference in favour of the smaller wheel. As this was on measured on the rear wheels, its effectively a 40rwkw difference (as you would lose another 20 fwkw (front wheel kw) at the front).

So yeah, changing rims can make a big difference.

Big wheels
Pros - Looks
Negs - higher Cost, less tyre life, less grip, less ride comfort, more unsprung weight, decreased fuel economy, increased brake wear, less braking ability, more fragile, higher chance of theft

So really, why would anyone run bigger wheels? (i only run 18s because 17s wont clear my brakes).

Cheers


I was talking to Matt Thomas from Joss today at the motor show and we got talking about unsprung weight. He said that for every kilo of unsprung weight it adds 4 times that onto the chassis. So it is very hard to get a firm rule of thumb for unsprung weight, everone has their own opinion on it. That is why he has gone carbon-ceramic brakes to try and reduce the unsprung weight further. The less unsprung weight, the less energy lost getting the car off the line. On a side note I asked him why he hadn't gone to carbon fibre rims and he said that of they get a knock like clipping a gutter the carbon can fracture but not break. With a proposed top speed of 360km/ph he said it is just not worh the risk.

I race bikes and my suspension sponsor has advised me in the past that 1kg unsprung weight = 7kg actual weight. We were looking at Carbon Fibre bike wheels which he ended up buying. 2.5KGs of weight removed from each wheel made a MASSIVE difference to handling, braking and acceleration. Granted 15kgs of extra rolling mass is a bit in bike terms, in car terms less so.....

[feistl]

15kgs

I assume this is a typo? Should be 35kg...

Which in bike terms could be 10% of the total weight.

[73.RSR]

What Koya's are they mate out of interest? I am looking at the Koya CR Teks myself in 18inch.
That's what I was looking at originally, I have the email at home and from memory they were roughly double the price of the Team Dynamic wheels and took 6-8 weeks to order.
These were delivered to my door in under 2 weeks from the UK with no customs fees (under $1k).

I did get the DHL letter trying to charge me for a quarantine inspection of $47 but I just mark the envelope, not at this address, return to sender.
If they choose to examine the goods they can pay for it.

[munz]

Haha thats awesome
I do the same when the electoral role try and send me fines/ change of address forms(comes thru Queensland transport when you change address)

[kangavxss]

What Koya's are they mate out of interest? I am looking at the Koya CR Teks myself in 18inch.

Koya endless 19 inch