CV8 monaro wheel and tyre combo

[Jracer]

Hey guys, recently picked up a cv8 monaro and very happy with it so far. However, i can't help myself and want to start modifying it to keep up with my mates Supra. I was planning on fitting 295 tyres to the rear but not sure what size rims id need or if gaurd rolling is in order. If anyone could give me a hand with this id be very grateful. Im just so keen to put that supra back in its place haha
Cheers everyone
Jackson

[Red CV8 R]

Im pretty sure 295s would need guard work no matter what the wheel. The trick with the Monaro is to get the right offset. That will determine how much work you will need. If you get something with an offset of say +48 to +52 on a 9.5" wide wheel you should only need a slight inner guard lip roll. Having said this, I did see a 19x9.5" with a +58 offset recently in the Holden stud pattern and I do wonder if they would fit without any work.

[CeeVee8]

Im pretty sure 295s would need guard work no matter what the wheel. The trick with the Monaro is to get the right offset. That will determine how much work you will need. If you get something with an offset of say +48 to +52 on a 9.5" wide wheel you should only need a slight inner guard lip roll. Having said this, I did see a 19x9.5" with a +58 offset recently in the Holden stud pattern and I do wonder if they would fit without any work.

I think you may run into inside clearance problems with +58mm. Something around 48mm with 275's would be better/easier although I doubt you will fit 295's with out a fair bit of work.

[feistl]

What sort of tyre do you plan on running?

Might be worth do some research on wider tyres...

Remember as you increase the tyre width you decrease the weight per mm2 on the rubber, and friction is a function of weight not surface area.

Effectively what I am trying to say is going a 10% wider tyre doesn't increase grip by 10%. In fact it will only increase the grip by the amount of adhesion the rubber creates. So if it's a sticky drag tyre it will have a good effect whereas on a harder compound the effect is less noticeable. In fact a skinnier soft compound tyre will give you more grip than a larger harder compound.

typically the advantage of larger tyres is more physical mass of rubber which is better able to deal the heat produced over a longer running time, eg a track car.

The other consideration is the increased unsprung weight of a larger tyre/rim. In a relatively low powered car this can be significant. (I've seen a loss of 20rwkw when switching from 17" to 19", so going a fat rim/tyre could be even worse.

In summary, for a street car you occasionally "race between the lights" a big tyre may not give you the gains you want. Choosing a softer compound may yield better response. And I assume you've already done the more critical mods of trutrac and suspension setup...

[Peter B - CV8]

Wheel & tyre combo will give a negligible "performance" increase (but will look nice).
I'd suggest you get the car custom tuned (look up mafless tune). It's usually good for an extra 20-30 kw's & should cost around the $1,500- mark. If you really want to go higher than this , maybe also consider an upgraded cam/head package (together with the tune). Budget for around the $2k mark - oh, you'll also need to upgrade the exhaust.. a full system ie headers, cats etc in stainless steel will probably set your back about $2k.
As you can see, it starts to get a bot addictive & pricey. Not sure what part of Qld you're in - but "PowerTorque" used to be the preferred tuner for most Qld owners.

[SASLS1]

A good set of semi slick road tyres on the OEM rims (17 x 8 / 18 x 8) and a Truetrac diff centre would be the best way to go IMO...
Over a mega wide wheel tyre, then doing as most people do...... putting the Cheapest POS Low Grip tyre on it they can buy......

Some people also totally compromise the handling and massively increasing inner rear tyre wear with their massive rear tyres, buy dialing in heaps of negative camber ( at normal ride height ) on the rear, to make the wheels fit under the guards, total useless...


VT - VZ stick with 17 or 18 inch rims, 19's are pointless, the sidewall is too small... 19's are only good for looks, nothing else...

Then to make it handle, lower it and set the front caster to Maximum " Positive + " as possible... just before the front tyres start to rub on the inner fwd plastic guards, with the wheels turned either way...

Remove the OEM offset caster bush, so both sides are 100% even positive caster. Then the car will handle identically around Left hand and Right hand corners...

Why max positive caster???...... because you can set the front negative camber to a normal average say " Negative - " 0.5 degree for good tyre wear cruising in a straight line driving on the street.

But...... having lots of positive caster, the more you turn the wheel Left or Right from straight ahead, you will gain Large amounts of Negative Camber as the wheel is turned, making the car go round corners like it's on rails...

Also gives great straight line stability, and the wheels will self center faster from a turn... Win... Win...

[Jracer]

Thanks so much for all the knowledge and advice guys! This is basically going to be a car that i might drive to work in if the bike wont start and will be taken to Queensland raceway for track time and the occasional drag. Cause I'll be tracking it was my reasoning for larger rear tyres. The current motor is coming out in a few weeks once suspension and diff have been done because i have a ready built LSX ready to drop into it. This LSX is making a bit over 700 hp at the crank so again, another reason for wanting wider tyres haha. Hope these little bits of info can help.
Cheers fellas
Jackson

[Red CV8 R]

I think you may run into inside clearance problems with +58mm. Something around 48mm with 275's would be better/easier although I doubt you will fit 295's with out a fair bit of work.

Its 29mm less inner clearance apparently (only 9mm outer clearance though which is where the issue normally lies) and while Monaros do have more inner room in the rear it may not be enough as you say but I'm not sure, if you were to run 275s it may fit.

[Red CV8 R]

Thanks so much for all the knowledge and advice guys! This is basically going to be a car that i might drive to work in if the bike wont start and will be taken to Queensland raceway for track time and the occasional drag. Cause I'll be tracking it was my reasoning for larger rear tyres. The current motor is coming out in a few weeks once suspension and diff have been done because i have a ready built LSX ready to drop into it. This LSX is making a bit over 700 hp at the crank so again, another reason for wanting wider tyres haha. Hope these little bits of info can help.
Cheers fellas
Jackson

700hp... I too would probably go 18x8" semi slicks (say 245s), although be careful if you do use it to drive to work over a long distance or in the wet.

[Jracer]

700hp... I too would probably go 18x8" semi slicks (say 245s), although be careful if you do use it to drive to work over a long distance or in the wet.

Semi Slicks are a damn good idea. How would a setup like that go on track is my only concern? Other than that, bang on. Ive seen toranas run 8s on 245s easy haha
Cheers mate

[SASLS1]

I've run Kumho KU36, and currently running Kumho V720 semi's on my daily (VZSS Thunder ute L76 6.0L /T56) awesome grip in the dry, zero tyre squeal hooking around corners, driving in the rain I just take it easy, no problem whatsoever... These semi's are more street oriented... there are better semi slick's alot more oriented for track days...

My only issue with the V720 which replaced the KU36, is they make alot of tyre noise (like a hum). They are not directional (left hand tyres and right hand tyre) like the KU36's, so the same tyres are on both sides of the car, with an outside marked on the tyre. SO...the tyres on the L/H side of the car are running forwards for example, and the tyres on the R/H side are running backwards (ie the tread pattern). I'm 99.99% sure this is causing the Hum noise...

Being a semi they wear out alot quicker than a normal road tyre (but the awesome corner grip in the dry is well worth the faster tyre wear IMO...), also having the same size tyres front and rear you can rotate them (front to rear / rear to front ) to even the tyre wear out. (Very good for a daily driver... as my rear tyres wear twice as fast as the fronts from just acceleration, no burn outs...)

There's no way I could put 245's on the front of my VZ ATM... (I would if I could...), with my current lowered ride height @ 320mm, from the center of the wheel, to the bottom edge of the guard front and rear (top of tyre 235/40/18 is level with the bottom edge of guard, so low but not stupid low...) OEM struts with yellow Koni inserts and king springs, max positive caster I could dial in, single OEM offset caster washer removed and std OEM negative camber...

I've seen alot wider tyres on the front of VT / VZ track cars, but there are so many factors involved with ride height, wheel & offset sizes, std OEM struts vs Coil overs, running heaps of static negative camber etc...


Sound like you need to get the car setup correctly for its main purpose "track days" as you said, with so much power (700hp) it ain't going to be easy...

Going the widest rear tyre (with really good rubber) in your situation with 700hp, that will still allow for the best rear wheel alignment setup for track days...

[feistl]

Good luck with the build, sounds like a good combo. Post some pics...

Again without hijacking the thread too much, in my experience rear grip in a commodore is going to be the least of your problems. Decent braking and cooling is far more important/harder to get right than rear end grip.

For drag racing a set of slicks should provide enough grip, remember if you are trying to get 700hp to the road in 1st gear/standing start the ENTIRE driveline needs to be upgraded... (Clutch, Gearbox, Tailshaft, Diff centre, Stub Axles, Rear Axles, Outer Stub Axles, Wheel Studs....) Sometimes having less grip from the tyres protects the driveline.

As for tyres, personally i recommend the Dunlop Direzza ZII Star Spec, they are a streel legal semi slick. They don't offer the fastest lap times but have a lot more tread depth compared to most semi slicks so they'll last a while on the street. They are also priced pretty well (less than $400 per corner last time i purchased a set). They also tend to handle the heavier cars better, some of the competition works better on striped out track cars but with 1800kg+ they tend to wear really quickly.

If you are circuit racing you tend to spend most of your time in 3rd/4th/5th gear so although 700hp is a lot a decent semi slick (265 width) should be able to handle it pretty well.

Of course if you are doing track work it may be worth considering a dedicated set of wheels/tyres and brake pads. That's what i've been doing, swapping pads and tyres at the track or the night before. I've yet to find ANY street pad that can handle extended track time with the grip of semi slick tyres. I run dedicated track pads from Race Brakes in Sydney, the pads are about half the price of a good road pad (say a DS2500) but they last a lot longer.... Of course rotor wear is increased significantly. But that can be offset by using a 2 piece rotor and buying replacement rotors at a good price.

EG, If you run the AP Racing 6 piston brakes (362mm front rotors) you can get them in a DBA 2 piece design. The rotor replacement (not including the hat which is reusable) can be had for $370ea on special. Not bad when you consider standard PBR rotors are around $200ea and have no where near the braking capacity. It actually ends up more economical to run race pads and just change the rotors regularly then using a pad which wears a lot faster.

Have a bit of a search on this forum, there are lots of good posts floating around with info on setting up commodores for the track. As mentioned though, honestly power is the least of your problems. They are a heavy car with an average suspension design, it takes a lot of effort/money to get them handling, braking and staying cool reliably.

What are the engine mods?

Speaking from experience (I have a 427 LSX with a Harrop supercharger) DONT run the standard sump. I'd be looking at an ASR racing sump (9L capacity and it gets rid of the stupid oil filter setup which causes problems) then run an external oil filter, (CM Racing Canister filters are ideal), oil thermostat and as big of an oil cooler as possible. If you are looking at running boost at any stage also seriously consider running LS9 oil squirters for the pistons.

The list goes on and on and on. Just remember, having a million horsepower is fun but if you can only do 3 laps at a time before overheating its kind of pointless. If the temperatures fluctuate wildly (tyre and brake temp) remember each time you go into a corner you won't know how much grip you've got. This means you can't improve as a driver and while the initial lap time will be quick you won't actually be driving fast.

Good luck

[whitels1ss]

I would have thought that on a build like this,
trying to beat a Supra with a built 700hp LSX fitted in a CV8
that picking out a wheel & tyre combination would have been a last concern?

How quick is your mate's Supra?

Sounds like it would be an awesome car buddy.

As feistl posted above, please post some pictures of the build.