Biggest aftermarket wheel sizes for a VF Commodore.

[vc commodore]

”Compliance“ means the ability to absorb bumps. If I meant that the tyre would be leaving the road I would have said “Conformance” which means contact with the road (grip).




Agreed. These bumps that aren’t absorbed by your tyres and now absorbed by your suspension, increasing the wear on those components.



Incorrect. If you could hypothetically put a one metre wide tyre on the front end of any car and turned the steering wheel the inside or outside of the tyre will lift completely off the ground purely based on the kingpin inclination angle. The scrub radius also loads up the tyres more the further away from the pivot point that part of the contact patch is.

This is an extreme example yes but these forces are still in play on any vehicle just to varying degrees depending on the wheels and tyres fitted and the suspension geometry.



I‘m quite sure that certain things can be done from an alignment perspective to improve the situation but most wheel aligners will just bang on the factory specs regardless. Also certain parts of the suspension geometry aren’t adjustable, so there’s that.




I wouldn’t say that going from 205 to 225 was a massive width change TBH and you still have decent compliance with a 50 profile but the fact of the matter is your tyre mileage would be better with the factory 205/60R15s. What I’m talking about is using ultra wide and low profile tyres (30 profile etc), especially on the fronts.

My “10,000kms” wasn’t a hard and fast rule, I’m just saying tyre longevity is compromised by using a wider and lower profile tyre, this is just a fact. Your example of 30,000 to 35,000 I would be unimpressed with myself and I would see it as being on the low side but the lowered suspension wouldn‘t help with that and driving style and patterns (highway, city, winding roads etc) vary the mileage considerably as well.



I’ve owned two VH commodores before with stock tyres and suspension and they were diabolical especially in the wet! I never had the money to change them out to better suspension and bigger wheels and tyres but if I would of had the money I would have in a heartbeat and screw the extra tyre wear as they were scary in the wet.

Tyre profile job isn't to keep the tread planted on the road surface....That's the shock absorbers job.

Front suspension on the VB to VP is identical.

Maximum tyre size from the factory on a VB is a 205/60X15

Maximum tyre from the factory for a VP is 235/45X17

So you are saying if I put a 235/45X17 on a VB, I will get less mileage than what I would with a VP

Front suspension design on a VR to VF is identical (yes minor differences, but the basic design is the same)

Maximum tyre size from the factory for a VR is a 235/40X18 (might be wrong)

Maximum from the factory on the front of a Vf is 245/40X20

So if I was to put a 245/40X20 on a VS, I'll get less mileage than what I'd get from the VF?

You mention factory specs again...Did you know there is a scope within those specs? Not 100% sure of the scope, but it's where you set the settings determines the wear on the tyres....eg, say the scope for camber is 1/2 degree positive to 1 degree negative....That is a big variation, so what do you say is the best setting to have to stop tyre wear?

Toe specs...Say they are from 6mm toe out to 6 mm toe in...Where do you set it? You can't have them as variable once set

Wear on components is another factor, but that's another area which isn't worth going into.....Same applies with pressures....The topic at hand is tyre sizing and honestly, width has nothing to do with accelerated wear

 

[Forg]

Tyre profile job isn't to keep the tread planted on the road surface....That's the shock absorbers job.

One comment - with his references to tyre profile & "compliance", he was talking about how (to generalise and I know this isn't ALWAYS true) a lower profile tyre doesn't have as much compliance - ie. it can't flex as much.
So the suspension & body get more shocks transmitted to them.
He wasn't so much talking about keeping the tread on the road.
I don't understand, myself, how that equates to tyre wear though. Body & suspension, for sure.

 

[J_D 2.0]

One comment - with his references to tyre profile & "compliance", he was talking about how (to generalise and I know this isn't ALWAYS true) a lower profile tyre doesn't have as much compliance - ie. it can't flex as much.
So the suspension & body get more shocks transmitted to them.
He wasn't so much talking about keeping the tread on the road.
I don't understand, myself, how that equates to tyre wear though. Body & suspension, for sure.

Correct. Lower profile in and of itself isn’t a major issue vs tyre wear but it does cause some extra wear the same as a wider tyre will also cause some increased wear.

Like I said earlier the manufacturer/engineers design the car and tune the suspension to suit certain tyre sizes. Stepping massively outside these bounds is bound to have negative effects, which I myself am not willing to wear.

 

[J_D 2.0]

Front suspension on the VB to VP is identical.

Maximum tyre size from the factory on a VB is a 205/60X15

Maximum tyre from the factory for a VP is 235/45X17

Your proposition reinforces my point. All the Commodores from VB up until VS when IRS was introduced IIRC were all the same suspension design with minimal to no changes so running the biggest size available in any of those year models would be fine.

VE and VF were clean sheet designs so I wouldn’t go any larger on wheels/tyres than the largest available factory fitment on VE up until end of manufacturing of VF S2.

 

[Forg]

Correct. Lower profile in and of itself isn’t a major issue vs tyre wear but it does cause some extra wear the same as a wider tyre will also cause some increased wear.

You mean on the vehicle rather than to the tyre, though, yeah?
I don't agree that the wider tyre will cause more wear by itself; using the extra grip will (ie. pushing the car juuust that extra bit hard enough into corners & accelerating juuust that extra amount hard enough that you would have lost traction with the narrower tyre but you don't with the wider one), but the amount of difference is going to be pretty much immeasurable in the overall scheme of things. However, I pretty much never use the extra width in that way, for me it's just an extra margin of safety should I (for example) need to drive near an SUV and the inevitable Stupid Behaviour needs to be urgently avoided.

VE and VF were clean sheet designs so I wouldn’t go any larger on wheels/tyres than the largest available factory fitment on VE up until end of manufacturing of VF S2.

Again, I beg to disagree!
I believe that if you installed a set of quality lighter-than-stock, yet wider, aftermarket wheels along with matching tyres, your unsprung weight is reduced and this can hence cause LESS wear to suspension components & the car itself.

 

[J_D 2.0]

You mean on the vehicle rather than to the tyre, though, yeah?
I don't agree that the wider tyre will cause more wear by itself; using the extra grip will (ie. pushing the car juuust that extra bit hard enough into corners & accelerating juuust that extra amount hard enough that you would have lost traction with the narrower tyre but you don't with the wider one), but the amount of difference is going to be pretty much immeasurable in the overall scheme of things. However, I pretty much never use the extra width in that way, for me it's just an extra margin of safety should I (for example) need to drive near an SUV and the inevitable Stupid Behaviour needs to be urgently avoided.


Again, I beg to disagree!
I believe that if you installed a set of quality lighter-than-stock, yet wider, aftermarket wheels along with matching tyres, your unsprung weight is reduced and this can hence cause LESS wear to suspension components & the car itself.

A lot of what you “win” or ”lose” by changing tyres depends a lot on the suspension geometry. Not toe and camber but caster angle (kingpin inclination) and scrub radius. The centre pivot point on the tyre is the ideal part of the tyre that can pivot directly on itself without scrubbing, everything outboard of this point has to scrub to be turned so the further away from the centre point the outside of the tyre is the more scrubbing needs to happen when the wheel is turned.

I‘m sure a good set of aftermarket wheels along with the proper aftermarket suspension components and alignment from a suitably qualified person could negate a lot of the potential for increased wear that is not related to using softer compounds and running higher tyre pressures on lower profile tyres.

Hypothetically decreasing unsprung weight with larger wheels could reduce suspension wear but lets be honest here, nearly everyone who puts rubber bands on their wheels wants to slam the car on its arse, which definitely increases suspension and tyre wear!

 

[vc commodore]

A lot of what you “win” or ”lose” by changing tyres depends a lot on the suspension geometry. Not toe and camber but caster angle (kingpin inclination) and scrub radius. The centre pivot point on the tyre is the ideal part of the tyre that can pivot directly on itself without scrubbing, everything outboard of this point has to scrub to be turned so the further away from the centre point the outside of the tyre is the more scrubbing needs to happen when the wheel is turned.

I‘m sure a good set of aftermarket wheels along with the proper aftermarket suspension components and alignment from a suitably qualified person could negate a lot of the potential for increased wear that is not related to using softer compounds and running higher tyre pressures on lower profile tyres.

Hypothetically decreasing unsprung weight with larger wheels could reduce suspension wear but lets be honest here, nearly everyone who puts rubber bands on their wheels wants to slam the car on its arse, which definitely increases suspension and tyre wear!

Half the issue here is, you are alledging that your mates put wider tyres on their cars and had inner edge wear issues as a result..

You are claiming scrub radiuses etc etc....The whole tyre face would be effected, not just one edge on both fronts....So time to give that part away

 

[vc commodore]

Your proposition reinforces my point. All the Commodores from VB up until VS when IRS was introduced IIRC were all the same suspension design with minimal to no changes so running the biggest size available in any of those year models would be fine.

VE and VF were clean sheet designs so I wouldn’t go any larger on wheels/tyres than the largest available factory fitment on VE up until end of manufacturing of VF S2.

You are trying to compare a car that was built in 1978, when 17 inch tyres were for exotic European cars and not even considered for the run of the mill taxi, to a car that was manufacturered in 1992 when it started to become the norm.....Sorry, but you are clutching at straws

 

[vc commodore]

One comment - with his references to tyre profile & "compliance", he was talking about how (to generalise and I know this isn't ALWAYS true) a lower profile tyre doesn't have as much compliance - ie. it can't flex as much.
So the suspension & body get more shocks transmitted to them.
He wasn't so much talking about keeping the tread on the road.
I don't understand, myself, how that equates to tyre wear though. Body & suspension, for sure.

I agree that tyre profile has nothing to do with the claim of tyre wear....So why a comment about compliance would come into the discussion is beyond me...

 

[vc commodore]

Correct. Lower profile in and of itself isn’t a major issue vs tyre wear but it does cause some extra wear the same as a wider tyre will also cause some increased wear.

Like I said earlier the manufacturer/engineers design the car and tune the suspension to suit certain tyre sizes. Stepping massively outside these bounds is bound to have negative effects, which I myself am not willing to wear.

I would love to hear your thoughts on my 1976 model valiant...OEM fitament was 185/75X14....These cars you'd get 30,000 to 40,000 out of a set of tyres....They are big heavy cars, with miles of suspension travel, up and down, side to side. Even when the cheese cutters are fitted to these cars, they have a bad habit of stuffing up idler arms within 12 to 24 months....

I fitted a set of 235/60X14 to this car...So a massive increase in tyre width....I managed to get 50,000 out of that set, before moving up to 245/60X14....Why did I get increased mileage out of them when you are making claims wider tyres reduce mileage?