Wheels & tyres - whats the best?

[Chilliman]

What I mean is, what combination of wheel/tyre size, offsets, and which tyres give the best grip, whilst retaining a degree of predictability and half decent wet performance? I've trawled back but can't find the answer I'm looking for! Much of the info is particularly subjective, and often based on what's aesthetically pleasing...

For example, is wider better? I've got 7.5" rims on the front (standard rear Estorils), which don't foul the wishbones, so could probably go to 8" with the right offset without fouling anything (that's an inch wider than the standard front 7"). Likewise the rears, could also probably go to 8" or maybe 9" without fouling anything. Such a set-up puts alot more rubber on the road, and therefore (presumably) a huge increase in mechanical grip.... Then there's diameter... the bigger the wheel diameter the lower the tyre profile.... meaning less wall flex.. there must come a point given the Chim's suspension geometry that a stiffer wall could have a negative effect on grip levels? Or 'break away' points?

Then there's track... is wider better? (on the Chim).

It's all very confusing (to me anyway)...

So, what's the optimum setup? I'm kinda thinking it might be 17" by 8" rims front and 17" by 9" rear might be best, maybe with R888's all round....

What's the collective opinion guys? If I go for new wheels I want to get it right first time

Cheers,

Chilli

Oh, and if anyone knows the optimum setup and which wheels are easily availabe in the right diameter/width/ET's then please let me know

[SILICONEKID343HP]

I would go for the SP12`s 17" and 18" they fit out the box and they would look great in metallic anthracite ,would look great against your car especially with the silver strip .

Think they come front 17" x7.5 ET 25 and rear 18x8 ET33

I have the poor mans version called Pro race 1.2`s

Not my car but the wheels look very nice .


http://www.actproducts.co.uk/shop/sp12-griffith-ch...

Edited by SILICONEKID343HP on Monday 21st October 18:11

Edited by SILICONEKID343HP on Monday 21st October 18:13

[Chilliman]

SILICONEKID343HP said:

I would go for the SP12`s 17" and 18" they fit out the box and they would look great in metallic anthracite ,would look great against your car especially with the silver strip .

Think they come front 17" x7.5 ET 25 and rear 18x8 ET33

I have the poor mans version called Pro race 1.2`s

Daz, hear what you're saying, but that's the same width on the front as I already have and only another half an inch width on the rears, with alot less tyre wall.. (like 2" less..) Might look good but would it give the best possible increase in grip?

[SILICONEKID343HP]

Chilliman said:

Daz, hear what you're saying, but that's the same width on the front as I already have and only another half an inch width on the rears, with alot less tyre wall.. (like 2" less..) Might look good but would it give the best possible increase in grip?

You could go 16 and 17"

[Chilliman]

SILICONEKID343HP said:

Chilliman said:

Daz, hear what you're saying, but that's the same width on the front as I already have and only another half an inch width on the rears, with alot less tyre wall.. (like 2" less..) Might look good but would it give the best possible increase in grip?

You could go 16 and 17"

The interesting thing (to me) is that if you look at a 997 turbo, which has similar (actually less) PTW and 0-60 times that we (supposedly) have, the wheels and tyres, especially the rim/tyre widths, are fecking mahoosive by comparison... Maybe they have more weight over the rears but I'm sure they're about half as wide again as my little 7.5" rears....

[SILICONEKID343HP]

Chilliman said:

The interesting thing (to me) is that if you look at a 997 turbo, which has similar (actually less) PTW and 0-60 times that we (supposedly) have, the wheels and tyres, especially the rim/tyre widths, are fecking mahoosive by comparison... Maybe they have more weight over the rears but I'm sure they're about half as wide again as my little 7.5" rears....

If you are happy modifying the inner arches and in some cases the outriggers then you can go much wider. 255`s on my rear caught the inner arch on one side and the tyre was very close to the outrigger.

The Griffith can run 265 no problem,seem to have more space.

[Chilliman]

Just checked, typical 997 rears are 305/30 ZR 19 - comapred with my 245/45/16's...

So that's 60mm wider.. which is nearly 2.5 inches... or a 33% increase in width.. Thats a huge amount more rubber on the road... So given that our (slightly) modded Chims have a better PTW ratio than a Porkah 997 turbo why are we running such (relatively) skinny tyres

ETA: what do the Tuscan race cars run???

Correct that, they're 315's... which is a 37% increase, or nearly 3" !!!! each side!!!

Just checked again it seems the standard 997 rear rim widths are 11"... that's 3.5" wider (each side) than the standard Chim!!!

Edited by Chilliman on Monday 21st October 18:44

Edited by Chilliman on Monday 21st October 19:05

[SILICONEKID343HP]

You could get someone like plastic man to make you some subtle arches then you could have any size you want..

You can fit 255/35/18 on the later cars . That`s wide enough with a set of R1r`s

[swanny71]

SP 12's are 7 x 17 and 8 x 18. I reckon the front wheels are a little narrow (made for 215/40/17) but the fit is perfect. Also means you can source proper tyres for them, I'm on Conti Sport Contact 3's which are brilliant.

[QBee]

My 888s are on SP12s and are sizes as above. 17 x 7 and 18 x 8, with 215/45/17 and 235/40 18 tyres.
Awesome on the track when hot, on the road I would go for R1Rs if I had the money.

Peter has 10 inch rears with his Image wheels on his 4.6 - give him a call for advice.

Generalising a bit, the wider wheels tend to be 5 stud fitting.....especially at the bigger sizes.

I have a feeling that the light rear end of the Chimaera needs a narrower rear wheel than a Porsche

[NickOrangeTVR]

Chilliman said:

Just checked, typical 997 rears are 305/30 ZR 19 - comapred with my 245/45/16's...

So that's 60mm wider.. which is nearly 2.5 inches... or a 33% increase in width.. Thats a huge amount more rubber on the road... So given that our (slightly) modded Chims have a better PTW ratio than a Porkah 997 turbo why are we running such (relatively) skinny tyres

ETA: what do the Tuscan race cars run???

Correct that, they're 315's... which is a 37% increase, or nearly 3" !!!! each side!!!

Just checked again it seems the standard 997 rear rim widths are 11"... that's 3.5" wider (each side) than the standard Chim!!!

The 997 is 400kg heavier than a Chim - I am not sure at what point extra width means ratio of width/pressure becomes self defeating. I think suspension + geo is much more important - keeping the body level during cornering etc - because when the car rolls camber etc all go out of shape and you lose traction.

[phazed]

My Image wheels are 17x8.5 and 17x10 with 235/40/17s and 255/40/17s which I believe suit the car well.

The fronts don't foul but I had to trim the rear inner arches as they seemed to be about 40mm thick!

The arches on my 99 car are a lot thinner by comparison so they should fit if I wanted them to.

[TA14]

Chilliman said:

SILICONEKID343HP said:

I would go for the SP12`s 17" and 18" they fit out the box and they would look great in metallic anthracite ,would look great against your car especially with the silver strip .

Think they come front 17" x7.5 ET 25 and rear 18x8 ET33

I have the poor mans version called Pro race 1.2`s

Daz, hear what you're saying, but that's the same width on the front as I already have and only another half an inch width on the rears, with alot less tyre wall.. (like 2" less..) Might look good but would it give the best possible increase in grip?

That's because Silverstone screwed up with the size of the rears for the Chim/Griff. There was some discussion about it at the time.