thoughts about track rims and tyres

[_Nathan_]

9" is the narrowest rim that a 265 cup can be used on, same with a 250 slick, both suggest 9-10.5 inch wheel. A 250/640/18 Dunlip slick is 10.1" wide, it is designed for a 9.5" wheel. I've had good discussions with the tyre and wheel people about the issue of the car falling over itself as the tyre tucks under and the consensus was to go to a wider wheel to stretch the sidewalls and reduce the wheel moving inside the tyre hence my suggestion of a 10" wheel. My car is heavier than the cup cars so horses for courses and not suggesting what you've found isn't right, just different to what I've seen on my car.

Nick bell ran 18x10 BBS and later OZ on his car to great effect, worth having a chat with him?

I've got some 18x10 team dynamic 1.3s waiting to go on, fingers crossed my offset calculations were right :D

[shimmy]

Originally Posted by _Nathan_

Nick bell ran 18x10 BBS and later OZ on his car to great effect, worth having a chat with him?

I've got some 18x10 team dynamic 1.3s waiting to go on, fingers crossed my offset calculations were right :D

ive done my own calcs and your offsets are well out mate


but then i realised you will be running big camber and also want to widen your track as much as possible

from a road car point of view my calcs show that if i want matching rims front and back and 265 tyres (18 or 19) then to maximise the space available inside the front wheel you need to increase the offset on the bigger rims to best size et32 to fit the front as efficiently as possible.

This means the same rims on the rears have a say 5mm bigger to make use of the space to the strutts.

this means that the tyres will be 14.2mm further out, that makes the perfect rim the 18x10 et 30 from the catalogue but i would prefer a 19x10 et32 and hope that the extra camber needed to tuck under the front arch is not too much (-3 hopefully)

obviously different fro you race car, different priorities

[_Nathan_]

Remember that the width of the tyre face doesn't change and it is the tyre that needs to clear the arch, not the face of the wheel. I'd have liked a lower offset but they couldn't make them any lower, we'll see

Found this useful: http://www.1010tires.com/WheelOffsetCalculator.asp

This car is running 18x10 ET11 all round:

[shimmy]

yep, understand, i have been working on rubber sizes as the michelin specs for Cups.

http://www.tirerack.com/tires/Spec.j...ilot+Sport+Cup


i am trying to tuck the new rubber as close to the strutt as the current one is, assuming that this is as close as you want to get. CSL fronts are et45 and with the 18x10 and 265 cup this means for the inside of the tyre to be in the same place you need an et32

this just leaves the question, what camber is needed to tuck the 265 under the arches if it is sticking out 14.2mm further?

[_Nathan_]

Well you know that an 18x9 ET27 (m3 rear) fits just fine and that sticks out 24mm more that an 8.5 et45 so I think it'd be fine, also remember that loads of people run 10-12mm spacers on the front, again with no issues.

[TANKSLAPPER]

I have done a little testing on the front wheel clearance

This was with 3 degrees camber

The standard CSL wheel as we know is 19 x 8.5 et 45 fits
BBS CH'S is 19 x 8.5 et 35 fits
BBS CH'S 19 x 8.5 et 35 with a 12mm spacers fits = to 19 x 8.5 et 23

The standard CSL rear wheel on the front 19 x 9.5 et 27 just touches the outer side edge of the arch.

The BBS CH'S rears 19 x 10 et 20 rubs a lot.

So my cal's, would be to go for 18 or 19 x 9.5 et32 for the front and the same for the rear with a 15mm spacers

The problem is I can not find a wheel manufacturer that make such a size wheel lol

[TANKSLAPPER]

Here's some photos of BBS CH'S rears 19 x 10 et 20 on the front they rub on the outside edge of the wheel arch, but they do clear the suspension strut.

If you take out the wheel arch liner then they may clear.

I not going first through the foxhole lol

[shimmy]

Originally Posted by TANKSLAPPER

So my cal's, would be to go for 18 or 19 x 9.5 et32 for the front and the same for the rear with a 15mm spacers

i dont think 9.5 or 10.0 will make a difference as the tyre section will be much the same so the opiton could be 19 or18x10 et 32

Team Dynamics Pro-race 1.3 (liuke Nathans) make a 18x10 et 30 which is guess would be the one to go for

Only troubles are;

1. Nathan uses them

2. Mazda Miatos use them as well

ALSO i just rang Rimstock and the Pro Race 1.3s with 18 inch 265 Cups weigh over 1 KG more than rear CSL rims with Cups

[TANKSLAPPER]

Originally Posted by shimmy

i dont think 9.5 or 10.0 will make a difference as the tyre section will be much the same so the opiton could be 19 or18x10 et 32

Team Dynamics Pro-race 1.3 (liuke Nathans) make a 18x10 et 30 which is guess would be the one to go for

s

I agree that 9.5 or 10 j will not make much difference as both the standard CSL wheel ie 19 x 9,5 et27 and the bbs 19 x 10 et 20 touch the arch liner in the same place.

The only problem I can see with team Dynamics 18 x 10j et 30 is they may just touch the suspension strut.

You can see from the above photos that the BBS 10j et20 wheel is very close to the suspension strut ie about 10mm

I suppose 18 x 10j et 25 would work in my case with KW club sports on.

[shimmy]

the standard front CSL tyre is 165.7mm from hub face to iside edge of tyre

the 18x10 et 30 TD Pro race with 265 Cups would be 163.9mm from hub face to inside edge of tyres

so these should not touch the strutts even with 10 inch rims




the standard CSL rears measure 160.9 mm so thye clear the strutts easily but foul the wheel arch more becasue more of the tyre is set out (hence the reason for an et30-32 being best)