Rim & Tyre width for better traction vs handling

[Ralph-Wiggum]

Hi Guys,

I have been doing a lot of reading in preparation of purchasing new wheels and tyres for my CL9, as my current Yokohama A.Drive R1's (AR01) 205/55/16 on the stock alloys are getting to close their use by date.

I drive the thing fairly hard and are just starting to attend hillclimb days. I was originally thinking I would go as wide as I could to increase the contact area on the road. I was thinking 17x8 rims with 245/40/17 with some Yokohama S.Drives (I might be a bit optimistic about what width will actually fit on the car, will do some more measuring on the weekend)

Then I came across some information to say that for best handling I should go for a rim that is 90% of the tyre width. Ok so 90% of 245 is 220mm or 8.68 inches which I feel is starting to get to wide for the guards.

I can then go back to a 225/45/17 which 90% would make 202mm or 8 inches.

What option is most likely to give me the best overall handling?

Is anyone running a similar setup?

[Baby Face]

okay.

first off unless you have lots of money when u get 8 inch rims then you will want 235/45/17 tyres
as this size is very common and even good tyres are cheaper in that size.

235 is pretty good for an 8 inch, 245-255 is going to be a lil too big and you may lose some stability.
225 is also ok no neticable stretch basically straight sidewall.
215 more stretched look. 205 is too low from a performance POV ok for stance stretch?.

im running 235 45 17 on a very grippy rear tyre because it was cheaper than anything decent i could get in 245/40/17.

for a euro i think 235 will definately be enough. unless boosted.
if you would really like more cornering performance mate a good tyre with a bit more camber try 1-2 degrees camber all sides?

[Ralph-Wiggum]

Hey Baby Face,

Thanks for the reply. I was looking at 245/40/17 as I was trying to keep a similar rolling diameter to reduce the impact on the speedo reading, I originally had a quick look around the net to get an idea of costs.

Your comment about the 235/45/17 being considerable cheaper is very true following further research, I feel for that sort of difference it is worth the -1.77% in accuracy. It also looks like I will need a minimum 8 inch rim to get away with these as well.

After fitting BC BR type coilover and reducing the ride height modestly I now have the desired -2 degrees in the rear according to my last wheel alignment. The front end is still sitting at 0 degrees. Might look at this in the future.

So my next question to all of you out there is, will I get away with fitting 17x8 rims on the CL9 euro with a +43 to +45 offset? is anyway running this at present?

My reasoning behind the +43 to +45 is, the stock rims are +55 and legally I can get away with a change in wheel track no greater then 12.5mm, which gives me +43. That said I am not sure what the chances are of ever being pulled up on this.

[Baby Face]

yehp 17x8jj rims required

what you said about the stretching of tyres over the rim is true, as it pulls on the sidewalls so that they are already tight and wont flop... this being said too tight and the tytres can be pulled off from cornering or hitting a kurb.
a 255 is gonna flop.
a 245 less so but too expensive with a 245 tyre so 235 is ya best bet, should be more affordable to get one with a good sidewall construction.

on a FWD car you will need more rear camber than front to help with handling, all manufacturers recognise this and many cars that even dont have rear adjustable camber will come with about 30' (0.5 degree).

Camber on the front wheels is good for applying power through corners and minimising understeer. however your front wheels wear fastest since they do most of the braking and all of the steering/power transfer.
the more camber you have the faster they will wear out and in a straight line you will have less contact path to apply brakes and power.
you need to find where you are happy.

now for offsets you will most likely be nabbed if your wheels are poking out, for inspection just swap the rims over.
my s2k recommended something like +55 offset or something which where the stock rims but my new 17x8s have 45 and they just fit (maybe stick out by 2mm) i would imagine that you should be fine with those spec, but keep in mind you will not be able to rotate the wheels. basically keep the +43s at the rear and +45s at the front.

adjust front camber to 0.5degree (ie 30' minutes)
if they do stick out a lil.

measure the distance from rim edge to fender.
then using your current rim specs enter the data into here
http://www.jdmconcept.com.au/wheel-offset-calculator