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      02-27-2013, 12:43 AM   #1
Jazzy
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Max width ZII tire on stock wheel?

I currently have 225/255 tires on stock wheels. I am about to order a new set of ZII's for autocross, but want to know if a 235 will fit up front with no issues or should I stick to the 225. Has anyone tried the ZII in this size?

Car is completely stock except for sway bar (running in D-stock).
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      02-27-2013, 05:48 PM   #2
Ginger_Extract
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If the ZII is at all like the ZI's, then they run wide. For example, I ran a 235 square setup on my Mazda, and they were closer to a 245ish in size. How much clearance do you currently have with the 225's, in terms of the strut (inside) and fender (outside)?
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      02-28-2013, 02:47 PM   #3
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I have run 235/255 Star Specs and PSS's on my stock 261's with zero issues street or track.
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      03-01-2013, 06:47 AM   #4
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I'm interested in this as well. Are your fronts 235/35 or 235/40? I'm assuming the rears are 255/35.
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      03-01-2013, 08:46 AM   #5
fe1rx
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Quote:
Originally Posted by Jazzy View Post
I currently have 225/255 tires on stock wheels. I am about to order a new set of ZII's for autocross, but want to know if a 235 will fit up front with no issues or should I stick to the 225. Has anyone tried the ZII in this size?

Car is completely stock except for sway bar (running in D-stock).
Since you want these tires for autocross it is fair to assume that your main concern is actually performance (in the literal sense, not in the way the word is often used in this forum).

1) I assume your OE wheels are 7.5" x 18" front and 8.5" x 18" rear.
2) 225/40R18 ZII tires are recommended for wheels from 7.5" to 9"
3) 235/40R18 ZII tires are recommended for wheels from 8" to 9.5"
4) the car has a 50:50 weight distribution so "should" have a square tire setup if neutral handling and maximum total cornering grip is your goal (which it should be for autocross)
5) for what it is worth, I have been using 225 Star Specs all around so I can say from experience that they help the balance. Also, they have enough tractive grip that the rear isn't overpowered too easily assuming you don't treat the throttle like a switch (which of course you don't in autocross, if you expect to do well). My suggestion is that you consider a square setup, even if you manage to fit 235s up front.
6) Whatever you do, you will be hobbled unless you replace the rear subframe bushings with the M3 parts. This is the single best handling mod you can do on your car after good tires. The original rear subframe bushings force the car prematurely into understeer by means of "compliance steer" or "passive rear steer". With the OE bushings (and a square tire setup), the handling feels quite neutral to about 80% and then the car feels almost as if the front tires are rolling over. With the M3 bushings the handling maintains the same feeling all the way to the limit and the sense that the front tires are rolling over disappears.
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      03-01-2013, 04:35 PM   #6
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I can attest to the above poster's comment about a staggered setup not helping the understeer. However I like the aggressive look of 255's in the rear. Is a 235/245 possible? Never see it around here.
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      03-01-2013, 06:10 PM   #7
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For those not familiar with autocross, the class OP is running in cannot change wheel diameter/width and must stay within +- 6mm of offset.

You cannot change bushings, it is violation of stock rules.

With that being said, OP stick with 225s. You "may" be able to fit 235s but you will lose grip. Let me explain.

Putting too much tire on a wheel isn't always the best thing. Under high g-load and corner load, the tire will start to shimmy back and forth on the wheel before it actually starts to grip. With that being said, your front end is going to feel light and un-responsive. The sidewall will also be too soft.

225 tire will stretch a bit on the wheel compared to the 235, so the tire will act more responsive because there will be no shimmy of the tire back and forth on the wheel.

For reference, I run 235/265 on my Z4M. I have 18x8 and 18x9. I could easily go 245/275 but it would be too much tire.

This is what my Hankook RS3s look like on my fronts, they are plenty of tire.

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