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      05-28-2012, 12:42 AM   #1
Drifty//
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Inflation of non-OEM sizes?

My car had 19" 220M's. I'm running 275/35R18's now (square). What should my tire pressures be for street? The sticker on the door sill says Front=33 PSI Rear=35 PSI. I did 35/36, for now.
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      05-29-2012, 10:34 PM   #2
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Anyone? I know a lot of you are running non-OEM tire sizes. Do I stick with recommended inflation?

If not, are there guidelines I should follow?
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      05-30-2012, 11:21 AM   #3
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i use this table

http://www.m3post.com/forums/showthread.php?t=519804
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      06-02-2012, 05:46 PM   #4
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Quote:
Originally Posted by kmarei View Post
Thanks for this and your many other helpful posts I've read while researching & prepping this car!

Here's what I found (thanks, tirerack!):
245/35-19 PS2: load index 93(XL) @ 33 PSI = 1178
265/35-19 PS2: load index 98(XL) @ 35 PSI = 1430

275/35-18: load index 95(SL) @ 26/27 PSI = 1164/1199
275/35-18: load index 95(SL) @ 33/34 PSI = 1407/1443

Note that the Dunlop Direzza Sport Z1 Star Spec have SL load range, whereas the Michelin Pilot Sport PS2 have XL load range. Therefore, I used your chart to get the load for the PS2's, but the chart I posted later in that thread to find the PSI for the SS.

So, it looks like I should be running 26/34 F/R on my Star Spec square setup. I'm a bit surprised at the bias. I think I'll actually do something closer to 29/32, since I'm guessing some of that bias was to give the front tires a larger contact patch for a bit more bite. Switching to 275's should reduce the need for that and I wouldn't mind a slightly larger contact patch in the rear.

I'll also be keeping an eye on how the tread wears.
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Last edited by Drifty//; 06-02-2012 at 06:07 PM. Reason: Fixed to use SL chart for Z1 SS tires
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