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06-09-2014, 10:25 AM | #23 |
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I went to the Tire Rack track this weekend for Windy City BMW's autocross. Kept the fronts at 34 cold and dropped the rears to 34 to match. The car felt decent and didn't seem to lose grip too much at the end of the runs. After 4 runs of ~55 seconds, the pressures were around 39 psi. I might drop them a pound more cold next time. How does the wear look? I got an alignment hoping for more negative camber up front (using camber washers) but it was apparently not possible due to my tires rubbing on the struts? Oh well, they put me at zero toe up front (might get a little bit of toe out next time) to help with the feathering. I haven't pulled the tires off to see how the wear on the inside is though...
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06-09-2014, 12:01 PM | #24 |
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Your tire wear looks just about perfect, I wouldn't touch it unless you have pyrometer readings across the tread. And even then the pyrometer readings will tell you more about your alignment settings than what you should be running for tire pressure.
The reason why your wheels are hitting the struts is because you're running wheels that are too wide or with too much offset. Once you shim you can easily run wider wheels/tires with LESS offset. I can cram 9" wide rims with ET30 with 2 shim washers. If I have to guess...That's a 9" wide front wheel? 35mm offset? You have 2 choices. Either go big or go home. Run 245mm wide on 8.5" or narrower wheel with no more than 38mm offset, or if you want to run 9" or wider, run it on 25-30mm offset with at least 3º negative camber. What I've found that works with up to 2 shims: 225-245mm wide on 8" rim, ET38-44. -0.7º to -2.5º camber 245mm wide on 8.5" rim, ET 35mm-40mm -1.5º to -2.5º camber 255-274mm wide on 9" rim, ET 25-30mm -3.0º or more camber The camber shims allow for a lot of negative camber adjustments without a lot of $$$, but it takes away inner clearance on wheels. Camber plates allows for a lot of negative camber adjustments but cost more $$$, but gives you much better range in inner clearance. Using a combination of both gives you the best flexibility in inner AND outer clearance, i.e, you can shim 1 washer, and dial in a lot of camber to run super wide (that's what I am doing) up front.
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06-10-2014, 10:40 AM | #26 | |
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I just bought the wheel/tire setup (fronts are 245/40/18x9+42) so swapping those out would not be an acceptable option in the eyes of the boss lady. As of right now, it looks like the camber plates are the way to go. I keep my wheel/tire setup and I will be able to max out my negative camber for performance and still go back to a conservative camber for street. Agreed, awesome info above! |
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06-15-2014, 01:19 PM | #27 |
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At yesterday's autocross, I dropped the rear pressure of my rivals down to 34 hot, and kept the fronts at 36. The car didn't feel too good to me, so I went back up to 36 rear and felt better to me.
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08-13-2014, 11:01 PM | #28 |
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Just an update - I put 5mm spacers on to clear the struts with 2 washers. Getting an alignment tomorrow, from what I've read it looks like 2 washers on stock suspension can yield ~2.4* negative camber, so hopefully I can obtain that. If that works, it will end up being 245/40/18x9 ET37 (42 and 5mm spacer) with -2.4* camber.
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