03-01-2020, 09:17 PM | #1 |
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losing grip at autocross
I just finished an autocross session this afternoon in my 2018 6sp LCI. I'm on Ohlins R&T coils, Titan 7 Ts5 wheels, on Michelin PS4S front 255/35/19, rear 257/35/19. The corners were really tight and this course was really tricky as it demanded good weight transfer control. Coming out some of the corners i would be losing grip and if it wasn't for the half traction i would've spun out 2 or 3 times. I know i could've shaved off 2-3 seconds off my fastest time but im not sure how. Right now im thinking of getting a new wheel and tire set up for track use. Any advice?
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03-01-2020, 09:54 PM | #3 |
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oh yea i love them, the look great but 19s aren't a great wheel size for BMW's im thinking of leaving these as my canyon and street set up and getting another set of titan 7's in 18s for my track set up, with a wider square set up.
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03-01-2020, 10:00 PM | #4 | |
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03-02-2020, 11:22 AM | #5 |
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When I switched to apex 18x10 square rims with 285/30r18 re71r’s, I immediately dropped 3 secs off the shorter autocross tracks. Versus my PSS 285/265 on stock rim set up.
I know the rims don’t matter (as long as not heavy) but the tire sure does make a difference. Pay attention to your car classing rules as my choice of rims bumped me into a different car class. But I don’t care as I was doing other mods anyways. |
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03-03-2020, 08:54 AM | #6 |
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As mentioned previously, get a better tire.
In the meantime, if you're losing grip in the rear, you can try lowering rear tire pressures and/or softening the rear ohlins. |
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03-03-2020, 02:33 PM | #7 | |
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As others have mentioned, some stickier tires will certainly help. However, if you’re currently on PS4S tires and relying on traction control to save you, you probably need to spend more time working on your inputs, as those are a very good non-200TW, non-r-compound tire. |
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03-03-2020, 04:34 PM | #8 |
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Also I found traction control very intrusive and slowed me down a lot. I ran with traction control on for my first few track days and first couple autocross events until I got more used to the cars handling and throttle inputs. Now I run with tc full off (long press). The car is really predictable and easy to correct/save once you are dialed into it.
My next step is to get a custom bm3 map with a nice linear throttle map for track/autocrossing. |
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03-03-2020, 06:05 PM | #9 |
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GeraldM2 double edged sword here. Yes stickier tires should help shave some time - and 18" open up some more options for the track - so you can see some benefit. The downside could be though that if you are reliant on DSC to keep you from spinning the move to a stickier tire could ingrain that even more. If you are thinking of going to full DSC off the transition is typically easier with a higher treadwear tire - and going full DSC off is typically faster. On average their limits are at a lower speed, they communicate better, and are easier to bring back than lower treadware tires - all typically making it easier for the driver to get used to having traction control off and being able to control the car. Also the longer you go with DSC on the more that mashing the throttle and relying on TC to keep the car in check can get ingrained in your muscle memory - can make it a harder habit to break later.
Now if you have no interest in going full DSC off - and their is absolutely nothing wrong with that - then grippier tires should definitely help. Also being at the optimum temperature & pressure would be beneficial - although with autocross I'm not sure how much of a chance there is to get the temps up in the tires? |
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03-03-2020, 11:21 PM | #10 |
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Autocross does warm up my tires. I start at 31 psi and each run I typically drop about 1.5-2 psi to stay at 32. Depends on how much down time in between runs. I mark my tires with chalk to see their roll over, and adjust from there. But that’s for my set up, but gives an idea of how the temps increase.
Open Track generates way more temp. |
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03-04-2020, 01:10 AM | #12 | |
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03-04-2020, 03:45 AM | #13 |
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I know a lot of people had said tires here but it's your inputs that are upsetting the car. We like to flex our ego's but spending time getting lessons will do far better for your lap times then tires. Throwing hardware at problem is just masking the root cause.
Even spend the $500 and do an M track day and talk with the instructors. Many of them can push lap times fairly close with DSC on. The benefit of it off is it will let you rotate the car and DSC is basically tuned understeer. |
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