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09-20-2010, 01:54 PM | #1 |
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Wear on the outer edges of tires... Solutions?
I'm noticing a lot of premature wear on the outer edges of my tires. What are some possible solutions?
- Camber, local SCCA techs don't seem like they're going to allow it, I've asked, showed them TIS and informed them it's normal dealership procedure, and they aren't budging. edit: No official input from an SCCA chief yet, just input from another racer who believes this is not stock-legal. - Front Sway bar? Will reducing the body roll prevent the tires from rolling over the sidewall? - Air pressure? I'm already ~4psi f/r over the recommended psi in the door jam. Should I try adding more? - Anything else? Remember, stock class legal.
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09-20-2010, 02:04 PM | #2 |
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Run more pressure at autox. On the side of your tire there should be a triangle on the sidewall near the tread. That's where the manufacturer considers the defining line between the tread and the sidewall to be. If it's worn past that triangle you need to run more pressure to compensate for the tire flex. If not then don't worry about it, hard driving and the natural pushiness of the 1 series do the small front tires no favors. My front ps2s look like in a way too. I'll snap a pic later.
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09-20-2010, 02:06 PM | #3 |
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Just looked a second time. You're still on the rfts? They degrade like crazy when abused at the track or autox. The tread starts to peel off in extreme cases
But the info up there ^ is still useful |
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09-20-2010, 02:06 PM | #4 |
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Actually I managed to get the triangle in the photos. Looks like I need more pressure then?
edit: Yes RFT, but Star Specs are going on within the next week or two when I get time.
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09-20-2010, 02:09 PM | #5 |
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Didn't see that. iPhone screens aren't the best to do this with. Yeah a bit more pressure for sure. But you can't judge it cold. You need to get some paint (the soapy water like stuff) and judge it at an autox
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09-20-2010, 02:11 PM | #6 |
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But that looks more like the rfts degrading (crappy bridgestone compound) more than normal wear. You see the cracking on the tread near the sidewall in the second pic?
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09-20-2010, 03:46 PM | #7 |
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That looks like normal wear for a autocrossed street tire. The heat/understeer turns them into hamburger.
The runflats will start shedding chunks of rubber. Beware. I have brand new Hankooks that look like that after 5 runs. Stiffer front bar may help. I just installed the Hotchkis bar . . . jury is still out whether it was a change for the better handling wise. I changed too many things at once. My temperatures are more consistant across the tread of the tire, so that's a move in the right direction. Tell your techs to RTF rule book on alignments in stock class. "Both the front and rear suspension may be adjusted through their designed range of adjustment by use of factory adjustment arrangements or by taking advantage of inherent manufacturing tolerances. This encompasses both alignment and ride height parameters if such adjustments are provided by the stock components and specified by the factory as normal methods of adjustment. However, no suspension part may be modified for the purpose of adjustment unless such modification is specifically authorized by the factory shop manual for non-competition purposes." Factory TIS explicitly specifies pin removal to allow camber adjustment. Rule book explicitly states you can do whatever alignment you like as long as it's using the factory procedure. |
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09-20-2010, 03:51 PM | #8 | |
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09-20-2010, 04:00 PM | #9 |
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In autocrosses/spirited driving, outers wearing more than inners (particularly front) is gonna be a way of life without modifications to gain/adjust negative camber and stiffness. Even with more tire pressure (i.e. no longer rolling over past the triangle marker), you're still going to beat up the outside edges way harder than the inside/middle. The Star Specs definitely hold up better than the stock RFTs, but you're still gonna see more abuse on the outer portion of the tread.
EDIT: This holds true even with the alignment pin removed and full -camber pulled in. Don't expect much out of this, as you only get about .5 degrees extra TOPS. If anyone has camber plates and a pyrometer, I'd be VERY interested as to how much camber is needed before the tire temps start evening out between the inside/middle/outer edges. I'm guessing somewhere in the 3 degree range to see consistent temps, so even camber plates might not reach this amount of camber.
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09-20-2010, 04:22 PM | #10 |
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I think all the things you suggest will help. The alignment pin will do a little as some extra camber won't hurt, and as mentioned this is now in the TIS and considered an acceptable way to adjust the front alignment by BMW (i.e. is legal in stock class). Adding a front sway will also help keep the outside tire from rolling over quite as much and as a benefit keep the body roll down as well. This is also legal in stock. Increasing the pressure should also help the rolling over as well. I think it varies from tire to tire, but see what works for you. Add a few psi to what you run now and see if that helps. If you're going for a competitive car in stock class do everything you can, especially since these are cheap/free/legal mods. Some better tires would help too, get those Direzzas on there! Good luck!
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09-20-2010, 04:23 PM | #11 |
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Yea, I'm aware it won't get me much camber, but if I'm getting an alignment done anyway, I figured it couldn't hurt.
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09-20-2010, 06:50 PM | #12 |
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Also, fatter tires. Bigger tires will give you more outside edge to roll onto
Edit: I'm running 235s up front . . . probably going to get 245s when I get slicks. |
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09-20-2010, 07:25 PM | #13 |
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How are you fitting that much tire without rubbing in D-Stock?
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09-20-2010, 07:34 PM | #14 |
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You know you can't tell us your running 235s up front without telling us what kind they are! And other mods? 225s are a tight enough fit with stock clearances (Star Specs at least)
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09-20-2010, 09:07 PM | #15 |
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I'm running Hankook V12s right now . . . they 235/40 and they fit without rubbing. These are my street tires.
With the pins removed, there is still an additional 1/8-1/4 inch or so between the tire and shock body. I've seen/heard no rubbing elsewhere. Only mod is a Hotchkis FSB. I have some 245/40 Hoosier R6 takeoffs on the way. (Yes, for a stock rim, no I'm not crazy) Those might rub |
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09-20-2010, 09:37 PM | #16 |
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I guess I should thank you Mark. I went to snag a pic of one of my tires for a wear comparison and I found a bubble in my left front. I was supposed to go autoxing on saturday on these tires...that couldve ended very badly for me. So thanks!
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09-21-2010, 02:07 PM | #17 |
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Wear on the outside of your tire is from the amount of 'push' our cars have along with not have camber for track use.
The way to prevent this is to do some work on your suspension and run camber plates while on the track. Cars that understeer 'push' like ours tend to wear the tires like this. What suspension mods to you have? First get the car balanced to prevent rolling, then work on the understeer by adjusting spring rates to fit your needs and address camber along with stiffing up the rear. If you only work on the front, then when you put more aggressive tires you will find your rear with skip and be unstable due to the soft bushings and spring rates of the car.
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09-21-2010, 02:37 PM | #18 |
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I have no suspension mods. I run in D-Stock class for autocross so I can't really do much in terms of suspension mods.
All I can do for suspension mods is: Stiffer shocks (stock height, mounts, and springs,) Front sway bar, and still waiting on the local techs to determine legality on the alignment pin removal.
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09-22-2010, 09:12 AM | #19 | |
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To get more camber without camber plates you can always look into the front arm control kit from HPAutowerks, this can add about -0.75 of camber depending on your drop height etc. For track you ideally want -2 to -3 camber depending on the track you are on...here in Portland people usually run an aggressive camber of -3 due to the amount of turns etc. spring rates get a bit confusing because really you need to dyno your car and measure forces etc on the corners to decided what spring rates are ideal...generally speaking you would be safe with 400lbs front 700-800 rear. They do make spring conversion kits for coilovers (swift springs and KW). Rear subframe bushing are another great modification to keep the back end stable and more responsive since you will get more feedback replacing the soft bushing we already have. You can go to solid bushing or stiffing polyurethane bushings. After you have what you want and can do for running in D-stock, then next best thing to do (no matter how many mods you have on your suspension) is to get it corner balanced. This is something people tend to skip over, but is probably one of the MOST important things to do for our cars when running them at autoX or track. good luck!!
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09-22-2010, 10:01 AM | #20 | ||
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And as for the front sway bar size, seems the competitive cars in DS are running the biggest bars they can get: Quote:
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09-22-2010, 11:20 AM | #21 | |
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09-22-2010, 01:00 PM | #22 | |
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Yea I dug up all the posts I could from Erik/Beth, some good info there, even if it is from 2008! Interesting how they say you want to maximize grip in front while actually reducing grip in the rear. I can see how that could make sense though. Next event will be Star Specs with an alignment (pin removal) as one of my region techs stated the mod should be legal if the Strelnieks did it during nationals. I'm hoping the tires alone, and maybe the extra camber will be a noticeable difference over the runflats. Everyone whose spoken to me about it has said I'm in for a treat, so this should be fun. After that, I plan to try a front sway bar. Probably do the Hotchkis following the Strelnieks' recipe or maybe something not quite as stiff, but still stiffer than the M3 bar (is there a 30mm out there?) Next after that will be an exhaust just because I want one then maybe stiffer shocks. I actually don't see myself spending the money and going to STU as my times are already competitive against STU cars in my region. I'll have better PAX in DS.
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