Tyre wear

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  • #573
    Tony Wong
    Participant

    Hi,

    I’ve never really done a full season of autox, so I’m unsure of tyre wear… but I was just wondering if I was doing something wrong or if its just the way it is. I have an 2011 m3 convertible, and the tyres (and car) have 7700 miles and the fronts are falling apart! There are some chunks missing from the outside of the tyre, and in some spots I can see the canvas. All the damage is on the outside of the tyre, the rest of the tyre is fine. And only the fronts, the rears are fine. So…

    1) Is that just the way it is?
    2) Perhaps I should not throttle steer? I don’t do it often, but there have been a couple of times where I’ve found it useful.
    3) Perhaps I should back off if the tyres start making sounds? (Which implies no throttle steer?)
    4) Perhaps its damage from those heavy understeer when braking cases when you plough straight forward?
    5) I dont bother fiddling with tyre pressures because I just want to have fun and improve my times with better driving and not by improving the car. Should I perhaps adjust pressures to get better tyre wear?
    6) ???

    Thanks!

    #574
    Brad Vaughan
    Participant

    My gut feel is tyre pressure.. Sounds like you are running too low.. I know Tim Woo in the ISF was seriously chunking fronts on his..

    Couple of things..

    How far on the outside of the tyre is chunking ?
    Whats brand, model of tyre ?

    I am a big fan of “tuning the nut behind the wheel” before looking at the car, but the tyre pressure is pretty critical. I spent a whole year wondering why I was 1 second slower than cars of identical spec. I was over driving the car, trying to find that extra time. Hitting the right tyre pressure and getting the same rubber as the equivalent cars made a lot of difference. Still had to lift my driving game, but the car felt more drivable. Particularly less understeer which is the killer.

    I wouldn’t fuss too much with tyre pressure, but make sure you get a setting that maximizes the car and then you have a stable platform to hone your skills. Either use the chalk or talk to somebody with the equivalent car.

    Sounds like you are up for some new tyres, so get some feedback from this group on a good tyre. I run a RE11 on a e46 M3 with 19″ rims, but your is a little heavier and might have some other tyre options.

    B

    #576
    Charlie Davis
    Participant

    As a former BMW service advisor for several years and BMW parts guy for the last seven, I’ve noticed that BMWs on performance tires often only get 12-16000 miles without autocross wear.

    That said, BMWs are often camber challenged, and understeer at lower (autocross) speeds, which is hard on fronts. Higher pressures will help, and camber plates will also help. New autocrossers tend to charge the corners hard and exacerbate the understeer issue. The phrase goes something like “Slow in, fast out. Fast in, out backwards”. That would be the part where the fronts finally find grip and the back is hung out to dry.

    Tires with really small tread blocks tend to have more of a chunking problem. The individual blocks squirm around and tear themselves apart, especially on the outside edges of the fronts.

    I would look into tires with larger tread blocks (I really like the Dunlop Direzza Z1 Star Specs), some negative camber and higher pressures (possibly over 40 psi) for autocrossing. I would guess that your camber is around zero to 1 degree positive and your car may have toe in. Up to -2 degrees is fairly friendly on the street and just a little toe in (maybe 1/8″) Other E9X autocrossers can help you with more precise numbers.

    Then, take it a little easier going into the corners, try to get more of your turning done early (also known as late apexing) and accelerate out of the corner. If a street tire is squealing (high pitch), that’s okay, but as the pitch deepens into more of a squalling noise, the tire is being abused.

    Charlie Davis

    #577
    Jeff Roberts
    Keymaster

    We teach… slow in, fast out. fast in, spin out. 🙂

    Totally agree with both comments… you can’t ask your car to do two things at once, like turn and accelerate. You get on the gas as you unwind the wheel and straighten the car out. If the tires are shouting, open the wheel until they sing instead. Even an inch movement in the wheel can do wonders. A singing tire is a happy tire! Treat your tires like a Faberge’ Egg and they will reward you with grip and speed.

    Watch all of the videos in the 4/14 video thread, listen to throttle application and tire noises, and watch the hand work on those where you can see it. You won’t hear any screamingly upset tires by those folks, just happily singing tires. Autocross is not track… you can cheat at the track by exercising your right foot on the straights, but at autocross you cannot do that. You must keep the car dancing on the edge of grip and balanced at all times.

    Unfortunately, Star Specs are not available in 19″ sizes. Tim settled on the Bridgestone RE11 for the ISF for that reason. You will roast tires until you prefect your technique, so I suggest going less expensive while you’re working yourself thru that. Hankook Evo V12’s are inexpensive and decent enough.

    Mod the driver before the car. If someone is out there running faster than you in the same car, it has to be technique vs equipment. Get rides with those people and have them ride with you, observe, listen, learn.

    #578
    Mark Mervich
    Participant

    Charlie and Jeff mostly covered the issues. Lots of air stiffens the side walls as does a low profile tire and negative camber is good too. I usually needed to get a new set of tires for the Subie every year, but my idea of a full season of autox is probably 2x many drivers 🙂 Seat time, conversations/ rides with other drivers and coaches all help the nut behind the wheel.
    Mark

    #579
    Charlie Davis
    Participant

    [quote=”jeffroberts” post=244]We teach… slow in, fast out. fast in, spin out. 🙂

    Totally agree with both comments… you can’t ask your car to do two things at once, like turn and accelerate. You get on the gas as you unwind the wheel and straighten the car out. If the tires are shouting, open the wheel until they sing instead. Even an inch movement in the wheel can do wonders. A singing tire is a happy tire! Treat your tires like a Faberge’ Egg and they will reward you with grip and speed.

    Watch all of the videos in the 4/14 video thread, listen to throttle application and tire noises, and watch the hand work on those where you can see it. You won’t hear any screamingly upset tires by those folks, just happily singing tires. Autocross is not track… you can cheat at the track by exercising your right foot on the straights, but at autocross you cannot do that. You must keep the car dancing on the edge of grip and balanced at all times.

    Unfortunately, Star Specs are not available in 19″ sizes. Tim settled on the Bridgestone RE11 for the ISF for that reason. You will roast tires until you prefect your technique, so I suggest going less expensive while you’re working yourself thru that. Hankook Evo V12’s are inexpensive and decent enough.

    Mod the driver before the car. If someone is out there running faster than you in the same car, it has to be technique vs equipment. Get rides with those people and have them ride with you, observe, listen, learn.[/quote]

    I’d definitely go for the RE-11s. I’ve used them and find them to be very responsive and they communicate well to the driver. They also wear well.

    I agree that you don’t want to do too many mods to the car, but the biggest deficiency that stock BMWs have is designed in push, mostly due to conservative camber settings. Why learn to drive around a serious handling deficiency, then make the car handle better later? Help the car a little, then learn to drive a better handling car…

    #580
    an nguyen
    Participant

    yes; i’ll add that some street tires squeal while others howl at/near the limit of their grip, so the sound you want depends. A coach riding shotgun may be able to suggest how loud your tires should be for max grip.

    [quote=”CharlieDavis” post=243]That said, BMWs are often camber challenged, and understeer at lower (autocross) speeds, which is hard on fronts. Higher pressures will help, and camber plates will also help. New autocrossers tend to charge the corners hard and exacerbate the understeer issue. The phrase goes something like “Slow in, fast out. Fast in, out backwards”. That would be the part where the fronts finally find grip and the back is hung out to dry.

    Tires with really small tread blocks tend to have more of a chunking problem. The individual blocks squirm around and tear themselves apart, especially on the outside edges of the fronts.

    I would look into tires with larger tread blocks (I really like the Dunlop Direzza Z1 Star Specs), some negative camber and higher pressures (possibly over 40 psi) for autocrossing. I would guess that your camber is around zero to 1 degree positive and your car may have toe in. Up to -2 degrees is fairly friendly on the street and just a little toe in (maybe 1/8″) Other E9X autocrossers can help you with more precise numbers.

    Then, take it a little easier going into the corners, try to get more of your turning done early (also known as late apexing) and accelerate out of the corner. If a street tire is squealing (high pitch), that’s okay, but as the pitch deepens into more of a squalling noise, the tire is being abused.

    Charlie Davis[/quote]

    #581
    Michael Costa
    Participant

    For those of use running stock run-flats on E90’s, what tire would you recommend changing to? I am perfectly fine with going to non-run flats, but I have heard, apocryphally, that E90 suspensions are tuned for the stiffer run-flats. Is there someting intrinsic to the stock E90 wheels that will only accept run-flat tires?

    I have 17k miles on my tires, well above the wear bars, but the BMW service techs are starting to harangue me about wear on the outer edge of the tires, suspecting misaligned camber. I actually think it is wear from 5 auto crosses and a couple of track days.

    #602
    Aleksey Kadukin
    Participant

    [quote=”fenax” post=240]…I have an 2011 m3 convertible, and the tyres (and car) have 7700 miles and the fronts are falling apart!…[/quote]
    Please keep in mind that you are driving a heavy car (E93 convertible with a hard roof) with a stock suspension and front weight transfers during harsh breaking overloads stock tires easily. As result, tires are overheating and starting to lose traction. Stock camber plays significant role to the tire wearing out from outside; you cannot do much without camber plates there.

    For the beginning, I would recommend getting a simple air compressor and tire pressure gauge (with a quick air bleed valve preferably), put extra air to the tires (I would start with 40 psi) before the runs and monitor tire pressure after every run. Tire chalking would give you preliminary idea if the pressure is enough but I would not use it as final tool since combination of car weight and stock suspension would enforce front tire sidewall rollover eventually. Check the tire pressure after every run; you should try to keep the pressure on the same level. Otherwise your tires would overheat and start loosing traction. You would probably need to bleed air out of the tires after first few runs until pressure stabilizes (it depends from tire model and initial pressure in the tire).

    #603
    Michael Costa
    Participant

    Blech…scratch my previous comment about it being wear from AutoX/Tracking. I took a good look at my tires in the sunlight…it’s uneven wear all right. Probably from mis-alignment. Damn new San Francisco garage door is too narrow, and I have bumped the edge a few times. My front wheel is almost certainly out of alignment.

    #689
    Tony Wong
    Participant

    So 1000 miles later and now my rears have the same problem… I can see canvas on the outside of the tyre and bits missing 🙂

    I guess I’ll try pumping up the pressures just to see if that reduces wear…. Also I do do a lot of autocrosses…. once a week 😀

    #691
    Matthew Visser
    Participant

    [quote=”macmacaman” post=252]For those of use running stock run-flats on E90’s, what tire would you recommend changing to? I am perfectly fine with going to non-run flats, but I have heard, apocryphally, that E90 suspensions are tuned for the stiffer run-flats. Is there someting intrinsic to the stock E90 wheels that will only accept run-flat tires?

    I have 17k miles on my tires, well above the wear bars, but the BMW service techs are starting to harangue me about wear on the outer edge of the tires, suspecting misaligned camber. I actually think it is wear from 5 auto crosses and a couple of track days.[/quote]

    The newer BMW non-M suspensions are tuned for the stiffer sidewall run flat tires. They do that by softening up the bushings on the control arms (wishbones and tie rods). Soon after I bought the car I changed from the stock 135i control arms to the M control arms. The ride got noticeably harsher. Then when the RFT were toast, I went to regular tires. The ride returned back to before I swapped out the original control arms. The difference was that the stiffer control arm bushings provided a better feel and less slop in cornering. You would be surprised how soft the stock bushings are to make up for the RFT.

    You can use either RFT or regular tires. If you go with regular tires you should get a mobility kit like they have on the M cars (as they have regular tires and do not have a spare).

    #708
    Michael Costa
    Participant

    Thanks for the detailed replied. I have been ruminating on it for a week. I really like the stiff ride of the 335i, so I am a little wary about going to non-RFT’s now. I suppose I could swap out the control arms to make up for it, but that might bump me up a class in AutoX. I am not too sure what that would do to my extended warranty coverage either.

    There was a good article in one of BMW auto parts magazines in the past year that covered and entire 335i to M suspension swap. It’s supposed to be pretty easy to interchange those parts. Did you swap out only the control arms,or did you do the sway bars as well?

    [quote] The newer BMW non-M suspensions are tuned for the stiffer sidewall run flat tires. They do that by softening up the bushings on the control arms (wishbones and tie rods). Soon after I bought the car I changed from the stock 135i control arms to the M control arms. The ride got noticeably harsher. Then when the RFT were toast, I went to regular tires. The ride returned back to before I swapped out the original control arms. The difference was that the stiffer control arm bushings provided a better feel and less slop in cornering. You would be surprised how soft the stock bushings are to make up for the RFT.

    You can use either RFT or regular tires. If you go with regular tires you should get a mobility kit like they have on the M cars (as they have regular tires and do not have a spare).[/quote]

    #709
    Matthew Visser
    Participant

    The control arms (wishbones, tierods, etc) are pretty easy. There are two per corner. In addition you will need different clips to route the brake sensors and also a new rod for auto-leveling headlights. I am sure all of that is documented in the DIY articles online. You are correct that they would likely not be covered under your warranty even though they are BMW parts. But they are also parts that I have never heard of failing so it should not be a problem.

    I did the swaybars from a E92 M3. The front is easy to replace but not that much bigger than the stock 35/335 bar. The rear is a pain as you need to drop the subframe. About a 4 hour job start to finish for a qualified shop to do. Also, unless you have a LSD, I would not go with the larger 23mm M3 bar. It is too much bar for an open diff.

    Feel free to find me at the next autox and I can give full details.

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