07-04-2019, 01:22 AM | #23 | |
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07-04-2019, 07:16 AM | #24 |
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Is the thinking here that the narrower the track, the higher the effective spring rate? Hence narrowing the rear track stiffens up the rear shifting resulting less understeer?
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2024 G20 M340i Melbourne Red/Cognac 2019 F87 M2 Competition 6MT, LBB, slicktop, exec pkg 2007 E91 328i Silver, slushbox, Eibach fr/E93 M3 rear sway bars, ARC-8 |
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07-05-2019, 12:41 AM | #25 | |
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If I go back to the stock 19" rear wheels (et40), instead of the Apex SM-10 with a et33, the rear track would be narrower. The other factor is a taller rear tire will increase forward rake of the car, which may to a degree also decrease understeer. |
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07-15-2019, 03:36 PM | #26 |
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I’ve started running lower pressures on my RE71s, and have had to resort to resetting the TPMS right before I start each run. A little annoying, but better than getting all the nannies turned back on in the midst of a run.
I have the H&R front bar, full stiff, and 275 square. Not really having issues with push. Maybe try slightly slower corner entry?
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07-15-2019, 09:32 PM | #27 |
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My best run from this Saturdays BMWCCA autox. Front Hotchkis bar full soft, zero front toe, 34 psi front/32 psi rear. I started the TPMS reset prior to each run. No issues with TPMS with this process. The car turned much better than with front sway on stiffer setting. Initial turn in is good, the mid turn understeer is still somewhat evident. Haven't got into the rear alignment yet, so perhaps something to be gained there. I believe I was just starting to hit the rev limit at about 64-65 mph. Maybe could have shifted to 3rd on the straight, but felt not much to gain. Next event may try higher rear tire pressures to get car to rotate more. Not usually my method of choice, but an option.
It was a very fun autox course, good competition, great people. |
07-16-2019, 02:11 AM | #28 | |
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What wheel size are you running in front? How low have you gone in front tire pressures? I've tried as low as 31 psi, probably not inclined to try lower since the 275 tires already look a bit squeezed on the wheels. My initial turn-in is pretty good, but I may be over driving the mid-corner. Maybe I can try to induce throttle oversteer, that could be fun. Next autox this coming weekend. Will try another combo of tire pressures. |
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07-16-2019, 12:01 PM | #29 | |
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I’ve tried everything from high-30s to low-30s over the last two seasons, and have settled in on 34 hot up front and 32-33 hot in the rear. No issues with shoulder wear in the front. My TPMS consistently registers ~2psi lower than my Longacre analog pressure gauge, so I’m right on the edge of where the TPMS will complain. I bought a second gauge to cross-check the Longacre against but haven’t done that yet. To be safe I just resigned myself to resetting the TPMS at the start of each run.
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07-16-2019, 02:53 PM | #30 |
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Thanks Chris! Although I like the look of the fuller wheelwell in the rear with the 33mm offset wheels, in retrospect I should have gone with the EC7 and 43mm offset. Narrower rear track for less understeer.
Will look into running the 285/35-19 on a stock rear wheel (et40mm) for the increase forward rake, and higher offset to get a bit more narrow track. Have you checked your alignment yet? I am guessing there may be some rear toe-in that I can decrease a bit too. I'm with you on the tire pressures. I've been fairly happy in that same range as you. |
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07-17-2019, 10:10 AM | #31 |
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Lol...I haven’t had it on a rack at all since delivery. One of these days I’m going to buy some toe plates and at least check that. I suppose I should probably get the alignment checked, but I hate paying what shops charge for it when there is so little that’s actually adjustable.
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07-17-2019, 10:50 AM | #32 | |
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I have a set of toe plates, and set the front toe to zero, but need to see where the rear toe is currently. Keeping notes of any changes, so can set back to original if needed. On my fronts, it was just a 1/4 turn of each side on the tie rods (marked), easy to reverse. I've read the rear camber is adjustable, but haven't looked back there yet, no clue what the setup is like there. Reviewing my video, and some comments for others, I have to accept that much of my car's turning issues is driver induced. Gotta work on my breaking points, turn-in locations, application of throttle. My timing is stiff quite off with this new car. So often I just enjoy the acceleration of the M2, then carry that wonderful speed too far into the corner, my bad. Will work on my driver skills! Hey CLH, do you autox up at Packwood? or Bremerton? Been a few years since I have visited up there. Beautiful area. Lots of good experiences at Bremerton starting in early 2000's. |
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07-18-2019, 12:42 PM | #33 |
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Yep, Bremerton and Packwood are the two primary venues for the clubs up here. I've been attending events there since moving out here in 2005. I make pretty much all of the BSCC (Bremerton Sports Car Club) events at BMP, and a good percentage of the SCCA events there as it's about 20min from my house. I haven't made a Packwood event in a few years...it's a bit of a haul to get there, and early in the season you sometimes have to deal with longer routes due to lingering snow.
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09-26-2019, 01:27 AM | #34 | ||
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I'm trying to go on Saturday and participate in my first event with the car.
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10-17-2019, 04:14 PM | #35 |
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For anyone interested, I'm selling two (2) Apex EC7 18x9 ET31 wheels in race silver which I bought in July, and mounted one set of BStones to for Nat's before trading my car. They are listed for $450 shipped OBO with TPMS sensors but without tires. Let me know if anyone has some interest.
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10-29-2019, 05:51 PM | #36 |
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I'm curious about the guys with the front sway bars....how effectively are you trail braking into the corner? I just got a 2017 M2 myself after spending a year in a C5 Z06 Corvette in AS, and an ND miata in CS before that...I know the ND was an absolute MONSTER with push in corner if I didnt trail brake when I put the front sway bar on...so now I'm curious on how it effects the M2. I've only had one event and took 10th in pax at STC in Pittsburgh with some Goodyear Super Car 3 tires, so I know its REALLY capable out of the box, but a stiffer sway bar would help with better transitional response, but would hate to lose the turning ability for it =/
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10-30-2019, 01:38 AM | #37 |
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I would say my initial turn in is pretty good with slight trail braking. Running the Hotchkiss front bar at full soft, the transition response is nicer than stock, tempted to go one hole stiffer but I'm still not fully content with the mid turn understeer. I just feel the car should be capable of more speed in mid turn, maybe I'm asking too much.
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10-30-2019, 07:10 AM | #38 |
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Ah ok. Sounds like the softest setting might work on on the Hotchkis (what I'm planning on getting). Unfortunately, I got the car at the end of the season, so all I can do is read everyone else's reviews and theorize lol
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11-04-2019, 12:39 PM | #39 |
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End of the season for me. Been fun with my '18 M2 LCI. Learn much about the car is available setup options.
In summary, for my B-Street class, I found I prefer the 19x10 oem rear wheel, with a 285/35-19 RE71 tire (40et offset). This is 0.5" taller in diameter than a stock tire, for slightly higher 2nd gear speed. The fronts I like the Apex SM10 wheel (30et offset) in 18x9, with a 275/35-18 RE71. This front setup cleared the fenders and strut body fine, but next year I would try to run a 8mm spacer for a wider front track. I have Apex extended studs. Ran my Hotchkiss front bar full soft, can't see running it much stiffer as I fought understeer and mid-turn push most of the year. I will admit the car turned quite well when the RE71 front tires had good tread, but with such limited camber, the outer tire edges wore quickly, and by 50-60 runs the car turned noticeably worse. Rotating the front tires side to side did not improve the situation. Seems in B-Street, the rear tires will last an entire season easily, probably need at least 2 pairs of front tires. On our last event of the season, my son and I ran the M2 in an SCCA STU class. Same rear whee/tire setup, but I installed GC front camber plates, home aligned approx. 3.5 deg camber, zero toe, had Apex SM10 18x10 wheels (et33 offset) with 275/35-18 RE71 in front, needing a 8mm spacer to clear the front strut body. The M2 is not currently officially listed in STU, but we entered under the NOC classing, at least for local event no issue. Anyway, the combo of wider front wheel, front camber, really transformed the car. Against some admittedly very excellent national caliber competition in well developed cars, our M2 was within 0.5 secs off top STU time (on a 71 sec course). I don't believe the M2 will ever be classed into STU by SCCA. It was great fun driving the car, and experiencing exceptional turning ability. The car's weakness was the rear end was too loose. With this setup, I would try more camber in rear. Unfortunately, to enjoy the M2 with front camber plates, there is really no good class for the car in SCCA. Locally, my STU (light) car would be fun, but I probably would not run for points, but in BMW club events the car would be comfortably in AAA autocross classing. Looking forward to next year! |
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11-06-2019, 01:16 PM | #40 | |
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I have a letter into the SEB from earlier in the year about a STSS class for AS/BS/SS cars, so maybe theyll end up doing something like that and stuff the M2 in there. Something to think about, a buddy of mine did the math and found that on a much smaller tire, the torque actually put to the ground ends up being similar to that of the M2C because its limited to the bigger rear. So unless you're banging off the limiter for really long periods of time, and arent comfortable with the heel toe downshift...its probably not worth it to run the bigger tire in the back. Also did you change out the front steering knuckles for more camber? That might help with your push if you havent yet. I'm also going to be playing with spacers on the front to see if I can get a wider tire up front. I know 285's have been done, but I'm not sure how much clearance that leaves up front.
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11-07-2019, 12:08 PM | #41 |
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I do believe the car turned slightly better with the 275/35-18 tires in rear, on 18x10 wheels. Overall diameter bit lower than stock, but noticed the grip on power was somewhat limited (this on a B-Street setup). The 285mm rear tire on 19" wheels certainly put the power down well, and I don't feel the power delivery is hurt due to the slightly taller tire, but we have some fairly open courses here. Small tighter courses, yeah, I would throw on the 275mm tires all around. Having spare wheels and tires I can swap depending on event or course, so that's nice. Yes, did the knuckles, and it was noticeable, until the front tire edges got worn down some, then it was awful again. I ran fairly full tread front tires at the last event, big course, grippy concrete. Even with lots of front camber, and 275mm tires on a 18x10 rim, I was surprised how significant the wear pattern was on the tread face, and that was with probably 3.5 deg neg camber. These cars really eat front tires up fast on camber.
It will be hard to put wider than 275 tires in front, at least on 18x9 wheels. Again, the attraction to a Street Touring type class allowing a wider wheel! I might even look at a 265mm front tire on 18x9 wheel for next year, just so the tire is less pinched. Not sure if sidewall rollover will be much better with a 265 vs. the 275 though. Still, I gotta admit the car is super fun to drive with front camber, wider front wheels/tires. The smile on my face lasted for days. As for power, the car is adequate, but in Street Touring I think you can do a piggyback like the Dinantronics Sport Tuner, for $250, get a very noticeable bump in power and torque in the mid range/lower end. |
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11-11-2019, 01:43 PM | #42 |
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I'm not partciularly worried about the pinch....just if it fits under the car. I had 295's pinched on a 9.5" wide wheel on my previous vehicle and it actually handled very well, but another half inch may be the straw that broke the camels back. Only one way to find out!
Yeah....these strut cars REALLY like camber. Some of my co-workers run a BMW very successfully in champ car and they have an incredible amount of camber to get even tire wear. Unfortunately, the nature of the game for us is just going to mean premature tire death. I'll likely be testing whatever the absolute largest tire I can stuff under the car, as well as 265's and seeing which ends up being faster....and hoping the SCCA gods answer my praryer and give us an ST* class to play in
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11-11-2019, 03:33 PM | #43 |
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Hey everyone, I'm checking in as a new BMW M2 owner who's looking to play in BS for AutoX next season (competed for years in an STX BRZ). I appreciate all the information in this thread so far and am now considering my tire choices...
I'm leaning toward conservative tire sizes for now so one thought I had was running a 275/40/18 Yokohama A052 in the rear with a 255/40/18 RE-71 in the front. I figured this might be a good combo given the two tires' strengths: The A052s are good at putting power down and the RE-71s provide great steering response and feel. The other good thing about RE-71s is that they can be flipped, so hopefully that would help get some extra life given our camber challenged front end. I'm also new to higher power RWD cars, so I thought this might provide a more planted rear-end while I get used to things. My only fear is that I might get more understeer than I'd like, but maybe I can manage that with toe settings. Thoughts? Devin, once I get things figured out, I'll be shooting you an email for an order... |
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11-12-2019, 03:45 PM | #44 | |
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For these cars, the RE71r's might be the best option because I dont think the yokohamas have as much of an advantage over the stones with the lack of camber the M2 can get,and the way we're likely to beat up on the fronts, the yoko's are probably going to be a much more expensive way to go.... With that being said, one of my good friends won FS at Nats on 265 squared Yokos on an E92 M3 that gets less camber than our cars...so YMMV
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