Autocross nerd thread: The Ultimate E9X A-Stock SCCA Autocross Build?

[kingkong954]

Great thread! M3 Newbie here... been autocrossing for 4-5 years. Mostly in a 95 Miata that I sold a couple years ago. Just now getting back into it with my 13 ZCP 6MT, and wow was I surprised to see this thing in F-Stock. Very very competitive.

One question for the group: tips on launching? I am having a hell of a time adjusting to this beast compared to the Miata!

[CSBM5]

Originally Posted by kingkong954

One question for the group: tips on launching? I am having a hell of a time adjusting to this beast compared to the Miata!

Other than the basics, one key with higher power cars is to get that initial weight transfer to the rear mastered before going for the full launch. I'm talking about a few tenths of a second in time here, but if you want the maximum grip from the rear tires, it's critical (just like any typical dragstrip launch).

I wrote up a post on this many years ago in relation to my M5 over on the M5board which is applicable to the M3...just different starting revs, amount of throttle, etc, since the M3's torque curve is dramatically different than the E39 M5.

Regards,
Chuck

[Richbot]

I use about 3000 revs and slip the clutch before going to wot. On the Hoosiers it will hook great after a little wheelspin unless the conditions suck

[kingkong954]

Originally Posted by CSBM5

Other than the basics, one key with higher power cars is to get that initial weight transfer to the rear mastered before going for the full launch. I'm talking about a few tenths of a second in time here, but if you want the maximum grip from the rear tires, it's critical (just like any typical dragstrip launch).

I wrote up a post on this many years ago in relation to my M5 over on the M5board which is applicable to the M3...just different starting revs, amount of throttle, etc, since the M3's torque curve is dramatically different than the E39 M5.

Regards,
Chuck

Nice video in there. Will take it to heart; thanks!

[Golddots]

Hi all!
I have a heavy loaded e90 m3 that I want to use for " F street". I ran last year a few events bone stock on Michelin super sports OEM size on 220's.
How much time am I losing on these vs rivals or zii?
Is the ad08r in OEM size a viable option to compete?
I don't know what else would fit on 19's.
I'm considering buying some 17" or 18" apex wheels specifically to play but I'm overwhelmed between offsets , what size wheel tire fits, brands, etc.
I would prefer to daily drive on a 19" tire that can play but I don't know if any zii sizes will fit or the ad08r will be competitive enough.
How much camber will I gain if I remove the set screw on my shock mounts?
If money is no object what size wheel, tire, and tire model would actually be competitive and be drive able?
Is it really necessary to maintain some kind of stagger on tire diameter to keep the abs system from going crazy?
Sorry if I have too many questions. But I haven't seen a specific " e9x m3 scca F street " thread anywhere except this one.

[Richbot]

Probably half a second vs the best uhp street tires.

Pulling pins is worth about half a degree of camber.

Sounds like your car is not a zcp so money no object, get a zcp or convert it if your car is a 2011, and downsize to 18", then run the zII rival or hankook RS3v2 which is available soon. Finding an 18x9 in the right offset is tough so you probably need a spacer. Lots of good 18x10et25 options out there for the rears. Barring getting a ZCP, best bet is probably what I did, MT1 with spacers. Light and good fitment with reasonable spacers, no need to blow thousands on custom wheels. I personally, having seen some data and finally driven them, would look elsewhere than the Rival. Good tire but a couple ticks off the best. 265/285 RS3 would be my choice for FSTreet, or the 255/275 ZII. Thatt's my personal preference though.

The 17" apex wheels that clear the m3 brakes are not legal in FStrreet. Wrong width, unless you can make one of the e46 fitments work over the brakes but I don't believe so. Width has to be an 8.5/9.5 if not zcp or 9/10 if zcp

If you must stay wwith 19's, the yoko is probably close but not quite as good as the others and unfortunately it is the only good option for a front tire amongst the contenders, most only have a 275/35 and 245/40 which is too tall for the front. I hear the rival may be getting some 19" options soon but I don't think they are ideal for the M3. 26" tall is really the upper limit for front tire diameter unless you want to buy lots of fender liners

Abs and dsc dont seem to care much about stagger. It's more because the best setup for the car calls for more rear tire since the front wheels are narrower. Better to add rear grip and balance any understeer that may introduce with the tuning options you have than intentionally run less tire. Need a good amount of tire to put down this car's power on street tires in 2nd gear in a corner

[CSBM5]

Rich are you thinking of Rivals on concrete ala Nationals? I'm finding that they work very well on the courses I've been on (all asphalt, some with rough aggregate) so far, but I've not had them on concrete. I'm such a fanatic about tires, that I'm almost tempted to buy another set of wheels to test with ZIIs. One thing were the Rival excels is tread life -- witness the recent experience of jcp907 where he is getting many multiples of run life on the edge wear using Rivals versus RS3s...see his thread on sccaforums.com.

[Richbot]

Yeah for asphalt they are definitely fine and plenty fast i just didn't like the feel

But then i almost won index taking only three runs on a 6 run day in a car i had never driven before so maybe a little weird feel is worth it lol. Just saw your pocs of the 275's and now I'm back to wanting to try the 275/295 setup again

[CSBM5]

Originally Posted by Richbot

Yeah for asphalt they are definitely fine and plenty fast i just didn't like the feel

But then i almost won index taking only three runs on a 6 run day in a car i had never driven before so maybe a little weird feel is worth it lol. Just saw your pocs of the 275's and now I'm back to wanting to try the 275/295 setup again

FWIW, my Rivals picked up a good bit of OPR off the Performance Center track. They looked almost like A6s after a run, well not quite that bad, but still they were sticky enough to acquire that crap on them (front tires, I suppose the rears were getting plenty cleaned on every corner exit). Then again, the PC guys were giving fun rides in M6 GCs and doing nice smoky drifts off the turns, so there was plenty of fresh rubber for the taking I guess.

If I put 295 Rivals on the rear, I'd probably like to take some front bar stiffness out (which I can't do with this old-style Dinan non-adjustable bar).

[Golddots]

Thank you richbot.
I'm fickle on 18" wheels now.
I might just mount some summer tires on my 19s.
If I wanted to run the yoko ad08r just for 2014 would the 265/35-19 or 275/30-19 work on 220m all around without spacers?

[CSBM5]

The 265/35-19 up front will probably cause issues as the diameter is large enough to potentially rub the fender liner when turned (side of tread face contract with liner). 275/30-19 square should work fine I would think.

[Richbot]

the 19's don't let you get away with as much pinch thanks to the shorter sidewall. I would go 265/30 in front and 265 or 275/35 in rear or even the 295/30 rear. Lots of people run the 275/30 295/30 combo on the zcp wheels though the yokohama is pretty wide and square so probably doesn't like being stuffed as much as some of the others and you ar giving up half an inch eith your 220's. Either way its not like you can rotate since the wheels are different widths


If you need a warm blanket on whether it will rub or not get stock sizes, probably not giving up much performance, but a little rub here and there never hurt anyone

[Golddots]

I'm more concerned with removing some stagger. I drove a DSP e30 and a c5 z06 on ra1s before my m3. I really would like to help turn in.
Looking at the tire rack site it looks like the 265/30-19 and 275/30-19 would work.
Anything better than PSS would make me happy.
Since these are supposedly good at dealing with heat would a water sprayer be necessary? No codriver and I'm in the DC area.
Thanks again guys.

[Richbot]

stagger doesn't have much to do with turnin it's dictated by front roll stiffness and alignment more than any difference in front and rear grip

If you want better turnin a big front bar is the droid you are looking for. Will also help with the rear grip if you stay with the narrower rears. Hell at the prices they want for the yoks you would barely notice the money you spend on the bar, lol

I have found that most times I thought I had an understeering car on corner entry I was actually overdriving this car. The fast steering rack and open diff on Decel make it easy to charge a corner too hard, it feels great until it's too late and you have nothing but power oversteer left to work with. Now corner exit if it won't pivot or if the car is refusing to rotate on throttle yeah you might have a problem. I have not found many situations where less rear grip would have been useful in this car, because in my opinion anyway it is faster driven on the outside rear tire rather than grinding it out on the fronts. The reason for that is like most stock class cars you are on the bump stops in front when loaded up and using all of the front grip, and you have no more suspension left to deal with surface changes. It's a fine distinction maybe but that's why I recommend what i recommend

[CSBM5]

FWIW, on my street setup (OEM 220 19"), I'm running PSS in 255/35 and 275/35 sizes and am very happy with that setup. No rub, no issues.

[Richbot]

Yeah that's my winter setup with DWS's definitely an easy button

[Richbot]

If anybody wants a set of stock/street legal lightweight wheels for non-ZCP cars on the cheap, I'm selling my set of MT1's for $700 plus shipping, pictures are earlier in the thread

[z3papa]

Bringing this back a little from the dead, I just bought an 11 ZCP pack and will be jumping into the FStreet fray for 2015. First time in a while back in a stockish car but I'm pretty excited about the change. Have been running STR for several years and wanted a change of direction. I would appreciate any thoughts folks have on the 2015 tire to get. I've read about the camber limitations and guess a stiffer sidewall Dunlop may be a better choice than the easy button RS-3 v. 2. I need to pickup a pair of 18x10 ARC-8's for my competition set of wheels/tires.

Ignore the signature -- those are the parts on my soon to be placed for sale in the spring, Z3 3.0.

[Richbot]

There's an F-stock thread now if you want to start posting in that one.

You already have a set of 18x9's? Apex now sells a nice set of HRE knock-offs that come in the right offsets both front and rear.

IMO, the car wants more camber in the front, but it's not terrible. You'll get close to 1.5 degrees and I actually rolled over the rear shoulders more than the front last time I autocrossed the car with 1.5 front/1.8 rear

If you don't care about contingency or rotating the tires, ZII in 275/35 front, RS3 in 285/35 rear would be a good idea Or RS3 in 275/35-19 rear (also available with the Dunlop). But really the RS3V2 is probably the tire. Maybe just do the 265 in front instead of the 275 if you're worried about pinching it, but I don't think the 275 looks all that pinched on a 9" wheel.

But if I were you I'd wait and see if BFG is going to update the Rival. I hear things.

Also, get a front bar.

[z3papa]

I do have 8.5", 9" and other wheel sizes of ARC-8 and would have them milled as needed to meet requirement. I'll check out the Fstock thread and definitely consider your suggestions. We met at the two St. Louis events I ran. Camber will always be an issue. BFG was doing testing as we left from Nat's.

[z3papa]

Originally Posted by Richbot

There's an F-stock thread now if you want to start posting in that one.

You already have a set of 18x9's? Apex now sells a nice set of HRE knock-offs that come in the right offsets both front and rear.

IMO, the car wants more camber in the front, but it's not terrible. You'll get close to 1.5 degrees and I actually rolled over the rear shoulders more than the front last time I autocrossed the car with 1.5 front/1.8 rear

If you don't care about contingency or rotating the tires, ZII in 275/35 front, RS3 in 285/35 rear would be a good idea Or RS3 in 275/35-19 rear (also available with the Dunlop). But really the RS3V2 is probably the tire. Maybe just do the 265 in front instead of the 275 if you're worried about pinching it, but I don't think the 275 looks all that pinched on a 9" wheel.

But if I were you I'd wait and see if BFG is going to update the Rival. I hear things.

Also, get a front bar.

Anyone think a Dunlop Star Spec Z2 285/30-18 would fit up front. Yes I know it will be pinched a little but realistically I'd probably go square with this set using ARC-8 18x9 and 18x10. I like the fact it's a fairly short tire at 24.8" and would take the abuse the front will dish out.

[Richbot]

Yes it will fit.