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

[CatchM3IfYouCan181]

[u2b]<iframe width="560" height="315" src="http://www.youtube.com/embed/T_j8mtsglro" frameborder="0" allowfullscreen></iframe>[/u2b]

here's a video of my last event as AS. came in hot on the last turn towards the finish so i pushed hard. no camber whatsoever and running on 19x8.5 and 19x9.5 oem's on RE-11's and stock suspension.

i will be trying out 18x10's w/ direzzas & double adjustables tomorrow for the first time running in STU.

(lol about the music, autocross videos can be very boring if you don't autocross so i added some humor)

[lacartus]

Great thread, thanks or all the updates.
I managed to find an E90 6mt no sunroof and plan to run it at a few local auto crosses in 2013. I think I'll start with scca stock class for now.

The Nov'12 FastTrack notes the SEB recommendation to move rom AS to FS, but says "Unless noted otherwise the effective date for all rule, class, and listing change proposals herein is 1/1/2014". Does that mean the e90 m3 is in AS for 2013?

Rich or anyone who test fit: can you confirm that the A6 295/30/18 front and 315/30/18 rear fit on stock 18s?

Catchm3: if you don't mind, what size tires are you running, 275/35/18 f&r? Front camber?

Thx

[Be Stock]

Originally Posted by lacartus

Great thread, thanks or all the updates.
I managed to find an E90 6mt no sunroof and plan to run it at a few local auto crosses in 2013. I think I'll start with scca stock class for now.

The Nov'12 FastTrack notes the SEB recommendation to move rom AS to FS, but says "Unless noted otherwise the effective date for all rule, class, and listing change proposals herein is 1/1/2014". Does that mean the e90 m3 is in AS for 2013?

Rich or anyone who test fit: can you confirm that the A6 295/30/18 front and 315/30/18 rear fit on stock 18s?

Catchm3: if you don't mind, what size tires are you running, 275/35/18 f&r? Front camber?

Thx

From the October Fastrack, page 15 and page 18, the move should be effective 1/1/2013. It was in this issue that the move was recommended to the BOD.

[Richbot]

They should fit. Read my setup notes

[lacartus]

Thanks. Looks like I'll do FS with Hoosiers.

[Richbot]

Had a National Tour Road Tour event at the Gateway Motorsports Park here outside of STL this past weekend. I ended up quickest on index, and 6th quickest on raw time out of the 67 people who showed up. Light turnout due to weather and uniqueness of the format running an autocross on the road course.

Quickest Sunday run, and quickest run of the weekend. Left some time out there, overdrove a couple spots and looked/felt slower than my quickest Saturday run but dropped a little more than a tenth even with a missed shift on the back straight.

Quickest Saturday run, tidier than my Sunday run. Might still be upside down until the Youtube editor gets done with it:

[m3kerry]

Congrats rich. That is really big time to beat sam. Those guys win everytime out for the most part.

[CSBM5]

Nice driving Rich. Looks like a fun course. That last 180 leading into the long straight to the finish looked like a fun challenge. It sounded like the S65 was a bit off its powerband coming off the corner although I'm sure 1st gear would not have been worthwhile. Of course it sure didn't show in the results -- good job.

[Richbot]

I thought about going to 1st, it probably would have been helpful but I wasn't competing against anybody so I didn't risk the (very likely) fustercluck that would have ensued if I had tried it That's the slowest corner I've encountered at an autocross this season, I wouldn't be surprised if I was down below 25mph.

[CSBM5]

So is the E9x M3 in F-stock for 2013?

[m3kerry]

Yes, it is in f stock and will have a real chance to win.

[CSBM5]

Originally Posted by Richbot

A good no-sunroof car is going to be a tough get. I wish you luck. I can tell you I do not miss the tech package at all, but I would miss the heated seats, fold-down seats are a must for transporting tires, and I would miss the homelink/dimming mirrors from the premium package

Well Rich it took a LOT longer than I ever expected (1 year hunt, I'm one patient fool I guess), but I bought a 2011 E90 M3 with no sunroof and the options I want (tech, premium, heated seats, 6MT). I had to settle for Silverstone II much to my wife's dismay, but once I found this 16k miles car with CPO that literally looks brand new, I jumped on it. The original owner never drove it in bad weather apparently, and took simply unreal care of the car. When inspecting it, I had to keep telling myself it wasn't a new car as I'd forget at times.

I *love* the S65. Having now had my S62-powered M5 for starting its 10th year with me, it's a great contrast, but I seriously have such a better appreciation for the S65 now (and I've only owned it for 3 days). After having spent time (2 days) in an F10 and (3 days) in an F30, I decided that BMW has left me behind with those behemoths as I have zero desire to own either one of those hulking beasts. So thoughts of an F80 M3 are dead to me, and I've been a BMW fanatic since 1971. Really weird. I think they're going to get hung out to dry with these monster-sized cars at some point like Detroit in the mid-70s.

Anyway, back to autocross. My plans are mainly *fun* as opposed to serious national level competition (yet anyway). I'm just going to run it in my local club's street tire pax indexed group as we have a ton of folks coming to compete in that class. The car doesn't have EDC, and so far I've been impressed with the stock shocks -- not sure if I'll go the route you did with shocks at some point. I wonder how well it'd work though with simple Koni SAs...might find out.


I plan to keep the E39 M5 forever, and after the direction BMW is going and how enamored I am in the 3 days with the E90 M3, I'm thinking this car is going to be with me a long time (which is typical with me...we still have the Volvo 850R wagon we bought 17 years ago, lol).

Chuck

[CSBM5]

Rich,

The TRMotorsport wheels you're using I checked on at TireRack, and they show the 8.5 front but a 10 rear. So I looked at the E46 M3 fitment there, and that shows a 35mm 9.5" available. I assume you're using that rear wheel? Hence I can actually get these still from TR in 8.5/9.5 sizes. It looks like using a 15mm spacer will get the offsets just right (legal).

I was hoping to run the BFG Rival in 275/35 all around, but it won't be available until June. Yokohama doesn't make the AD08 in that size, so I've pondered running a staggered tire size. I was thinking 265/35 front and 295/30 rear, but that makes the fronts actually larger diameter than the rears (not sure what if any issues that might cause with ABS, etc, given the car is designed the other way around).

Anyway, that rear 9.5 they have listed under E46 M3 is the same wheel you're using?

[Richbot]

Chuck - Congrats! You and I feel the same. BMW peaked with the S62, S54, S85, and S65. Get off my lawn.

There are some cheaper options out there for the stock springs like the DA konis from TCKline, you don't have to go full retard like I did.

That's correct, I'm using their ET35 9.5" MT-1. For some reason they don't list it as an option anymore for the E9x, probably because it requires a spacer to fit properly and their 10" wheel doesn't. I'm using a 12.5mm spacer in the rear (for an effective 22.5mm offset, .5mm furhter out from stock) and a 15mm with the ET45 front (for an effective offset of 30mm, 1mm inset from stock) with their 8.5" and 9.5" MT1. I can't speak to the MT1-R but I really like the MT1, it's the best bang for the buck out there IMO.

The ABS doesn't care about the tires sizes much and seems to work really well no matter what weird combo I have on the car. DSC is a different story as it can get much more sensitive without the factory rolling diameter stagger, but there's a button next to the shifter that makes it irrelevant in about 1 second. For street tires you might look at the 265/35 and 285/35 Hankook RS3

[CSBM5]

Thanks for the input Rich on the wheels and tires. I forgot about the RS3 -- that sounds like a plan for the time being, so I'll check into those. I do have a set of A6s, 275/35, from the year before last that I could use in F-stock for the first few events and then switch to TIR class once the Rival is available. They've been stored well and have only seen about 10 runs on the M5. I'll have to think on that option too.

Anyway, this is going to be a fun season. I plan to take the car to the next CCA autocross at the Performance Center as I have a history there of three FTDs and one 2nd FTD with the M5, and I'm pretty sure I will be faster in the M3. I also hope to make it to an SCCA event at the Michelin Proving Ground in Laurens, SC this Spring too in addition to my local club events.

Regards,
Chuck

[CSBM5]

Rich,

How is your front bar working out? I tried to run some numbers on the stock versus various aftermarket options, but the stock bar is hollow, and without cutting one in half, I don't know the inside diameter. So I ran across a FAQ on Turner's web site on the H&R front bar where someone supposedly did the calculation for a 27mm solid H&R versus stock, and they claim that one is 1.425 times the stiffness of the stock one. I assume the moment arm is equivalent to the stock bar.

I'm looking at all of this since I ended up buying a Dinan 28mm solid front bar on sale for 40% off, and I'm wondering if this will prove to be too much front bar on street tires. Interestingly, Dinan adds this bar to their spring kit (i.e. moving from their stage 1 to stage 2) without changing the rear bar, so clearly a car with just their springs versus springs + front bar is going to be a good bit different, but they must feel it isn't too much bar. All that is an aside...

So if I assume Turner's H&R vs stock calcs are correct, then the Dinan 28mm bar (same moment arm as stock) should be: 1.4252 x (28^4 / 27^4) = 1.65. Hence it is 65% stiffer than the stock bar.

So far just driving it a bit since putting it on last night, it feels fantastic, and slaloms are going to be great I think. I do note the aggressive outside front loading on sharp turn-ins, so I'm wondering how much steady state understeer is increased. I have the pins out and struts all the way in for max negative camber already btw. I will find out this weekend in any event, but I was just curious what you think of front bar stiffness increases vs stock so far.

Since my last post, I've been talking with numerous different sources about street tires versus wheel widths (a couple of multi-time national trophy winners, and a couple of tire engineers), and the net is that it seems to be a consensus opinion that a street tire will not respond anything like a Hoosier A6 to "fat-tire-narrow-wheel-stuffing". Hence I'm going to stick with the overall recommendation to try to match wheel width to tread width, so I'm going to try the new BFG Rival in 245/40 and 275/35 sizes. I did get the TRMotorsport wheels from Tirerack (8.5/9.5). The 275 Rival isn't available until June, so for now I bought the wheels with 245s all around. I know it's going to be a pain to put down power and probably make the car tail happy, but it's only for a few events until June, and then I will have an extra set of 245s for the front.

I think ideally I would like to have had a 255/35 up front, but from tests various folks have done, even a small bit of oversizing street tires seems to be slower -- just the opposite of R-comps. Perhaps it is related to the very stiff sidewall construction of R-comps versus the street tire -- I would very much like to get a fuller understanding of the whole subject (and I'm working on that -- background is in mechanical engineering, have been studying tires for 6-7 years now, daughter is a tire engineer now too).

Regards,
Chuck

[Z K]

Originally Posted by Richbot

Quickest Sunday run, and quickest run of the weekend. Left some time out there, overdrove a couple spots and looked/felt slower than my quickest Saturday run but dropped a little more than a tenth even with a missed shift on the back straight.

Quickest Saturday run, tidier than my Sunday run. Might still be upside down until the Youtube editor gets done with it:

Geez, the courses are so much different than the local/regional SCCA courses run in San Francisco! Our lap times are generally close to 30-40 seconds and no way are they as wide and high speed as what's in your video. Also because of high turn outs (300 cars) we only get 3 runs per driver.

Here's a lap I ran last month:

[Richbot]

We have good courses here, we are blessed with a decent lot size though the surfaces are low grip

The RD sport bar is bigger than the dinan bar, no idea if it is stiffer, but the lever arm is also shorter. For street handling it 'd be perfect on the middle setting, for autocross it is just about perfect on the r-tires on the stiffest setting. If i was running street tires i might back it off but probably not

I hear you on the pinched street tires not working, but again most of the testing is done on cars that can utilize a wider rim and aren't limited by the Stock ruleset. I think the 275/295 rivals might be the hot ticket, that's what i would try first, but that's because conventional wisdom went the same way with r-compounds until people showed that heavy, fast cars like more tire almost to the point of absurdity, and the 275/295 would be much less pinched than the A6's I'm running. Maybe i will do a test with the rivals later this year and settle the question for myself anyway

Keep us posted on the rivals, I just got some PSS as street/rain tires for the stock wheels, really interested in how the rivals wear

[Modena NYC]

Rich, in the vids you posted above...do you have the m perf exhaust installed? sounds stock.

[Maypo]

Wow, ZK, that is a nasty little course. Which site is it?

[CSBM5]

Rich,

What do you think of the 2014 rules changing stock class to street class?

Sway bars on both ends allowed, camber plates allowed, 140+ (200+ for 2015) tires so R-comps are gone, etc... The Rivals are good to go as they are rated 200. Incredible tires btw, amazing. I love them. I can't wait to get them in the bigger sizes though.

I'd like to find a camber plate that *doesn't* raise the stack height. I think there might be one out there now, but I can't recall its manufacturer (I think they made it for the 1M and maybe the M3 too). I know the GC plates I have on my M5 do raise the height by about 1/4" even though GC claimed otherwise.

2014 is going to be an interesting year. I wonder if Hoosier is now going to get into the street tire business.

Oh, and remote reservoir shocks are outlawed in 2015.

[Richbot]

It's just a proposal.

I think we should change to street tires and see what happens rather than throwing the baby out with the bathwater.

Kindof the latest chapter in the book of futile attempts to make playing with cars cheaper