E92 M3 ZCP in SCCA Solo F Street

[mills84]

Originally Posted by Rexpelagi

NOC = "Not Otherwise Classed"

Translation: "All E9x's go to STU unless they are classed in another ST class, including the M3"

For example, the E92 328i is already in STX, so that is "otherwise classed" and wouldn't fall into STU.

The competitive STU RWD cars can fit 18x11's and 285's within the stock fenders, and should weigh 30xx-31xx lbs (ie, Corvette and 350Z). Obviously the Corvette makes power too. The E9x M3 would be fine for locals and if you just wanted to have fun, but I don't see it as a national threat.

Thanks. That's exactly what I was looking for!

[Richbot]

Originally Posted by Rexpelagi

The competitive STU RWD cars can fit 18x11's and 285's within the stock fenders, and should weigh 30xx-31xx lbs (ie, Corvette and 350Z). Obviously the Corvette makes power too. The E9x M3 would be fine for locals and if you just wanted to have fun, but I don't see it as a national threat.

By my count, an nutty-cocoapuffs STU M3 could get to around 3300 maybe 3250 in STU on light fuel (battery + seats + midpipe is an easy 100+lb drop from Street, and we have a few Street E92's that have weighed in around 3450 on low fuel) make around 380whp, you can fit 18x10.5's in front with 285's, and there's room for 11's in the rear. I don't think the weight is the killer, I think it's just too tall compared to the vette and Z car IMO. CG matters, a lot, in autocross, and the only reason the boost buggies have a shot against the sports cars is torque and traction (and it's a point of debate whether they have a chance unless it rains), but the M3 has none of those advantages and all of the same disadvantages of the sports cars AND the boost buggies, except it can run more tire than the AWD cars. So yeah, DOA for nationals IMO, but would be a riot to drive

[thasuperdude]

Ok. I've revisited as much info as I could. I still have some questions
I'm trying to decide/justify going with an 18" wheel/tire set-up over the 19" OEMs I have on the car. Is there a big performance improvement going down to an 18" wheel over the 19s? I know the gearing is a little smaller, but I can only run a 8.5/9.5 wide wheel not being a ZPC car. Has anyone experimented with this? Is the advantage totally worth cost of a second set of wheels?

My wife and her friend entered FS in our SouthEast Divisionals and are in love with the car. They "have" to finish the other 2 events to trophy, so they totally sandbagged me on "borrowing" the car for an event. It was only a matter of time. So, the car needs tires, the DWs are fine, but they're not the ZII's we're use to running in STX. And as time passes, I'll be running the car more as well. Might loss my E30/36 SM ride sooner then I'd like. For me, Nationals is a fun time to smoke everyone a pig and play 4-Square at the ATL tent. All while there's the world's largest motorsport's competition going on around me.

[CSBM5]

Overall gearing is the same with the factory 18 or 19 setups since they kept the tire diameters the same. However, those of us running square setups usually have smaller than stock diameter tires on the rear (one good reason is that you can't fit the rear diameter up front without rubbing the fender liner due to the diameter being too large). I would like to try 295/35-18s on the rear at some point however, so those would be closer to the stock (265/40) diameter out back fwiw.

The problem trying to stay with 19s is availability of the tires you want in the sizes you need...there essentially is no availability.

[Richbot]

If it were me, I'd have a hard look at running the 18x8.5 with the 275 RE-71R on the front and the 19x9.5 and the 275/35-19 rear. It's becoming clearer from data that the RE71R is one of the tires to have, if not THE tire. This would hurt gearing slightly but give you very, very good rear grip especially on accel, which is a place this car can use an advantage since the 5.0's pull harder in 2nd gear at 35mph, but have to manage the limits of traction if the wheel is turned.

275/35-19 fits easily on the rear of these cars, btw, and that size is available (with a good 18" front) in ZII*, RE71R, and Hankook IIRC. The 275/35-19 is currently the biggest size available in what might end up being the best tire available, finding a way to get the best tire on the car in the biggest size is pretty important. This is also the size the Mustangs run (either on a 9 or 9.5" wheel), for parity purposes it's a good idea not to leave that on the table. Same deal on the Camaro 1LE, one of the guys running that car recently tested the 275/35-19 RE71R and went much faster than wider Hankooks.

[z3papa]

The gearing is much more aggressive with a 275/35-18 over the 19"s as the diameter is 1" smaller and you don't need the added top end in 2nd.

[lacartus]

I've run the RE71 at two events, -1.5 front camber
265/8.5-18 33psi and
275/9.5-18 31psi

I think the 275 would work on the front of my car given that the 265 is wearing evenly (no Hoosier shoulder yet). Some pictures of the tires under load on the course here, sorry, no closeups of the tread. (Blue FS #11)

[Melchior]

Originally Posted by Richbot

By my count, an nutty-cocoapuffs STU M3 could get to around 3300 maybe 3250 in STU on light fuel (battery + seats + midpipe is an easy 100+lb drop from Street, and we have a few Street E92's that have weighed in around 3450 on low fuel) make around 380whp, you can fit 18x10.5's in front with 285's, and there's room for 11's in the rear. I don't think the weight is the killer, I think it's just too tall compared to the vette and Z car IMO. CG matters, a lot, in autocross, and the only reason the boost buggies have a shot against the sports cars is torque and traction (and it's a point of debate whether they have a chance unless it rains), but the M3 has none of those advantages and all of the same disadvantages of the sports cars AND the boost buggies, except it can run more tire than the AWD cars. So yeah, DOA for nationals IMO, but would be a riot to drive

My numbers show closer to 3200 lbs for a base manual. I weighted my 2011 E92 DCT w/ carbon roof which is heavily optioned. I had KW Clubsports, Eibach swaybar, Challenge sport Xpipe (HFC + Resonators), AA pulley, and 1/2 tank of gas when I weighed it, everything else stock.

3508 lbs
- 37 lbs for my titanium no-name exhaust (not much else to gain)
- 24 lbs 4 gal less gas (I've run on empty at autocross/ track w/o starving)
- 8 lbs for no washer fluid
- 53 lbs for lightweight battery (assumes 7 lb Deka)
- 74 lbs for lightweight seats to 25 lbs min
- 16 lbs wheels relative to ZCP (weighed on) for ARC8 18x10.5
+ 4 lbs for tires relative to ZCP (weighed on) for 285 Dunlops
- 37 lbs Essex Ft/RR BBK (claimed; my StopTech ST-40 Ft was -16 lbs)
- 44 lbs Manual Transmission
- 10 lbs for no options (?)
- 5 lbs removing spring helps ft/rr and shorter springs
- 5 lbs floor mats
= 3199 lbs


I don't think a 275 or 285 is gaining much on a 11" wide wheel. My 18x10.5 w/ 285s Dunlop ZII* are already slightly stretched. The thrust curves for a FBO car actually exceed what I expect a FBO corvette to pull in 1st and 2nd gear, so it does have some advantage. The E92 will also be almost 2" narrow than a C5 (71.7" vs 73.6").

You're right, the high CG will hurt, and combined with strut front suspension it will be challenging. I think locally it could be a threat, and Nationally could be a trophy car.

[z3papa]

I'm not even going to start considering this debate after having just come down from a STR build as I don't have $15k begging me to blow on such a car. I will say you can lose more weight with aluminum body struts/shocks over the KW Clubsports.

[Richbot]

The stock (cast and machined aluminum) struts are the lightest struts available for this car. Everything else is heavier. You could probably lose some weight converting to coilover with the stock struts, but yeah. Not a place where you're losing much weight.

[Richbot]

http://www.m3post.com/forums/showthread.php?t=1120853

For anyone wondering about 285/35-18's on the front of these cars, there's an answer for ya

Cliff's notes: 285/30-18 is a piece of cake, the 35-series tire will rub a bit

[z3papa]

As for the fronts, I'm a believer but I've had no rubbing with 285/35-18's in rear with ET25.

[Richbot]

Yep tons of room in the rear, besides the stock sizes I've had 275/40's, 295/35's, and 315/30's on back of this car and never a hint of rub.

[chono]

Congrats to John L. - picked up the FS win by 0.45 at the Bowling Green match tour in his E92 M3.

I'd post a link to sololive - but it is solodead right now.


-'chono'

[z3papa]

Congrats John for the result in Bowling Green. Resources dried up and I was not able to get down to Blytheville to do likewise which would have made FS into a stand alone class.

[Richbot]

Originally Posted by chono

Congrats to John L. - picked up the FS win by 0.45 at the Bowling Green match tour in his E92 M3.

I'd post a link to sololive - but it is solodead right now.


-'chono'

Yeah but winning a match tour just means he's good at math.

Though beating Jadrice at math is no mean feat

[Rexpelagi]

Originally Posted by Richbot

Yeah but winning a match tour just means he's good at math.

Though beating Jadrice at math is no mean feat

Heads-up racing - Jadrice has a 2015 GT now. No math needed!

His plan is to go to ESP with the 2015, but he may stay in FS for awhile.

I was able to put some good runs in the morning on Saturday which ultimately got me the win. In the afternoon he was faster by 0.15s, but the new format is day 1 morning best plus day 1 afternoon best, so I ended with a slight advantage overall. Day 2 sets the qualifying order for the shootout now, and has nothing to do with day 1 times. Effectively it is 2 separate events.

Here's my fastest run from the weekend (Sunday the same course was faster by about 0.7s for whatever reason - this run is 0.13s slower than Jadrice's fastest run - also on Sunday). There was definitely room for improvement - there were a lot of places to set yourself up for failure on the course and it was hard to get every one right.

This is the first time I've seen the 2015's run and I was very impressed with their pace. Jadrice is running a very minimal setup right now (camber and tires basically) and the car was flying (although no doubt much of that is him ). Still, I didn't expect the 2015 to be *that* fast basically out of the box. David was also laying down some very fast times in his 2015.

There is some work to do. I had to run a different setup than Sean and I ran in San Diego to get the car working at NCM, but the lot surface is very smooth and atypical. Also, I tried the 265/275 stagger and I don't think it is working as well. My second set will be 275 square, matching Sean's. I also think I will re-examine exhaust options. I had a set of deletes made up but they are too loud for me to drive to events with, and the factory muffler system is way too painful to install on-site. Currently the only thing not stock on my car is the Dinan front bar (along with the wheels and tires).

Still, overall I'm very happy - amazing competition and a great result for the first event in the car.

[CSBM5]

Congrats John! Right at the end it looks like you pulled up to Dick's 2015 (local club friend) perhaps.

So you were running the RE-71R in 265/35-18 and 275/35-18? Interesting to hear comments on stagger as I'm reluctant to try 275/295 just for that reason.

Is your Dinan front bar their new design that is tubular and adjustable? (just curious as I'm using the older, solid non-adjustable one). If so, do you have any thoughts on the range of adjustment vs desired setup?

Regards,
Chuck

[Rexpelagi]

Originally Posted by CSBM5

Congrats John! Right at the end it looks like you pulled up to Dick's 2015 (local club friend) perhaps.

So you were running the RE-71R in 265/35-18 and 275/35-18? Interesting to hear comments on stagger as I'm reluctant to try 275/295 just for that reason.

Is your Dinan front bar their new design that is tubular and adjustable? (just curious as I'm using the older, solid non-adjustable one). If so, do you have any thoughts on the range of adjustment vs desired setup?

Regards,
Chuck

Chuck,

Yep, that is Dick! I ran with him at many events last year too.

It is tricky to compare using experiences on totally different lots over a thousand miles away from each other, but based on what I remember the car had much better turn-in but was still balanced on the square setup. We were able to run full stiff on the Dinan bar and it still felt great. In contrast, I had to go to full soft on the Dinan bar to get the stagger working.

Yes - we both have the adjustable version. Especially with the stock suspension still in place it is nice to have a way to adjust the car for various surfaces. The adjustment does make a difference too.

[z3papa]

Thanks for the insight. I concur with your observations on stagger. Still need to source a bar.

[UNCbigM]

Nicely done! Congrats!

Yeah, I had heard the plan was for Jadrice to head to ESP from the start. I'm hoping he does that sooner rather than later...

[UNCbigM]

Anyone else autoxing this weekend? I'm at MCAS Cherry Point tomorrow.