E92 M3 ZCP in SCCA Solo F Street

[ChezT]

[QUOTE=z3papa;19568694]The real ticket is downsize to 18x9/18x10 with RE71R's in 275 square or 265-35/285-30. The 18's wheels are much lighter than 359's, the consumables are cheaper, and you have better clearance. I sold my 359's even they were nice looking wheels. By the way, did you do any Nat'l events in STR? If so, our paths may have crossed previously.[/QUOTE

With the new 285/30/18 sizes available, would it make sense to just run 275/35 up front and 285/30 in the rear? Or is squaring it off on 275 going to be the most balanced approach? I'm running 18x8.5/17/9.5 in F street

[z3papa]

[QUOTE=ChezT;19613937]

Originally Posted by z3papa

The real ticket is downsize to 18x9/18x10 with RE71R's in 275 square or 265-35/285-30. The 18's wheels are much lighter than 359's, the consumables are cheaper, and you have better clearance. I sold my 359's even they were nice looking wheels. By the way, did you do any Nat'l events in STR? If so, our paths may have crossed previously.[/QUOTE

With the new 285/30/18 sizes available, would it make sense to just run 275/35 up front and 285/30 in the rear? Or is squaring it off on 275 going to be the most balanced approach? I'm running 18x8.5/17/9.5 in F street

That's a question I've seriously asked myself. Here is why, the diameter size of the 285/30 (24.8" -- 11.4" section width)is appreciably smaller than the 275/35 front or even a 265/35 (25.6" -- 10.4" section) front. While I could care less about whether you are creating a rear ward rake for appearance sake, I do think you might unweight the front just enough to throw off balance to make understeer a bit pronounced compounded by the wider rear section width. Only testing will tell. I may try it and later regret it but it's a consideration worth trying since it means putting serious corner exit power down and there is plenty of space.

[Neuner]

Surprise delivery from UPS this past Thursday.. did I get the right ones?

[CSBM5]

Are you going to try 285/30 square?

[Richbot]

[QUOTE=z3papa;19617843]

Originally Posted by ChezT

That's a question I've seriously asked myself. Here is why, the diameter size of the 285/30 (24.8" -- 11.4" section width)is appreciably smaller than the 275/35 front or even a 265/35 (25.6" -- 10.4" section) front. While I could care less about whether you are creating a rear ward rake for appearance sake, I do think you might unweight the front just enough to throw off balance to make understeer a bit pronounced compounded by the wider rear section width. Only testing will tell. I may try it and later regret it but it's a consideration worth trying since it means putting serious corner exit power down and there is plenty of space.

This is pretty much the exact setup the m3 GTS runs with (taller front than rear, but 255 front 285 rear). It'll be fine I think

I question whether the 285/30 would put down power Better than 275/35. Forward Traction benefits more from a taller sidewall than more width. Benefit is really the better gearing IMO

[z3papa]

Difference in top speed is 67 (275/35) vs. 64.5 (285/30). That may just enough to convince you to stay with the 275's as I encounter the need to approach or exceed 67 on about 50% of Nat'l courses.

[Richbot]

Yeah that's a big deal too. I'm not sure the car needs shorter gearing the 275/35 is already more than 1/2" shorter than stock. The gearing is just about perfect

Maybe a prosolo tire!

[z3papa]

Originally Posted by Richbot

Yeah that's a big deal too. I'm not sure the car needs shorter gearing the 275/35 is already more than 1/2" shorter than stock. The gearing is just about perfect

Maybe a prosolo tire!

I've thought about that too but am registered in 2 of the 3 Ohio events and Blytheville, all of which are notoriously fast. Combine that with the declaration that Pro's will be 10% longer and the chances are they will push close in FS trim to over 65 mph at some point on course. Last year really exposed the Mustang's top of 58 mph in 2nd which made many to abandon FS because they had problems going to 2nd under load corner such as a sweeper. I'll still plan on a 2/3 shift on occasion but would prefer to minimize it.

[0versteer]

Originally Posted by z3papa

The real ticket is downsize to 18x9/18x10 with RE71R's in 275 square or 265-35/285-30. The 18's wheels are much lighter than 359's, the consumables are cheaper, and you have better clearance. I sold my 359's even they were nice looking wheels. By the way, did you do any Nat'l events in STR? If so, our paths may have crossed previously.

Just the local match tour (rocky mountain). we had a baby during Lincoln last year, so i didnt get to make it.

Thanks guys, thats what i thought. 19s on RE71Rs are only $100 or so more than the 18s. will 265/35 and 285/30 fit on the ZCP wheels without rubbing up front? because i cant seem to get enough camber up front.

[CSBM5]

Originally Posted by 0versteer

Just the local match tour (rocky mountain). we had a baby during Lincoln last year, so i didnt get to make it.

Thanks guys, thats what i thought. 19s on RE71Rs are only $100 or so more than the 18s. will 265/35 and 285/30 fit on the ZCP wheels without rubbing up front? because i cant seem to get enough camber up front.

I don't think you'll get away with such a large diameter up front without rubbing; plus you would also have a fairly large inverse diameter stagger front to rear, which I personally wouldn't run.

Since you have ZCP and 9/10" wheels, if it was me, I'd try out 285/30-19 square? The 285/30 is officially spec'd for a 9.5-10.5 wheel, so there's no huge issue running them on a 9", and it would be an interesting experiment for sure assuming there are no clearance issues (not sure about inside clearance towards the strut as I believe the ZCP wheels have a bit more offset to the inside (ET31?) up front. I've got a set of 10x18 ET25 wheels with 275/35 NT-01s and have no clearance issues.

Wait, I don't think the RE-71R is available in 285/30-19...

Chuck

[Richbot]

Plenty of room to the strut with that tire. It's a 26" tall tire so I'd expect fender liner rub.

275/30-19 would fit all around no problem

[CSBM5]

Originally Posted by Richbot

Plenty of room to the strut with that tire. It's a 26" tall tire so I'd expect fender liner rub.

275/30-19 would fit all around no problem

Are you referring to a 285/30-19? Those appear to be 25.8" versus a 275/35-18 at 25.6" -- hence my thought that 285/30-19 square might work at only 2/10ths larger diameter. I don't think it matters anyway since that size isn't available in any tire one would want to run.

[Rassilon]

I wish re71r has more 265-285/40r18 sizes 😐

[z3papa]

Originally Posted by edwardgtxy

I wish re71r has more 265-285/40r18 sizes 😐

I'd wager that a 265/40-18 is about as tall a tire as you'd want to run and the 285/40-18 is going to be too tall with passengers in the rear for even a stock suspension.

[Gcode]

Hey guys,

Noob question here. I've been autocrossing for about 1.5 years in local events and I've become an autoX addict now (with a non competitive car - E93)

I was thinking about getting a Dinan front sway bar for my car, and for what I read in this thread, the softer setting work best for the M3.

Correct me if I'm wrong, softer setting on Dinan's anti-roll bar = " <-- more understeer" in the picture below:

[CSBM5]

Originally Posted by eL fUcHiLa

Hey guys,

Noob question here. I've been autocrossing for about 1.5 years in local events and I've become an autoX addict now (with a non competitive car - E93)

I was thinking about getting a Dinan front sway bar for my car, and for what I read in this thread, the softer setting work best for the M3.

Correct me if I'm wrong, softer setting on Dinan's anti-roll bar = " <-- more understeer" in the picture below:

No the picture is depicted correctly in that they are conveying that "in general" you create more understeer with a stiffer front roll bar setting (steady state cornering). The bar stiffness increases as you decrease the moment arm length, so the shorter you make that moment arm (as in the picture), the stiffer the bar will be. Hence it is a "stiffer setting" in this case not softer. The softest setting would be the furthest hole out on the moment arm.

[Richbot]

Originally Posted by z3papa

I'd wager that a 265/40-18 is about as tall a tire as you'd want to run and the 285/40-18 is going to be too tall with passengers in the rear for even a stock suspension.

There is toooooons of room in rear. I have yet to rub anything under any conditions, from a 315/30 Hoosier to a 295/35 continental to a 275/40 Michelin.

Lots of people run 285/35-19 which is basically the same as a 285/40-18 would be (does anyone make anything fast in that size? I can't find one) and report rubbing but that's been with a spacer to stancebro the car

[admranger]

Originally Posted by CSBM5

No the picture is depicted correctly in that they are conveying that "in general" you create more understeer with a stiffer front roll bar setting (steady state cornering). The bar stiffness increases as you decrease the moment arm length, so the shorter you make that moment arm (as in the picture), the stiffer the bar will be. Hence it is a "stiffer setting" in this case not softer. The softest setting would be the furthest hole out on the moment arm.

So the E90 chassis doesn't need a super stiff bar up front to combat the adverse camber curve of the strut suspension (like the E36 and E46 did)?

I knew they improved the rear suspension quite a bit but wasn't aware that they'd worked some magic up front too. Good to know!

[CSBM5]

Originally Posted by admranger

So the E90 chassis doesn't need a super stiff bar up front to combat the adverse camber curve of the strut suspension (like the E36 and E46 did)?

I knew they improved the rear suspension quite a bit but wasn't aware that they'd worked some magic up front too. Good to know!

Oh, the E90 is definitely a lot better up front than the E46...ages ago "enjoyed" cording that outside "edge of death" on A6s in D-stock in a ZHP in ~20 runs. 20 runs to the cords on $550 worth of front tires was such fun. The E90 (in my experience) does benefit from a stiffer front bar in transitions (as it should) on an autox course, but the national champ car (in this thread or the other one) apparently was running a mid-stiffness setup with the front bar fwiw. I've found *much* better outer edge wear on the E90 vs E46 ZHP also; sure it'd be nice to have -2.5 in stock class, but as it is (about -1.6 with pins out vs about -1.4 on the E46 pins out, so essentially same static camber), it's definitely a better setup than the E46 in my experience.

[z3papa]

Originally Posted by CSBM5

Oh, the E90 is definitely a lot better up front than the E46...ages ago "enjoyed" cording that outside "edge of death" on A6s in D-stock in a ZHP in ~20 runs. 20 runs to the cords on $550 worth of front tires was such fun. The E90 (in my experience) does benefit from a stiffer front bar in transitions (as it should) on an autox course, but the national champ car (in this thread or the other one) apparently was running a mid-stiffness setup with the front bar fwiw. I've found *much* better outer edge wear on the E90 vs E46 ZHP also; sure it'd be nice to have -2.5 in stock class, but as it is (about -1.6 with pins out vs about -1.4 on the E46 pins out, so essentially same static camber), it's definitely a better setup than the E46 in my experience.

Actually John's car which was driven by Bryan H. to the Nat'l championship had a Dinan bar set on the softest setting which was 10% stiffer than stock. John told me after Nat's he feels that worked well for Ohio events since he liked the increase grip in corners and better transition grip but less so at Lincoln where the grip levels overwhelmed the softer settings causing excess body roll. I run mine on medium after trying soft.

[admranger]

Good stuff. Thx. I've been thinking about getting a front bar for my E90M3 for the rare track event I do anymore (COTA this year!)

[chris381]

I've been wondering where to run the Dinan bar. I'm 2 events in with it on the mid setting, and one event with the 275 RE71's, and I like it so much I'm afraid to touch it. Might just leave it as is and keep going.

I feel like I'm cheating with the tires compared to the PSS's I ran all last year.