E92 M3 ZCP in SCCA Solo F Street

[Type_Yarr]

Originally Posted by CSBM5

That was my thought too. I would think it would be overkill and ruin rotation as you mentioned, but I was curious if anyone thought about such a setup. Outside the box thinking, but something like a stock FSB but an adjustable rear bar and use the 305s out back (or the 315 Rival S').

Interesting concept. I would be worried you'd be net negative with either too much body roll or lifting the inside rear to the point the diff can't get any power down. I wonder if anyone with both front and rear adjustable ARBs would be willing to test this approach out?

[CSBM5]

Originally Posted by Type_Yarr

Interesting concept. I would be worried you'd be net negative with either too much body roll or lifting the inside rear to the point the diff can't get any power down. I wonder if anyone with both front and rear adjustable ARBs would be willing to test this approach out?

Maybe it would, "at best", turn out to be a setup that would be highly course dependent to be successful. The large front bar makes such a fantastic change in transient conditions and helping hold that inside rear tire down as you mention.

Speaking of which, you've cut to the core of my thought process here! I have front and rear bars, but only the rear is adjustable. I don't SCCA class autocross the car currently and only take it to a club event where FTD wins (very informal), so I added the Eibach adjustable rear bar.

I can say the car feels really nice now, and more balanced of course. I took it to a cca event on the wet handling track at Michelin last Fall, and it was superb with this setup -- drifting through multiple corners and sweepers, all drift-linked together, was not only a lot of fun but extremely controllable. I was on my street 220Ms, Michelin PSS tires, 255/35-19, 275/35-19, for that event. Ended up winning the timed portion too trying to keep slipping at a level where no time was lost on course -- totally different objective to the first part of the day. Anyway, I'm glad I had the rear bar on for that event, and I've left it on since. (as an aside, it's a major PIA to swap that rear bar, and far easier/faster to just unhook a few things and actually drop the subframe a good bit, as opposed to Hotchkis partial lowering method which I used and was sorry).

I have a potential event coming up this Sunday, but the weather is looking iffy at the moment (45-55F and rain). I have a fresh set of 275/35-18 RE-71Rs on 10x18 square ARC-8s, and the thought occurred to buy a pair of the PS7 11x19s (on sale now for $205 each with free shipping since Apex is discontinuing the PS7) and use the huge rear tires if I can make use of them and not turn the car into a push mobile.

[Richbot]

I've mentioned before I think the hottest of hot setups on this car would take advantage of the bigass 19" rear tires and adjust balance with chassis setup (toe fo days!), but you'd have to throw all yours etup notes away and start over. Basically putting a Corvette setup on the car without the Corvette's suspension advantages...

Would not want to give up the extra roll stiffness up front without substitution of some racier bumpstops than stock (still legal, right, or did tehy change that?) and the front bar helps the confused, slow-acting stock diff by keeping that inside rear down. This car still has plenty of power to smoke the inside rear on 315's in 2nd if you're not careful with the throttle in a corner, been there done that on Hoosiers for a couple seasons back in the day, so it's not as if putting a 305/30-19 'Stone the back or whatever magically makes the car into a 911

[Richbot]

Originally Posted by Richbot

The sidewall issue with the 285 is exactly what got me thinking "why not both" with diameters on an FS M3 that and national courses routinely peaking above 70mph means the 285 could have you making a few too many 2-3 shifts right at the moment when the M3 is finally accelerating as hard or harder than anything else in the class (7500+rpm in 2nd). So what chuck was saying about the sidewalks on the 285's is wahat I was getting at and yeah the extra width is nice on the 305/30-19 but you also get a tire that can put ALL the power down ALL the time

Just not sure if getting the balance right would be possible with all that meat back there

Oh hey look at that from back in April

Somebody do it and take pics because even if it sucks to drive it'll look rad

[CSBM5]

Originally Posted by Richbot

Oh hey look at that from back in April

Somebody do it and take pics because even if it sucks to drive it'll look rad

Well, this is an incredibly long thread... Your prior comments about the not only the larger width rears but especially the larger diameter in the rear, using diameter stagger, still stick with me and hence likely hounding that question out of me.

For example, I'm damn curious now how the car would behave with 275/35-18 front and 275/35-19 rear for example...I know it takes away tire rotation benefits and all, but I would really like to drive back-to-back the 275/35-18s all around and then the 18/19 setup.

So there we have an RE-71R experiment all designed:


275/35-18 all around

275/35-18 front, 275/35-19 rear

275/35-18 front, 305/30-19 rear

Now I'd like to do the above a second time using non SCCA legal wheel widths too (10" front, 10.5 or 11" rear).

[Richbot]

You and me both. That would be a fun test day.
But you know what would be funner? An ESP car!!!

[z3papa]

OK -- I'll bite next spring on trying this out as I was one of the guys who thought outside the box and ran 285/30-18 at Nat's this year. I may roll with 275/35-18 front/315/30-18 rears Rival S as I'll have a bit more "adjustability" at my disposal since I bought some custom DA Koni units when I was in Lincoln for cheap. My concern is if the 315 will stick out too far which may require a 32ET rear to fit closer into the body. My thought is with 10" rears, it may be doable but an expensive lesson if it doesn't.

For the record, here is my thoughts from the past two seasons. All this assumes 18" wheel sizes and RE71R's. The 285/30-18 square set is extremely confidence inspiring and very noticeable on any dig out laden courses but also less compliant on rough surfaces due to the short sidewall, and can result in shifts if you need to be more than 65 mph (both courses this past year at Lincoln). The 275 square was more compliant and at times faster since it didn't suffer from shock on rough surfaces but would also be more prone to some dig courses. 265/275 or 285 was workable but definitely had less grip on sweepers. Finally, here is my real issue. On reliable points of data, Rival S' even in the larger sizes which are not 1.5 variety, were always faster relative to the RE71R's on concrete, and slower on asphalt. Many of my very local events are on concrete, regional on asphalt, Nat'l regional on concrete, and ultimately Nat's on Lincoln concrete. I'd be willing to give up some competitive performance at Chicago (Rt.66) region events where I've been in the top 6 season long for better contingency and better performance Nat'l.

[Richbot]

315/30-18 Hoosiers fit with room to spare on ET23 stock 9,5j wheels

so 4mm further out and 8mm further in...should be fine

Where fitment probably needs to be spot-on is the 305 19, might need to use the allowance for more like ET28-30 I agree for that tire

[CSBM5]

It's been a couple of years since I had some Rivals, but don't they have a tread to sidewall profile similar to the R1? Meaning the section width is carried out to the tread face; perhaps not as fully as the R1 but close. Hence rubbing/clearance issues may exist for a given size that aren't there with a different tire.

Having just bought and mounted up some RE-71Rs (275/35-18 on ARC8 10" wheels all around), these tires also appear pretty hefty out to the tread face too (from doing a quick eyeball comparison to the Michelin PSS 275/35-19 rears).

Hoosiers (A6, R6) have the typical taper from the tread to the sidewall max section width, so they fit where an R1/R1S rub dramatically. Years ago I was running the A6 275/35-18 on my E39 M5 with no issues at all. Switching to the BFG R1 immediately caused massive rub of the rear fender lips on major compression/bumps. It was enough that the tire caught the forward portion of the lip where the factory didn't continue the lip roll (compared to normal E39), dug into tire, pulled the lip down pointing at the tire, and then proceeded to gouge the tire.

The 305/30-19 is just 0.1" smaller diameter than the stock 265/35-19, so it will essentially expand the tire envelope at the same diameter location as stock. I'm guessing there are going to be rubbing issues with this tire.

[The Father]

Don’t know if this helps:

Car came with 10X20 rear wheels 29offset

275/30 V12. The V12s are significantly wider than my 275 RE71 and there’s no rubbing.

[The Nebulizer]

Originally Posted by z3papa

OK -- I'll bite next spring on trying this out as I was one of the guys who thought outside the box and ran 285/30-18 at Nat's this year. I may roll with 275/35-18 front/315/30-18 rears Rival S as I'll have a bit more "adjustability" at my disposal since I bought some custom DA Koni units when I was in Lincoln for cheap. My concern is if the 315 will stick out too far which may require a 32ET rear to fit closer into the body. My thought is with 10" rears, it may be doable but an expensive lesson if it doesn't.

My best guess from my survey of fitting setups and my tire fitting formula is that 315 on an 18x10 wheel would fit under the fenders with just the right offset. I believe you are at about -1.6 camber in the rear, right? I'm calculating et26 is optimal with less than a millimeter to spare inside and out at 315mm. But we know the tire will be pinched on a 10" wide wheel, so that should leave a few more millimeters on each side to be safe.

[Richbot]

315/30-18 A6 fit with tons of room to spare on a 9.5 et23

[Type_Yarr]

So this has me wanting to buy some 12mm spacers and trying those 315/30/18 rivals from the M2 next year. I'll see if I can convince him to do a back to back swap since he hasn't run 275s in the rear.

On a different note, what's everyone's thoughts on shocks? Can OEM ZCP get it done at a national level? Or are pimp shocks worth that last couple tenths?

[Richbot]

They have already gotten it done this year. But Jeff is a bit of an alien

[Neuner]

Originally Posted by Richbot

They have already gotten it done this year. But Jeff is a bit of an alien

& 2015 too..

[z3papa]

Originally Posted by Type_Yarr

So this has me wanting to buy some 12mm spacers and trying those 315/30/18 rivals from the M2 next year. I'll see if I can convince him to do a back to back swap since he hasn't run 275s in the rear.

On a different note, what's everyone's thoughts on shocks? Can OEM ZCP get it done at a national level? Or are pimp shocks worth that last couple tenths?

Winners in 2015 and 2017 both were on EDC shocks in a ZCP car. Will pimp shocks help.....probably but not required.

[Type_Yarr]

Thanks for the info guys. It's good to know the ZCP dampers can hang at the pointy end, that it's still within driver noise. I wasn't sure how many people are running DAs or even ZCP.

I've run OTS Koni yellows on a previous car, but to be honest I don't feel like a similar SA would be a difference maker compared to the ZCP in sport mode.

For those who have run aftermarket dampers, what's your experience been like? Any data or reference points? ie. For me the Dinan FARB was worth a rough average of 1.2% improvement on run times.

[Richbot]

Nobody has been willing to give up the lower ride height or half-inch wider wheel width at the pointy end.

Brian qualifies as a certified alien as well so keep that in mind when looking at 2015 but I guess it's the same philosophy that leads Sam to leave relatively dumb simple shocks on Corvettes and proceed to kick butt...the shocks usually aren't where the time is really

My opinion is if it were not for the wheel downsize rule, any M3 could get it done because 19" front tire options that don't rip the fenders out of the wheel wells would be tough to manage on ZCP cars (though a 275/30-19 would probably do the trick, can't recall if anyone's making a hot one of those right now) but maybe that's naive, wheel width is a big deal, ride height matters (and the ZCP cars can get more front camber because they're lower)

I think the main reason people haven't done it is it's expensive and not necessary. I don't think the stock ZCP setup are the end of the line on development, especially the rears. I had MCS 2-way remotes on my (AS, then briefly FS, on Hoosiers, non-ZCP E90, now retired from competition) car. I miss them a lot. And they were better in every way especially over transitions and bumps than the ZCP and non-ZCP cars I have driven. The extra support for the front end, particularly, was really really helpful, and the car was a lot happier on the bumpstops. ZCP has the same rates within a few lb/in of the stock springs, just with less travel, so you're on the stops more, hence the famous JC review re ZCP making the car worse, because he's old and soft

That said Maybe necessary if the competition makes a leap forward with the newer cars coming out, but they're all likely to be running factory adaptive dampers too for the foreseeable future

[Fitzpadj]

Joining in on the fun.

Picking up a 2011 M3 ZCP E92 for FS. Has a couple modifications that need to be reversed such as coilovers and wider wheels.
Just ordered:
18x9 +30 Apex ARC-8 Fronts
18x10 +25 Apex ARC-8 Rears
Bimmerworld Race axle-back
Dinan Front Sway Bar

Trying to pick up a set of stock ZCP springs and EDC shocks, or is it pointless and I should order other shocks? Aside from MCS, what other options have been proven? Would like to avoid $3k shocks this first year if I can.

Has anyone built a lighter single exit exhaust?

Are people using lightweight batteries for just the autox weekend and then switching back and having no issues with battery registration? I have a Braille from my race car that would be convenient to use instead of buying a whole new battery.

[z3papa]

Originally Posted by Fitzpadj

Joining in on the fun.

Picking up a 2011 M3 ZCP E92 for FS. Has a couple modifications that need to be reversed such as coilovers and wider wheels.
Just ordered:
18x9 +30 Apex ARC-8 Fronts
18x10 +25 Apex ARC-8 Rears
Bimmerworld Race axle-back
Dinan Front Sway Bar

Trying to pick up a set of stock ZCP springs and EDC shocks, or is it pointless and I should order other shocks? Aside from MCS, what other options have been proven? Would like to avoid $3k shocks this first year if I can.

Has anyone built a lighter single exit exhaust?

Are people using lightweight batteries for just the autox weekend and then switching back and having no issues with battery registration? I have a Braille from my race car that would be convenient to use instead of buying a whole new battery.

Cashmore had a single exit exhaust if I'm correct. Lightweight batteries are not class legal and easy to spot so save yourself some hassle and $$.

[Fitzpadj]

Originally Posted by z3papa

Lightweight batteries are not class legal and easy to spot so save yourself some hassle and $$.

Even better! I hate lightweight batteries.

Previous setups were *SP cars so I gotta pay attention.

What pads are people using for low heat high torque? And reading through there is a lot of conjecture about tires.

Seems the RE71R is the one to go vs the SUR4G.

For local/match tour/pros, anything but Nationals itself, I would think the 285 all the way around with its shorter gearing would be the one to go, but it seems like most use the 275?

[Richbot]

You pretty much have to stay with the stock true dual setup until after the diff (secondary cats are about 18” in front of it) so I don’t see why a single would be lighter than two pieces of pipe with a couple turndowns on them, you’d basically just be giving back all the weight you lose in the 2nd pipe with your merge pipe and a crossover to get it to exit in one of the stock locations

Please put turndowns on your bimmerworld exhaust and then sell it to me when you part out kthnx, I love everything about that exhaust but the tips

The stock pads are a damn fine pad for autocross the stock system is pretty much perfect and falls in the don’t make it worse category for me anyway never a heat issue even hotlap autoxing the car (and I ran the car back in the dark ages on Hoosiers when you almost couldn’t get abs to engage). As soon as you are hauling down from real speeds 100+ repeatedly they start to suck