Track - Staggered or Square?

[JNoSol]

Originally Posted by slavearm

Just at big willow yesterday. Go staggered. Just look at everyone in the dirt for proof. Too much torque. No amount of weight bias is going to make up for that. This car does not understeer... it oversteers... ALOT. You need the extra meat out back to help balance it out.

If staggered, it's much easier to find the wider tires on 19" wheels. Anyone tracked with Forgestar wheels? The ZE40 looks awesome as well.

[Gearhead999s]

Originally Posted by JNoSol

If staggered, it's much easier to find the wider tires on 19" wheels. Anyone tracked with Forgestar wheels? The ZE40 looks awesome as well.

I ordered a set of F14's in 19 x 10 25p & 19x 11 37p in January and I am still waiting for them.Today I was told I will have them in May.My 1st weekend on track is the weekend of 25-26.I am not very impressed!

[JNoSol]

Originally Posted by Gearhead999s

I ordered a set of F14's in 19 x 10 25p & 19x 11 37p in January and I am still waiting for them.Today I was told I will have them in May.My 1st weekend on track is the weekend of 25-26.I am not very impressed!

Sorry to hear that, bro. That sucks.

[CSBM5]

Having no experience with the F8x platform yet other that talking to some very experienced people who have driven the car substantially on track, I'd wager that if you're going to run a square setup it might be best to run a larger (stiffer) front sway bar. It will help significantly putting power down coming off corners/elements.

This is an aside and may/may not be applicable to the F8x, but my E90 M3 is setup for F-street SCCA autocross class meaning that I'm limited to the changes that can be made. Hence stock wheel widths are required. I have a set of lightweight stock width wheels with 275/35-18 square tires (BFG Rivals). I've also pulled the camber pins (got -1.6°) and installed the large, solid Dinan front sway bar, zero front toe. The car does *not* suffer from understeer at all. To the contrary, this season as soon as BFG releases the Rival S in 295/35-18, I'm going to run 275/295 on it as there are numerous places I can gain by having more rear grip (especially when the S65 is on the boil between 6500-8400rpms).

Continuing... I also have a set of ARC8 10x18 wheels with 275/35 NT-01s that I use for CCA autox/time trial events at the PC. Again, zero problem with understeer, and I can definitely use more tire out back also.

One caveat here is the differential. On the E9x of course its the standard visco-lock thing which other than the static lock is open when decelerating -- very nice on corner entry to have that, especially at slow speeds. If the F8x has some active work going on that creates more locking on deceleration, then the whole understeer on entry could be a different story.

Has anyone seen data on how the differential in the F8x is mapped versus it's input variables? I'm curious now how BMW has programmed locking during deceleration. Perhaps they've done it such that low speed stuff, say 40-50mph and under, the diff is open while more decel locking is applied as speeds increase -- at least that is what I'd expect/want I think. It would be very interesting to look at how the diff locking is mapped versus vehicle inputs.

[nicknaz]

Originally Posted by slavearm

18x10 +25 275/35/18
18x11 +35 305/35/18

The 275 for the front everyone has in stock. The 305 rears usually need to be ordered, but are available.

How does the 275/35/18 look with the stock suspension? Is there too much wheel gap?

[MaynardZed]

Originally Posted by nicknaz

How does the 275/35/18 look with the stock suspension? Is there too much wheel gap?

This is the track section. All we care about is hitting the perfect apex and getting low lap times...

...and yes, there would too much wheel gap with stock springs to look good while your at the track with that tire.

[JNoSol]

@CSBM5 Unlike the E9x M3s, the F8x actually suffer from oversteer and slippage during acceleration. With 275, there's wheel slip even on 2nd gear and most part of 3rd. The car is extremely tail happy, even when taking a 30mph turn. Combine the tail happy attitude with 420lb of tq, there's a deadly combination for a spinout.

I'm really considering staggered reading from the feedback of more experience track guys with the F8x. 265 front should clear K&W CS easily and 305 rear would be sufficient.

[CSBM5]

Originally Posted by JNoSol

@CSBM5 Unlike the E9x M3s, the F8x actually suffer from oversteer and slippage during acceleration. With 275, there's wheel slip even on 2nd gear and most part of 3rd. The car is extremely tail happy, even when taking a 30mph turn. Combine the tail happy attitude with 420lb of tq, there's a deadly combination for a spinout.

I'm really considering staggered reading from the feedback of more experience track guys with the F8x. 265 front should clear K&W CS easily and 305 rear would be sufficient.

That was the point of my post -- that even the E9x can benefit from 295s out back as 275 square with my setup (camber pins out, Dinan large front bar) still results in situations where I need more grip out back from apex to track out/or coming off elements in an autox when the S65 is on the boil. No issues with understeer in my E90 on turn-in nor mid corner -- that car is very surprisingly rotatable on turn in.

If anything the F8x needs much larger rears than fronts due to exactly the reasons you specify (which was why I made the above post). I would put a large front sway bar on the F8x to tame down the oversteer on track out and help the inside rear grip better reducing power on oversteer and also the amount of locking needed by the LSD on track out. I could see a square setup working perhaps with a large front sway bar, more front camber and spring rate changes, but if it was my F8x, I'd want something like 295 or 305 square.

Regards,
Chuck

[slavearm]

Originally Posted by nicknaz

How does the 275/35/18 look with the stock suspension? Is there too much wheel gap?

The tire is almost exactly the same size as the stock 19. So just as much gap as the stock 19s. Doesn't really bother me, but I can't stand the 1.3" min drop on almost every kit out there right now.

[CanAutM3]

Originally Posted by slavearm

1. I am not going to say much to this because I don't really want to start a flame war, but that only matters during turn in. The moment you get to the apex and put the hammer down, it doesn't matter anymore. What matters is how much traction you can generate with your rear wheels.

2. You can deal with most of that by handling weight distribution with the brake and throttle.

This is not 100% aligned with my understanding of tire dynamics.

The front tires do not only work during turn-in: as long as the car is under lateral load, the front tires need to do their share, which is proportional to the normal (meaning vertical) load they carry.

To be fast around a corner, you need to decelerate all the way to the apex and then accelerate from there. On the F8X, this means that the front tires need to carry more lateral load than the rears for a good proportion of the turn (turn-in to the apex). Not much you can do to alter the general front weight distribution bias using brake and throttle here. During the first portion of the turn, a huge amount of work is done by the front tires to slow down the car and to have it change direction.

As you stated, where more rear grip comes-in handy is from apex to corner exit, where forward thrust needs to be combined with lateral traction (friction circle).

I am not saying a staggered setup isn't beneficial from a performance point of view. I am wondering how well it will be possible to balance tire wear (with the fronts working so hard) to maximize tire life with such a setup.

Originally Posted by slavearm

3. A front weight biased car rear wheel drive car will tend to oversteer. Which is why you add more traction to the rear to counter.

This simply isn't true. It all depends with chassis handling dynamics and tuning. Power oversteer has nothing to do with the handling balance of a vehicle. I know plenty of front weight biased RWD cars that are understeering pigs.

[CanAutM3]

As a general question to those who run a staggered track setup, what hot pressures are you running front and rear?

[MaynardZed]

Originally Posted by CanAutM3

As a general question to those who run a staggered track setup, what hot pressures are you running front and rear?

I shoot for 33-34 hot fronts and 32-33 hot rears. R888 tires. Seems quite low for this size car, I know, but it's what has worked best for me with this tire.

[gthal]

Originally Posted by slavearm

I'd probably just recommend at this point you take your car to the track instead of arguing with people who have on a forum.

CanAutM3 has a significant amount of track experience so what he says actually comes from experience I have lots of track experience myself but my interactions with him suggests that he knows more than me and a heck of a lot more than most people around here. Just a FYI.

[slavearm]

Yah I am not trying to be a dick or call him out. No reason for it. Probably came across wrong, and maybe I took his comment wrong. Apologies.

To his concern about front tires, I will say even with track tires, the front sidewalls take some abuse. Needs more neg camber in the front for sure. You would have to have them mounted to the other side to even it out.

[CanAutM3]

Originally Posted by slavearm

I'd probably just recommend at this point you take your car to the track instead of arguing with people who have on a forum.

Thanks for the advice, I might try that

[JNoSol]

@evanescent03 Have you mounted your square ET33 with 10mm front spacers? Please share the photos once you do.

[evanescent03]

Originally Posted by JNoSol

@evanescent03 Have you mounted your square ET33 with 10mm front spacers? Please share the photos once you do.

still waiting, man ... EAS thought they had them, then didn't, then offered me the set off their car and I accepted ... there has been a little bit of confusion but I'm hoping they get shipped by the end of the week.. I need em
soon! brake pads and fluid this weekend.

[FTS]

Originally Posted by CanAutM3

I am not saying a staggered setup isn't beneficial from a performance point of view. I am wondering how well it will be possible to balance tire wear (with the fronts working so hard) to maximize tire life with such a setup.

I think you are right; I never have been able to balance tire wear, on any car, even the Evos and STis I had running square setup, but it is probably me more than anything else. My concern about wear running staggered is more about left to right, not rear to front. When I feel it is time, I just have the tires swapped on the wheels; unfortunately most (actually all) tracks I visit are run CW.

I maybe off base, but I think most people are making too much of this wear issue. I budget for 8 tires for a season, I change when ever they wear out; I generally only get to use 4 new tires at the beginning of the season and all other times it is a mix. I am not getting why this tire wear is such a big issue I really think you will be robbing yourself from fully enjoying this car on track with a square setup.

Originally Posted by CanAutM3

As a general question to those who run a staggered track setup, what hot pressures are you running front and rear?

Not that it is anything definitive the way I was driving, but I settled on 36 front and 35.5 rear last event. I need to collect couple of more event data before I start lowering them and compare the data.

[CanAutM3]

Originally Posted by FTS

I maybe off base, but I think most people are making too much of this wear issue. I budget for 8 tires for a season, I change when ever they wear out; I generally only get to use 4 new tires at the beginning of the season and all other times it is a mix. I am not getting why this tire wear is such a big issue

It is a simple question of cost for me. Nothing pisses me off more than throwing away a tire that has plenty of thread meat left on it but has the shoulders corded . On my previous M3s (as I likely will on my M4), I ran stock suspensions except for camber plates, so there was a non-negligible amount of tire roll-over up front (suspension roll and soft bushings). First season with either car, I always ended-up throwing away tires that could have had much more life; until I was able to find the proper alignment and tire rotation recipe. After that, I could easily double the life of my tires (from 4~6 days to 8~12 days). That is not negligible to me.

Proper rotation front to rear has been an important element of my recipe. I see having the ability to do that rotation on the fly at the track as an important advantage, especially for 2 or 3 day track events.

Originally Posted by FTS

I really think you will be robbing yourself from fully enjoying this car on track with a square setup.

A staggered setup is not out of the question for me. For now, I ordered 4 18x10ET25 APEX EC-7 wheels. When APEX come up with a proper 18x11 EC-7 option for the F8X, I may very well buy a pair. With 6 wheels, I could have the opportunity to play around between setups to balance wear while better leveraging the performance potential of the car.

[nicknaz]

Originally Posted by MaynardZed

This is the track section. All we care about is hitting the perfect apex and getting low lap times...

...and yes, there would too much wheel gap with stock springs to look good while your at the track with that tire.

Is that track forum code for calling me a poser? j/k

I'm planning to use a street type tire (Bridgestone RE11 etc) for a while and daily it as well as track it so the wheel gap does matter to me...

(and I don't like moving to an R tire too soon in a new car.. would rather slide it around at slower speeds for a bit)

[gthal]

Originally Posted by nicknaz

Is that track forum code for calling me a poser? j/k

I'm planning to use a street type tire (Bridgestone RE11 etc) for a while and daily it as well as track it so the wheel gap does matter to me...

(and I don't like moving to an R tire too soon in a new car.. would rather slide it around at slower speeds for a bit)

RE11 is all you need for a tire on this car IMO. I ran RE11 on my E92 M3 for an entire track season and it was a great tire. Notably better than PSS on the track.

We tend to get caught up on tires and go to those with extreme track capability but an RE11, AD-08, etc is tons of tire for all but the most hard core

[brian99997]

I'm on my 2nd set of Hoosier R6's (265/295 on the stock 19's) and shoulder wear really isn't a problem since I got the RDSport sway bars and M adaptive. I do toss the fronts a little before the rears due to the rears wearing. The R6 is very specific to this but sliding the car isn't rewarding on this tire so I am probably saving more rear tire than some. It is quite rewarding lap time wise with the stock PSS though, 4-6 degrees of slip angle is not unreasonable with those. If I do ever get around to buying wheels and had my ideal tire it would be a 255 in front and a 305-315 in the rear to balance not only tire wear but turn in and corner exit (which is helped greatly already with the right alignment)

btw, I run 36f 38r psi hot for the best lap time. I personally like this tire really high though, I love 44/48 on the GT3.