Most aggressive wheel/tire track setup

[CrookedCommie]

Can you explain more?

My comment was 100% sarcasm.

[Obioban]

I believe he’s referring to the negative camber required to clear the fenders. But we’ve already established that this is actually needed on the race track based on tire/tread temperature data. There’s absolutely no compromise here, on the contrary.

On the street though, that much negative camber will wear tires unevenly and actually provide less grip. But then again you don’t need that much tire/wheel on the street. This is a race setup.

Since no one has mentioned it, the real question should be about scrub radius. Sure there is some compromise here but the benefits far outweigh the negatives imo.

I think people run too much camber on track, too, out of necessity because they run the cars too low. Run the car higher and you're in a better portion of the camber curve, less static camber required.

[lcrain]

No, scrub radius has nothing to do with the control arm. Those control arms can widen the track without affecting scrub radius like low offset wheels do.

Got it. That makes sense. I will admit, my understanding of scrub radius is rudimentary at best. So the offset and width of the wheel is what stands to change the scrub radius.

[silaciM3]

Scrub radius can be addressed with aftermarket control arms, like those made by SLR. They also make a “mini kit” which allows the use of a stock control arm with a roll center correcting outer ball joint/bearing setup. I have the mini kit on my e36 m3.

No, scrub radius has nothing to do with the control arm. Those control arms can widen the track without affecting scrub radius like low offset wheels do.

[lcrain]

Since no one has mentioned it, the real question should be about scrub radius. Sure there is some compromise here but the benefits far outweigh the negatives imo.

Scrub radius can be addressed with aftermarket control arms, like those made by SLR. They also make a “mini kit” which allows the use of a stock control arm with a roll center correcting outer ball joint/bearing setup. I have the mini kit on my e36 m3.

[silaciM3]

I believe he’s referring to the negative camber required to clear the fenders. But we’ve already established that this is actually needed on the race track based on tire/tread temperature data. There’s absolutely no compromise here, on the contrary.

On the street though, that much negative camber will wear tires unevenly and actually provide less grip. But then again you don’t need that much tire/wheel on the street. This is a race setup.

Since no one has mentioned it, the real question should be about scrub radius. Sure there is some compromise here but the benefits far outweigh the negatives imo.

[r4dr]

I'm curious too. Because a 9.5" et35 is so close to the strut it sometimes needs a 5 mm spacer with thicker struts according to Apex. So a 10" et35 would be even closer wouldn't it? 6.4 mm closer to be exact.

Unless that is irrelevant if you can put your perch above the tire.

[sc_tr0jan_m3]

Somebody should let all the racers, shops, and suppliers know that a 18x10ET25 squared setup is compromised.

Can you explain more?

[CrookedCommie]

It depends how much you're willing to compromise running larger tires and/or optimal camber. :P

ET25 is already compromised IMO. ET 35 with a 10mm spacer in the rear is the functionally optimal setup, IMO, if your spring perch is above your tire.

Somebody should let all the racers, shops, and suppliers know that a 18x10ET25 squared setup is compromised.

[silaciM3]

Yeah not much room left there.

I wish someone made OE looking fenders that were maybe 20mm wider. That would make this really easy!

Only ones I could find:
https://www.fibre-factory.co.uk/prod...le-front-wings
https://www.ebay.com/itm/BMW-E46-M3-...AAAOSwWxJeHNDh

It does seem that running a wider wheel just slightly widens the tire for a given size, so that's probably part of it as well.

Definitely. Here's the same 255/35 tire mounted on 9.5 and 8.5 wheels.

[BBRTuning]

Very helpful, thanks.
And totally agree about the camber settings and the need for wider wheels.

Do you happen to have any pics with the 10.5”? Seems to me 18x11 won’t fit without some serious fender work, which I don’t mind for a track setup. Just gotta figure out how much is needed.

I wish someone made OE looking fenders that were maybe 20mm wider. That would make this really easy! I also ended up slotting the fender mounting holes a bit to pull the fenders another roughly 5mm further out. For whatever reason I had a harder time with clearance on the driver side. I think my fender clearance issue is being exacerbated by the Rival S sidewall, which sticks out further than most (mostly due to the lip protector built into the tire). When then I throw on my 18x10 +25 and 275/35 NT01 setup, it now fits with tons of clearance, even though theoretically the tire fitment should be almost identical between the two setups (only 3mm further inward due to difference in wheel offset). It does seem that running a wider wheel just slightly widens the tire for a given size, so that's probably part of it as well.

[lcrain]

Very helpful, thanks.
And totally agree about the camber settings and the need for wider wheels.

Do you happen to have any pics with the 10.5”? Seems to me 18x11 won’t fit without some serious fender work, which I don’t mind for a track setup. Just gotta figure out how much is needed.

To fit an 18x11 you will need either fabricated metal fenders or some kind of aftermarket flare. Really depends on how big of a tire you want to run and ultimately what you intend to do with the car. For a fun HPDE car, I don't think going that big is worth the hassle. For a race-car, it is worth the hassle, IMO, but depends on the rules allowed for the class you intend to run. NASA ST, for example, running that big of a tire will incur a penalty. NASA GTS you can go as big as you want. I recently went with an 18x11 Bimmerworld TA5R on my GTS-3 e36 M3. Going that big allows me to run 315 hoosier a7 which is a significant advantage, especially in the first lap or two of a race when my tires are up to temp and my competitors are not.

[sc_tr0jan_m3]

Agreed. They look good though!

TCDesign is one of the top fabricators in the west coast. He did my half cage and works on many of the top racers on the west coast. Great guy too.

[silaciM3]

that car had to have a TON of body work to fit those wheels. the fenders are NOT stock.

Agreed. They look good though!

[silaciM3]

I've run both my street/canyon setup (18x10.5 +22, 275/35-18 Rival S 1.5 square) and dedicated track setup (18x10 +25, 275/35-18 NT01 square) without rubbing although the 10.5 +22 setup did take quite a bit more work. Fenders are rolled/flared and pulled out a bit. I have only 3mm clearance on the inside to the strut so I couldn't run a higher offset if I wanted.

From tire pyrometer data I've found that my car needs about 3.8-4.0* front camber (on NT01) to see good temperature spread (~10* spread from outer to inner). I ran 3.5* at Laguna earlier this month and saw about 15* hotter on the front outsides, which is significant considering that track has a lot of fast straightaways. The point being, 3.5*+ front camber for track setup is expected and not simply a compromise to make the tires fit.

I'll eventually change to 10.5" for the track set too. The typical R-compount "275" width tire is too wide for a 10" wheel, IMO. These cars are heavy and we need as much support for the sidewall as we can get. Especially in the case of the NT01 which already has a pretty weak sidewall.

Very helpful, thanks.
And totally agree about the camber settings and the need for wider wheels.

Do you happen to have any pics with the 10.5”? Seems to me 18x11 won’t fit without some serious fender work, which I don’t mind for a track setup. Just gotta figure out how much is needed.