Track - Staggered or Square?

[rich8566]

Originally Posted by 97supratt

Did you check your tire pressures? The rs3 is a much stiffer sidewall tire, has nothing to do with stagger or square.

I concur - the RS3s have a much stiffer sidewall. And yes, I did check pressures fanatically with the MPSSs - the MPSS sidewalls are just too soft for track duty and they roll over too easily. But I must say the tires have excellent feel and stick! I guess my point on going square was two fold:

1. Going square means I can rotate the tires to all four corners.

2. Going square enabled me to get a set of dedicated track day tires that are far more suitable for high speed track duty.

[97supratt]

Originally Posted by rich8566

I concur - the RS3s have a much stiffer sidewall. And yes, I did check pressures fanatically with the MPSSs - the MPSS sidewalls are just too soft for track duty and they roll over too easily. But I must say the tires have excellent feel and stick! I guess my point on going square was two fold:

1. Going square means I can rotate the tires to all four corners.

2. Going square enabled me to get a set of dedicated track day tires that are far more suitable for high speed track duty.

+1 those are great reasons for going staggered.

[Kung Fu English]

Originally Posted by CanAutM3

I am not sure I follow your statement. If you want to go "stock", it implicitly means going with a staggered setup.

I am not sure how much of the thread you read, but it is about staggered or square track setup, meaning mainly focused on R-comp tires. It is not really about street tires vs R-comps.

If you want to go with the stock setup, then staggered is perfectly fine. It is how BMW designed it.

I personally usually prefer square for a dedicated track setup because it allows to better optimize tire wear through rotations. I ran a square setup for my first track season with the M4, but found I could not fully leverage the strong mid range power of the S55 due to insufficient rear grip, hence why I eventually went staggered.

I was wondering if you or anyone else could answer this.

Can you explain how wider tires give you better grip?

I had a hot argument last year with some friends about wider tires and grip. I said of course they give more grip, they are wider and have a larger contact patch. But after some calculations and discussions with engineers and physicists it turns out the contact patch will actually be the same.

I'm still trying to figure out HOW it works from a physics standpoint that wider tires give more grip?

Is it just because they are taller and thus take more rotational force to spin them? Or something with heat or something? Or just the shape of the contact patch?

I mean of course they are better but why?

Also if it is because they are taller would it stand to reason 275/40/18 would be better than 275/35/18, at least in the rear?

[CSBM5]

It's the shape of the contact patch that changes/matter, and it appears you weren't talking to tire engineers? This has all been discovered decades ago. The wider the tire, the shorter, front to back, the contact patch but the wider it is. Now you look at the limit of adhesion and how the distribution of the load occurs across that wider contact patch, the distribution of slip across the contact patch, etc, etc. A decent book to read on the subject is: http://insideracingtechnology.com/booktiredescrptn.htm.

A quick excerpt to get started on contact patch theory is here: http://insideracingtechnology.com/tirebkexerpt2.htm

[CanAutM3]

Originally Posted by Kung Fu English

I was wondering if you or anyone else could answer this.

Can you explain how wider tires give you better grip?

I had a hot argument last year with some friends about wider tires and grip. I said of course they give more grip, they are wider and have a larger contact patch. But after some calculations and discussions with engineers and physicists it turns out the contact patch will actually be the same.

I'm still trying to figure out HOW it works from a physics standpoint that wider tires give more grip?

Is it just because they are taller and thus take more rotational force to spin them? Or something with heat or something? Or just the shape of the contact patch?

I mean of course they are better but why?

Also if it is because they are taller would it stand to reason 275/40/18 would be better than 275/35/18, at least in the rear?

Tires are a very complex piece of hardware and over simplified physics do not properly depict their behavior.

The first point of consideration is the tire's construction. The load the tire carries is shared between the inflation pressure through the contact patch area and the tire's carcass. The tire's carcass behaves like a spring. The more the tire carcass needs to deform, the greater load is carried by the carcass. A narrow tire needs to deform more than a wider tire to generate the same contact patch area, hence the narrower tire transfers more load to the carcass and therefore needs to have a smaller portion of the load carried by the inflation pressure, which results in a smaller contact patch area.

The second point of consideration is how the tire's tread grips the road. It is a combination of standard friction (grip=normal load times friction coeficient) and the tread elements interlocking with the road surface irregularities. Do to this latter component, a larger contact patch will generate more grip (more elements interlocking with the road = more grip).

Naturally, these are not infinite and there comes a point of diminishing return. But as a general rule of thumb, a wider tire will indeed generate more grip. There are however other trade offs from wider tires.

[scottn2retro]

Just finished a shakedown weekend at Cal Speedway on Hoosier R7's. 275's up front and 295's in back. Car was awesome.

[spr]

You mean your et was net with spacers right? Before doesn't make sense.

Originally Posted by scottn2retro

At Laguna Seca we finished with 300x18 tires on all four corners with the following setup:

Front: 300x18 tire on 18x10.5" et25 wheels with 12mm spacers

Rear: 300x18 tire on 18x11" et44 wheels with 5mm spacers

We started on 3mm spacers in the rear, but with the lowering of the ride height and the super compression of the rear suspension in the Corkscrew, we started wearing through the fuel neck inside the right rear fender well. So we'll look into our options in the rear (maybe see if a larger spacer will fit.

[scottn2retro]

Originally Posted by spr

You mean your et was net with spacers right? Before doesn't make sense.

No, I wanted people to know what the whees sizes/offsets were and the sizes of spacers being run with them.

[scottn2retro]

Not only do we run wider rear tires, we also tried taller rear tires. Did not adversely the ABS at all

[racr100]

Originally Posted by wigaster

A group buy just finished for Apex's ARC-8 wheel in a 19X11 that was designed for the f8x. I participated and am expecting delivery in june. This is a brand new wheel. If you call them you may be able to get in on the action. Price is very reasonable. I bought it so I can run a 305 re-71 in the rear. They have a matching 10" wheel for front developed at the same time. You can run a staggered setup with 275 up front and 305 in the back if you wish

I wonder how did the order turn out. Are these wheels available now for normal ordering? What is the offset on these wheels?

[wigaster]

Originally Posted by racr100

I wonder how did the order turn out. Are these wheels available now for normal ordering? What is the offset on these wheels?

It didn't work out. Apex didn't get enough interest so the group buy got cancelled

[elbala]

Originally Posted by M3Tooner

This is not new news, and many already know about this but for the unaware, I wanted to share my experience with staggered setup of 275/35/R18 + 305/35/R18 NT-01 with stock factory alignment and no other suspension mods on a 2016 M3 Comp Pack. This setup makes the car understeer significantly because the rear has SO much grip but the front has none (relatively speaking). It made the car really frustrating to drive, and chewed the F-up on my front outside shoulder in two days. By the way, I drove with DSC off the whole time.

After fighting with the car all weekend, for the last session of the second day, I decided to swap in my factory 20" CP wheels with factory MPSS tires and go for a try. Wow, what a difference! The improvement in turn-in and reduced understeer was so welcomed. Car was much more balanced and enjoyable to drive even though I had to take it easy on the throttle because the rear would step out much sooner.

I was trying to see if I can get away from using camber plates since I don't plan to drive at 10/10th all the time. Lesson learnt, I should have included camber plates in the setup when i decided to use R-compound tires in a staggered size. OR just went with the largest square setup I can fit. Come to think of it, even with square setup on R-compounds, increasing front camber may still be a must. Anyone tried that?

Now I just have to flip the tires on the wheels and hope they last a few more days with increased camber. I will be ordering camber plates soon. Probably GC since Vorshlag couldn't figure out how to make it work for the F8x yet.

I am not sure what to do, what happened to you is exactly my worry. I bought Apex SM10 19x10 et 25 front and 19x11 et 44. I was planning on going 275 front tire and 305 rear tire but not sure if I will have too much understeer. The only suspension mod I have is swift springs. Maybe that will help compared too what happened to you since you had OEM suspension. Did you modded your suspension afterwards and you were able to get the 275/305 setup to work?

[elbala]

Looking for suggestions. I bought Apex SM10 19x10 et 25 front and 19x11 et 44 back what tire setup should I get? I was thinking in getting RE71 275Front and 305 back. Just worried too much understeer with 305 in the back. Sadly the RE71 does not have 295 in 19inch. Or should I go with the same set up as stock; 265front and 285 back? Suspension I only have swift springs. No camber plates. This set up will be used 90% for track use. Maybe 10% I'll use it on the street to change the look from the OEM 666m wheels. What do you guys suggest based on track experience. Car is tuned, stage 2 Bm3 OTS.

[Suds]

For a reference: I went 265/35 front and 285/35 rear. Very controllable with understeer and oversteer. Also works great with really late trail brake.

What I like about RE71's, you can swap the inside shoulder for the outside, basically swap sides on the tire and get twice the track days out of them.

[Suds]

Let's see how the pictures turn out?

This shows about 5 hours of track time at COTA on a flipped tire, other shoulder was heavily worn.

I started taking pictures of my tires every session or two just to track tire wear.

[elbala]

Originally Posted by Suds

For a reference: I went 265/35 front and 285/35 rear. Very controllable with understeer and oversteer. Also works great with really late trail brake.

What I like about RE71's, you can swap the inside shoulder for the outside, basically swap sides on the tire and get twice the track days out of them.

That is awesome. Very worn inside but swapping sides is a big help. Did you lose a lot of performance after 4 hours. I ask because I have read reviews on the Michelin Cup2 that after 1 hours (3 - 20 min sessions more less) the tire is basically gone. What wheels specs where you running?

[OhioRiderAaron]

Originally Posted by elbala

Looking for suggestions. I bought Apex SM10 19x10 et 25 front and 19x11 et 44 back what tire setup should I get? I was thinking in getting RE71 275Front and 305 back. Just worried too much understeer with 305 in the back. Sadly the RE71 does not have 295 in 19inch. Or should I go with the same set up as stock; 265front and 285 back? Suspension I only have swift springs. No camber plates. This set up will be used 90% for track use. Maybe 10% I'll use it on the street to change the look from the OEM 666m wheels. What do you guys suggest based on track experience. Car is tuned, stage 2 Bm3 OTS.

You really should have camber plates if you're 90% track and only 10% street.

Originally Posted by elbala

That is awesome. Very worn inside but swapping sides is a big help. Did you lose a lot of performance after 4 hours. I ask because I have read reviews on the Michelin Cup2 that after 1 hours (3 - 20 min sessions more less) the tire is basically gone. What wheels specs where you running?

Based on my experience, they grip very well until most of the tread is gone.

[Suds]

It was between 80F-98F when I was on the track at COTA in June a few weeks ago. The tires maybe fell off a little after 10-15 minutes but stayed very consistent. I replaced them with re71s.

Originally Posted by elbala

That is awesome. Very worn inside but swapping sides is a big help. Did you lose a lot of performance after 4 hours. I ask because I have read reviews on the Michelin Cup2 that after 1 hours (3 - 20 min sessions more less) the tire is basically gone. What wheels specs where you running?