Track forum general chit chat

[uncle ben]

Looking for some suggestions on what to try.

My setup,

I’m running 265front, 285 rear Goodyear supercar three tires, mcs 2wnr, vorshlag camber plates, spl rear toe links. Mcs is set at 8comp/8rebound front and rear. Front camber at -3. Running tires at 31psi hot.

My problem,

Still overdriving my front tires. Rear hooks up great and I almost never loose traction in the rear. WOT mid corner and exit, rear is planted. Front tires wearing on outside shoulder quite badly, and even though I feel like I’m using the whole tire, I still feel like the car is slow to rotate and turn in. Also as temps increase and the day warms up, the front begins to understeer and push even worse.

Really hoping you guys can make a few suggestions on where to make some changes. Thanks!


* I was thinking of adding another 1/2 degree of negative camber and increasing the rear compression and rebound to 12/12

[SYT_Shadow]

Originally Posted by uncle ben

Looking for some suggestions on what to try.

My setup,

I’m running 265front, 285 rear Goodyear supercar three tires, mcs 2wnr, vorshlag camber plates, spl rear toe links. Mcs is set at 8comp/8rebound front and rear. Front camber at -3. Running tires at 31psi hot.

My problem,

Still overdriving my front tires. Rear hooks up great and I almost never loose traction in the rear. WOT mid corner and exit, rear is planted. Front tires wearing on outside shoulder quite badly, and even though I feel like I’m using the whole tire, I still feel like the car is slow to rotate and turn in. Also as temps increase and the day warms up, the front begins to understeer and push even worse.

Really hoping you guys can make a few suggestions on where to make some changes. Thanks!

You need a square setup. There is no reason to run a 265 tire up front when a 295 fits

Run a square 10.5 setup with 275/285/295 square tires. Your understeer will go away

Front tires do most of the braking and most of the turning. You have a platform that's more or less 50/50 in terms of weight distribution. Your rear tires are almost on vacations. Look at any BMW OEM racecar: every single one uses square tire setups

[uncle ben]

Originally Posted by SYT_Shadow

You need a square setup. There is no reason to run a 265 tire up front when a 295 fits

Run a square 10.5 setup with 275/285/295 square tires. Your understeer will go away

Front tires do most of the braking and most of the turning. You have a platform that's more or less 50/50 in terms of weight distribution. Your rear tires are almost on vacations. Look at any BMW OEM racecar: every single one uses square tire setups

Thanks. I think that will be my next upgrade. I’ve been reading the 18” square thread and will most likely be ordering a set of 18” square wheels.

You are right about my rear tires being on vacation, they have 4 track days vs my fronts 2 track days, yet show 1/2 the wear.

[SYT_Shadow]

Originally Posted by uncle ben

Thanks. I think that will be my next upgrade. I’ve been reading the 18” square thread and will most likely be ordering a set of 18” square wheels.

You are right about my rear tires being on vacation, they have 4 track days vs my fronts 2 track days, yet show 1/2 the wear.

Fortunately by now the fitments are well known. A ET36 will only require a 15mm spacer, vs a 20mm spacer with a ET40 fitment. Either of those is a direct fit in the rear.

Go for 10.5, it's the goldilocks fitment for these cars!

[EGbeater]

Originally Posted by SYT_Shadow

You need a square setup. There is no reason to run a 265 tire up front when a 295 fits

Run a square 10.5 setup with 275/285/295 square tires. Your understeer will go away

Just wanted to mention if you want to run bigger tires with maximum heat capacity for more than just 1–3 hot laps, and if you're okay with modifying the front fender liners + limiting your steering lock to about 2/3 and slightly Dremeling/shaving the inside edge of the attachment point of the front bumper cover to the (steel) fender, 315/30-18s or 305/30-19s square on 11" wheels works too! Speaking from experience with both fitments (with MCS 1WNR, 4.1 degrees negative camber in front; you need to run a very short front coilover spring—120mm/4.72", no helper—to make the 305/30-19s work).

[SYT_Shadow]

Originally Posted by EGbeater

Just wanted to mention if you want to run bigger tires with maximum heat capacity for more than just 1–3 hot laps, and if you're okay with modifying the front fender liners + limiting your steering lock to about 2/3 and slightly Dremeling/shaving the inside edge of the attachment point of the front bumper cover to the (steel) fender, 315/30-18s or 305/30-19s square on 11" wheels works too! Speaking from experience with both fitments (with MCS 1WNR, 4.1 degrees negative camber in front; you need to run a very short front coilover spring—120mm/4.72", no helper—to make the 305/30-19s work).

I don't want to rain on your parade, it is always impressive to fit a 11" 305/315 up front!

The thing is, tire fitment isn't a wider-takes-all situation.
4 degrees of front camber is detrimental to handling, as is such a short front spring. 5" already a compromise, and 4.7 is worse.
With a 10.5" wheel and a 295 tire you don't need to run more camber than what is strictly needed and you can retain more suspension travel

Remember camber is needed to stabilize/optimize temperatures in the tire in turns, but it is detrimental to our braking stability and performance. This is why 'race' camber plates typically have caster adjustment and we will strive to maximize it: by maximizing caster we increase dynamic camber and are able to run less static camber. To say it differently, you have more camber when turning than when going straight which helps reduce the straightline disadvantages of camber while retaining the necessary camber in turns to keep the tires happy

[uncle ben]

What would be an indicator that you are running too much negative camber on the front? What would you experience?

Inner shoulder wear on tires?

Poor straight line stability?

Increased brake distance?

Loose back end?

Just curious. Thanks!

[Suds]

On my 2019 M2 I am running camber at -3.7 front and -2.2 rear.
My front tires are still wearing to much on the outside shoulders but I am running a square set up. So 4-5 track days and the fronts go to the rear for a few more days.

On my 2019 M4 I never got more than 5 track days on an offset set of tires.
This was switching the tires across the axle too.

[SYT_Shadow]

Originally Posted by uncle ben

What would be an indicator that you are running too much negative camber on the front? What would you experience?

Inner shoulder wear on tires?

Poor straight line stability?

Increased brake distance?

Loose back end?

Just curious. Thanks!

braking would degrade, tire life and performance would degrade, but then again none of us are pro pilots and I don't think it would be easy to tell the difference. The same as it isn't easy to tell the difference between a set of 295 tires and another set at 305

It's not like you run 4 degrees of camber and a 4.7" spring and the car starts trying to kill you. I expect the performance degradation is small, same as the expected performance increase between a 305 and a 295 tire is also small.

I'm sure data would tell the story and it's why people have to invest massively to get 11" to fit properly

[SYT_Shadow]

Originally Posted by Suds

On my 2019 M2 I am running camber at -3.7 front and -2.2 rear.
My front tires are still wearing to much on the outside shoulders but I am running a square set up. So 4-5 track days and the fronts go to the rear for a few more days.

On my 2019 M4 I never got more than 5 track days on an offset set of tires.
This was switching the tires across the axle too.

In an M car the rear tires are almost on holidays!

[EGbeater]

Originally Posted by SYT_Shadow

I don't want to rain on your parade, it is always impressive to fit a 11" 305/315 up front!

The thing is, tire fitment isn't a wider-takes-all situation.
4 degrees of front camber is detrimental to handling, as is such a short front spring. 5" already a compromise, and 4.7 is worse.
With a 10.5" wheel and a 295 tire you don't need to run more camber than what is strictly needed and you can retain more suspension travel

Remember camber is needed to stabilize/optimize temperatures in the tire in turns, but it is detrimental to our braking stability and performance. This is why 'race' camber plates typically have caster adjustment and we will strive to maximize it: by maximizing caster we increase dynamic camber and are able to run less static camber. To say it differently, you have more camber when turning than when going straight which helps reduce the straightline disadvantages of camber while retaining the necessary camber in turns to keep the tires happy

I understand your points and considered this before going down this road. I talked to several race shops that have built and campaigned successful BMW track cars; some insisted basically what you're saying (camber beyond about 3.8 degrees has diminishing returns or lap times fall off the other way, due to reducing braking performance or degrading the inside tire's grip) and other techs/trackside support people said their experience showed that as much as 5 degrees of front camber can be faster than less camber.

I think as little as 3.5 degrees of negative camber will work with 315/30-18s on 11"-wide wheels, because that's what I had with my old Vorshlag camber plates, when I first tested this fitment on track with old Hoosier A7s in 315/30-18... but I can't say definitively, with FRESH tires, because those hand-me-down tires had well worn/rounded outer shoulders.

I'm not an engineer, and not a good enough of a driver to provide data points on lap times with the wider tire setup vs the narrower ones. I do believe that all else equal, the larger/wider/heavier tire will have better heat capacity over a narrower one, and my rudimentary pyrometer testing immediately after hot lapping on 200TW RE71Rs last season indicates that I tend to overdrive the tires (both front and rear), so perhaps I *personally* will be faster on laps 2 or 3 with wider tires, because I typically can't crack off a killer 1st hot lap during time trials competition while the tires are still cool/below being overheated... the trick for me to be faster is having my brain to be "warm" and my driver confidence peaked before the tires are cooked.

The highly variable human component (me) ruins all science.

[jfritz27]

Originally Posted by EGbeater

I understand your points and considered this before going down this road. I talked to several race shops that have built and campaigned successful BMW track cars; some insisted basically what you're saying (camber beyond about 3.8 degrees has diminishing returns or lap times fall off the other way, due to reducing braking performance or degrading the inside tire's grip) and other techs/trackside support people said their experience showed that as much as 5 degrees of front camber can be faster than less camber.

I think as little as 3.5 degrees of negative camber will work with 315/30-18s on 11"-wide wheels, because that's what I had with my old Vorshlag camber plates, when I first tested this fitment on track with old Hoosier A7s in 315/30-18... but I can't say definitively, with FRESH tires, because those hand-me-down tires had well worn/rounded outer shoulders.

I'm not an engineer, and not a good enough of a driver to provide data points on lap times with the wider tire setup vs the narrower ones. I do believe that all else equal, the larger/wider/heavier tire will have better heat capacity over a narrower one, and my rudimentary pyrometer testing immediately after hot lapping on 200TW RE71Rs last season indicates that I tend to overdrive the tires (both front and rear), so perhaps I *personally* will be faster on laps 2 or 3 with wider tires, because I typically can't crack off a killer 1st hot lap during time trials competition while the tires are still cool/below being overheated... the trick for me to be faster is having my brain to be "warm" and my driver confidence peaked before the tires are cooked.

The highly variable human component (me) ruins all science.

Not sure if my thinking is off here, but would it not also be true that as the tire gets wider, the amount of negative camber needed to achieve a given effect (relative to the width) lessens? Imagine the extreme example of an imaginary front tire that is 3 feet wide and miraculously fits. In my head it seems that you simply wouldn't need as much negative camber to utilize the grip of such a wide tire. (I recognize this extreme example ignores some other geometry changes in the suspension that are probably relevant)

[PrimeBMW]

I thought I would post here as my Pirelli scrubs might be a perfect fit for some. I will have 305/645/18 front and 325/660/18 rear scrubs available. Typically 4-6 heat cycles with lots of rubber left. *wheels not included 😉
I'm not sure on price

[M1500Z]

Camber discussions seem to distill down to the spec or number—I guess to make it easy to digest over the internet. But there's a lot of context around the system and variables that should be considered when discussing that number. If negative camber is largely used to offset the positive camber gained from body roll in a corner, how can we compare numbers without having an idea of how much grip a car has (tire, aero, etc.) and how much it can resist that roll (spring, anti-roll bar)?

I'm not implying that people don't understand this, just that providing those details with your experience will help color the conversation.

My M2 specific data point

• -3.2º front -2.4º rear
• 780 lb front 640 lb rear springs
• M2 CS R sways set to soft
• Falken RT660 275/35 square

I was previously running -3.6º and the inside shoulders were wearing much too fast so I've reduced the camber close to a .5º and am trying again. This was with a 0 toe setup. That higher camber number was a carryover from when I was running Öhlins R&T with a 550 lb front spring and the car was rolling a bit more. My relatively inexperienced opinion is that while there is an optimum setting, being within a couple tenths of a degree is prob not going to amount to a significant difference in wear and performance.

[uncle ben]

What are “scrubs” and why do people sell/buy them?

[Driver407]

Originally Posted by uncle ben

What are “scrubs” and why do people sell/buy them?

Lightly used slick tires. Usually from qualifying or testing runs. Then teams or shops sell off the old tires. Saves hobbyist hundreds of dollars to taste that juicy juicy slick life.

[D_SheerDrivingPleasure]

Originally Posted by irokdayellup

Lightly used slick tires. Usually from qualifying or testing runs. Then teams or shops sell off the old tires. Saves hobbyist hundreds of dollars to taste that juicy juicy slick life.

How consistent is the quality?

Also, with all that grip, is oil starvation a concern?

[sly1types]

Originally Posted by D_SheerDrivingPleasure

How consistent is the quality?

Also, with all that grip, is oil starvation a concern?

The stock system is rated to 1.3G. On DHs I will hit 1.3, but I have ran logs never seen any oil pressure drop.

Bimmerworld has a longer sensor/spacer that allows extra capacity, I think it will bring the car up to almost 8qts. This allows the car to go up to 1.4G.

Next time I change the oil I will be adding this sensor.

[D_SheerDrivingPleasure]

Originally Posted by sly1types

The stock system is rated to 1.3G. On DHs I will hit 1.3, but I have ran logs never seen any oil pressure drop.

Bimmerworld has a longer sensor/spacer that allows extra capacity, I think it will bring the car up to almost 8qts. This allows the car to go up to 1.4G.

Next time I change the oil I will be adding this sensor.

Yeah, I've been waiting to install the oil sensor/spacer. My first attempt failed b/c I was unable to remove the studs. I'll try again soon. Until then, no slicks.

[sly1types]

Originally Posted by D_SheerDrivingPleasure

Yeah, I've been waiting to install the oil sensor/spacer. My first attempt failed b/c I was unable to remove the studs. I'll try again soon. Until then, no slicks.

What's was the issues? Can't you just double nut it? Do you have a base model? Kind of looks like the new sensor is longer then a thicker spacer?

What is your plan for the second attempt?

Without the sensor and slicks you are right at the limit…

[D_SheerDrivingPleasure]

Originally Posted by sly1types

What's was the issues? Can't you just double nut it? Do you have a base model? Kind of looks like the new sensor is longer then a thicker spacer?

What is your plan for the second attempt?

Without the sensor and slicks you are right at the limit…

I have a zcp. The oem studs are too short to accommodate the spacer.

I tried double nutting but the studs use flange nuts which made it impossible for my wrench to grab securely. I also tried my bolt extractor tool but the studs are thin like toothpicks and I couldn't get that to work either. My next attempt will use a vice grip to manhandle out the old studs.

I have limited patience, skill and confidence when it comes to this stuff. I'm sure you'll be fine double nutting.

[jfritz27]

Originally Posted by D_SheerDrivingPleasure

I have a zcp. The oem studs are too short to accommodate the spacer.

I tried double nutting but the studs use flange nuts which made it impossible for my wrench to grab securely. I also tried my bolt extractor tool but the studs are thin like toothpicks and I couldn't get that to work either. My next attempt will use a vice grip to manhandle out the old studs.

I have limited patience, skill and confidence when it comes to this stuff. I'm sure you'll be fine double nutting.

D -- did you try the wheel stud removal tool? Is that what you were referring to? If you have access to a small torch, applying some heat to where the stud threads in to the pan (30-45 sec) may help get them out. Or just getting some appropriately sized non-flanged nuts from hardware store to make double nut method easier.