Squirrely from high speed braking question

[intercool]

I noticed my E92 getting squirrely from high speed braking before turn 10 at Road Atlanta. If I'm below 140mph, it brakes great. Over ~140mph, it got squirrely on me a couple of times. The instructor thought it was probably from my suspension. Any suggestions?

E92 fairly stock suspension with 3 degrees camber on Nitto tires.
Stoptech ST40's with track pads.

[roastbeef]

Get some monoballs. Should help quite a bit.

[redpriest]

Originally Posted by intercool

I noticed my E92 getting squirrely from high speed braking before turn 10 at Road Atlanta. If I'm below 140mph, it brakes great. Over ~140mph, it got squirrely on me a couple of times. The instructor thought it was probably from my suspension. Any suggestions?

E92 fairly stock suspension with 3 degrees camber on Nitto tires.
Stoptech ST40's with track pads.

Dinan monoballs, like roastbeef said, and problem solved.

[doogee]

It's most likely your struts/springs combo. What kind of mileage are on them?

Monoballs are not required.

I had the same issue until I swapped my stock suspension out for some good coilovers.

[intercool]

Previous owner did these Mods:
Vorschlag Camber plates >>> -3.3 negative camber on front end
H&R Sport springs
HD Bilstein shocks with EDC function.
Powerflex Race bushings installed in most front and rear postions.
Bimmerworld Precision Front Lower Control Arm Bearing installed.
Stop ST40 BBK in all four corners.


Excuse my lack of expertise in suspension setups. Do I need monoballs with the above setup?
I'm also about to install Bilstien Clubsport coilovers, so wondering if I need to hold off on the monoballs or they are must haves.

[dparm]

Don't take this personally, but are you sure it isn't a technique problem? I used to have problems with this until I focused on braking "correctly".

[intercool]

straight line braking. Also did same thing when an instructor drove it...

And not taking anything personal, my on track experience isn't as advanced and i have no ego.

[elim11]

Could it be due to aggressive alignment. If you think about it, with -3.3 camber, you have less tire contact patch against the ground?

I remember having some similar issues when first getting some more aggressive alignment (-2.7 camber front). I asked my alignment guy and thats what he explained.

But I think it is a potentially a multi-factor problem: Alignment, driver brake technique, suspension pieces, etc.

For me, additional track time and brake technique solved a majority of it, and really just knowing what to expect and how to avoid it.

[cenix]

I would check alignment and tire pressures first. Also, just a thought, if you're slowing the car from 140 mph, depending on how much speed you're reducing to, you're transferring a lot of weight to the fronts and the rear will get light.

[cherry-m3]

Originally Posted by intercool

straight line braking. Also did same thing when an instructor drove it...

And not taking anything personal, my on track experience isn't as advanced and i have no ego.

All the things listed above can be factors. Monitor tire pressure and check track conditions on brake zones as they can get greasy and filled with rubber.

Proper brake technique especially with grabby brakes is also important.. think of the braking zone as 12345 in terms of least to most pressure.

Also you stated having a BBK upfront, are you stock on the rears?

[warp10]

I think you are running to much camber. also i agree braking technique can be a factor here.

Do you have in car video or data we can see?

[Candide13]

OP, do you have some more details about what you describe as "squirrely"?

[intercool]

Thanks for the input all! I will work on the most important mod, improving the driver and then see if the coilover suspension and monoblocks make a difference in the further future.

[Redd]

Some twitchiness under hard braking is normal with a lot of cars. Car shd not swap ends though. Could also be worn shocks causing too much weight transfer to the front.

[VictorH]

What exactly do you mean by the car is squirrelly? In my car with stock calipers but running track pads my car at RA prior to 10a and prior to turn 1 used to feel uncomfortable same at VIR prior to turn 1 and at the end of the back straight.

If you are experiencing the rear of the car "dancing" around but still tracking relatively straight that's not that uncommon. I don't think it's a "braking technique" issue, I suspect your under maximum threshold braking and the car just feels a bit wobbly in back. Not uncommon some cars do it and some don't. I've felt the same sensation in late model Porsches as well. Slightly unnerving but not really a problem.

Are you still tracking relatively straight under heavy braking? I honestly don't think the mono-ball upgrade will have any bearing on straight-line braking performance. If you trail brake into some of those corners listed above it will be a bit more solid (with the mono-ball upgrade) but I don't think there's any detectable difference in a straight line.

[intercool]

Exactly. Back end dancing around but tracking relatively straight. definitely unnerving.... lol

[roastbeef]

Originally Posted by intercool

Previous owner did these Mods:
Vorschlag Camber plates >>> -3.3 negative camber on front end
H&R Sport springs
HD Bilstein shocks with EDC function.
Powerflex Race bushings installed in most front and rear postions.
Bimmerworld Precision Front Lower Control Arm Bearing installed.
Stop ST40 BBK in all four corners.


Excuse my lack of expertise in suspension setups. Do I need monoballs with the above setup?
I'm also about to install Bilstien Clubsport coilovers, so wondering if I need to hold off on the monoballs or they are must haves.

no monoballs, the precision fcab's are essentially the same thing.

what pad compounds are you running?

[dparm]

Originally Posted by intercool

straight line braking. Also did same thing when an instructor drove it...

And not taking anything personal, my on track experience isn't as advanced and i have no ego.

At your next track day, try adjust your braking technique to see if that helps. Just focus on that for an entire session.

I used to have a bad habit (probably from driver's ed) of just mashing the pedal as hard as I could. This certainly works, but if you come off the gas too fast and get into the brakes too fast, the weight transfer is very abrupt and unsettles the car. I found that being a bit less violent made a world of difference, but it was tough to condition my foot not to just slam the pedal.

[bigjae1976]

I got the same thing in my E90 with the stock brakes and same pads front and rear. Went away with a 4 wheel BBK. I suspect that you need a little less front bias. One time, I ran pagid yellows on front, blacks on the back wit the stock brakes and the car felt fine. The pagid blacks have more bite and torque than the yellows.

[admranger]

What tires are you running on track? I've had the squirrelly feeling when I was on full tread depth RA-1s (putting a heat cycle in the rain tires back in the day). If your tires are near full tread depth, you can get this feeling.

bigjae1976 is spot on with brake bias perhaps being the issue. Since your instructor had the same issue (and not all "instructors" are the same quality, but we'll assume yours was competent), brake bias may be the cause assuming it isn't tires.

[cherry-m3]

Could also be from the suspension dipping under maximum braking. Stiffer springs and shocks should help with that.

[bigjae1976]

Originally Posted by roastbeef

Get some monoballs. Should help quite a bit.

ROFL! ...that's messed up!

Hopefully others get the unintended joke. ?