[AWC-F87]

Hey guys does anyone experience the car wagging a little on track under heavy braking? What's the solution? 2018 m2 on v3s, hawk track pads, lines and motul fluid.

I notice under very high speed hard braking I feel this.

[bentom2]

Originally Posted by AWC-F87

Hey guys does anyone experience the car wagging a little on track under heavy braking? What's the solution? 2018 m2 on v3s, hawk track pads, lines and motul fluid.

I notice under very high speed hard braking I feel this.

Yes, I noticed this on stock suspension. Was a bit disconcerting in 140mph braking zones.

I did front torque arm bushings and rear toe links with my coilover install, and one of them settled the rear of the car down under heavy braking. Since I did them all at once, I can only speculate, but I’d blame the rubber bushings in the rear toe links allowing the car to toe out and allow it to wag a bit.

Hopefully someone that was more methodical with their suspension upgrades can confirm.

[ASAP]

Similarly... has anyone noticed the car wags on acceleration?

If you do a quick acceleration run at higher RPMs from say 30-60, the car will wiggle and the rear end will go side to side... as if the rear arms are just shifting weight from one side to the other.

[Kohner86]

I feel it on both heavy breaking and acceleration on my stock M2C. While I suppose it's not really supposed to be doing that it does add to the fun and squirrelly personality the car has.

[AWC-F87]

I don't notice the wag under acceleration only hard braking.
Coming down the front straight of big willow at 140 and threshold braking into trailing for turn 1 it is not a good feeling having the car wag around.

I'm curious if anyone has felt a difference with suspension settings, stiffer/softer?

I may start looking into more rigid bushings as well.

[kpaso]

Were you running full DSC off? I've heard that this doesn't happen with all nannies off, but it happens whenever they are on.

I get it often as well with Euro MDM on under heavy braking sometimes.

[AWC-F87]

Originally Posted by kpaso

Were you running full DSC off? I've heard that this doesn't happen with all nannies off, but it happens whenever they are on.

I get it often as well with Euro MDM on under heavy braking sometimes.

I run in sport. Not sport plus with everything off. I have yet to get the car on a skid pad to really drift it and feel how it slides. Until then I won't run a high speed track like willow with everything off. Personally I don't think that will make the difference.

I am talking about hard breaking. 140 to 70-80mph in a second or two. Threshold braking.

It's not scarey, but it's not an amazing feeling having the car wag a little. Especially while steering with one hand to down shift with the other

[Caduceus]

Originally Posted by AWC-F87

I run in sport. Not sport plus with everything off. I have yet to get the car on a skid pad to really drift it and feel how it slides. Until then I won't run a high speed track like willow with everything off. Personally I don't think that will make the difference.

I am talking about hard breaking. 140 to 70-80mph in a second or two. Threshold braking.

It's not scarey, but it's not an amazing feeling having the car wag a little. Especially while steering with one hand to down shift with the other

Send it for a wheel alignment and check the rear toe. This is a symptom of insufficient rear toe-in. There are other causes, of course, but this is one of the more common.

[kpaso]

Originally Posted by AWC-F87

I run in sport. Not sport plus with everything off. I have yet to get the car on a skid pad to really drift it and feel how it slides. Until then I won't run a high speed track like willow with everything off. Personally I don't think that will make the difference.

I am talking about hard breaking. 140 to 70-80mph in a second or two. Threshold braking.

It's not scarey, but it's not an amazing feeling having the car wag a little. Especially while steering with one hand to down shift with the other

Yea what you're describing is exactly what I was reading about in another thread. It goes away when everything is off, which confirmed for that OP that it was from the traction control system.

It also happens to me sometimes under heavy braking at Laguna Seca or Thunderhill, at the same level of braking, and I have a proper track alignment as well.

[AWC-F87]

Originally Posted by kpaso

Yea what you're describing is exactly what I was reading about in another thread. It goes away when everything is off, which confirmed for that OP that it was from the traction control system.

It also happens to me sometimes under heavy braking at Laguna Seca or Thunderhill, at the same level of braking, and I have a proper track alignment as well.

Very interesting. I may need to give that a try! I will be back at big willow next month.

I'm just not 100% confident you run the car with all traction control off for a full lap yet.

I will at least give it a go into turn 1 at willow and see how it feels to get a baseline.

[kpaso]

Originally Posted by AWC-F87

Very interesting. I may need to give that a try! I will be back at big willow next month.

I'm just not 100% confident you run the car with all traction control off for a full lap yet.

I will at least give it a go into turn 1 at willow and see how it feels to get a baseline.

I hear you. It's not the best feeling when the car squirms under heavy braking, but I have a lot of confidence in BMW's TC systems, so I eventually got used to it.

[UntzUntzUntz]

This reminds of what the Supra is facing with their bump steering issue. Even though OP specified this occurs upon braking, everything else seems to be closely tied together. Issues in the rear surface only when at higher speeds, cars are developed by BMW around the same timeframe, toe seems to be the main culprit. I'm no expert but I speculate maybe a similar engineering mindset was reflected on the M2 when being developed?

[m2cWW]

Originally Posted by AWC-F87

Very interesting. I may need to give that a try! I will be back at big willow next month.

I'm just not 100% confident you run the car with all traction control off for a full lap yet.

I will at least give it a go into turn 1 at willow and see how it feels to get a baseline.

Hey man! I was on Big Willow a few mondays ago. Threshold braking into turn 1 didn't yield waggle- it very well may be the track alignment that is killing you here. I'm running .1 toe in per tire in the rear and -2.4 camber, and -3.2 camber in the front with 0 toe.

Did you experience notable under or over steer on any other turns so we can have a sense of what's happening with your current alignment?

By the same token, I'm not sure what your track experience looks like or what your braking technique looks like- so it may be an initial braking application thing? Did you notice it when you had to brake late on turn 3 into the beginning of the omega?

Did you happen to see your tire temps around when you felt the rear start slipping around?

[AWC-F87]

Originally Posted by m2cWW

Hey man! I was on Big Willow a few mondays ago. Threshold braking into turn 1 didn't yield waggle- it very well may be the track alignment that is killing you here. I'm running .1 toe in per tire in the rear and -2.4 camber, and -3.2 camber in the front with 0 toe.

Did you experience notable under or over steer on any other turns so we can have a sense of what's happening with your current alignment?

By the same token, I'm not sure what your track experience looks like or what your braking technique looks like- so it may be an initial braking application thing? Did you notice it when you had to brake late on turn 3 into the beginning of the omega?

Did you happen to see your tire temps around when you felt the rear start slipping around?

That's rad you were at big willow. I really like that track.

As far as experience this was only my 4th event. BUT I am an ex amateur pro motocross racer. So I am very comfortable going fast, learning lines and pushing things.

You know that's a great point, coming out of turn 2 full throttle and then braking hard late for turn 3 into omega I don't notice it as much. But I'm not going nearly as fast as I am into 1.

My coach was having me brake late for 1. We were passing the first braking cone then trailing off at the second, turn in for the apex then back to full throttle.

I'd have to pull my alignment spec sheet out. But I definitely need more camber. I'm only at 2.9 front that I know. My coach was thinking 3.1-2 for the front. I'm not sure where my toe is at.

I definitely want to sort something out a little so that next month when I head back to big willow I can test and see if something improves.

[richard in NC]

I too notice the tail wagging under hard braking on track. Mostly near threshold from triple digit speeds. What helps is easing into them. Of course that backs up your braking point but the car is better behaved.

A performance shop did suggest a rear toe change for an alignment. In the spring I'll be looking into that along with more track focused pads.

[m2cWW]

Originally Posted by AWC-F87

That's rad you were at big willow. I really like that track.

As far as experience this was only my 4th event. BUT I am an ex amateur pro motocross racer. So I am very comfortable going fast, learning lines and pushing things.

You know that's a great point, coming out of turn 2 full throttle and then braking hard late for turn 3 into omega I don't notice it as much. But I'm not going nearly as fast as I am into 1.

My coach was having me brake late for 1. We were passing the first braking cone then trailing off at the second, turn in for the apex then back to full throttle.

I'd have to pull my alignment spec sheet out. But I definitely need more camber. I'm only at 2.9 front that I know. My coach was thinking 3.1-2 for the front. I'm not sure where my toe is at.

I definitely want to sort something out a little so that next month when I head back to big willow I can test and see if something improves.

Man I hope I get to see you at the track one of these days then! Would love to have another M2 to compare notes with honestly.

Based on what I'm hearing, it's only happening when you are moving a lot of weight from the rear to the front (plenty of downforce coming into turn 1 getting removed from the rear, plus all the weight moving forward). Might have to do with the rear bushings like you said, but it's very possible that it has to do with rear camber (only really able to achieve a notable amount with modified arms back there I think?).

Also, are you running a wing back there or anything like that?

[M2C AW]

I too experience some “squirm” when threshold braking. I see the rear trailing links have some relatively large rubber bushings, similar to the toe links. I think I’ll swap-in a set of the Fall Line links and see if the spherical bearings help..by reducing toe changes under heavy braking.
The M2 has a high center-of-gravity..and a relatively short wheel base...so there’s that too..

[M2C AW]

Lots of squishiness potential here. So between the toe links and these trailing links....lots of opportunity for less squishiness.

[AWC-F87]

Hey guys!

I'm not running big aero. Just a lightweight plastic lip and a m carbon trunk spoiler. If you can even call that a spoiler lol.

No massive bird killer or aggressive front spoiler. I want to find the limit with out aero before I add aero.

As far as easing into the brakes, I suppose I could, but at the rate of speed im talking about it would kill a good lap time. So I'd rather find the culprit and change it.

I plan on running Global time attack one day with this car and I want it dialed before I ever enter a real race.

I'm thinking before my next event on January 23rd I'm going to try and get the thrust bushings and rear toe arms. Then have another alignment done.

[Megator]

Originally Posted by kpaso

Yea what you're describing is exactly what I was reading about in another thread. It goes away when everything is off, which confirmed for that OP that it was from the traction control system.

It also happens to me sometimes under heavy braking at Laguna Seca or Thunderhill, at the same level of braking, and I have a proper track alignment as well.

I run TC off and get the same thing... sometimes its so bad that I need to input steering corrections to keep the car pointed in a straight line.

As others have said short wheelbase + high CG + most of the weight over the front axle = light rear axle = it can move around under braking.

I checked my rear toe and it should be at 0.1-0.15 degrees. Might invest in some toe arms and see if that helps.

[kpaso]

Originally Posted by Megator

I run TC off and get the same thing... sometimes its so bad that I need to input steering corrections to keep the car pointed in a straight line.

As others have said short wheelbase + high CG + most of the weight over the front axle = light rear axle = it can move around under braking.

I checked my rear toe and it should be at 0.1-0.15 degrees. Might invest in some toe arms and see if that helps.

Wow, great to know.

I also wonder if people running -2.5 to -3 rear camber are more inclined to get this with less rear tire contacting the ground under heavy braking in a straight line?

[m2cWW]

Originally Posted by AWC-F87

Hey guys!

I'm not running big aero. Just a lightweight plastic lip and a m carbon trunk spoiler. If you can even call that a spoiler lol.

No massive bird killer or aggressive front spoiler. I want to find the limit with out aero before I add aero.

As far as easing into the brakes, I suppose I could, but at the rate of speed im talking about it would kill a good lap time. So I'd rather find the culprit and change it.

I plan on running Global time attack one day with this car and I want it dialed before I ever enter a real race.

I'm thinking before my next event on January 23rd I'm going to try and get the thrust bushings and rear toe arms. Then have another alignment done.

I think your toe arm situation till make a big improvement...fingers crossed!!