Need Advice: Track Day - Rear wheels like to dance during high-speed braking

Gansan

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The dancing under braking is due to the stability control. Turn it off (hold the button down for several seconds) until it says it's completely off. I did this procedure from willimo:

I am topping this ancient thread because according to the manual, you can only turn the VSA all the way off in R+ mode, and you simply hold the VSA button down for 15s, until the dash says "VSA is completely off!"
There is another super complicated procedure that some people are using but the simple one above worked for me to stop the braking dance.
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ImTheStatMan

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Don't think an alignment itself will fix the issue. Pretty sure this is from changes in toe while the rear wheels are being unloaded during hard braking. I believe this is why Honda stiffened the rear lower B arm/bushing on the 2020s - less dynamic toe change. Interesting how one member noted elimination of the issue from upgrading rotors and pads - a big difference in brake bias could cause the issue.
I have upgraded pads in the front only, so I’m leaning towards bias or dynamic toe. I do recall Matt Farah mentioning this issue in his review (at the same track, Road Atlanta, coincidentally).
The dancing under braking is due to the stability control. Turn it off (hold the button down for several seconds) until it says it's completely off. I did this procedure from willimo:



There is another super complicated procedure that some people are using but the simple one above worked for me to stop the braking dance.
I did do this
 
OP
OP

ems657

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Thank you all for the great inputs. I also completely turned off the annoying stability control before each session (by holding the button for 5 seconds). :)
 

Lust

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Don't think an alignment itself will fix the issue. Pretty sure this is from changes in toe while the rear wheels are being unloaded during hard braking. I believe this is why Honda stiffened the rear lower B arm/bushing on the 2020s - less dynamic toe change. Interesting how one member noted elimination of the issue from upgrading rotors and pads - a big difference in brake bias could cause the issue.
Wonky toe will definitely cause squirming on the track. I've encountered it before. You really want to have minimal to no toe in the rear and 0 toe up front to a little toe out.

I will personally be running 0 toe all around. Getting the RV6 suspension components will help eliminate dynamic changes in the toe under load.
 

Gansan

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Thank you all for the great inputs. I also completely turned off the annoying stability control before each session (by holding the button for 5 seconds). :)
No, I think you have to hold it down until it enters a second mode. The first mode you entered doesn’t completely disable it.

edit: ok, I tested it and my estimate is about 7 seconds, which means you probably did it right.
 
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ImTheStatMan

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No, I think you have to hold it down until it enters a second mode. The first mode you entered doesn’t completely disable it.
Can’t speak for OP but I turned off the second mode (R+ mode, hold for 10+ seconds until it says VSA fully off). This didn’t get rid of the problem.
 

Gansan

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Can’t speak for OP but I turned off the second mode (R+ mode, hold for 10+ seconds until it says VSA fully off). This didn’t get rid of the problem.
I edited my post above, but I believe you. For me it really did make the braking a lot more stable. The wiggling I’m referring to was a very harsh and clearly artificial thing and not the chassis naturally acting the way it does.
 

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You don't need VSA fully off to get rid of the squirm. I ran a 1:43 at Laguna with VSA partial off.

 

ImTheStatMan

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I edited my post above, but I believe you. For me it really did make the braking a lot more stable. The wiggling I’m referring to was a very harsh and clearly artificial thing and not the chassis naturally acting the way it does.
OK thanks. In my case, I wouldn’t describe the movement as harsh. It is unsettling though as it requires some steering input to counter and, for me anyways, only occurs in the heaviest braking zone.
 

Lust

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OK thanks. In my case, I wouldn’t describe the movement as harsh. It is unsettling though as it requires some steering input to counter and, for me anyways, only occurs in the heaviest braking zone.
You could be encountering split mu braking. If you're braking so hard that you're engaging ABS, this could definitely throw things off. Which brake pads are you running front and rear?
 


ImTheStatMan

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You could be encountering split mu braking. If you're braking so hard that you're engaging ABS, this could definitely throw things off. Which brake pads are you running front and rear?
Project Mu club racers up front, OEM rear
 

Lust

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Project Mu club racers up front, OEM rear
It might be worth it to try matching pads front and rear. I've had success using PMU CR rear pads and ST43 pads up front, though usually not recommended to have different pads F/R
 

ImTheStatMan

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It might be worth it to try matching pads front and rear. I've had success using PMU CR rear pads and ST43 pads up front, though usually not recommended to have different pads F/R
Thanks, I was kicking around that idea and I’ll definitely do it now. Next track day is in a month, I’ll report back on whether or not this solves the problem.
 

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Don't think an alignment itself will fix the issue. Pretty sure this is from changes in toe while the rear wheels are being unloaded during hard braking. I believe this is why Honda stiffened the rear lower B arm/bushing on the 2020s - less dynamic toe change. Interesting how one member noted elimination of the issue from upgrading rotors and pads - a big difference in brake bias could cause the issue.
I've experienced the issue as well. Based on your suggestion, would these potentially correct the issue?

https://www.rv6-p.com/rv6-fk8-trailing-arm-spherical-bushing.html
 

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