Toyota Supra, Ruined by Bump Steer?!?!

kona61

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Thank you for sharing this, my conclusions are that the more you lower your car the higher the chance of experiencing bumpsteer but this can be fixed by having a space on the control arm (or new control arms as mentioned in the video)

The good thing is that all these solutions aren't that hard to fix, they'll take time and it sucks that owners will need to dish $ out to fix the problem, but every car has a weird flaw (e9x has rod bearings, e46 has the fractured chassis problems etc..) and if this is the only problem then that's good news
I'm still doubtful it's true bumpsteer. I can't imagine that BMW would make such a large oversight on the CLAR platform. I'm sure that it would have been caught in prototypes, testing, and even just the principles they use to build these cars.
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I'm still doubtful it's true bumpsteer. I can't imagine that BMW would make such a large oversight on the CLAR platform. I'm sure that it would have been caught in prototypes, testing, and even just the principles they use to build these cars.
According to Matt Farah the 2021 doesn't have any bump steer thanks to the suspension changes
 

kona61

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According to Matt Farah the 2021 doesn't have any bump steer thanks to the suspension changes
He's wrong. Bump steer is a result of suspension geometry. Revised bump stops would only help if it prevented the suspension from fully cycling, which I highly doubt they did and the rest of the changes were just tuning and electronics related. Also, it seems that all the bump steer concerns occur from hard braking at very high speeds, something you never encounter in Tujunga/ACH/AFH, etc.
 

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a Japanese pro driver describes it at 22:17



he's a pro driver so i guess pinpointing that the "rear brakes had been activated" is accurate. he then does a "tail wagging the dog" kinda motion, quite like how motor trend described it. Seems like a traction control/brake vectoring issue (as in a "software" issue).
at 23:27 he further explains that the rear hit a bump and lifted a bit and that "triggered the [traction] control".

He's wrong. Bump steer is a result of suspension geometry. Revised bump stops would only help if it prevented the suspension from fully cycling, which I highly doubt they did and the rest of the changes were just tuning and electronics related. Also, it seems that all the bump steer concerns occur from hard braking at very high speeds, something you never encounter in Tujunga/ACH/AFH, etc.
I totally agree.
 

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So really to resolve the issue we are going to have to hope we can get some kind of softgware update that doesn't also require our cars to be retuned and probably bench flashed if they're already tuned?
 

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From his explanation, I think if you take away some of the suspension travel by dropping it and adjusting the toe alignment then you should be able to reduce it.
I was thinking the same thing, without going too aggressive on rear toe, I would expect with less travel (lowered car & stiffer springs) and a bit more toe-in for the rear, when the suspension begins to travel have enough toe-in under load to not go neutral or worst toe-out with low load (under barking scenario).

This may be viewed as band-aid approach, and I'm certainly not qualified experience wise to come up with a permanent engineering control fix.
 

trakday

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This is a real issue, ive tracked my car 6x in 2020.... its dissapointing.
 

Bflood

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This is a real issue, ive tracked my car 6x in 2020.... its dissapointing.
Not to insult but have you tried anything to fix it? From listening to Jackie, and judging from you avatar, your stance looks to be too low.
Are you running coilovers or just springs? Have you upgraded any of your other suspension components to SPL or something comparable?

This car was not meant to be seriously tracked out of the gate and will take money, time, and patience to dial it in.
 

trakday

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Not to insult but have you tried anything to fix it? From listening to Jackie, and judging from you avatar, your stance looks to be too low.
Are you running coilovers or just springs? Have you upgraded any of your other suspension components to SPL or something comparable?

This car was not meant to be seriously tracked out of the gate and will take money, time, and patience to dial it in.
I am running the HKS height Adjustable Sleeve over's, The springs have a higher rate. Doesnt matter because the car had the same bump steer anddddd Numb steering feel before the upgrades. Now with the upgrades...car is enhanced, feels tighter but the issues are still there. No reason to go deeper into modifying a car in my case if the steering is NUMB and Bump steer is there. The entire Subframe in the car needs to be reworked. SPL Kinematics will help but to a certain degree.
Like you said, "this car isnt meant to be seriously tracked out of the gate" - This is somewhat true, but ive been tracking cars, different cars for over 16 years now and this platform is not the best out of the box by any means! Mazda Miata's out of the box, especially the newer RF's are Leagues ahead from this chassis when it comes to how a car should feel on the circuit. Even the Subaru BRZ/FRS feel much more livelier, you can FEEEEEEEEL what the car is doing....that is what its about!
 

trakday

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NYCDriver

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a Japanese pro driver describes it at 22:17



he's a pro driver so i guess pinpointing that the "rear brakes had been activated" is accurate. he then does a "tail wagging the dog" kinda motion, quite like how motor trend described it. Seems like a traction control/brake vectoring issue (as in a "software" issue).
at 23:27 he further explains that the rear hit a bump and lifted a bit and that "triggered the [traction] control".



I totally agree.
I've tracked the car multiple times and noticed this only happened once to me at Palmer Motorsports coming out of the high speed straight away into a corner going ~130mph. I came into the turn bad and the rear shook as described. I also noticed It doesn't always happen and didn't see it at any other tracks.
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