Lowering and Suspension Geometry

underdonk

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'21 Supra 3.0 Premium
There is a lot of discussion in the forums re: bump oversteer on these cars and the differences between the '20 and '21 models in regards to suspension. There are also a few really solid YouTube videos discussing this phenomenon, how certain people have tried to address it, and some speculation re: potential design issues and non-design-related causes, noting that the issue got worse when cars were lowered. There's also a good thread on the forums in which some folks are experiencing the front of their car pulling to one side from a stop under power, and at least one user who experienced it to a greater degree after lowering their vehicle. In addition, there are a few examples of lowered vehicles having an issue with sway bars rubbing on tie rods enough to cause them to snap. At this point, all of this information leads me to believe that lowering one of these cars simply through the act of replacing springs is not advisable at this time. The benefits don't seem to outweigh the reported problems and unknowns until this can all be hashed out. Can anyone tracking their cars comment on the benefits vs. any of these issues? I have a set of aFe sway bars and Eibach springs on the way and I'm thinking about holding off on the springs until some of these issues are hashed out. I personally think a post-lowering or post-delivery alignment to ensure the car is within factory specs or setup for the track will do a lot to help most of these issues, but only time will tell as more data comes in. I'm not sure I want to risk it until them. Note I'm having none of these issues on my '21.
 

OneTimeAccount

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2021 Supra 3.0 Premium - Turbulance Gray
Interesting observations. Only negative I have noticed was some rattling from improper installation of my springs. I have only tracked mine once on lowering springs (Swift) and it was in the rain without a proper alignment done yet, so I can't say if any of that is true.

I will be installing some SPL lower control arms and getting an alignment before my next track day in two weeks. I will report my findings. I am also curious if lowering springs hurt track performance. If they do, I will revert back to stock since I care way more about performance and track speed than aesthetics.
 

MisterSkiz

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2021 Toyota Supra, 2008 Lexus IS-F
I wish we had a true tested/configured application for suspension for this car. Many of the lowering springs are not matched to the shock valving which result in a bouncy ride or in the worst case - result in losing mechanical grip.

Swift is supposed to be one of the top end Japanese springs that actually are tested and lower the car with fewer coils than the competition.

The GT4 runs KW suspension, but I was not able to pull up any configuration settings for it:
Suspension, Steering, & Brakes
Front suspensionMacPherson strut
Rear suspensionMultilink
Shock absorbersKW adjustable racing dampers
SteeringElectric, rack and pinion
Brakes (Front)Six-piston racing calipers (Brembo), Steel 390mm brake discs
Brakes (Rear)Four-piston racing calipers (Brembo), Steel 355mm brake discs
Tires Front/Rear305/660-18 Front / 305/660-18 Rear (Pirelli)
WheelsOZ five-hole 11 x 18in
 
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