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Motorsport Wheel Alignment Fundamentals

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Discussion and questions related to the course Motorsport Wheel Alignment Fundamentals

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I recently started watching the alignment course and am trying to apply some of the learnings to my wife’s BRZ that she runs in the 86cup in the states. We bought the car in a mild state of ‘tune’ w Tein Flex A, camber plates and a host of other things. I was wondering:

for stock control arms, what should the minimum height be for rear axle (center of axle to fender)? In this car, the static condition has hubs higher than the diff. I am concerned the car is too low. If you can share a good target for front and rear height that would be greatly appreciated. (I realize there are a lot of variables that go I to it)

Hi Friso!

You're right that there are so many parameters it's impossible to give you an answer for your case! Things like suspension travel range, roll centers, combinations of springs and bars, aerodynamics etc etc.

What I would recommend as a starting point is to set the ride height based on your available suspension travel. The first step is to ensure the tyres can not come into contact with inner guards or chassis at full compression (remove springs and bump stops), adjust the lower mount (if you have one) based on this. Then set your ride height such that 1/3 of your available travel is available in rebound and 2/3 available in compression. This ensures you are making use of the available travel you have for the components you have. This is a sensible starting point!

As a reference, the RaceCraft GT86 is set using this approach. With the MCA Red coilovers we have, this give us a setting of ~370mm from the center of the wheel the guard on the rear, which is quite high, but it does give us an appropriate travel range for this car.

Hi Tim -

Thank you for actionable feedback + example! I'll attempt this shortly and report back. FWIW - the car currently sits at about 350mm VS your 370 (i.e. lower).

The car in question came to us with some modifications, one of which I'm suspecting has to do with the occasional snap oversteer: the rear sway bar links appear to be normal length, but the car is lowered a fair bit, with the result that the sway bar is angled up noticeably when static. Add some cornering roll and a bit of curb and the effective spring rate MUST spike as the sway bar transitions from connecting L/R to becoming a hard-stop... fun times.

Friso,

What you mention about the ARB arm going vertical is a good point, if this happens you will indeed make the suspension almost solid. If there is not the ability to shorten or reposition the link then you may need to find another solution.

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