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When to check and set bump steer as well as corner weighin?

Motorsport Wheel Alignment Fundamentals

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Hey guys,

I'm in process of sorting out a build I have been working on for a few years and about to get into alignment setup. First I'll get a close ride height set and from the class it looks like I should set the alignment in this order. Set caster first, followed by camber, and then followed by toe. So should bump steer be checked after all this alignment is set? Then finally corner weighting?

Thanks for any feedback,

Sean

I would suggest "bump steer" be checked, and corrected if required, before ANY of the other setup chacks are made, because if there is an issue the changes may require a suspension redesign and/or steering rack/linkage redesign.

Depending on the suspension type, and adjustment methods, you may be able to adjust the caster and camber as one operation (may need several tries) but, normally, I would do the camber and then caster because the equipment I was using would make that the logical order. That said, even a simple strut can have up to three different methods for camber adjustment, and at least two for caster. In your situation, when you're happy with the bump', I'd do whichever is easiest, then the second, recheck the first, etc., until I was happy with those and then set toe as required.

Hi Sean,

The process and order you describe is more or less what I would recommend to start with. That doesn't mean I necessarily disagree with what Gord says - it really depends how close your car is to the factory from a geometry perspective. If it's still close, and not running at a crazy ride height, then you may not have too many problems with bump steer. If however your setup is a long way from factory then checking the bump steer first may not be a bad idea.

Ultimately, when you're sorting the initial setup of a car for the first time, everything is usually so far out you really need to run through the whole process to understand exactly where you are to start with.

The only thing I'd modify about your process is that the corner weighting, ride height and wheel alignment all affect each other to some extent. So in reality, you're paying attention to all of them throughout the process. After setting base ride height, then wheel alignment you then check and adjust the corner weights. While you're tweaking corner weights, you're keeping an eye on ride heights as these two things usually need to be compromised on together. After you've done that, you'd do a final pass on checking the wheel alignment settings. It's at that point that I normally check and adjust the bump steer.

That process I just outlined is more aimed at the regular setup procedure you go through pre-event on an existing car, rather than a "first-ever" setup for a new car. If you just want to see where you are, I recommend carryout out that process, but don't get too hung up in getting all the settings perfect the first time. You'll learn a lot by just moving through the process quickly to see where you're at, what deficiencies you have and what problems you have to solve.

Maybe it's time for use to produce a flow chart for this!

NP, Tim, I was thinking of more a scratch build, or rather modified setup, and as you say, most OEM are pretty good. As he moves from the OEM, the more important it'll be to check everything, such as roll centre(s), available travel, interference points, camber gain, etc.

Oh, while Sean's checking 'bump' steer, and everything else, to establish some base-lines, it may also be time to check the Ackerman angles, especially if he's going to be running on tight and/or low grip surfaces.

If the OP could give some more details on the vehicle, the mod's, and the intended use, it may be possible to comment further?

Thanks guys for jumping in on the comments and providing feedback and when and how and what order to possibly follow. I'll share a bit about the build to see if you guys have any experience with them. I'm building a Factory Five Racing GTM Supercar that uses C5 Corvette donor parts for suspension. Upper and lower control arms and spindles are all donor parts and I've got a set of custom valved Bilstein coil overs. Normal C5 Corvette suspension uses cam bolts for adjusting suspension, but a gentleman developed a system of laser cut spacer plates that will allow me to make consistent and predictable changes at the control arm adjustment points by 0.75mm at a time depending the configuration of the plates used.

So right now the alignment is WAY off being it was all just put together and eyeballed. Knowing this, I think I need to take a stab at running through all the alignment steps as I originally noted, but going back and checking certain things along the way. That way I can also get a feel for what adjustments are affecting others.

Other than dealing with a newly discovered leak from my transaxle (I'll need to pull the whole back end of the car apart to remove it) I'm getting pretty stoked to jump in and apply what I have picked up in the courses here.