JMZ

How much does raising the strut spindle height help with eliminating bump steer on lowered cars? I know this is common practice on race cars. My car is a will be a "bitchy" stret car that gets driven to the track for d.e. and autox but not a full blooded race car.

Steve Weiner-Rennsport Systems

JMZ;

Raising spindles does 3 things for you:

1) Restores lost suspension travel from lowering.

2) Raises front roll center back up where it should be. This helps prevent the inside front wheel from lifting, and also lowers lateral weight transfer so the front doesn't feel like its "tipping over as much".

3) Helps correct bump steer.

You still must fine tune bump steer with either a steering rac kit, shims, or (best) the ERP Bump Steer kit to really minimize that. This REALLY pays big dividends in handling and control.

The amount you can raise the spindle is limited by your tire diameter, since the front lower ball joint/A-arm gets very close to the inside of the wheel rim.

Cary

JMZ, Bump steer is corrected when the arc of the steering arm correlates with the arc of the lower A-arm simultaneously in motion. Raising the spindle takes the steering arm up but, leaves the A-arm down actually upsetting the harmony between the two. Depending how high you raise the spindle the rack spacers alone may not be enough in which case you’ll have to use something like an ERP bump kit. At that point the amount your spindles are raised will determines the thickness of the spacer. I’ve seen where people have used the ERP long spacer bump steer kit on stock front struts and they've actually over corrected the bump steer making it worse than it was to start with. The only way to be sure is to actually bump test the car after finishing all the changes. If you don't have access to a bump steer gauge another way to check for toe change is as follows: first remove the springs or torsion bars, set the car on a jack with it being 1.00 inch above desired ride height. Check the total toe then let the car down to its actual ride height and re-check the toe. Now, go 1.00 inch below ride height and check it yet again. This is a very crude method but, will serve its purpose. When you finally determine the correct length spacer on the bump steer kit, there will be zero, or close to zero change throughout that entire range.

Cary
ERP