Bump Steer Made Easy

Racing Car Technology Online Training in How to Bump Steer Your Race Car: 

You can measure bump steer accurately, using only a single point laser you can buy from the hardware store.

The laser is pointed at a mirror fixed to the hub, with the laser beam reflected back to a target. The laser point moving on the target shows toe change very accurately.

The old way of checking bump steer is no more. No more clunky bump steer gauge.  (See "Longacre Bump Steer Gauge demo" on YouTube.) 

The end result we want from the bump steer measurement and correction process is clear.  Whether road or race car, we simply want zero change in toe in - toe out, as the wheel moves in it's normal range of bump and rebound travel.  (In some modern vehicles such as the Lotus Elise, bump steer is used to modify handling.  We don't suggest you try this on your race car because the results would be uncertain.)

This course is a complete, practical guide to what you need to know about bump steer, and how to go about fixing it. There are a lot of possibilities depending on your race car. We can help you directly with this. You contact us within the course with your questions and we can discuss. 

Suspension workshops do not measure it because car manufacturers do not make any provision for the adjustment of bump steer.  With un-modified late model cars, it should not change from factory specs. Older vehicles and race cars are a completely different matter - we do need to check it, and fix it if it's out.

What happens is that all the steering and suspension settings interact. So if for example, you change the caster, this can affect the bump steer, especially with with strut suspension.

You can see there is quite a lot to know around bump steer and what you do for different vehicles.

For modified race and road cars, checking the bump steer should be a high priority in the initial set-up of your car.  The regular changes you make to suspension geometry will more than likely put the bump steer out.  Fitting steering rack kits or roll centre height adjusters to strut cars are just two examples where bump steer correction will most certainly be required. 

All purpose built race cars and other vehicles with fully adjustable suspensions should be bump steered regularly to make sure bump steer hasn't changed.