Bump Steer Made Easy

Uncategorized Nov 09, 2016

When it comes to bump steer, if your like most racers, you're thinking bump steer could be important, but haven't got to checking your car yet.

Regular mechanics and alignment shops don't do bumpsteer. Specialist racing services might - but at what cost?  Are they accurate?  How accurate do they need to be? Will they know how to fix it safely?

With our new on-line training course, "Bump Steer Made Easy", a mirror, and a simple laser you can buy from the hardware store, you have everything you need to check your bump steer. Then, to fix it, follow our practical advice as to how to do just that.

Adding to our problems with bump steer, many of us now race independent rear suspension cars, where live rear axle once ruled.  In changing anything affecting the suspension geometry, for example ride height, it's interesting to see what affect the change has on the bump steer curve. 

With our instructions, checking your bump steer is incredibly easy and straight forward. 

There's been a lot written about bump steer, much of it not helpful and sometimes way over the top. One race car engineering book I have devotes 14 pages to the subject! Give us a break. Bump Steer Made Easy is all you need to know about bump steer. We'll show you basic wheel alignment know-how, so you can measure to the accuracy required, and then interpret the results, just by watching the laser point on the target. (Forget about writing down a bunch of numbers.)

Fixing Bump steer problems?  You may be surprised to know - if your suspension has a toe link (or "tie rod") then we can effectively eliminate bump steer, even if it looks pretty ugly when you take your first bump steer measurement.

Our new course, "Bump Steer Made Easy", shows you how to 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 horizontally on the target shows toe change you have, as you jack the suspension up and down.

Could We Use Toe Setting for Suspension Tuning?

Potentially, yes. It is clear that dynamic toe change could have quite an influence on the rate of change of tyre slip angle. But for our purposes, when we do not have access to high end analysis tools, end result we want from any 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.

Bump Steer for Racing

Road car 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. Older vehicles and race cars are a completely different matter - we do need to check it, and fix it if it's out.

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, such as more caster, 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 must be bump steered regularly.

Now you can check bump steer accurately with out an expensive and hard-to-get bump steer gauge. These gauges are a pain to use.  (See "Longacre Bump Steer Gauge demo" on YouTube.) With the laser, as you will learn here, once you have worked out how to attach a mirror to your hub or disc, it's plain sailing and you'll just be reading off the bump steer on a simple target.

To measure bump steer, we put the car on jack stands or a two post hoist, remove a spring from one corner of the suspension and re-assemble the suspension. We can now move the wheel up and down without restriction from the spring. With the suspension position set at ride height, we then move the suspension in the bump and rebound directions, over the normal travel of the suspension, and measure the toe change.

To buy our Online Training, click and go to the sales page : "Bump Steer Made Easy"

To check out all our training courses in suspension set-up and tuning, including "Bump Steer Made Easy", go to the main menu item "Course Offers" at the top of the page.