Dave Griswold

especially with Koni Coilovers? If so, what did you do to correct?

Thanks a lot,

Dave

Greg Amy

Bump steer is purely a function of the suspension geometry, and it not affected by the height of the car. However, it may be encountered sooner if the car is lowered or raised (assuming the designer has optimized design with the car at a certain height.)

The only solution for bump steer is a re-design of the geometry, such as moving the points on the car where the suspension parts attach or changing their lengths.

GA

Dave Griswold

but do you know if there is any issue with bump steer in the A4 when lowering a car 1.3 to 1.4"? That's about where most common spring apps drop the car.

Thanks again,

Dave

WClark

I lowered from sport to "Eurosport" which is about 1.5" below stock. I notice no bump steer problems. Of course the lower springs are also firmer so the suspension operates not only over a different starting point but a different range. This multilink setup seems to maintain camber pretty well so maybe that is a reason.

When I go to 225 tire width (summer tire) I notice more tramlining than with 205 (winter tire) width, but that isnt bump steer.

Dave Griswold

Thanks, that's what I was hoping to hear!

PWR

The bump steer changes as the wheel moves up and down. The reference "Bump Steer" refers to the fact that the steering changes (either toes in or toes out) as the suspension goes through it's range of motion. The sever change in toe-in/toe-out will manifest it's self by sudden or more accute changes in direction of the vehicle when the suspension is close to being fully loaded but not on the bump stop.

Lets assume that the bump steer is zero when the stock suspension is at it's static rest height. As the wheel goes upward (compresses) the steering typically toes in and when the suspension goes downward past the static height the suspension toes outward (I'm reciting this this based on some suspension tuning I did twenty years ago).

Therefore, when you drop the suspension the steering will be toed outward. That's why you need an alignment every time you change the springs and the ride height of the car.

To understand what or how much bump steer you have you need to measure it. This is done with the springs removed (springs only hold the car up) and jacking the raising and lowering the car and measuring the results. A simple bump steer tool can be built out of several pieces of plywood and stove bolts. The best reference for this tool and approach to measurement is in a book called "How to make your Car Handle". Once you have collected the bump steer data information you are now able to detemine if you need to raise or lower the steering arm/steering rack. Steering arms (attached to steering boxes) can be reformed (heated and bent) to reduce the bump steer. It's a trial and error process but that's how I did it the last time. If you have a steering rack you usually have only one choice (i.e. raising the rack). This can be done by placing washers under the steering rack. Again trial and error and a lot of measuring is required the detemine the correct number or thickness of washers.

Now having said all that, if you've only drive your car on the street and lowered the car 20-30mm bump steer shouldn't be a problem.

However, I would recommend buying the book and reading it. It's got some good basic suspension tuning info.

Dave Griswold

Thanks a lot!! Good info and I'll look for the book.

John/TSR

..spacers at the tie rod ends, (where they join the steering knuckles) to bring the static back into the middle of the range (old time fix). Probably the best way is shimming the rack up or down to zero it out at static.

Depending on the position of the steering rack, whether it's a "front steer" or "rear steer" design (rack in front of wheels, or in back) and the design geometry of the knuckles and steering arms, the bump steer can be "toe-in" or "toe-out". Minor bump probably isn't noticeable on the street, but whoa-**** it's noticeable when you're pushing the car hard.

And, if you're not careful, you can develop bump steer problems in the back, too. Ask me how I know.....

Dave Griswold

How do you know???

JimmyKO

I have H&R Coilovers.. when I had them installed at a shop.. i noticed bump steer .. I didn't pay much attention to it.. until after 2000 miles on them... my tires were bald.. LOL.. get the toe problem fix!!