Bump steer

[xenonxt]

Bump steer is used to tune understeer/oversteer balance but it also causes poor steering feel on rough road surfaces and increased tyre wear. What should be optimum value for sedan.Some say it should be negligible?

Thanx a lot in advance!

[Paul Assan]

Hi,
I own Mercedes Benz C220 Estate, when on highway and decide to apply brakes suddenly at 120 kph the steering wheel wobbles, Why that? Please help.
Paul.

[MagicRat]

Originally Posted by Paul Assan

Hi,
I own Mercedes Benz C220 Estate, when on highway and decide to apply brakes suddenly at 120 kph the steering wheel wobbles, Why that? Please help.
Paul.

Paul,
Welcome to AF.
You will likely get better results if you start a new thread to ask your question, because it is not related to the opening post in this particular thread.

However, I would suggest you have a pulsing brake, where the braking force on one or both front wheels is uneven (as the wheel rotates) due to a warped rotor or contaminated rotor surface. Generally speaking, the rotor needs to be machined or, if ti's too thin and/or rusty, replaced. This should be done to both front brakes; and new pads should be installed at the same time. The calipers should also be inspected for smooth and consistent operation.

It is also possible that you may have worn steering and/or suspension components. All steering and suspension components, like the ball joints, tie rod ends etc should be inspected for wear and excessive play.

[KiwiBacon]

Originally Posted by xenonxt

Bump steer is used to tune understeer/oversteer balance but it also causes poor steering feel on rough road surfaces and increased tyre wear. What should be optimum value for sedan.Some say it should be negligible?

Thanx a lot in advance!

Why does this sound like a homework/exam question?

[MagicRat]

Originally Posted by xenonxt

Bump steer is used to tune understeer/oversteer balance but it also causes poor steering feel on rough road surfaces and increased tyre wear. What should be optimum value for sedan.Some say it should be negligible?

Bump steer, in the conventional sense occurs when the suspension alters steering geometry as it moves through its travel. This is generally a bad thing.

Usually steering geometry must remain consistent for safe operation.

Suspension geometry sometimes incorporates changes in wheel camber and toe as the springs compress. This is intended to compensate for body roll during cornering but sometimes produces undesireable steering changes.

As an example, semi-trailing arms are notorious for producing trailing throttle oversteer in corners due to this action. More than one Porsche 911 has explored roadside ditches due to this characteristic. My Supra also displays this tendency, and, when used properly, it is an aid in cornering, but imho this was not the Toyota's engineering intention.