Strut Tower Brace...will it help bump steer?

[sigep174]

I have an '80 911 SC. That has been lowered and has larger than factory wheels and tires on it. In a deep corner I do experience a bit of bump steer and was curious if anyone had an opinion on whether or not the increased rigidity from the brace would reduce that at all.

Thanks,
JJ

[schumicat]

not sure but if lowered a bump steer kit (spacers on rack) is a good idea. I believe host sells (Weltmeister kit).

[sigep174]

A profile of the car, so you don't think I am running 22's on it from the description...

[rattlsnak]

A strut brace won't help that. The quick way is to install the rack spacers, the best way is to get your spindles lowered, or put the elephant kit on which raises the connection point. It's caused by the angle of the tie-rod end where it connects to the spindle.

[911pcars]

Originally Posted by rattlsnak

A strut brace won't help that. The quick way is to install the rack spacers, the best way is to get your spindles lowered, or put the elephant kit on which raises the connection point. It's caused by the angle of the tie-rod end where it connects to the spindle.

Yes. Bump steer is a suspension term (toe change during suspension travel) that affects vehicle stability. A strut brace is a device designed to add rigidity to the chassis. Inter-related, but independent.

S

[aston@ultrasw.c]

I though the main symptom of bump steer was the inability of the car to travel in a straight line. i.e. constant, small adjustments of the wheel being required.

Do you experience this?

Or, has the OP identified a second symptom?

[RWebb]

might be a bit of body flex that creates an effect on bumps when the bump steer happens

[HawgRyder]

It's all about geometry.
Don't you wish you had paid attention in class now?....LOL
The pivot points for the a-arms and steering rack (tie rods) should be equal.
Think of like this...the distance between the inner part of the a-arm...and the end of the steering rack are a certain distance apart.
If the center line of the spindle and the outer part of the tie rod are the same distance apart...AND...the vertical line up of both inside and outside lines are parallel...then the up and down motion of the wheel will stay in the same line all the way through the suspension travel....(whew).
It's like a parallelogram (back to geometry) if you secure one vertical side and pivot the outer side through its travel...the outer side should remain parallel to the inside line.
Race car designers have known this for years...but there are some reasons for violating these rules...like allowing some camber change as the wheel travels upward in relation to the chassis (gives better bite on corners).
How 'bout that?....LOL
Have fun
Bob

[Cory M]

no

[Craig_D]

^^^+1

It has nothing to do with a strut brace, it's the angle of your tie rods in relation to suspension travel. Like was said above, raise the steering rack (cheap way) or raise your spindles (expensive but the proper way, and the way the factory race cars were setup).

[joe payne]

Front tire pressure?

[RWebb]

could chassis flex alter the angle of the tie rods in relation to suspension travel enough to feel?

[911pcars]

Originally Posted by RWebb

could chassis flex alter the angle of the tie rods in relation to suspension travel enough to feel?

Yes, but you might be hard pressed to separate the difference unless there is some effort to reduce bump steer or increase chassis rigidity. In terms of our 911s, a package of "bump steer" spacers is cheaper than installing a strut bar. I'd start there. Increasing chassis rigidity where it really counts is usually not answered by bolt-on accessories.

Sherwood

[911SauCy]

Originally Posted by Craig_D

^^^+1

It has nothing to do with a strut brace, it's the angle of your tie rods in relation to suspension travel. Like was said above, raise the steering rack (cheap way) or raise your spindles (expensive but the proper way, and the way the factory race cars were setup).

Does adding a bump steer kit screw up an alignment/corner balance?

[Driven97]

Originally Posted by aston@ultrasw.c

I though the main symptom of bump steer was the inability of the car to travel in a straight line. i.e. constant, small adjustments of the wheel being required.

Constant adjustments needed on a smooth road too is likely toe out, or perhaps worn bits.

On bumpy / wavy roads only it's likely bump steer.

[HarryD]

Originally Posted by 911SauCy

Does adding a bump steer kit screw up an alignment/corner balance?

I would think so since you are affecting your front end geometry. If it was me I would find a local shop that sets up Porsche race cars and have them dial in your suspension. I had Jeff Gamroth (Rothsport Road and Race) do mine. It was well worth the money together my suspension properly set up.

[Craig_D]

Originally Posted by 911SauCy

Does adding a bump steer kit screw up an alignment/corner balance?

You'll want to have an alignment done, but you wouldn't need to re-corner balance unless you change the ride height of either front wheel.

All the bump steer spacer kit does, is move your steering rack up to help match the factory designed tie rod angle for the stock height. Mind you, "stock height" is the European ride height which is slightly lower than the US ride height.

Hope that makes sense.

[911pcars]

If you lowered the ride height, the alignment must be reset.

If you lowered too much and the suspension is stock, you could run out of suspension travel and bottom out. That's in addition to excessive toe-out when the suspension compresses with a softly sprung chassis.

Suggest upgrading the torsion bars to firm up the suspension. Compatible shocks follow.

Much info on suspension setup in the archives.

S

[Hydrocket]

In our local PCA magazine, "The BahnStormer", they had an article about whether strut tower braces were worth it. So they rigged up a measuring device and hit the track. When they came back, chassis deflection was VERY small.

You can read about it here...the story is within the first dozen pages or so. Kinda interesting.

http://rsp.pca.org/BahnStormer/Bahn_2012_08_web.pdf

[911pcars]

Originally Posted by Hydrocket

In our local PCA magazine, "The BahnStormer", they had an article about whether strut tower braces were worth it. So they rigged up a measuring device and hit the track. When they came back, chassis deflection was VERY small.

You can read about it here...the story is within the first dozen pages or so. Kinda interesting.

http://rsp.pca.org/BahnStormer/Bahn_2012_08_web.pdf

Long a mystery as to whether a strut bar really helps much. At some point, someone saw a factory race car and paid the factory a compliment by copying it.

However, the body sheet metal on 1988 911s is thicker than on earlier cars. Might still show little difference, but it would have been good to repeat the test with an early chassis or with a larger sample.

Sherwood