Front suspension and steering, how do you know you need to rebuild the steering? Options

[DRPHIL914]

I am wondering this as I have been driving my car this week with the great weather and fall temps here in SC, and I have noticed something that just doesn't feel right, and I am not sure I can put my finger on it, or even describe what I am feeling but I feel like my steering should be super tight, since a few years ago we did all the bushings bearings turbo tie rods ball joints brakes etc etc, everything but the steering rack itself and I didn't replace the front strut inserts because the feel fine.
wheels are 16'x6" 205/55 Potenza AE11's. 4 years old about 5,000 miles of use, lots of good rubber on there yet, but regardless will have to replace in another year just due to age of the rubber...

so with that, here is what I think it feels like, kind of like it wants to jump around or shift off track. no vibration , no rattle , and I can grab the tire/wheel with car parked and try to move it back and forth and don't feel any play like if you had a loose or work tie rod or ball joint etc.,

what I guess I am wondering is if it is time to pull the steering rack and replace it with a rebuilt one from 914rubber. if that hockey puck thing is getting old and worn, what would that feel like or how would that present itself? And can I remove it by just disconnecting the inner tie rod ends and not have to mess with my alignment? ive not done a steering rack on a 914 before..

as always , advice from those that have done this is appreciated.

Phil

[rhodyguy]

Sort of a 'shudder' in the front end? Rack spacers that elevate the box to help maintain proper tierod geometry. Simple and cheap fix.

[DRPHIL914]

Sort of a 'shudder' in the front end? Rack spacers that elevate the box to help maintain proper tierod geometry. Simple and cheap fix.

ok I am or was a dummy regarding this so here is a good explanation of it-
"bump steer for dummies" :

-here is a nice explanation of bump steer and why it occurs - as you said the tie rod geometry and/ or the control arms and tie rod geometry is whats happening,
specifically it is the "toe should stay as close to even as possible all the way thru wheel travel up and down" . when a bump kicks the tire up that upward motion will cause the tire to go in or out if the tie rod is too short or too long so it kicks in or out, but that is exactly what I am feeling on my steering wheel .

so

- https://www.bing.com/videos/search?q=what+i...amp;FORM=VDRVRV

so maybe my tie rod and steering rack are not in line, need to do a full alignment then as well, check the standing neutral toe position, - what is the rack spacer you are referring to Kevin?

[Superhawk996]

so maybe my tie rod and steering rack are not in line, need to do a full alignment then as well

As a generalization, static alignment (setting toe, camber, and caster) do not affect bump steer which is dictated by vehicle ride height, and suspension geometry changes from jounce to rebound.

Bump steer can be measured via dial indicators, a flat plate bolted to the hub, and then stroking the supension through it's full range of travel from full jounce to full rebound. Once you have that curve of toe change vs. suspension position, you will be able to see where the toe is changing and what needs to be done. This is not something that most people will choose to do but it is necessary to prep a decent race car.

Most likely you've induced the negative effects you don't like with ride height changes, and changes to wheels/tires, and spacers The turbo tie rods only make the effect worse by providing a more direct road feel feedback to you by elimination of the rubber isolation in favor of a metal ball joint. The turbo tie rods also make the vehicle affect worse because the low compliance of the turbo tie rod makes the bump steer effect more immediate, and more effective overall since you're not losing efficiency in deforming a rubber tie rod isolator.

[DRPHIL914]

so maybe my tie rod and steering rack are not in line, need to do a full alignment then as well

As a generalization, static alignment (setting toe, camber, and caster) do not affect bump steer which is dictated by vehicle ride height, and suspension geometry changes from jounce to rebound.

Bump steer can be measured via dial indicators, a flat plate bolted to the hub, and then stroking the supension through it's full range of travel from full jounce to full rebound. Once you have that curve of toe change vs. suspension position, you will be able to see where the toe is changing and what needs to be done. This is not something that most people will choose to do but it is necessary to prep a decent race car.

Most likely you've induced the negative effects you don't like with ride height changes, and changes to wheels/tires, and spacers The turbo tie rods only make the effect worse by providing a more direct road feel feedback to you by elimination of the rubber isolation in favor of a metal ball joint. The turbo tie rods also make the vehicle affect worse because the low compliance of the turbo tie rod makes the bump steer effect more immediate, and more effective overall since you're not losing efficiency in deforming a rubber tie rod isolator.

makes sense.- dynamic not static measurements and testing,. trial by error could drive you crazy. Going back to standard tires and 4 lug is not happening so I have to figure out how to at least improve it as much as I can with what we have. I am not autocrossing the car just 1-2x per year trip to the mountains. if alignment and then some spacers to improve the geometry and reduce the bump steer some then that would be great. First I think getting in there to make sure we have the right starting point with the steering rack and tie rods lined up correctly so ride height adjustment if necessary and go from there. I didn't adjust the ride height but we reomoved everything when we did new A-arms and bushings and tie rods. so the mechanic at the time at Woodmans was George, a 50 year Porsche mechanic. I have to ask him what he thinks about it. they did the aligment but now both are retired!! ( I know he works a bit out of another shop here locally, but mostly rebuilding 911 motors- lots more $$ in that lol!)