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

Is the tendency to steer or shift "off track" associated with bumps and/or changes in the road surface?

Sounds to me like you are describing bump steer.

FYI - bump steer doesn't only mean from a road bump. When cornering and the car rolls from one side to the other as weight transfer occurs, you also get bump steer even if on a perfectly smooth surface.

yes, I think so. - so educate me on "bump steer" is that like "cow tipping"

Could be a bad tire, try rotation and a test drive. See if anything changes, no cost diagnostic.

will do, but after being pointed in this direction, just did a search and watched a couple videos etc and I think we are on to something, I do think it is bump steer. if there is irregularity or a bump it pulls the car one side or the other , this is what happens. so now the question is why am I feeling bump steer? is it worn parts or just poor alignment? and how do we correct it. I have had an alignment done one time a few years ago when Bob Woodmans shop put in the new turbo tie rods and my new A-arms and bushings etc. that was when I had different wheels, 2 years later I switched from the 14" rims to the 16" rims I am currently running. wider tires etc might also be part of this and why I feel this now and didn't used to?

sounds like I need full realignment and leveling. basically it has to do with the geometry of the alignment of the rack and the control arm and if they are lined up correctly and do they stay on a proper plane when now moving up and down with the strut as the tire hits a bump. not sure I exactly have it down but will study this more so I can comprehend it, not sure if I can fix it myself but someone can !!! I don't like feeling that bump jump at 60 or 70 mph!!!!

Have you replaced the rubber "hockey puck" that connects the rack to the steering shaft?

no, that is really the only thing I have not done. I also have the new front sway bar drop links from Tarrett I got at Okteenerfest last year, and was going to install them but I know if this is not done correctly will result in increased bump steer as well. I should do that also, but I am just wondering if the tire/wheel combo are causing enough change because I don't remember having this with the 14",5" wide 914/6 fuchs I had on the car back when we ran Tail of the Dragon at Okteenerfest 5 years ago. I have 1/2" spacers on the front, I might take those out and see if it changes it and do the rotation like Garland suggested and see how it feels.
Phil

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?

Suspension geometry is complicated. 914's and McPerson struts in general don't have great bump steer characteristics (zero bump steer being the ideal case).

You may also be feeling the effect of a changed scrub radius that occurred when you changed wheels & tires. Wider wheels and/or wheel spacers typically lengthen the scrub radius unless you changed the wheel offset to compensate for it's effect. That increased scrub radius affects steering efforts and how much distrubance is put into the steering system when you encounter a bump or surface irregularity.

Lowering your vehicle below stock ride height will also have adverse affects on bump steer. This is where bump steer spacers come into play to raise the rack back up. BEWARE adding spacers will only compound the problem if your car is running ABOVE OEM ride height.

There are no simple answers. Study up on steering geometry and it's effects. I highly recommend Carrol Smith's books Engineer to Win, Tune to Win, and Prepare to Win as a good starting point for the layman.

Once you understand more about geometry, then decide what experiments to try. Only you can determine what makes you happy and what feels best to you.

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!)

Here is a great link about rack spacers and bump steer 914World:

Link to rack spacers post

You can also do some reverse engineering and math w.r.t wheel offsets that may have increased your scrub radius.

If you know the offset of your old 4 lug 14" wheels and the offset of the new 16" + spacer, find the difference.

You then have an idea of how much change you're fighting. I suspect it may be more than just the 1/2" spacer you added.

Bottom line, you could look for a new 16" wheel with more offset that would put the center of the tire contact patch back where it was at with the 14" wheel/tire combo.

Keep in mind scrub radius and bump steer are different things but too much of either will make things squirrelly.

I can't imagine 6x16 Fuchs would give you a problem but anytime you have a front suspension issue, it's worth throwing on a different set of wheels. If it makes a difference, you've usually narrowed down your problem quickly.

Here is a picture from side and one of under looking at a-arm and tie rod. Looks pretty normal for height and level- how much angle of the arm from parallel should there be?

Try snugging up the bolts on the u joints in the steering column. I found that mine were a little loose and that tighten up the steering.

Alignment AFTER you attain the ride height you want. Put the rack kit in and see how much that alone changes things. Are the tie rods somewhat parallel to the horizon/level now?

Yes agreed , and yes I think very close to level here is a better picture,
Also when you say “rack kit” ?

@DRPHIL914

Rhodyguy is asking about the steering tie rods to the knuckle. You would like to see them close to parallel to the A-arm that you're showing. From what I can see of the tie rod in the background things look plausible.

I'll just tell you from experience that while a visual inspection isn't a bad thing . . . this will take some trial and error effort part changes. You're probably fighting a couple of differnt contributing factors here including those meaty, performance oriented tires. Wide tires with big solid block tread patterns without many sipes are only going to add to the tendency to "hunt" and/or follow road contours without steering input on your part.

Are you driving on a lot of rain grooved concrete highways by chance? Is that part of where your directional stability concerns are coming in at highway speeds?

@DRPHIL914

Look at the picture of your tire positon vs. the intersection point where the McPherson strut would intersect the ground.

Unless what I'm seeing is an optial illusion of the photo, you have an outrageous King Pin Offset & large positive scrub radius. Typically, a McPerson strut likes some negative srub radius.

Ideally, you would like that intersection to occur at or near the center, slightly outboard of the contact patch. In your case the intersection appears to be near the inboard edge of the tire.

Get the front wheel spacers out of there if you can without having the tire rub other things.

http://www.car-engineer.com/suspension-des...hicle-behavior/

Just snapped a couple shots for comparison.

73 white flared 9” rims, w/turbo tie rod ends

Click to view attachment

72 silver narrow body stock

Click to view attachment

thanks for explanations. the roads are not really grooved like you say but my main commute road was resurfaced a few years ago and is getting some shallow holes from that thin layer getting broken up so like here at there are a lot of those small holes or spots., speed limit is 60 but traveling with traffic tis more like 65-70.
I thought about the tires and treads and since I need to change had thought about a less pure performance tire and more of a compromise of performance/all season and even going to a 195/60 rather than a 205/55. more of a standard tread, slightly higher side wall, might feel better, I looked and my tires are almost 6 years old so I probably could change that very soon

ok will pull the spacers too, really don't need them. i had then in there when i had 7" rims in rear but went back to the 6" all around.

- looking at those pictures Garland, your A-arms are parallel with the ground and mine are not, but could be a bit of an optical illusion. Scrub radius etc lol i am learning stuff today ive been ignoring and not taken the time to really dig into!. But all really interesting! need to get in there and look closer at the alignment and measure the camber, caster, toe in etc etc .

I'm hoping it's an optical illusion. Look at Garland's photos, note the bottoms of the ball joints are partially tucked within the wheel. Due to the ange of the strut (inboard at top) that intersection to the ground plane is going to occur closer to the center of the tire contact patch.

Garlands's 9" rim seems to be tucked in a bit further. This isn't rally about rim widths, but rather about wheel ofset and the length of the scrub radius.

The other thing to keep in mind is that one person perceives as stable, controlled, and responsive can be another person's darty and unstable. It all depends on what you're used to driving and how readily you adapt between vehicles.

Arms look to be just off parallel.
I was involved in the alignment on the flared car, with rack spacers, and a wheel spacer. We set the ride height first, lower then stock, but with still being able to correctly set toe, and camber/caster.

Click to view attachment

@Garland

Who did your aligment? I no longer have a go to shop in the metro area. I have a long time unitl I need a shop but it would be great to have a shop that actually has worked on a 914 once before.

Last time I went to one with a 914 they insisted they needed a special tool to loosen the top mounts. When I provided them with the allen wrench. They refused to do the job stating they had to have the "special tool".

I used to use a little shop called Bruces Alignment on Woodward Ave, in Royal Oak back in the day to do my Miata alignment for Autocrossing but unfortunately the Yuppie / Trendy empire of Royal Oak & Birminham eventually made that retail space on Woodward to valuable and forced Bruces out of thier space.

This could be as simple as adjusting toe angle, which has a significant effect on straight ahead feeling of steering stability. An off toe will cause the steering to wander a bit at speed, rather than steering steady straight ahead.

Special tool is a joke. You can take apart an entire 914 with a shoebox of tools.

When I bought mine it was the pucks, longer bolts and some washers. IIRC. I prob bought them at pelican.

bingo.

Superhawk996 really knows his stuff but I think we've jumped to the conclusion you have bump steer problems without any real evidence to say why. Unless your car is lowered substantially from stock, bump steer is less likely to be the cause. it sounds to me like you have a lot of toe out. when was your alignment last checked?

as far as rebuilding the steering rack - that sounds like a last resort in my mind, given the complexity of the job; However, if you end up replacing the rack, you'll maintain your alignment settings or (preferentially) get a new alignment.

one other thing - the front US ride height was raised (as I understand it) compared to euro ride height, without any need for adjusting bump steer, which means to me that you can lower the car below euro ride height without major bump steer.

this is what I would do in order of complexity:
1. check and confirm that alignment is correct
2. check and confirm no significant bumpsteer (I forget the exact dimensions but I'm thinking less than 1 degree throughout the entire suspension travel)
3. if that doesn't help, look at the hockey puck. replace if bad (requires removing fuel tank)
4. rebuild steering rack

I don't necessarily dis-agree with @Jmitro in that we may have gotten a bit ahead of ourselves w.r.t. to bump steer but based on the desription initially offered, it aligns very well to the symptoms of bump steer.

We do know the wheel/tires were changed and front wheel spacers were added which can make the 914's inherent bump steer characteristics worse.

I have assumed alignment is OK based on @DRPHIL914 description that all components were checked, replaced recently, are not loose, and I'd assume properly aligned at that time these components were swapped.

Let me modify the Jmitro sequence only to do what is free and easy:

1st step - Remove the 1/2" front wheel spacers and then report back.

Lacking any other changes in wheel offset that could have occurred going from 14" to 16" wheels, the front wheel spacer immediately adds scrub radius. Increased scrub radius increases steering & parking efforts, and decreases straight line stabiltity when there are road induces disturbances (bumps, lane ruts, or road camber).

Increased scrub radius only compounds any other problems that might be there.