Should I shim my power steering rack?

[FAST4DR]

Since I have the intrax springs and I have cut one coil out of them... Should I shim the steering rack? I am assuming the tie rods had a little droop and now they are probably going to be level with the rack. Isn't this going to create toe out bump steer when I hit a bump in a hard turn?

Will

 

[shojuan]

It won't hurt and it's not that hard.

 

[Hack]

I had bumpsteer issues with standard (uncut) Eibachs. It is worse now with the coil overs, even with the rack shimmed. I also experience an unsettling sensation when changing lanes on a heavily crowned road. Almost like a bad center drag link feels. Performing an improptu poll of other coil over users at the convention revealed that I am the only one with this problem. I guess it is just because I have them set lower than most (if not all?). I should raise it back up, but it feels great on the track, where it counts.

Back on topic, I would recommend shimming.

 

[Toolman]

Shimming eh? I might try that.

 

[FAST4DR]

I ended up shimming the rack with 1/4" thick washers. It's all I could put in there with the current length of the bolts that hold the power steering rack down. Don't know how much difference they will make, but it can't hurt.

Will

 

[Todd TCE]

I'm impressed that people actually understand this! People are learning, times are a changin'. For the better I might add.

 

[shojuan]

I ended up shimming the rack with 1/4" thick washers. It's all I could put in there with the current length of the bolts that hold the power steering rack down. Don't know how much difference they will make, but it can't hurt.

Yes, the bolts don't have much extra length at all but some is better than none. Your steering geometry is closer to the stock design geometry than it was.

Todd, why the surprise? I understood the need for this back when I was a kid driving around my 914! (now a rusting pile of poo in my back driveway ) I can't believe I'm 33 and I still have my very first car in my backyard. Back on topic maybe I should scan in some photos from one of my layman's handling books so more people here will understand.

 

[Todd TCE]

I think you'd be one of the few as the exception to the rule. Good for you. Others; take note and crack open a book instead of a monitor some time.

 

[Hack]

Just read a great book on design and construction of competition suspension. I do not recall the title (something to the effect of above) or the author. What is important is that I actually understood and absorbed some of the information inside.

 

[RI-SHO]

Excuse my ignorance but where exactly would I be placing these 1/4" shims, on the big rack bolts themselves? Or other location?

I would think I would benefit from this seeing as my SHO is dropped 2.75" front and 1.5" rear, gotta love badly made SS springs .

 

[shojuan]

Don't expect any miracles in the bump-steer department with that much drop, but any help is welcome help, right? There are two studs on the bottom of the steering rack which go through two holes in the subframe to which are attached two big nuts (torque spec on those nuts 100 ft-lbs ) When you remove the nuts you can lift the rack up by hand enough so the studs come up above the subframe holes then slip your shims between the subframe and rack studs and onto the rack. I used 9/16" hardened washers. I *think* I might have been able to slip 3 onto each side. It took a bit of perseverence. Terry Richards suggested slotting the washers the rack raising method isn't working out with intact washers. Then you won't have to lift it as much to be able to slip the washers in place. Personally, I like knowing that mine aren't slotted and that the washers aren't going anywhere.

Make SURE that you leave enough threads on the studs so that the nuts can be tightened down to spec and still have a couple threads poking out. That is MUCH more important than any benefit you are going to get from the shimming so don't get too greedy!

 

[Dave Kegel]

I had bumpsteer issues with standard (uncut) Eibachs. It is worse now with the coil overs, even with the rack shimmed. I also experience an unsettling sensation when changing lanes on a heavily crowned road. Almost like a bad center drag link feels. Performing an improptu poll of other coil over users at the convention revealed that I am the only one with this problem. I guess it is just because I have them set lower than most (if not all?). I should raise it back up, but it feels great on the track, where it counts.

Back on topic, I would recommend shimming.

Are you sure you're alignment is good? There's no way you should have had bumpsteer issues with eibachs. I had the same symptoms you describe after I did all the suspension work on my car, and the problem turned out to be too much toe out. I'd double-check your front toe settings, I'll bet that's part of the problem.

Dave Kegel

 

[Toolman]

He has coilovers.

 

[Hack]

Dave, I had the Eibachs in there for about seven or eight years and always had a bumpsteer issue. The car was aligned many times during that stretch. As Tim pointed out I now have coilovers, and the bumpsteer has of course worsened. The miles driven between shimming the rack and switching to the coilovers were so few that I cannot say for sure if the b.s. was eliminated or not.

 

[NotSoSlowSHO]

I figure if you wanted even more "shimmage" you could weld in towers on the subframe for the rack to bolt to.

Or just find longer bolts.

I like to fabricate though... and that would be a lot of stress on longer bolts...

 

[FAST4DR]

Excuse my ignorance but where exactly would I be placing these 1/4" shims, on the big rack bolts themselves? Or other location?

I would think I would benefit from this seeing as my SHO is dropped 2.75" front and 1.5" rear, gotta love badly made SS springs .

Here are a couple pics of the shim I used and how much bolt is left sticking out of the nut.