Bump Steer (Again)

cashman · 02-19-2009, 07:45 PM

Hi All,
Ok, first, I think I have spent hours reading every post there is regarding bump steer and I still have some questions. My Front is 24 1/2, rear is 24 on 16" wheels (I know this is not the most technical way to take the measurement but appears to be the most generally accepted on this forum). The car runs and handles great. It does not bottom out but is a little rough over the bumps. I do get some bump steer which led me to do some winter exploration. I do not use it as a track car and am not interested in the $300 spindle upgrade.

The tie rods definitely are not horizontal and rise up toward the wheel. Upon inspecting the the steering rack, there appears to be 2-3 washers that raise the rack 8mm. Question #1 - Are these washers the previous owners attempt at raising the rack or does the factory setup have some washers?

Taking measurements, it appears I would almost have to raise the rack an additional 12mm to make the tie rods horizontal. Question #2 - The bump steer kit appears to be about 9mm thick, can I add this to the existing 8mm worth of washers? Question #3 - At what point is too thick of a spacer not practical/safe.
Much thanks in advance.
Mark

Kevin Stewart · 02-19-2009, 08:20 PM

without a guage it would be hard to give you any info, see if there is anyone local that can bump it for you, Kevin

Bmxrams80sc · 02-19-2009, 08:29 PM

I have the same question about fabricating your own spacers to raise the rack. What is the size of the kits out there? (spacer thickness)

Bmxrams80sc · 02-19-2009, 08:30 PM

It would save the hassle of ordering one plus making parts is always fun!

911pcars · 02-19-2009, 09:48 PM

Once you discover the thickness of the spacers, purchase new bolts and add that additional length. Adding rack spacers only provides a ball park fix anyways. The available space above the rack limits how much you can compensate.

Has anyone ever tracked the bump steer dimensions at factory height, then lowered X" with rack spacers? I'd be surprised at a response.

Sherwood

EarlySport · 02-19-2009, 10:31 PM

You're definitely limited in how far you can raise the rack by the rack itself and the steering shaft protruding too far through the splines on the steering uni.

I don't think you can get much more than the weltmeister spacers provide.

cashman · 02-20-2009, 06:12 AM

Thanks for the reponses. I realize a guage is the best and most accurate way to make the complete adjustment. I would be happy with just an improvement and I know right now I am nowhere close as the tie rods are about a 1/2+" High on the wheel side.

So from the responses, it looks like the Weltmeister kit is about as high as you can go without interference. I am still lookig for the answer to question #1 - Are there supposed to be any washers between the rack from the factory? Do I add the spacer on top of these washers or remove the washers and insert the Weltmeister and gain 2mm. Or is 2mm not even worth gaining?

JFairman · 02-20-2009, 09:08 AM

When I installed the Weltmeister kit in my '87 there were no washers between the rack and crossmember.
The anodized aluminum spacers in the W kit were around 10mm thick and came with 2 sets of longer bolts. It took a prybar to gently lever the rack up and push the spacers in to place under it and there is a fuel line on mine above the rack that would be really squished if you pushed it up any higher.
The steering column linkage splines and bearing mount in the smuggler box need to be loosened, adjusted, and retightened to let the rack be raised without stressing it.

The Weltmeister kit is so inexpensive, and has the right bolts so I would get the washers out of there and put it in... peace of mind and if it raises things a couple mm, it will help a little.

Good time to inspect the fuel lines, sway bar mounts, and the horn for the alarm while you're under there.

Zeke · 02-20-2009, 11:55 AM

The spacers commonly sold are about 3/8th of an inch. You usually lower your car a lot more than that. There are no factory wahsers.

Years ago, we didn't have the selection of steering products we have now. I would buy an adjustable steering arm kit from Elephant or Rebel Racing (just to name 2 out of a few).

One reason is that most of the time the spacers require some work on the steering u-joints. Of the 2 cars I have done this to, I had to machine a small amount of additional flat on the angular shaft for completely free, non-binding steering action. This is necessary in order to move the u-joint up the shaft enough.

Man, I can't even imagine how many cars there are on the road with a small amount of binding.

moneymanager · 02-20-2009, 11:58 AM

I think your question will be answered when you slide the washers in...it's pretty tight in there. I've made this change but I run my car on the track and frankly I can't tell any difference there, and certainly not driving on the street. To seriously address bump steer I think you need to change spindle height and add one of those ERP or Smart Racing kits. And at least some of the experts don't even get to this until they've changed torsion bars, revalved shocks, etc etc.

911pcars · 02-20-2009, 12:50 PM

Quote:

Originally Posted by milt

The spacers commonly sold are about 3/8th of an inch. You usually lower your car a lot more than that. There are no factory wahsers.

Years ago, we didn't have the selection of steering products we have now. I would buy an adjustable steering arm kit from Elephant or Rebel Racing (just to name 2 out of a few).

One reason is that most of the time the spacers require some work on the steering u-joints. Of the 2 cars I have done this to, I had to machine a small amount of additional flat on the angular shaft for completely free, non-binding steering action. This is necessary in order to move the u-joint up the shaft enough.

Man, I can't even imagine how many cars there are on the road with a small amount of binding.

Milt's correct. It doesn't take but a millimeter of interference between the steering shaft and the u-joint to limit the range of steering.

The rack spacer kit is cheap enough. However, an equivalent substitute are the correct number and thickness of U-shaped washers (used for general purpose wheel alignment) and longer bolts.

Sherwood

burgermeister · burgermeister's Garage

I measured mine, with the stock rack location and with an 8mm spacer between the rack and the crossmember.

Note that the amount of steer for a given amount of vertical suspension travel does not change much with ride height. This suggests that lowering the car does not change ride steer. Reducing jounce travel (also a result of a lower car, and at 24.5" fender height you are probably 50+mm lower than stock) would increase steering wheel kickback though. Sure does on my car.

Raising the rack reduces ride steer for a given amount of suspension travel. This would also tend to reduce steering wheel kickback.

So my interpretation is that raising the rack covers up the ill effects of insufficient jounce travel.

Raising the spindles is different - that changes the distance between the LBJ and the tie rod end, and this would definitely require correction.

cashman · 02-20-2009, 01:50 PM

Sounds like I need to add the Weltmeister spacer, raise my front suspension so the tie rods are horizontal, take the measurement of the front fender, raise the rear to be 1/2" lower than the front. This would be the ultimate street rip-roaring set up. Wow, I might have to rename this the "Ultimate Bump Steer Thread" (Without spindle adjustment)

C4 Pazzo · 02-20-2009, 09:18 PM

You are not going to be able to add the Weltmeister spacers on top of the existing washer spacers. As others have said you will get binding of the steering wheel. I'd just add some washers to the existing ones. You may need to get longer bolts, but you'll have more flexibility on the height with washers than with the kit.

911st · 02-20-2009, 10:36 PM

There are no washers under the steering rack from the factory.

It is generally accepted that adding the Welt spacer kit is a fair starting point and sufficient for most. It lifts the steering rack as far as it can be lifted.

Moving the spindle up only makes bump steer a bigger issue as it increases the angle difference between the tie rod and the a arm putting them on dissimilar arcs.

It is not necessary to set the tie rod level. This may not fix the issue.

You are trying to get the tie rod angle closer to the same angle of the a arm with a turn but not so far that they are the same angle. The angle of the tie rod changes with turning of the wheel.

With suspension compression, generally the a arm pushes the bottom of the tire away from the center of the car. Bump steer is when changes in the tie rod angle do not follow the changes front track.

Stiffer springs reduce suspension travel and thus lessen bump steer.

Good night for now.

RWebb · RWebb's Garage

FWIW:

Calling All Suspension Experts