Bump Steer Kit

[Autoban]

My car is lowered and does not have a bump steer kit. I am going through a repair on my steering rack right now (Play in Steering Mechanism) so I am going to order the kit. Of course after I install the kit the toe in will increase. Does anyone know how many turns (or fraction of a turn) the tie rods have to be turned back in to get the toe in about where it was before? Of course I know I need to get a proper front end alignment after all, but this would get me started since the nearest shop who can do a good alignment on an old 911 is about 75 Miles away.

Juergen

[Flieger]

Careful with those kits. If you don't have raised spindles they can cause more bump steer than they eliminate, depending on how low the car is. Personally I am fine without it and my car is pretty low- so low the A-arms hit the chassis occasionally.

The rack spacing type probably would be fine, but don't use the ones that move down the outer tie rod end.

[whiz05403]

I ordered the kit for my 87 and it turns out I already have it. I could sell you mine for cheap.

[kshafer1]

I had the ERP bump steer kit installed along with a full front suspension refresh and the bump steer is insignificant now. I had alignment and corner balance done at the same time so I can't really answer the question you asked, but I can say these kits do work because the bump steer before was quite annoying.

[Autoban]

I was thinking about the washers to raise the steering rack. I have access to a machine shop, I think I will measure my car to get the exact height I need and just make a pair of washers to get the tie rods level.

Juergen

[douglas bray]

I ordered the spacers from our host and they were on my desk when I go to work just a bit ago. It is interesting that they come with two sets of bolts and instructions that single out some SC's as needing the shorter bolts. Would not want to screw this up. Basically, the spacers are 10mm so you need to use the bolts that are 10mm longer that what is currently on your car.

[911pcars]

The term, "bump steer" is commonly misunderstood. It really refers to toe-change during suspension movement. The ideal is zero toe change throughout the suspension travel. If it's off, the vehicle may exhibit unsettling handling during cornering as the suspension loads and unloads. Independent front and rear suspensions can have potential bump steer issues.

The popular bump steer kits (longer bolts and spacers) are mere approximations for ride heights lower or higher than the factory spec.. Don't worry about getting it exact because it won't be, just maybe closer.

The bump steer kits by ER, Rebel Racing and others can provide more accurate adjustments. However, many people only use the adjustment spacers to visually align the tie rods horizontally, then call it a day - also an approximate setting.

For those who prefer to accurately minimize bump steer, here's the technically correct method of achieving that objective:


As you can see, it takes some equipment and effort to do it right. On a track car, it's an essential adjustment for best handling. For a street-based car, not as critical, but YMMV.

Sherwood

[DRACO A5OG]

OP, use the string method. If you have fuchs, measure equally away from the center caps then measure the readings. You can use four jack stands and string for a quick and dirty.

I found my driver side did not move and only need to adjust the toe on passenger side to bring her to zero.

[Autoban]

Originally Posted by DRACO A5OG

OP, use the string method. If you have fuchs, measure equally away from the center caps then measure the readings. You can use four jack stands and string for a quick and dirty.

I found my driver side did not move and only need to adjust the toe on passenger side to bring her to zero.

The center caps on front and rear wheels are the same distance (so front and rear track is the same)? If I put a string on each side of the car and measure equal distance front and rear from string to center cap then the string is parallel to the car? Of course I use 1/4" spacers in the front and 22 mm spacers in the rear, so I have to account for that (I know, I have to make things more complicated).

Juergen

[douglas bray]

Toe String method:

Find the center of the car in the front and in the back.

Set up strings at the center line of the hubs, that run parallel at equal distance from the center, on either side of the car. I usually go about two inches out from the widest axle.

Center the steering wheel.

Measure both leading and trailing edge of your wheels so they are the same.

If anything, give yourself a slight toe-in of 1/16" and adjust to feel. Granted, over 30 years of doing this, all my cars have been street cars.

I also have Longacher plates when I want to do it quick and dirty.

[Autoban]

Originally Posted by douglas bray

Toe String method:

Find the center of the car in the front and in the back.

Set up strings at the center line of the hubs, that run parallel at equal distance from the center, on either side of the car. I usually go about two inches out from the widest axle.

Center the steering wheel.

Measure both leading and trailing edge of your wheels so they are the same.

If anything, give yourself a slight toe-in of 1/16" and adjust to feel. Granted, over 30 years of doing this, all my cars have been street cars.

I also have Longacher plates when I want to do it quick and dirty.

I'll try this after I get my steering rack back in the car.

Juergen

[Oh Haha]

DB- what would the difference in measurements, front and back of the front tires, be to get to the 1/16 toe in?

I will be doing this method after I install my steering rack as well.

[Chuck.H]

Just a note on bump steer - I've noticed that not enough toe-in can cause a similar feeling to bump-steer, in that as each wheel hits imperfections in the road, it can cause direction changes as the car comes off 'pointing forward' steering and goes towards the side with the bump. With a little toe in (or a little more toe-in) the wheels don't get moved enough to cause steering changes when running over minor bumps.

Too much toe-in causes the steering to be 'dull' though -- you don't want that either.

HTH,
Chuck.H
'89 TurboLookTarga, 382k miles

[javadog]

Originally Posted by Autoban

I was thinking about the washers to raise the steering rack. I have access to a machine shop, I think I will measure my car to get the exact height I need and just make a pair of washers to get the tie rods level.

Juergen

You can only move the rack a small amount, so don't make the spacers before you understand how much movement is possible. Also, make sure to not put your steering shaft in a bind.

JR

[911pcars]

No need for custom washers. Stacking regular washers work fine. C-shaped alignment spacers are more convenient (easier to remove and replace).

Yes. Loosen the U-joint clamp at the steering shaft to allow the rack to move from its original resting position.

[douglas bray]

Originally Posted by Oh Haha

DB- what would the difference in measurements, front and back of the front tires, be to get to the 1/16 toe in?

I will be doing this method after I install my steering rack as well.

Honestly, I have no idea what that 1/16" gets you in "degrees of toe in". I got that number online somewhere. It helps to center and settle the front end.

As an aside, back in March I set my rear toe to as close to zero as I possibly could then went on a long, 500 mile trip. At freeway speeds over 80 mph the back end of the car felt like it wandered side to side ever so slightly. Dialed in just a sub-fractional amount of negative toe in the rear and that wondering has since vanished. The spring plates are made so that zero toe is all the way to one extreme. It's as if they knew we would want lots of negative rear toe.

[Oh Haha]

Thanks DB. I'll give that number to the alignment guy. I should be close to where it was before removal as I marked the threads.



This may help those in re-installing the steering rack:

I installed my new rack boots with the rack on the workbench. I centered the rack on the bench and noted the orientation of the steering shaft mounting hub on the rack.

To install the rack back into the car I left the tie rods ends and the lower steering shaft off and slid it in from the passenger side. I had it in and secured in less than 10 minutes.