Bump steer kit fouling

[stevepatfred]

Hi everyone. Been working away on my 86 930 rebuild and ran into a snag, couldn’t get the steering shaft to not foul with the bump steer kit on the steering rack. Both u-joint bolts are loose and still it wouldn’t work. Removed the spacers and all good again. Has anyone had trouble with this? Anything I’m missing?

[doswald]

Steve, yes, I ran into the same issue on my ‘71T. The bump steer spacers change the angle of the shaft and, in some cases, cause the shaft to bind. I found several threads in which people discussed cutting the shaft to eliminate the interference. This may also require elongating the cutout for the u-joint bolt. Rather than do that, and having to then refile the splines, I decided to remove the bump steer spacers and stay with the stock setup. If I lower the car enough in the future that bump steer is an issue, I’ll use a more sophisticated solution.

Dho

[doswald]

Steve, yes, I ran into the same issue on my ‘71T. The bump steer spacers change the angle of the shaft and, in some cases, cause the shaft to bind. I found several threads in which people discussed cutting the shaft to eliminate the interference. This may also require elongating the cutout for the u-joint bolt. Rather than do that, and having to then refile the splines, I decided to remove the bump steer spacers and stay with the stock setup. If I lower the car enough in the future that bump steer is an issue, I’ll use a more sophisticated solution.

Dho

[911pcars]

Yes. The solution is to shorten the steering shaft slightly so it doesn't bind within the u-joint. A few minutes at the grinding wheel followed by deburring the splines with a triangular file and wire wheel should be sufficient to complete the bump steer mod.



Sherwood

[Harpo]

Sherwood can you tell us how much material you removed?

[911pcars]

Originally Posted by Harpo

Sherwood can you tell us how much material you removed?

Can't tell you exactly as I performed this mod once, years ago. However, that amount is revealed as you move the steering rack upward. Before starting, take a pic of the factory steering u-joint assembly to establish the factory spacing.

Before moving the steering rack, loosen the steering u-joint clamp so the steering shaft moves with the rack and into the u-joint (keep steering wheel straight ahead). Take another pic. The difference between the first and last pic will show how much to remove. You may have to trim more if the relocated rack still binds the steering shaft/u-joint. In addition, there are two u-joints in the steering shaft assembly that can accommodate some readjustment.

I would guess it's slightly less than the thickness of the rack spacers provided.

I can't speak for all "bump steer" kits on all 911 years/models. You should be comfortable knowing how much material to remove from the shaft(s) before continuing. Hope this helps.

Sherwood

[stevepatfred]

Thanks for all the reply’s. Seems to be luck of the draw if it Fouls or not. Wonder why that is?!


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[Walt Fricke]

Steve

On my 2.7, I had no trouble with binding with the usual spacer system. The rubber mount for the needle bearing accommodated the angularity of the shaft well enough.

But isn't the reinforcing cross member mount - one vertical bolt each side into a threaded receptacle welded into the tub - different on the 930? In fact, shorter, so the cross member sits higher to begin with? Which would mean the 930 steering rack, sitting on top of the cross member, will be higher up to start with?



On my non-Turbo tub I experimented with adding some washers to raise the rack even more than the standard aftermarket spacers raise it. It bumped into the tub sheet metal, and put the intermediate steering shaft bearing in quite a bind. I removed the extra bits.

The U joints are designed to fit onto the splines in only one rotational orientation - designed so that the irregular motion of the first joint is cancelled out by the irregular motion of the second joint. All U joints have this motion unless the two shafts are coaxial (in which case a U joint really isn't needed). However if you grind the slot for the pinch bolt in a shaft to make it wider, you can give yourself a bit more axial motion for adjustment than what it came with.

There are two versions of the U joint. Early cars had forged joint housings - the part which clamps on the shaft. Later ones (2.7, for instance) have stamped housings. I think there is no functional difference, and suspect dimensionally they are the same also - the stamping being simply less expensive to manufacture?

Adjusting bump steer out at the end of the steering arm is a better way of doing things, though those kits are a lot more expensive than just two thick spacers and two longer bolts.