Bump Steer Thoughts

[dlund]

I'm putting together a Berrien chassis buggy and working on the steering column. In order to get the column at the angle that matches the body and have a straight line to the steering box, I had to rotate the steering box up a bit. The rotation of the steering box plus the lightly loaded front end of course puts the tie rods at a fairly extreme angle and I'm anticipating bump steer issues. So...

Looking at the steering box and tie rods, it seemed as though the obvious solution was have inner tie rod ends mate to the bottom of the pittman arm, not the top as it does stock. With the Berrien chassis I have more room here than a normal pan so this looks like a viable option that would put the tie rods at an almost perfect (flat) angle with the buggy normally loaded. How to do this the next question.

Thought 1 was to flip the pittman arm over. I think the toothed shaft coming out of the steering box isn't tapered, but the two tie rod end point holes are not symmetrical so I'm afraid that might have some unintended consequences.

Thought 2 is to do the opposite of what the guys running lowered beetles, and lots of other vehicles do. They flip the outer tie rod end at the spindles from top to bottom to get back to a more normal flat tie rod angle. What I think would work in my case is to flip the inner tie rod ends from the top of the pittman arm to the bottom. I haven't checked but I assume the taper on the tie rod ends is the same for inner and outer. In that case these or something similar should work:

http://www2.cip1.com/ProductDetails.asp?ProductCode=C12-6613-11

Any Comments?

Dave

[manxdavid]

If you use those taper adapters make sure your Pitman arm is post '68 with the larger tapers as drilling an earlier one would leave it really thin. You'd need to use post-'68 tie rod ends with those adapters like it says in the listing anyway.

[dlund]

The whole front end is '74 vintage, so is has the larger tapers.

[BL3Manx]

Another option is to keep your steering box at the stock angle and put a couple U-joints in the steering column.

[VOLKSWAGNUT]

Beetle steering shafts and columns have no lower bearing.. thus requires the straight and solid connection to the steering gear to support it.

The coupling at the steering gear provides lower support to the steering shaft and also keeps the shaft at one fixed length.
If you alter much past a straight shaft the steering wheel will wobble as you turn it as the lower coupling tries to fiight the now imperfect circle.
If you were to ad U joints mid shaft, the lower shaft would no longer be supported and it would flop within the coulmn tube and attempt to move the shaft in and out ..

A lower bearing or bushing would need to be added as well as a shaft lock to keep it from traveling in and out.


As for this issue and question.. IMO...
I say the flip kit bushings for the inner tie rods may work well provided your steering damper clears your frame, as its shaft angle would then be lower.
Thats an easy fix by changing the damper mount.

Flipping the pitman arm probably wont work as it is offset biased to one side.

_________________
aka Ken {o\!/o}
Its your vehicle- stop askin' for approval-do what YOU like for cryin' out loud
Better to roll em' how you want and wear em' out-than lettin' em' rot out
Its about the going not the showing
Rebuilt to drive not decorate
WANTED: Local Eatin' Joints, Triple D for TheSamba contributions here http://www.thesamba.com/vw/forum/viewtopic.php?t=570510
Search "VOLKSWAGNUT" on YouTube since you cant watch a "certain" BELT change video round here
Usually and often edited

[dlund]

Appreciate the positive comments. I like the idea of doing it this way and keeping the simplicity of the stock column configuration.

I'll mock it up tomorrow and see how it all looks. I have an old set of tie rods I can just grind the shafts down on so can test this without drilling out the pittman arm.

Dave

[EVfun]

I have seen people cut the 7° taper on the other side, 1/2 depth, so the tie rod end fits the same from either side.

You can put 1 universal joint in the steering linkage without needing a second bearing in the steering column. I wish there was a ready-made u-joint made to replace the rag joint.
_________________

[BL3Manx]

[VOLKSWAGNUT]

Yep... That's 100% true...
To use a stock bearing at the lower tube requires a spring or lock to keep it all seated properly.
There are after market self supporting bearings available.
I personally use a bushing and collar shaft lock inside the tube when needed.

Just note...if the shaft and box are out of line and fixed length shafts are used even with U joints the main steering shaft needs to be secured from in and out travel as well.
Using a flex or sliding secondary lower shaft helps the issue but the main shaft still needs to locked from in and out potential.

Just noting not arguing...

Way more than one way to configure steering.

.
_________________
aka Ken {o\!/o}
Its your vehicle- stop askin' for approval-do what YOU like for cryin' out loud
Better to roll em' how you want and wear em' out-than lettin' em' rot out
Its about the going not the showing
Rebuilt to drive not decorate
WANTED: Local Eatin' Joints, Triple D for TheSamba contributions here http://www.thesamba.com/vw/forum/viewtopic.php?t=570510
Search "VOLKSWAGNUT" on YouTube since you cant watch a "certain" BELT change video round here
Usually and often edited

[dlund]

"I have seen people cut the 7° taper on the other side, 1/2 depth, so the tie rod end fits the same from either side."

This is exactly what I was considering. Yes, you have less areafor the tie-rod to to arm contact point, but I prefer this to drilling out the entire thing for a sleeve where you remove a lot more material from the pittman arm.

Hope to get this mocked up today but other obligations may interfere

Dave

[wythac]

Are you making your own tie rods? If so. Think about using heim joints instead of the outer ball joints. Drill out the tapered hole on the spindle, use bushings and a bolt to set to proper height.

[dlund]

I think I'll stick with the simple approach first which is just the flip of the inner tie rod ends. Stock Tie rods. Just taper ream half way in from the other (bottom) side.

Which raises another question. Does anyone know the exact taper for the stock tie rod ends? I can't seem to find a spec anywhere. I took some measurements tonight and came up with a 10:1 taper or just under 6 degrees. I do see there are 10:1 tapers. Anybody have the correct number?

Dave

[wythac]

The simple solution I recommended allows for fine tuning adjustment. Make sure before you modify your pitman arm that you achieve the angle you desire, because it won't be adjustable.

These parts aren't so unique or expensive that you can't change it later if it doesn't work. Good luck with your project.