Bump Steer

[chevykevy]

I'm a new member to the site and have been reading nearly all of the posted tech questions. i was reading a thread about power steering conversion on a 68, which coincidentally I have as well. I am planning on spacing a gear box from my frame the suggested 1/2 inch with some type of spacer and was wondering how tp maintain proper bump steer. Is bump steer the equal amount of travel in both the left and right turning directions? I'm obviously new to the truck rebuilding stuff.

Thanks,

ChevyKevy
Yellowstone N.P
68 Chevy LWB project

P.S Does anyone have a throttle rod from the firewall to the carburetor from a 69 or 70. I am looking for one with a longer section of rod after the 90 degree bend toward the carburetor to clear the kickdown bracket.

[71swb4x4]

Welcome to the board.
I am not totally sure here, but I always thought that bumpsteer was when you had the steering geometry wrong - so when you would hit a bump it would move the steering linkages and turn your tires a bit - not sure though.

Shawn

[walker]

I think what he is talking about is total wheel movement from left to right. That is controled with your steering linkage and tie rods. If you were to move your steering box 1/2" to the left you would screw the left tie rod in 1/2" and screw the right tie rod out 1/2". You may also be able to move your steering arm in the opposite direction you moved the steering box by a spline or two. Not sure, as I have not done this mod, just speculating. Also, it seems to me that you have to change your steering arm and center link, use the later model inner tie rod ends and an adapter sleeve to do this.

[Ole Blue]

71swb4x4 is on the right track. Bump steer is toe in or toe out caused by suspension travel. Bump steer can be found in either bump or rebound, or both bump and rebound. It is caused by the relationship of suspension pivot points ie upper and lower control arms, tie rods etc. Bump steer is plotted or measured by the amount of toe in or out per each inch of bump and rebound of suspension travel.

[Slammed67]

If your steering shaft is the one piece style, DO NOT space out your steering box. It'll put too much stress on the lower steering column bearing. This will score a groove on the shaft which will cause it to break eventually. Trust me on this one...... it happened to me! Does your frame not have the indention for a power steering box? I thought '68 + had the provisions for a power steering box.

[chevykevy]

Slammed 67,

My frame doesn't have the indentation but I have acquired a tilt column from a 72 with a two piece shaft to replace the current column. From what I've heard, the early 68's did not have the indent but the later 68's do.?? Thanks Kevin

[Classic Heartbeat]

Every 68 I have seen has had the frame indented for the later model steering gears. If you shim the stearing gear 1/2" out from the frame you will cause it to be off center. That will make it feel super sensative and cause the truck to bump steer. I found that out myself on a 67 3/4 ton truck that I have. If I drove it over about 40 mph, it didn't feel safe. I pulled the steering gear heated the frame and indented it. Solved the problem. WES www.ClassicHeartbeat.com

[67dragtruck]

I did the same with a torch and a hammer. Not to bad to do and solved the problem.

Tom

[chevykevy]

Thanks for the info., I think I'll try that torch and hammer trick

Kevin