F-100 Bumpsteer Issue..Sorry for long post

B Duncan

B Duncan

Member
Hey Group,

My truck has developed a bad bumpsteer problem. It started all of a sudden, but I need to give a lil history. Please bear with me! I have owned my 53 F-100 for over 12 years. 6 years ago I added the standard eye mono springs to lower it 3". I had radial coker classics for tires. When these tires wore, I was unable to afford radial white walls, so bias coker classics are on the truck now. These tires have been on the truck for 3 years. Last year I hit a pothole in the road and for the first time I thought I had lost a tire. I had to come to a complete stop to get the front end to quit shaking. I know these bias tires drive different than radials, but nothing ever like this has happened. Last week I installed a rebuilt stock axle with new kingpins, tie rod ends and a new drag link. Toe is set at 3/16", and I have added 4 degree shims (read online that this would cure bumpsteer). Took the truck on a test run and bumpsteer was worse than before. Any thoughts or ideas on how to fix this? Less caster, or will I have to install radial tires... The Bias have been balanced 3 times since this first happened. No change! Thanks in advance as always guys.
 
At this point in your front end wobble problem: Check tire pressure and it is better to be a too high than a too low of tire pressure. Is your tire gauge accurate? Most are not. To me, I like 1/8" toe in better than 3/16". But then I like radials better than bias ply too. The tie rod has to be perectly straight or it will bow during a pot hole encounter and will start a wobble between the front tires. On one of my cars that had this problem, I had to put on a heavier tire rod to prevent the front end wobble. The last resort is to add an anti shimmy damper to the tie rod. Those can be bought at about any parts store.
 
I will check tire pressure again. Thats a good idea. The tie rod tube is also new, so I know it is straight. Thanks for the tips!
 
Any play in the system can contribute to feedback. If spring hangers/shackles, king pins, & steering linkage are tight. Check for play in the steering pitman arm with wheels straight ahead. There should be no play there. The condition of shock absorbers has also been known to contribute to problems with steering.

Tire pressure and condition can cause problems as was mentioned. If problems persist, try another set of tires. The carcass of the tire that hit the pot hole might have been damaged. Condition of wheels for bend or out of round can affect steering.

Kerby
 
are you talking about bump steer or wouble there two different items if it,s wouble i agree with rotor wrench. you either bent something. or possably broke something in the steer box it,s self. i do not think tires are your problem back in the day when most of us had no money we put any tires we could get. usley from a junk yard we used to call them may pops because they might pop at any time . but we never had wouble on account of them unless they were out of blance i even ran two different size tires on the front and still had no bump steer. if its bump steer then it,s a geometry problem.check for play & set the front end back to factory spec.
 
How is your drag link? It should be parallel to the ground, and be sure the end joints are not loose.
 
The drag link is new and adjusted per my shop manual specs. It doesnt wobble, its just when I hit a bump a certain way. The steering box has a little play. I can move the wheel 3/4" before i can see the tires move. I am going to double double check the tightnes in the box to see if it has loosed some from the frame. Everything else is brand new. Tie rod ends, tie rod tube, king pins, draglink, ect. I wish I knew an exact caster angle. I have some additional shims, but its alot of work taking them in and out. My only other guess is that the tires have been damaged. It is really frustrating having to drive the truck like I am walking on ice.
 
Park the truck, wheels straight ahead, on a the most level pavement you can find. Using a flat surface that is either vertical or horizontal on the front axle you can check it with a magnetic angle finder; I think you can get them at any hardware or home improvement store for about $10. Caster for an F100 should be 3 or 4*and toe with bias plies 1/16".
 
Thanks again. I will adjust the toe back to 1/16" I have 4 degree shims installed. We will try this and see what happens!
 
Bump steer usually is when a bump or hole is hit by either wheel the vehical will dart side ways to one side or the other .if this is your problem one of your steering arms is bent either up or down from the other .They both should be the same heigh from the ground at the tie rod ends John.
 
I am looking to borrow a set of radial tires to see if that might change things. It that is the case, new tires might be in my future.
 
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