Bump Steer Question

[Big Secz 26]

So as some of you may have seen on previous threads I am battling a bad bump steer problem. I ordered the Pro-Motorsport Bump Steer elimination kit which relocates the outer tie rod end down one inch.

 

I got under the car today and looked and my outer tie rod is angled downward already and the kit I ordered will end up lowering it down yet another inch so it will be angled down even more. I thought, and correct me if I'm wrong, bump steer due to the tie rods would show if the tie rods were angled upward.

 

Does anyone have any pictures of good tie rod orientation?

[LoneWolf2U 136]

This is a pic of the 68, But it is the same set up.

Note how the tierods are at the same angle as the lower control arms

even with it on the lift.

When it is on the ground they follow the same plane.

[69gmachine 15]

The real problem with our car's original design is that the tie rod assembly does not go through the same arc as the lower control arm, even if you set them up at the same plane at any given suspension angle.

 

Looking at the pic Mach1Rider provided, you can see the real cause of the problem. The pivot points on the center link are too far inboard to fall on the imaginary line that extends through the pivot points of the upper and lower control arms.

 

If for example, the pivot point of the centerlink were lined up perfectly with the pivot point of the LCA (with wheels straight ahead), and the tie rod assembly was the same length as the LCA, then it would not matter what angle the tie rod was relative to the LCA, they would still go through the same arc, and therefore result in no bump steer.

 

When you move the pivot point anywhere along that imaginary line, there becomes one unique length of the outer tie rod assembly that will result in zero bump steer, and the outer point must lie on the arc defined by the pivot point of the lower ball joint. However, when you move it way off of that imaginary line (like our centerlinks are), the best you can do is find a location that minimizes bump steer through the normal travel range (which is what people do when they add all the lowering spacers to the outer tie rod).

 

This is why I gave up on the original design completely and designed my own steering and suspension. I hope this helps.

[Big Secz 26]

Here's a pic of my current set up. I'll take better pics in tomorrow in during the day. But you can see it looks like the tie rod is not quite parallel to the lower control arm.

Edited October 9, 2011 by Big Secz

[Big Secz 26]

Got the car in the garage this morning and took another picture. The car is jacked up in this picture. You can see how the tie just slightly is at a different angle than the lower control arm. So this is probably adding to my bump steer problem. While the car was up I checked for play in the wheels and discovered that my driver's side tie rod end is bad which is probably another contributing factor.

[LindenBruce 27]

Those ball joints look old. Are you sure they are tight and serviceable? How about the idler arm? Bruce

[Big Secz 26]

Those ball joints look old. Are you sure they are tight and serviceable? How about the idler arm? Bruce

 

I did the standard tire shake test to where side-to-side play equals bad tie rod ends and top-and-bottom for ball joints and there was no play at all in the tires top and bottom. So I think I can get away with my ball joints for another year. Next year I'll work on replacing all of the front suspension components.

[dlinebar 2]

FYI I did the tie rod test as I had bump steer issue as well. I wound up replacing the Idler Arm and that fixed the problem.

 

Dan

[danno 128]

What are the mods to your car? Have you changed the brakes, steering, or suspension?

[DRASTiK 22]

grabbing the wheel at the top and bottom to check for play is checking wheel bearings. While it's jacked up, place a pry bar under the tire and see if you can make it move upwards vertically. This will check for ball joint play.

[Big Secz 26]

What are the mods to your car? Have you changed the brakes, steering, or suspension?

 

 

No mods to the brakes, stock drums. Suspension is fairly stock except for some 620 springs. The stock steering setup has been swapped out for a Borgeson kit.

[gsxrken 21]

You can also measure your bumpsteer if you have a 1" dial indicator and some patience.

I charted mine on excel. As 69GMachine said, the mustang architecture is what it is, but if you go with some stiff springs and sway bars so that you don't get much travel, you can tune for your suspension's typical location and limit it to a large degree.

[Powershift 19]

We sell a bump steer gauge at MM.... not sure if it will work on a vintage Stang though.

 

http://www.maximummotorsports.com/store/index.php?main_page=product_info&cPath=71&products_id=193

 

You could also call Maier Racing if you want bumpsteer info....

http://www.maierracing.com/

Edited October 11, 2011 by Powershift