Originally Posted by masraum (Post 10615765)

I always thought it was ok for the tie rods to angle down some, but it's not ok for them to angle up. The problem is usually for cars that have been lowered so the tie rods angle up.

Originally Posted by A930Rocket (Post 10615784)

You might be right. When the car is lowered and the tie rods angle up, toe in is affected as the wheel goes up I believe.

Originally Posted by Flieger (Post 4255788)

It is more the change in toe than the change in camber. Toe change is affected by the relative movements of the tie-rod to the A-arm (different arcs).

If the A-arm is pointing down and the tie rod is level (stock suspension setting), then under compression, the hub/A-arm moves out but the tie rod gets shorter. Therefore, the toe turns out under compression. This is bump-understeer.

If you lower the car: A-arm level, tie rod up, zero toe-alignment at this ride-height.
Under compression, the tie-rod still causes toe-out.

If you add dropped tie-rod pickups, the tie rod will not get shorter at a faster rate than the A-arm. Therefore, less toe-out bump steer.

Theoretically, you could make the tie rods angle down while the A-arm was level. This is bump over-steer. The toe turns inward on the wheel in bump, causing steering input tightening the turn.

Camber effects complicate the severity of the bump steer.

Originally Posted by Bill Verburg (Post 4256227)

Yes & No, at static loaded rest the steering arm is presumed to be at the mid point of it's travel range and this is ideally the point were camber and toe changes are linearly correlated to wheel travel, out of this sweet spot the changes in camber and toe are non linearly correlated to wheel travel and cause excessive extraneous steering inputs to be even more undesirable. Ideally the steering arm and lower control arm will always be parallel and move thru the same arc minimizing camber & toe changes(which cause bump steering) but that can't happen because the pivot points for the 2 arms are in different planes both horizontally and vertically. So you can only minimize the difference in arcs over the relatively narrow sweet range of travel, to limit travel you use big springs and stiff shocks, to minimize arc difference you start in the middle of the travel range and start w/ parallel to the ground for the steering arms and as close to that as possible for the A arms.

Here is a '73RS that could stand to be lowered a tad, you can see that the steering and A arms are at different heights and have different pivots so they move in different arcs, a washer type bump steer kit will lower the steering arm pivot to be nearer the plane of the A arm pivot but they will never coincide.
http://forums.pelicanparts.com/uploa...1224766620.jpg

http://forums.pelicanparts.com/uploa...1224766646.jpg



??? bump steer is caused by a vertical suspension movement on one side of the car that cause the wheel on that side toe toe in or out causing a corresponding change in vehicle yaw, in a turn the same effects are still in extent, but now the turn is causing one wheel to move up and the other to move down, one wheel is trying to turn more than the other,the 2 wheels will steer in different arcs because of built in ackerman and because of the camber/toe changes caused by wheel movement

I agree w/ the latter but the former is misleading, the A arm has max Y axis displacement when it is parallel to the ground, the arcs can only move horizontally inboard from there, The effect is to shorten the effective length of the arm at the lower end of the steering axis, the steering arm is doing a similar thing in a slightly different arc but if both start horizontal then you have a better chance of staying in the linear ranges for camber/toe changes


camber curves are typically S shaped w/ a relatively linear portion at the middle of the S that is where you want your ride height to stay in the linear middle portion of the curve

The spindle is raised to maintain full shock travel, at the same time it allows the A arm to start in a more horizontal position on a lowered car again, starting at horizontal is good because you stay in the sweet spot for camber/toe changes more of the time

You will always have some bump steer, it is in the nature of the suspnsion design used, all you can do is minimise it.

Kevin's suggestion actually measuring is good( and very interesting to be able to see) but unnecessary.

If you stay at RoW ride height, or ~ 25.5" at the fenders w/ stock 16" wheells and tires then the factory specs are great, they did all the work.

the lower you go from there the more other "stuff" needs to be done, go to ~ 25" and the washers are needed, go to 24.5" and raised spindles and Steering arm kits are needed

Originally Posted by A930Rocket (Post 10615871)

Thanks guys. The top picture is one of a Mustang with a bump steer kit.

The bottom two pictures show my control arms with the tie rods parallel to the A arms. Tire wear is good and most of my driving is highway with no off road (it’s 2 WD and I just wanted a slight height adjustment with slightly bigger tires).

Originally Posted by asphaltgambler (Post 10616079)

From the pics above - your angle from the inner tie-rod pivot point is too far down (vertically measured) in relation to both upper and lower control arms. With the truck on a level surface, wheels ahead - the tie rod assy should be close to the same plane as the lower control arm.

And of course - it isn't .

MO is the best way to resolve this is (hopefully) someone makes an aftermarket steering knuckle that places the tie rod arm higher so the angle is not so extreme. I'm sure there is someone out there that has these as lifted trucks are very common place.

I'm not a fan of those tie-rod end extender's - unless they are the only solution and very short - like 1" or less.