Packard Forum Index » Post-War (1946-54)

Hi All,
Has anyone come across this term and what is it? This was iniated by a friend of mine who has a 1933 Buick very similar to my Packard. He was talking about a recent occasion he had with his car and I have also experienced with my 34. He developed a severe wheel wobble at low speed when he went over a drain cover and said that the steering became uncontrollable until he slowed down. During the discussion I told him that I had experienced this in the past but it cured after having my shocks rebuilt. He stated that all his shocks had also been done. Another guy joined the conversation and said that back in the fifties he owned a 1934 Packard and had also hit this problem. On taking his car to garage they told him that he had bump steer. What is it and how does one cure it on a fixed axle car.
All info will be gratefully received

Terry

When this occurs at lower speeds as you indicate, you can probably eliminate wheel balance or alignment; I'd start by checking for looseness in the suspension and/or steering. Worn spring shackles, loose spring perches on the axle, loose wheel bearings, worn tie rod or drag link ends, steering gear box, etc. Badly mis-matched front tires could also be a cause.

Sticking or dragging brake shoes. Feel wheel, hub cap or brake drum for excessive temperature difference from one side ot the other (DON"T BURN HAND!!!).

Worn spring schackels. incorrect installation of springs. Springs must be normalized BEFORE shackls are tightened. Tie rods that have been installed and not normalized (thus binding against each other on wheel drop or bump) can cause the problem.

One of the problems with most cars built prior to the early 1960's is that they were designed to run with with negative caster (top of king pin setting forward of bottom of king pin). That was due to road conditions and other factors not present today. For todays modern driving requirements try setting POSITIVE caster. Probably require reversing springs. Not sure how to reverse castrer for your particular car.

IF worn parts are not immediately convenient to replace then try a 'steering stabilizer'. ez to install, looks like a shock absorber mounted horizontal and parallel to axle. Anchored to axle and attached to tie rod. See a JC Whitney book or a 4wd supplier for a kit. However that mite not cure the problem if there is excessive wear, but excessive wear should have shown up as other more chronic symptoms.

I thought bump steer was the change in geometry of the steering as the suspension moved through its travel. In other words, a car with no bump steer will hold its alienment as the tires hit bumps.

A car with bump steer problems would have a tire toe in or out when it hits a bump. This sets up a really weird feeling when going around a curve, hitting a bump with the outside tire and having the car dart in an unexpected direction.

Thanks guys, I'll relay all this info back to him and see how he gets on and then report back. This may take a while.

Hi folks:

Let me give you the SAE definition of bump steer:

"Bump steer, or orbital steer, is used to describe what happens when the steering linkage is not level: the front tires turn inward or outward as the wheels and suspension move up and down. The vehicle direction will change without moving the steering wheel."

The only Packards capable of bump steer are 19th series and later Clippers, and post war cars.

Back in the 1970's GM tried to argue it's way out of building crooked cars by arguing that certain kinds of bump steer is beneficial. Yuk.