Thread: Straight Axle Front Ends

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On my 32, I have the first straight axle I have had on a car. This is a Pete and Jakes front axle with a Vega Steering Box. All new.

I have had the car alligned. I still notice that when I am on the highway doing 50 mph, plus. My steering feels very tight. What I mean is that if I hit a medium or large bump in the road the car kinda of turns or hops on me and I have to do a quick jerk of the wheel to keep it straight. Almost feels like the steering may be too tight? I have a Vega Box. The car does NOT pull or hop at any time other than this.

Over the past 15 years I have owned many muscle cars from the 60's, that never did this. Then again, they were not straight axles.

Is this a common thing for straight axles front ends and I just have to get used to it? Can the Vega Steering be adjusted to maybe allow a little more "play" in the wheel?

It's called bump steer.

Likely your axle is "swinging" sideways on the front shackles, not uncommon with a transverse spring. The sideways movement induces a steering input. The normal correction is to have a panhard bar (Pete & Jakes has one on their site and your right side "batwing" may already have a mount). It attaches to the left frame rail via a bracket.

If you don't want to weld on the bracket you could go with an old roundy roundy racer trick of a dead perch, see Deuce Factory, they make them.

One other posibility is to add a damper to the tie rod, see SoCal Speedshop, though that won't stop the perch movement, it slows down the bump steer action.

Bob- I forgot to mention. This thing already has the Pete and Jakes Pan Hard Bar............

Are the drag link from the Vega box and the panhard bar both parallel with the front axle?

If not, you will get bump steer.

Then it's time to start checking other things. In addition to Jack's comment go through the entire front suspension to make sure everything is tight that's supposed to be tight, and straight that's supposed to be straight. You might want to load and unload the front suspension and see if there is any apparent bind in the four bars (or do you have hairpins?) during travel. As an example, if the bars on each side are not close to even in length (perhaps a poor installation or compensating for prior damage) they won't follow the same arc on compression/extension which will induce steering.

When the alignment was done was it the two fronts only or did they check all 4 wheels? Could be your rear suspension is setup wrong and you're getting some steering input caused by a bind/loading in the rear.

I have built and driven many cars with straight axles, Vega boxes, cross springs and a Panhard bar, and they all steered very well.---Just a thought--Make sure that the front panhard is anchored to the frame on the drivers side, not the passengers side, and also, if you run a rear Panhard make sure that it too is anchored to the frame on the drivers side of the car.

All great info for me to check into. I appreciate it! Lot's of work to do.

I should have sold our big house 3 years ago, so now I could be in our little house and HUGE climate controlled garage so I could do all this stuff during the winter..........

Another aspect I should have mentioned, though it might not apply as I think you said this car doesn't have many miles on it. I bought a '32 roadster a few years back that did a nasty little dance when hitting bumps in the road. Turned out the front bushings on the rear ladder bars were split. Just something else to consider.

Well. Guess I will look into a rear panhard bar. I checked this weekend and my front panhard bar is welded to the drivers side of the frame and runs parallel with the front axle.

This is what my mechanic suggested to me today.

Lon,
I would look into a rear panhard bar, it really should have one. I would be happy to recheck it, but when we aligned the car, the rear was good. Our machine uses digital cameras to image the whole car, so they way the software works is to look at the vehicle as a whole. Meaning it is impossible for us to take readings or just look at the front, we get readings for the rear as well. Thus the term “complete” vehicle alignment. Since the front alignment is based off the rear, the machine will not allow us to do a front wheel alignment if the rear is out of whack. Make sense?

Update per Pete and Jakes.

I have a Triangulated rear end. No Panhard bar for these as they act as a panhard bar already.

They are guessing since I run 295/50/15 tires I am getting tire movement and hop. Rear end is wider than front and following different track in road. Also, high air pressure will ride tough but lower air pressure (like I have) is also causing this jump/sway I am feeling when hitting bumps and the tire side walls are moving on me at 55 mph and faster.

Said to check all connections with the rear end, but if the car is alligned and the front already has a panhard bar, this is probably what I am feeling.

I'm not sure I buy the tire issue. I originally had 295/50/15s on my '34 w/ Pete and Jakes chassis. I had no problem because of the big/little tire combo. There may be something to the air pressure idea because of the flexible sidewalls in radial tires.

Did you check to see if the drag link and panhard bar were parallel to the front axle?

Coupling your other post about the rear being offset to one side more than the other I'd suggest the triangulated four bars are not equally adjusted which could be causing them to follow different arcs, inducing slight steering input from the rear. If it's not adjusted length perhaps it's indication of damage or improper bracket placement when fabbed. Adding a panhard bar to a proper triangulated 4 bar would be superfluous.

I believe it is the rear end mounting. If you jack the back of the car up, put jack stands under your frame then unhook your rear suspension and put a jack under your rear end then watch it go threw it's travel it should be obvious as to what is going on.
Ken

Originally Posted by Ken Thurm

I believe it is the rear end mounting. If you jack the back of the car up, put jack stands under your frame then unhook your rear suspension and put a jack under your rear end then watch it go threw it's travel it should be obvious as to what is going on.
Ken

Ken, when you say, "unhook your rear suspension", you are talking about the shocks, right?

Mike,
Yes, anything that suspends the rear end, shocks, coil overs, torsion bars or leaf springs. Not what holds the rear end in the car 4 bar of ladder bars or what ever you are using. Sometimes the panard bar is way to short and that radius will affect the steering also. But if you just take the suspension off and watch what is going on you will see. I agree with Bob, with the rear end in of center, thats a pretty good indication it just isn't set up right, it's just an adjustment.
Ken