vibration from old-school cragars

eljefino

eljefino

Joined
Jun 15, 2003
Messages
40,452
Location
ME
1966 Biscayne

Has older Cragar 2-piece rims with BFG T/A 245/60r14s in back. Kumho 205/75r14s in front. Tires are at 35 psi. Chevy recommends something in the high 20's.

Had vibration at 55 mph that went from nothing, to the-rear-is-gonna-fall-off with a 2 mph bump in speed.

Pulled rear wheels. Rebalanced. One may have been out 2.75 oz. Tires have maybe 1/8" of runout. I've had others like this that were still livable, particularly on the rear axle.

Pulled the hub adapter rings, wirebrushed the rust off, got the hubs. Wasn't bad, but worth doing. These rings are steel and have a little split in them like a piston ring so they fit snugly on the hub. Rims have the elongated lug holes so they fit either 5x4.5 or 5x4.75.

Now the shake happens at 60.

I don't think my shocks are dead-- the car handles decently. But I wonder if I'm getting some harmonic imbalance exaggeration. Or could be a driveline issue I guess.

Next step? I like the rims for looks, even though the staggered setup is stupid behind my inline-6.
 
There's a lot to unpack here.

I get the impression that the vibration is in the rear (feel it in the seat) and not the front (feel it in the steering wheel) If so, swap the fronts and rears (just for this test). The vibration ought to move to the steering wheel. If it doesn't, then the problem is in the drivetrain, likely U joints (although U joints should show up at a lower speed.)

My guess is that the vibration will move, so it would be the tires and/or wheels.

A couple of thoughts: I don't think Chevy used hub piloting in 1966, so I am not sure what good the hub rings are doing.

Second, 1/8" is HUGE!! That could be pretty much all wheels.

So how much work do you want to do? If you really want to get down to it, find a place with a Hunter GSP9700 (or the like) Hunter Equipment Locator and get the force values for both the tires and the wheels. That ought to dictate your next step. Wheels ought to be a fraction of tires (about 1/3 or 1/4). If not, then you're going to have to either fix the wheels or replace them.

A quick and dirty method would be to rotate the tires 90° relative to the wheels and see what happens.
 
eljefino said:
1966 Biscayne

Has older Cragar 2-piece rims with BFG T/A 245/60r14s in back. Kumho 205/75r14s in front. Tires are at 35 psi. Chevy recommends something in the high 20's.

Had vibration at 55 mph that went from nothing, to the-rear-is-gonna-fall-off with a 2 mph bump in speed.

Pulled rear wheels. Rebalanced. One may have been out 2.75 oz. Tires have maybe 1/8" of runout. I've had others like this that were still livable, particularly on the rear axle.

Pulled the hub adapter rings, wirebrushed the rust off, got the hubs. Wasn't bad, but worth doing. These rings are steel and have a little split in them like a piston ring so they fit snugly on the hub. Rims have the elongated lug holes so they fit either 5x4.5 or 5x4.75.

Now the shake happens at 60.

I don't think my shocks are dead-- the car handles decently. But I wonder if I'm getting some harmonic imbalance exaggeration. Or could be a driveline issue I guess.

Next step? I like the rims for looks, even though the staggered setup is stupid behind my inline-6.
Click to expand...
baautocare.com

Is Your Car Shaking? 3 Common Problems That Cause Cars to Vibrate

Have you ever been driving your car and it shook so much you felt like you were on an amusement park ride? Well, here are three common problems that can cause a car to shake.
baautocare.com baautocare.com
 
Thanks all. If it bugs me too much I'll probably go back to plain-jane steelies and a sensible tire size. Something off an s10 or something.
 
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