WOW... that never occurred to me.  If someone would be kind enough to check some dimensions I could measure/check, I would be REALLY appreciative!  That might be a logical explanaition as to why it is intermittent, wouldnt it?

Ron Grove

Wauconda, IL

OK, so i just checked my car, and compared it to the chassis parts catalog diagrams.  It looks in the diagrams like the upper a-arm mount should have a longer part (compared to the bolt hole) towards the back of the car.  Both of mine are installed that way, assuming thats correct.  ....

Also, per franks earlier comments, I had always thought that a bent spindle wouldnt matter... that since it didnt rotate that any bend, etc. would be consistent at any wheel angle, so would not be an issue.... Am i wrong?  Im having a hard time visualizing how a bent spindle would cause these types of issues?

Also, the car now has radials, but had the problem with bias ply as well

Thanks!!!!!!

Ron Grove

Wauconda, IL

Also, per franks earlier comments, I had always thought that a bent spindle wouldnt matter... that since it didnt rotate that any bend, etc. would be consistent at any wheel angle, so would not be an issue.... Am i wrong?  Im having a hard time visualizing how a bent spindle would cause these types of issues?

I guess it would depend on where it's bent, but I really suspect the hub more than the spindle. Not really sure how much run out is acceptable, as a guess I'd say .030 should be OK.

Frank/Rebop

Bristol, In ( by Elkhart) 

If I am understanding this thread correctly it sounds like you have checked everything but the hub itself.  I like Frank's idea,  switch hubs and see if the vibration appears on the left front. 

It might be that the bearing bore centerline does not agree with the centerline diameter of the exterior shoulder that locates the wheel and bolt circle of the 5 studs.  Locate a dial indicator in such a way that it can touch each stud as the hub is rotated and see if they all describe the same dia circle.  Even better measure the runout of the shoulder.  My guess is that the hub machining should quite precise, say within .002 or .003 thou especially the shoulder to the bearing bore runout.     

Doug T

The Highlands, Louisville, Ky.

Ron:

Looked at my '56 Bird, the long end of the shaft is toward the rear of the car, as is yours.  On the Bird, it it was reversed, the A arm wouldn't clear the inner fender, so it has to be correct.

The discussion has mentioned hub runout, but what is the runout at the tire tread.  Maximum allowable is pretty small, maybe 1/8" or less.  Of course, none is best.  If you have .030 runout at the hub, it should be a lot more at the tire tread.  Has the drum been removed from the hub?  If so, the swaged part of the wheel stud may be preventing the drum from seating flat on the hub.  That would give you that tight/loose feel when you turn the wheel because the brake shoes would hit on the lowest point of the drum as it rotated.  Did that make sense?  Sometimes the things I see in my mind don't come out of my fingers to the keyboard in an understandable form.

John - "The Hoosier Hurricane"

John, that makes sense as well as all the other suggestions, surely with the car jacked up and spinning the tires would show any noticable runout which would encompass most of the other variables. wheel shimmy often is result of too much negative castor angle, i would suggest take car to good wheel alignment place where they are used to checking and dealing with front end problems, like excessive play in power steering control valve and idler arm etc also with convertibles they are very flexable in the chassis due to no roof and require the body to be fastened tightly to the frame for rigidity otherwise the f/end can flop around on bumps and uneven roads. We will all be keen to find the problem. Good luck. regards aussie bill.

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

Thanks to everyone for the replies/ideas so far!  Im going to try switching sides this weekend.  My guess at this point is that it is probably a bad hub, and probably needs new tie rods after all the beating from the vibration (the tie rods have about 14k miles on them).

Ill let you all know what i find out this weekend.  THANKS!!!

Ron Grove

Wauconda, IL

I bought new tires, had them mounted and balanced, and they vibrated.  The tire guy marked the hub to the wheel and the wheel to the tire, then he got his dial indicator out and went to work measuring lateral and radial runout.

Stamped production wheels are not round.  Neither are molded tires.  You established everything is tight and within alignment specs.  I assume your universal joints are good and your rear axles run true. Vibration occurs as a result of imbalance (static or dynamic) and/or out-of-round (radial or lateral) conditions. 

My tire guy pulled the tire off the wheel and measured wheel runout.  Finding it within specs, he remounted the same tire turned 180* and measured runout again.  Runout improved and my vibration problem went away.  Runout stacks up between components.

You can use a 'turned' aluminum wheel on your hub to detect eccentricity if it is suspect.  You can also mark your stamped wheel for 'high' runout, advance it two studs, and measure it again to detect any difference.  That will show an off-center hub.

Assuming your car is mechanically sound and axles run true, the only thing left is drum and wheel balance.  The farther out from the pivot (radius) the more a small imbalance will show (we go by gram/centimeters).  Some tires are manufactured with a heavy spot on the crown.  If it is excessive the tire must be replaced.

If unequal weight is on both sides of the tire/wheel assembly’s circumferential centerline, the tire/wheel assembly has a side-to-side wobble or wheel shimmy.  A good tire company will do everything they can to make sure your wheels don't vibrate.

  - Dave

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

One of my buddies installed a robot for Honda (?) at the Marysville, Ohio plant - maybe a sub-asembly plant ? Dunno.....

Anyway, he told me they actually spin each completed painted and baked steel wheel to find the "heavy" side - and all of the tires come marked with a belt "lap" position. I would guess these points are assembled 180° apart ....again I dunno....but apparently there is a balance (and probably a reduced balance weight cost) reason to doing this sort of matching operation.

Would there be an advantage to checking the spin balance of replacement (steel) rims - before you go to the trouble of putting tires on them? Might sort out some problems.

 
 Steve Metzger       Tucson, Arizona

We have had problems with tires changing position on the rim, at the assembly plant.  Our tire machines mount at least five tires per minute.  If there isn't enough soap, that mounting machine will rip a new tire (we tear about five/shift).  The soap lubes so well, our rims sometimes spin inside the tire at the Roadability (scuff) machines.  You know what that does to the wonderful dynamic balance operation that just happened minutes before.

Spin the wheel for balance?  Any cost-saving and weight-reduction methods are a plus.  The real imbalance happens at the crown of a tall tire.  14 grams (1/2-oz) of crown-imbalance at 300mm (11.8") radius on a 175/70R14 tire is VERY different than the same weight on a larger diameter tire crown.  The imbalance may be from a heavy OR light spot.

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected