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Front end vibration at 65 MPH


1inxs
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I have finally completed getting my 50K mile barn find 1964 Studebaker Avanti out on the open road. I have driven the car for a near 100 mile road test. Since getting it back on the road when I reach 60 MPH I start to get a pretty stout front end vibration and it is major at 65 MPH. The new tires have been balanced and it doesn’t appear to be tire balance. The car had been sitting since 1969 and part of what I had to do is rebuild the front brake calipers. At some point I seem to remember that in order to set up the front disc brakes properly, I was supposed to used shims and verify the calipers were centered perfectly with the rotors. Not something I would usually do, but I ignored that step of my front break installation. 

Now my question is- Does it sound quite possible or even likely that my front end vibration would be due to the centering of the rotors in the calipers? Has anyone got other suggestions for what may be the cause? Thanks in advance, Robert

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The disc brake calipers do need to be centered on the rotor with shims.  These aren't floating calipers like modern cars, so they won't center themselves.  If the caliper is significantly out of center, then when the brakes are applied the cylinder closer to the rotor will push first and try to bend the rotor.  That would likely cause a vibration.  But, it sounds like your vibration isn't under braking conditions. If so, then the calipers would have to be quite a bit out of center to cause a vibration (when not braking), and I wouldn't think a brake vibration of this type would be quite as speed dependent as your symptom.

So, I would guess that the vibration is something else.  But, I would check the centering of the calipers to ensure that the brakes will work correctly.

--Dwight

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Dwight is right, calipers can not cause this. Maybe you've lost a balance weight during the test trip. An other cause could be excessive play on the steering system?

Edited by Kodjo
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Has the front suspension been thoroughly greased?  Pack a lunch, bring a Shop Manual,and don't get out from under until each zerk show grease going where it is supposed to go.  Special attention to the steering gearbox.  It requires a special semi-liquid lubricant and they're almost always dry.

Again, Shop Manual adjustment of the PS valve at the Pittman arm.

Check each of the six or so tie rod ends for play.  Check the center pivot bearings for wear.  Check wheel bearings for correct play.

Has the front suspension alignment been adjusted?  By modern standards, the Studebaker front suspension design has insufficient caster to self-center at speed.  Crank in all the caster the adjustment will allow.  

Does this Avanti still have the original steel wheels?  What tire width are the new tires?

Vibration at speed which comes and goes is almost always a tire/wheel balance issue.  First, switch front and rear tires.  Does this change anything?

jack vines

 

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A tire could be out of round...all tires have a high spot...just the nature of manufacturing.  All rims have a high spot...the high spot on the tire could be mounted on the high spot of the rim...it happens.  Rotate the tires on the rim 180 degrees, rebalance and try again.  If it's the same...the problem is elsewhere.  If it improves or changes otherwise it's the tire/rim combination.    

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Dwight, Kind of what I thought. When I rebuilt the calipers, I installed them the same as they came off. Shimmed same as factory install, but I thought I’d gauge it like the manual suggests.

Kodjo, I’ll take a closer look at the steering play, but it seems pretty tight. The car only has 50k miles on it. I will have the tire balance checked to see if it tossed a wheel weight. 

PackardV8, I have went through and made sure every zero was removed, cleaned and reinstalled to accept grease properly. I’ll have to research the steering gearbox and make sure to service it. I don’t recall seeing anything in the manual to give me a heads up on servicing it. I appreciate the heads up.I serviced my bearings. It’s funny that you mention alignment because I was going to take it in for one just for a baseline on when it was serviced. Still has the steel wheels and tire size as close o original as I could get. I will have the balance checked and if that doesn’t work,I’ll switch them front to rear and verify the outcome.

Gunslinger, I checked for out of round or flat spots but there was  nothing obvious.

I appreciate you guys suggestions. I will check those mentioned items and when I correct the issue I will post a follow up.

 

Thanks

Robert

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The original 15 x 5" steel rims are inadequate for use with modern radials.  There seems to be widespread agreement on this.  Perhaps they are adequate for use with bias-ply tires.  This is supposing that you're satisfied with the going-to-crash-any-minute feeling that you get when driving with bias-ply tires.  Also, the steel is so thin on those rims that modern tire store equipment will easily bend them.  (I had that happen.)  So, make sure that you don't have a bent rim.

--Dwight

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An update to the front end vibration. I have reached nearly 200 miles on the Avanti since becoming roadworthy again. Today I took it out on the highway and reached speeds of 75 mph and I had no front end vibration. My goal is to drive until I reach 500 miles and then I’ll do an inspection of the car and drive train. The car is driving and handling quite nicely at this point. 

Thanks again for the suggestions

Robert 

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How long was this car sitting after you had the tires balanced? I have an out of round issue with any car that i do not drive regularly. It works itself out after a few miles.

Just another thought.

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Some tires…particularly made with nylon…tend to flat spot after sitting.  Once driven and the tires heat up they straighten out and ride smoothly.

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I appreciated the insight! The car didn’t get moved around a lot since the tires were put on a couple months ago. Maybe that was enough to cause temporary flat spots.

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