Drivetrain vibration in 1966 Corvair

007

Messages
724
Location
Clermont, Fl
Thread starter
My good buddy has a 1966 Corvair and has some over 55 mph vibration issues. He has 14" OLD style Crager wheels with 205/70 14 BFG TA Radials. This is the second set of new tires he has purchased in less than a month hoping to alleviate his issue with no luck. Tire installer sold him on the second set of more expensive tires thinking that was the problem but it was not. Any ideas??
 
Have the shop take the tires off and spin the rims first and check for bent ones, and also how far out of balance the rim itself is. Does it feel like it's in the front, rear, or both? If only one end, swap both tires front to back and see if the vibration follows the swap, or if it stays. That will tell you if its wheel/tire related or some other drivetrain/bearing issue.
 

JHZR2

Staff member
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44,449
Location
New Jersey
Get a vibration analysis app for your smart phone - I use a free one called VibrationAnalysis. Take a reading at actual 60MPH and another at a recorded actual speed where the vibration is worst. Verify your tire size's true rpm/mile rating. From there all it takes is math to determine what in the drivetrain is causing the worst vibration. https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/4891490/1 Knowing what frequency you're truly feeling will be helpful. You'll get something like this if it's legit wheel and tire: [Linked Image from i.imgur.com] And this when fixed: [Linked Image from i.imgur.com] Note the y axis. When you know the number of tire RPMs/mile, and are at 60MPH, so its one mile per minute, the math starts to get easy. Since the diff ratio is known, if its that, it will be mathematically the harmonic that is the ratio multiplier of the tire RPM, or more specifically Hz (oscillations/sec).
 

007

Messages
724
Location
Clermont, Fl
Thread starter
Thanks for the feedback guys. My buddy is very frustrated and does not want to throw good money after bad.
 
Messages
188
Location
NC
I had a '65 Corvair Corsa 180 turbo, 4 speed with a factory limited slip transaxle. Loved that car. Ran it in many gymkhanas until the engine surrendered. It was shod with 14" Michelin X tires. The only vibration I remember it generated was from my overheated girlfriend in the passenger seat.
 
Messages
427
Location
Texas
In high school ( in the late 60s )my friend had a Corvair. He found that added weight really helped it's handling. He had a hundred lbs of barbell weights in the trunk, I remember because he borrowed them from me and never returned them .
 
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1,890
Location
Somewhere in time
With a vehicle of that age, it could be nearly any part of the drive train or suspension. Unless your buddy has replaced the rubber bits within the past 5 years you've got to assume they're worn or dry rotted or both. There's likely a lot of work to do here.
 
Messages
1,378
Location
Ontario, Canada
Originally Posted by Trav
Check the U joints and anything else connected to the drive axles, these types of components are a common cause of vibration.
+1
 
Messages
35,843
Location
ME
Originally Posted by DuckRyder
Do the only Cragers have those slotted holes and oblong washers? Got any stock wheels?
This is what I was thinking.
 
Messages
4,728
Location
Fort Worth, Texas
Originally Posted by DuckRyder
Do the only Cragers have those slotted holes and oblong washers? Got any stock wheels?
Those "Uni-Lug" wheels were junk when new, Aftermarket Duplex-washered lug nuts were also trash without Uni-lug wheels thrown in the mix. If one dismounted the tires & put a dial indicator too these Cragers on the car...I guarantee excessive runout would be found!
 
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595
Location
Vancouver, BC Canada
Originally Posted by GSCJR
Originally Posted by Trav
Check the U joints and anything else connected to the drive axles, these types of components are a common cause of vibration.
+1
If memory serves, the rear half-shafts do not telescope... on the '65 and later (specifically). Meaning that they act as the upper wishbone... or link... and they run in compression. Like how the first few Corvette Stingrays were.... I guess, all the way up to the early 90's ??? The U Joints have to be in good nick. Same as the Jaguar IRS.
 
Last edited:
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24,072
Location
MA, Mittelfranken.de
It could have something to do with the wheels also as others have posted or a combination of both. I am not that familiar with those wheels, I remember them from years ago but don't have a lot of experience with them. One would hope that when they did the tires they checked the wheels alone for run out and out of round, damage, etc before mounting the tires. With today's scan tool and parts changing gang doing even that small job proper may be asking too much.
 
Messages
1,448
Location
iowa
Sometimes you can visually see a potential vibration on other peoples cars going down the road with tires bouncing up and they have no idea what's going on. I would try following the car down a wide road while watching all four wheels. My first car was a 1964 Corvair Spyder I wish I still had.
 
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