# Vibration



## Praxis (Feb 23, 2014)

I need help! My 1967 GTO has a very noticeable “vibration” at speeds in excess of 45-50 mph. I feel it through the floor into the seats and also the steering wheel. It is relatively minor by any standards but is very very noticeable and distracting when I drive on highways. It gets worse the faster the car goes.
For reference, the car is a fully restored car, massively built engine, stock front end suspension with all new shocks, bushings, bearings, etc. Automatic trans with Gear Vendors overdrive, custom driveshaft has been balanced and rebalanced, rear suspension lowers are custom and threaded for adjustment, pinion angle id 3 degrees matched at front at the OD. Rear shocks need replacement which will happen soon. Axle bearings are good.
Wheels are original rally 1’s with new reproduction redline radials.
The mechanics who work on this are race mechanics. Very trained. They have checked everything and all is correct except the tires. They took them to be rebalanced and were told the tires are not round, and that these tires from this manufacturer (I don’t want to mention brand names) are all out of round some, bad job of molding. The mechanics sent me videos of the car on the lift, in gear running, the tires are actually elliptical just a bit.
Is this my vibration? Please feel free to suggest we check things we may have already checked, no one is perfect.
If it turns out to be tires, what tires are all you running on your GTO’s? I would like to keep the redline look and also radials, but most importantly I want to go down the highway smoothly. Please include the brand names of the good tires you use. My wheels are stock 14”.


----------



## O52 (Jan 27, 2019)

Diamond Back tires uses new tires of which they remove all side markings and then bond a new white, blue or red line. They're not recessed like the originals. 





White Wall Tires & Custom Redline Tires - Classic Car Tires Online


Diamond Back Classic Tires is an online tire shop that creates custom tires for classic cars. Diamond Back creates white wall tires, redline tires, blueline tires, goldline tires and other vintage tires for pre-1976 vehicles including Corvettes, Mustangs, prewar cars, postwar cars, European cars...




dbtires.com


----------



## Sick467 (Oct 29, 2019)

Out of round tires will cause some horrible vibrations. Are they all out-of-round? Any rotating part can cause vibrations and some that do not rotate (think out of aligned steering/suspension components or warped brake parts). It sounds like you have covered many of the possible concerns, but egg shaped tires is a bad thing...especially if it shows up on a video. That's bad! 

One thing that I have had happen is a drive shaft that was too short and did not insert into the transmission far enough. The drive shaft was balanced, but because there was not enough spline contact between the yoke and the transmission output shaft, the yoke would **** ever so slightly to one side and cause an out-of-balance situation and the vibration would show up, and get worse, at higher speeds.

BUT, egg shaped tires would be my very first change. I do not run redline tires, but have had good luck with the Copper Cobra's on two of my cars. Stay away from the M/T Sportsman S/T's. I had two of them (two separate times) swell up and darn near lodge themselves in the wheel well. Just regular highway driving too. M/T would do nothing about it since they were a few months out of warrenty even though they only had a few thousand miles on them. I switch to the Coppers.


----------



## Lemans guy (Oct 14, 2014)

Yes, tires will do that, and you can feel it and now see it. I use Cooper cobra’s been very good, keep em well balanced, but they are not redlines


----------



## Praxis (Feb 23, 2014)

Thanks for the replies so far. Looks like we are getting a consensus on tire brand. I will miss the redline look, but will likely prefer the smooth ride!!
As to the driveshaft splines, my guys thought of that too and rechecked it, the splines go into the tail the correct amount.
Keep the suggestions coming please, and I will start to look into the new tires.


----------



## Praxis (Feb 23, 2014)

Lemans guy said:


> Yes, tires will do that, and you can feel it and now see it. I use Cooper cobra’s been very good, keep em well balanced, but they are not redlines


Cobra GT’s? What size do you run?


----------



## Lemans guy (Oct 14, 2014)

225 60R15. Front and back, that way I can rotate them


----------



## Lemans guy (Oct 14, 2014)

Summit has great prices on those, even beats the online tire guys sometimes, I order them and put them on


----------



## LATECH (Jul 18, 2018)

out of balance tires shake. U Joints that are bad will vibrate. There is a difference.

Are you sure you have a shake or a vibration?


----------



## PontiacJim (Dec 29, 2012)

Check U-joints:









Universal Joints - They Do Wear Out


Something that I am sure many do not think about - Universal Joints. They do wear out and need replacing. The most common test is to grab your driveshaft and shake it about to see if there is any play or movement. But this doesn't tell you the condition inside the U-joint like the needle...




www.gtoforum.com


----------



## GTOJUNIOR (Aug 7, 2011)

Do you have access to another known-good set of mounted tires? (i.e. a local friend with the same size)
I would suggest swapping them on for a test before biting the bullet on a new set.


----------



## Praxis (Feb 23, 2014)

LATECH said:


> out of balance tires shake. U Joints that are bad will vibrate. There is a difference.
> 
> Are you sure you have a shake or a vibration?


Not sure how to choose. The steering wheel will “shimmy” starting at about 45 mph but it is a very short frequency very rapid one so very similar to vibration. The sensation up through the seats would be more a vibration above 50 mph. I know my u-joints are new, and the mechanics who installed them certainly checked that they were good because I know new doesn’t always equal good, but will definitely recheck those. Thanks.


----------



## Praxis (Feb 23, 2014)

GTOJUNIOR said:


> Do you have access to another known-good set of mounted tires? (i.e. a local friend with the same size)
> I would suggest swapping them on for a test before biting the bullet on a new set.


Totally agree, and sadly no, no one I am familiar with has anything similar. But I will ask the mechanics what they might know of.


----------



## Praxis (Feb 23, 2014)

Lemans guy said:


> 225 60R15. Front and back, that way I can rotate them


My wheels are stock 14 inch so likely I will need something more in the 70 series?


----------



## LATECH (Jul 18, 2018)

Praxis said:


> Not sure how to choose. The steering wheel will “shimmy” starting at about 45 mph but it is a very short frequency very rapid one so very similar to vibration. The sensation up through the seats would be more a vibration above 50 mph. I know my u-joints are new, and the mechanics who installed them certainly checked that they were good because I know new doesn’t always equal good, but will definitely recheck those. Thanks.


Steering wheel "shimmy" is a shake and is an out of balance tire most likely.
The Vibration in the floor is drive line related. Bad U joint, bent driveshaft, bent driveshaft yoke from installing a U joint,etc


----------



## Praxis (Feb 23, 2014)

LATECH said:


> Steering wheel "shimmy" is a shake and is an out of balance tire most likely.
> The Vibration in the floor is drive line related. Bad U joint, bent driveshaft, bent driveshaft yoke from installing a U joint,etc


Thanks, I plan to recheck all those before buying new tires.


----------



## LATECH (Jul 18, 2018)

Praxis said:


> Thanks, I plan to recheck all those before buying new tires.


Check the wheels to be sure they arent bent also.


----------



## Praxis (Feb 23, 2014)

LATECH said:


> Check the wheels to be sure they arent bent also.


Wheels were checked and are round. Thanks.


----------



## PontiacJim (Dec 29, 2012)

Maybe the car just gets scared when you go over 50MPH? Maybe it was formerly owned by a little old lady who only used it to drive to church and never got over 40MPH?

Assume the massively built engine is a Pontiac?

The tires can get flat spotted from sitting for long periods. A friend let his tires sit on his car for 15 years in a garage as he worked on it periodically. Finally got it street worthy and we took it for a ride. It had a vibration. Tires were flat spotted on the tread that was on the ground. Can't fix that, it is like they are now molded that way, so he had to get new tires. They can also be "heavy" in one spot or another which can make the wheels shimmy. Have the tires re-balanced by a different shop to make sure the previous balance was not done by someone who was incompetent.

You could also have a bad/loose wheel bearing.

Your front end has been completely rebuild, but I would be pulling/tugging/turning everything as someone watched all the parts. A worn idler arm can do it and is often missed. You also assume the parts used are correct for Pontiac and/or your car. If they have been replaced, there is no guarantee they are correct, or even of good quality anymore.

You might want to contact Gear Vendors to see what they have to say about pinion angles. With the custom driveshaft, which I assume is shortened, the factory pinion angles may not apply. Pinion angles can change as you increase the speed of the car and this can cause vibration. 

BUT, if your mechanics say the tires are a little "elliptical," then it is going to shake/shimmy the faster you go. Time for new tires and hope that is it.


----------



## LATECH (Jul 18, 2018)

Road force balance the tires. That will tell you if a tire is out of round, or has a hard spot in it.
Tires are not supposed to be " elliptical" in shape...LOL


----------



## Praxis (Feb 23, 2014)

PontiacJim said:


> Maybe the car just gets scared when you go over 50MPH? Maybe it was formerly owned by a little old lady who only used it to drive to church and never got over 40MPH?
> 
> Assume the massively built engine is a Pontiac?
> 
> ...


Thanks. I will do all the above!


----------



## Praxis (Feb 23, 2014)

LATECH said:


> Road force balance the tires. That will tell you if a tire is out of round, or has a hard spot in it.
> Tires are not supposed to be " elliptical" in shape...LOL


Where I live, NO ONE does this!


----------



## LATECH (Jul 18, 2018)

Wow. And I thought I lived in the styx


----------



## @2018 Mardi (Jun 2, 2021)

LATECH said:


> Road force balance the tires. That will tell you if a tire is out of round, or has a hard spot in it.
> Tires are not supposed to be " elliptical" in shape...LOL


Hello all… Just thought I would share this. I had a motorhome that sat for a long period of time on new tires. When I finally drove it, it was much like what you’re describing. I found a place that planes tires. This was a common practice years ago during the energy crises because tires, even new, are never perfectly round. People would have them planed right out of the box to conserve fuel. This is not widely practiced these days and tires have gotten better, however, there are still some places that do it. Just have to call around to see if you can find a tire shop in your area that still does this… just a suggestion. They didn’t even remove them, they just jacked it up off the ground and the portable unit they use spins the wheel with a motor. Works kind of like a lathe.
Very interesting to watch… good luck!
Judge Jeff


----------



## @2018 Mardi (Jun 2, 2021)

LATECH said:


> Road force balance the tires. That will tell you if a tire is out of round, or has a hard spot in it.
> Tires are not supposed to be " elliptical" in shape...LOL





LATECH said:


> Road force balance the tires. That will tell you if a tire is out of round, or has a hard spot in it.
> Tires are not supposed to be " elliptical" in shape...LOL





LATECH said:


> Road force balance the tires. That will tell you if a tire is out of round, or has a hard spot in it.
> Tires are not supposed to be " elliptical" in shape...LOL


----------



## 67ventwindow (Mar 3, 2020)

@2018 Mardi said:


> Hello all… Just thought I would share this. I had a motorhome that sat for a long period of time on new tires. When I finally drove it, it was much like what you’re describing. I found a place that planes tires. This was a common practice years ago during the energy crises because tires, even new, are never perfectly round. People would have them planed right out of the box to conserve fuel. This is not widely practiced these days and tires have gotten better, however, there are still some places that do it. Just have to call around to see if you can find a tire shop in your area that still does this… just a suggestion. They didn’t even remove them, they just jacked it up off the ground and the portable unit they use spins the wheel with a motor. Works kind of like a lathe.
> Very interesting to watch… good luck!
> Judge Jeff


The Lost Art of Tire Shaving








With Tire Shaving, a Flat on an AWD Car No Longer Means Replacing All Four Tires - Consumer Reports


Conventional wisdom is that when you need to replace a single tire on an all-wheel-drive vehicle, every tire should be replaced. Consumer Reports says tire shaving provides a more affordable option.




www.consumerreports.org


----------



## bo.alexander50 (Nov 29, 2021)

Praxis said:


> I need help! My 1967 GTO has a very noticeable “vibration” at speeds in excess of 45-50 mph. I feel it through the floor into the seats and also the steering wheel. It is relatively minor by any standards but is very very noticeable and distracting when I drive on highways. It gets worse the faster the car goes.
> For reference, the car is a fully restored car, massively built engine, stock front end suspension with all new shocks, bushings, bearings, etc. Automatic trans with Gear Vendors overdrive, custom driveshaft has been balanced and rebalanced, rear suspension lowers are custom and threaded for adjustment, pinion angle id 3 degrees matched at front at the OD. Rear shocks need replacement which will happen soon. Axle bearings are good.
> Wheels are original rally 1’s with new reproduction redline radials.
> The mechanics who work on this are race mechanics. Very trained. They have checked everything and all is correct except the tires. They took them to be rebalanced and were told the tires are not round, and that these tires from this manufacturer (I don’t want to mention brand names) are all out of round some, bad job of molding. The mechanics sent me videos of the car on the lift, in gear running, the tires are actually elliptical just a bit.
> ...


I was gifted some lightly used red line tires from a good friend. I experienced a sever vibration from them. I bought 2 new red lines (same manufacturer) because of of fitment problem - ordered smaller size for the front. Same vibration with new tires. I raised the vehicle and turned tires and checked for "roundness". All tires were out of round. I took car to tire shop that shaves tires. I had the new front tires shaved and the problem was much better. When the weather get warm I will have the rear tires shaved. The next set that I buy will be Diamond Back brand.


----------

