Handling/Vibration

[naa10104]

Hello,

Have a 73 Convertible which I purchased a year ago. It came with brand new Magnum 500 wheels, and new radial TA tires. Since purchase I have put app. 600-700 miles on the car. I have had all the front end components replaced and aligned, new gas/hydraulic shocks. Tires are properly inflated. I have always noticed a slight vibration in the steering wheel over 60 MPH that seemed to get a little worse as the speed increased. Also, a general cyclic sort of vibration at speed that you could feel in the steering, but also throughout the car. Overall not terrible. It felt much like a tire being unbalanced. I had noticed that there were no wheel balancing weights visible on the outside of the rims. Last week I took it to a shop and had all four wheels balanced. The mechanic remarked that the wheels were out of balance (?). Today I drove it on the highway and all the above symptoms are much worse ... at 65 - 70 MPH I needed to reduce speed ... it is that noticeable. Any suggestions as to what the problem might be ? If I assume that all the wheels, tires, front end components, balance etc. are good what could be causing this ? The car tracks straight and true and is satisfactory below 55 MPH. Could it be wheel bearings, drive shaft issue ? I am at a loss and would appreciate any advice ... thanks.

 

[c9zx]

Find another shop that does "lug centric" balancing. If the are "Wheel Vintiques" Magnum 500s they specify lug centric balancing. From what you have described it sounds like an out of balance condition to me. Chuck

 

[naa10104]

Find another shop that does "lug centric" balancing. If the are "Wheel Vintiques" Magnum 500s they specify lug centric balancing. From what you have described it sounds like an out of balance condition to me. Chuck

Thanks

 

[luxstang]

What Chuck said.

If it is a cyclic vibration that comes in "waves" on the freeway, it might be an issue with the angles in the driveline.

I read that that kind of vibration is caused by the different angles on the transmission output shaft and the input haft of the rear end. (I think it was Hemmings but I'm not sure)

Though not in a straight line, they should be parallel to each other.

I know Tremec even makes a phone app for measuring your angles to get rid of that vibration.

Mine used to have it, after the AOD went in it stopped and today when I took the first spin with the shorter rear end it was back. It's because the rpms are higher now and before the rear and swap I never got into that rpm range on the freeway anymore.

On mine it's definitely not the rims.

Check your rims first (lug centric balancing) and if it doesn't help, check the angles on the drivetrain.

 

[c9zx]

Mike this may be of some help. Chuck

http://www.iedls.com/Education-Zone.asp?CID=3

 

[luxstang]

Thanks Chuck. That was what I was referring to.

It was not that exact document I read but something with the same info.

I need to look into that. I guess the lowering changed the angles quite a bit.

 

[Don C]

Chasing the cause of vibrations can be time consuming and frustrating, as they are often due to different sources that can combine/mix to make things worse. Your cyclic vibration is a good example, one source by itself may not be noticeable but when combined with another vibration that is at a different frequency will be very noticeable. An example is a driveshaft that is a little off and a bad harmonic balancer on a car with an automatic transmission. The torque converter has enough slip so that the engine speed is a little higher than the driveline (when in 3rd gear) and when the vibrations are 180° apart they cancel each other, but when they are in sync will be very noticeable.

Causes of your front end vibrations may come from different sources, wheel and/or hub runout and out of round, brake drum or rotor imbalance or runout, wheel bearings, and of course tire balance. I believe your tires were correctly balanced to begin with, and as Chuck said the guy that rebalanced them did not use lug-centric but instead used hub-centric. It's also not unusual to have to rebalance new tires after 500 or so miles.

 

[naa10104]

Chasing the cause of vibrations can be time consuming and frustrating, as they are often due to different sources that can combine/mix to make things worse. Your cyclic vibration is a good example, one source by itself may not be noticeable but when combined with another vibration that is at a different frequency will be very noticeable. An example is a driveshaft that is a little off and a bad harmonic balancer on a car with an automatic transmission. The torque converter has enough slip so that the engine speed is a little higher than the driveline (when in 3rd gear) and when the vibrations are 180° apart they cancel each other, but when they are in sync will be very noticeable.

Causes of your front end vibrations may come from different sources, wheel and/or hub runout and out of round, brake drum or rotor imbalance or runout, wheel bearings, and of course tire balance. I believe your tires were correctly balanced to begin with, and as Chuck said the guy that rebalanced them did not use lug-centric but instead used hub-centric. It's also not unusual to have to rebalance new tires after 500 or so miles.

thanks all ... another mystery to solve

 

[naa10104]

Chasing the cause of vibrations can be time consuming and frustrating, as they are often due to different sources that can combine/mix to make things worse. Your cyclic vibration is a good example, one source by itself may not be noticeable but when combined with another vibration that is at a different frequency will be very noticeable. An example is a driveshaft that is a little off and a bad harmonic balancer on a car with an automatic transmission. The torque converter has enough slip so that the engine speed is a little higher than the driveline (when in 3rd gear) and when the vibrations are 180° apart they cancel each other, but when they are in sync will be very noticeable.

Causes of your front end vibrations may come from different sources, wheel and/or hub runout and out of round, brake drum or rotor imbalance or runout, wheel bearings, and of course tire balance. I believe your tires were correctly balanced to begin with, and as Chuck said the guy that rebalanced them did not use lug-centric but instead used hub-centric. It's also not unusual to have to rebalance new tires after 500 or so miles.

thanks all ... another mystery to solve

So the saga continues ... went to G & C in Chantilly today to have my Magnum 500 wheels balanced on the road force machine. They are certain that the wheels are properly balanced and that the tires and wheels are good. They did use an adapter that holds the wheel on the machine via 5 studs and lugs as opposed to a cone. This improved the issues but did not fix the problem ... it basically put the vibration issue back to where it was before the last guy just spun balanced the tires on an old style machine.

I spoke with a technician at Vintique where these wheels are manufactured and went into great detail with him about the issues I am having. He said they sell a great many of these wheels and have very few problems with them. He said that based on what I told him a center ring to mate the wheel to the hub is really not necessary and probably would not help. He stated that the "conical" lugs and lug openings are shaped in such a manner to seat the wheel properly. He also stated that even if this was a contributory issue it would not cause such an extreme problem. He felt confident that the problem lies elsewhere.

So I am open to any suggestion as to what my next steps should be ... Don't want to start tearing things apart without a plan. Was going to look at the drive shaft and see if it has lost any balancing weights ... dont know exactly how to check the driveline angle or harmonic balancer. Open to any suggestions ..... thanks very much !

 

[Don C]

The method that Chuck referenced is the best way to check the angles.

I would start with measuring the run-out and out-of-round of all four wheels and tires. Look for bulges or depressions in the sidewalls, which may indicate some belt issues on radial tires, which will balance OK, but show up when driving.

When you're looking at the weights on the driveline rotate the driveline and look for any dings or gouges in the tube. Also, while you're there, check the u-joints for looseness, and make sure the cups are seated in the yokes correctly.

 

[mustang7173]

naa10104

How did your convertible drive before you rebuilt your front end? + 1 on above possible solutions. Also, check out Open Tracker Racing's front end specifications. I have heard of front end technicians not setting the specifications correctly due to not having the correct measurements.

Front End Specifications form Open Tracker Racing

http://opentrackerracing.com/technical/

Keep us posted on your findings!

mustang7173

 

[detritusmaximus]

If the problem is in the 55-75 range it is almost certainly something rotating....if that doesn't sound obvious enough.

I noticed you say the second balance was on a road force machine. I assume this would be a 'dynamic' balance instead of the typical static balance? A dynamic balance will detect imbalance side to side as well as circumferential. A distorted tire can be balanced for rotation and still have a vibration due to an imbalance across the tire. This is why wheel weights just on one side of a wheel will balance it, but don't cancel a vibration, sometimes they need to be on the opposite side or even dead center inside the wheel. This goes directly to what Don C said. A side to side wobble issue would show up in the steering wheel much like a bad tie-rod.

Any chance of flat spots on any of the tires? How long did the car sit with new tires on it before you bought it?

I went thru a similar situation with Kumho tires. great tires (well, they used to be), but occasionally I'd get one that would balance but still vibrate. The belts inside can be laid incorrectly or separate.

 

[Carolina_Mountain_Mustangs]

I have a big issue with what your wheel supplier said about not fitting the hub. The design of a wheel is that the center opening is what supports the main weight of the vehicle and centers the wheel. The lugs are just to hold the wheel on. Maybe the manufacturer is making the wheels so they will fit on Mercury products also which have larger center openings in the wheel. If you look at a set of factory 73 aluminum wheels the center hole on the Mustang is smaller than a set for Mercury.

The rear axles have an extension in the center that fits the center hole in the wheel just like the front hub does. Yes you can run wheels that have a larger center hole there are thousands out there that way. It is not the way OEM designs wheels and they do it for a reason. If you have a dial indicator and can get the point on the center hole and rotate and it is not centered I would really be suspect of the wheels. A little bit off in the center ends up being a lot when thrown off the dia. of the wheel.

If you have a friend with similar car you can swap wheels I would do that and if it stops it is either the tires or wheels.

Have you driven in another car and watched the wheels from the side?

It is just a problem solving thing change one thing at a time or you will not know what the cause was.

Good luck and keep us posted.

David

 

[c9zx]

If the rear tires are close to the same size as the fronts, exchange them and see if the vibration moves from the steering wheel to the seat of your pants. If it does, you'll have narrowed the problem to two tires and two wheels. If it doesn't change, start looking for loose or failed parts. New doesn't always mean good. I hope you can make some progress on finding the problem. Chuck

 

[mjlan]

I was going to suggest what Chuck said...

Maybe even find a buddy with a Ford product and swap all four wheels/ tires. That would eliminate that from the equation...

Older tires can flat spot if they sit, another possibility is cord or belt separation, but that usually makes balancing impossible.