Frontend Shimmy

[Parkman Jim]

Hello everyone,
I am new to the forum and hope I am posting in the correct area.
I have a 99 Winnebago on the Ford F53 chasiss that vibrates beginning at 55 and increasing to shaking the whole unit over 60. Have replaced steer tires, new shocks and frontend alignment. On a recent trip I stopped to have the steer tires rebalanced and that helped a bit, but still have the shakes. Would you recommend an RV dealer or a truck suspension facility - any suggestions?

[Don/Lou]

I recall a service bulletin regarding out of round wheels on this year F53
Ford had special stud adaptors to center the wheels on the hubs as the centre hole was not concentric to o.d. of wheel
I would take it to a Ford truck service centre -they should be able to find the TSB
Don

[ga traveler]

Quote:

Originally Posted by Don/Lou I recall a service bulletin regarding out of round wheels on this year F53 Ford had special stud adaptors to center the wheels on the hubs as the centre hole was not concentric to o.d. of wheel I would take it to a Ford truck service centre -they should be able to find the TSB Don

these rims were made in mexico. They were out of round. If you can find aluminum wheels to fit your front wheels, that will cure your problem.

[Horseshoe]

This is my area of expertise since I represent a manufacturer that does mounting and balancing of these vehicles. I have been doing it for 31 years and have just installed new equipment in two truck and RV places and trained the techs.

First off, I doubt it is a static (non loaded) out of round problem. That should have been found years ago. Secondly, out of round rims/tires usually can be felt at almost any speed. The harmonics of tires usually cause vibrations in the 50 to 65 mph range, depending on their circumference.

It has been my experience that centering errors in mounting them on computer balancers is the biggest problem. I get calls every couple of weeks to go into the field and troubleshoot vibration issues. In almost all of the cases the wheels were not properly centered on the balancer due to wheel design and the weight of the assemblies.

There are two easy ways to fix these problems, but both require you to take the vehicle to a truck shop who has the equipment and the technicians do it properly. One way is to do a spin balance on the vehicle using a strobe balancer. The technician can jack up the axle and spin the tires with a high speed spinner and repair the vibration. When the tires are spun, they will vibrate your vehicle once the tires are off the ground and the vehicle is on jack stands.

The second one involves finding someone with a modern balancer that not only spins the tires, but puts a load roller against it to simulate the road. It applies about 1,200 pounds of force to the tire to see if there is any "road force" in the assembly. What that means is that the tires might be round when there is no load, but deform when the load is applied. The 'out of round' spot will always be felt at the speeds you describe. So, the tire "thinks" it is on the road after the roller engages. That same balancer has a program to insure the wheels are centered before it spins them. Ford and all manufacturers have the same problem with this, and the proper methods to find and repair them are basically the same. The engineers almost always say to use the road force method.

As was just said, changing the wheels to aluminum will also fix the problem, unless it is a road force problem with the tire itself. That is about a 50/50 proposition.

[Parkman Jim]

Thank you all for the good information. I was leaning toward the Ford truck dealership, but Horseshoe after your post, I think a well equiped truck shop will be the way to go.

[TXiceman]

In addition to checking the wheel and tire for roundness, check the front wheel bearings. Also have them check for drive line alignment and drive shaft balance.

Ken

[ga traveler]

Quote:

Originally Posted by Horseshoe This is my area of expertise since I represent a manufacturer that does mounting and balancing of these vehicles. I have been doing it for 31 years and have just installed new equipment in two truck and RV places and trained the techs. First off, I doubt it is a static (non loaded) out of round problem. That should have been found years ago. Secondly, out of round rims/tires usually can be felt at almost any speed. The harmonics of tires usually cause vibrations in the 50 to 65 mph range, depending on their circumference. It has been my experience that centering errors in mounting them on computer balancers is the biggest problem. I get calls every couple of weeks to go into the field and troubleshoot vibration issues. In almost all of the cases the wheels were not properly centered on the balancer due to wheel design and the weight of the assemblies. There are two easy ways to fix these problems, but both require you to take the vehicle to a truck shop who has the equipment and the technicians do it properly. One way is to do a spin balance on the vehicle using a strobe balancer. The technician can jack up the axle and spin the tires with a high speed spinner and repair the vibration. When the tires are spun, they will vibrate your vehicle once the tires are off the ground and the vehicle is on jack stands. The second one involves finding someone with a modern balancer that not only spins the tires, but puts a load roller against it to simulate the road. It applies about 1,200 pounds of force to the tire to see if there is any "road force" in the assembly. What that means is that the tires might be round when there is no load, but deform when the load is applied. The 'out of round' spot will always be felt at the speeds you describe. So, the tire "thinks" it is on the road after the roller engages. That same balancer has a program to insure the wheels are centered before it spins them. Ford and all manufacturers have the same problem with this, and the proper methods to find and repair them are basically the same. The engineers almost always say to use the road force method. As was just said, changing the wheels to aluminum will also fix the problem, unless it is a road force problem with the tire itself. That is about a 50/50 proposition.

You know a lot more about balancing tires than i do. I never balanced a tire in my life. However Ford came out with a bulletin advising all dealers that Rims in this era were made in mexico. They were out of round. (Ford's word's not mine) If I remember correctly, they would replace the rims if they were more than three thousandths out of round. (not positive that is the correct number)

[Parkman Jim]

TXiceman, thank you, will do
ga traveler, thanks, I will check with Ford on this. I think I have a good checklist to hopefully solve this problem before I pull out what little hair I have left.
A friend recommended this forum and I see why, alot of great info from knowledgable folks. Thanks so much.