Violent front end shaking/Wheel supplier needed.

[The_Handier_Man1]

From: Coachmen1972  (Original Message)
Sent: 8/9/2007 11:49 AM

Well...we made the 700 mile round trip without major incident......yeah!

There was only one fly in the ointment.....an occasional violent shaking of the front end accellerating through 45mph. I made the mistake of balancing the front wheels one more time before I left, without making a test drive.....turns out that the very minute shaking I had before got a lot worse and apparently got out of control around 45mph.

I was able to power through the shakes, and although they never quite went away life was manageable around 60mph. Fortunately the trip was all interstate, so I only had to deal with the problem at gas stops.

Has anyone else ever experienced this?

I watched the tires being balanced and there are some BIG weights on there. The "tech" was complaining that the wheels were not quite round....

So, I will replace the front wheels with new wheels and tires. I will also check alignment, Hopefully this will take care of it.

Southwest Wheels no longer lists our wheels on their site. Has anyone bought wheels from them recently? Any other suppliers?

Thanks, as always. Oscar.
1972 Coachmen on M300 chassis.



From: DaveVa78Chieftain
Sent: 8/9/2007 1:28 PM

Check king pin play.  I had simular shakes which was due to excessive king pin play.  Partially cleared up by greasing the joint but came back once the grease worked out.

Dave



From: denisondc
Sent: 8/9/2007 5:42 PM

You have experienced the standard RV wheel shimmy! It happens about that speed on motorhomes because the unbalanced mass of the wheel/tire resonates on the (slightly flexible) spindle/front suspension at about that speed - maybe 400-500 rpm. So: There has to be something still unbalanced enough or un-round enough to get the shimmy started. It could be a wheel that is bent or whose mounting surface where it bolts to the hub is not flat, or a bent hub, a tire that was made badly or has become defective. On one piece wheels with tubeless tires it can be a tire that was never fully/evenly seated on the wheel.
Assuming you have the front wheel toe-in set about right, and there is nothing 'loose' on the front steering or suspension, and the steering box is adjusted with some preloading: You could try moving the front wheels to the rear axle, and putting one of the rear axle dually pairs on the front. I have one wheel with a slightly bent mounting surface that lives on the rear axle and causes no problems. On the front axle - it always causes shimmy. I once had a used recapped tire on the RV that looked nicely round round when I jacked it up and spun it - but the tread rubber was delaminating from the carcass rubber. If I had been able to spin that tire up to 458 rpm (which is 45 mph with my 31" tall tires) I would probably have been able to see the tread lifting away from the carcass. Certainly I would have seen the tire doing a violent wobble. The few times I have had my tires balanced, it gets done with the tire lying horizontally and motionless on a 'bubble balancer'. That doesnt guarantee the tire will still be in balance mounted on the hub and spinning at 'highway speed'.
If your kingpins are really loose - they wouldnt originate shimmy themselves. But any shimmy from an imbalanced or out-of-round rotating mass would be worse.
Certainly www.universaltire.com carries most of the old sizes, but they dont try to be the low-price leader. I prefer to just ask for the tires I need at places that handle Light Truck tires - as opposed to the franchise chains that handle tires for modern cars. Some of them are willing to turn away from their computer keyboard and either pull out a hard copy listing of tires, or call a tire distributor. If not, I go to the next Light Truck tire place. I expect to have to wait a few days or a week for my 7.50-17 bias ply tires to be shipped in.



From: Coachmen1972
Sent: 8/9/2007 10:57 PM

Thank you, O great one.....always the fountain of wisdom.

I'm glad it's not unique. Kingpins are new, and tight, so are wheel bearings and spring bushings. Not sure about pre-loading on the steering.....can you tell me more?

I am very suspect of the wheels and tires. I do have a very knowledgeable independent tire dealer who will no doubt find what I need.

I guess I could do a quick swap between front and rear, but as the rear wheels are also almost four decades old, I think I will put two new one piece wheels on the front.

As asked above, Southwest wheels does not seem to list the coined wheels anymore....any other sources?



From: Coachmen1972
Sent: 8/10/2007 11:54 AM

I found the wheels......16", coined to take an LT235 tire.....

http://www.hendersonwheel.com

$120 each plus shipping......OUCH!



From: Coachmen1972
Sent: 8/10/2007 12:29 PM

Called my tire guy, he can get the wheels too......$86 each. Much better.....Tires 130.00 mounted and balanced.....

It's a serious chunk of change but I'm biting the bullet. If this is a sensitive area I have to know that the wheels are good.....



From: rustyescott1
Sent: 8/16/2007 3:00 PM

try Quality trailer products in Azel TX , 800242 4882 ,qtrailer.com, 501 redbud lane . last i talked to them they had 90 + wheels in stock ,90 to 100. each .may make better price for bulk . i'm 40 miles from them , don't know where ur at , but will try to help any way i can . contact me at rustyescott@yahoo.com .  rusty



From: 75Travco
Sent: 8/17/2007 6:00 PM

The old Travco - on a 1973 RM-350 chassis - had a shake in the front end that started at around 45 mph and got progressively worse with increasing speed.  Had the same shake with:
old bias tires with old rims
old bias tires balanced with old rims
new radial tires newer rims
new radial tires balanced with newer rims

Turned out that the front wheels were not centering on the hub.  The flanged lug nuts don't tend to center the wheel; it can easily move 1/16" or more off center, which creates 1/8" or more total runout.  This was pointed out by the mechanic at Hagerstown Spring & Alignment during an alignment check.  The shop used a large electric motor with a smooth metal flywheel to spin the wheel (while mounted on the vehicle) up to highway speed.  There was a fairly violent shake, even at low speeds!  Looking closer at the tread as the tire spun, it was easy to see the runout.  Now I used three coned lug nuts to center up the wheel before installing the flanged nuts.  Works great, no more shake.

Also it turned out the alignment was fine.  The Denison method for setting toe-in works great.  This shop was pretty impressive; they can make springs, and even had a big hydraulic press for bending the front axle beam to adjust camber.



From: denisondc
Sent: 8/18/2007 5:37 AM

Im only used to the 5 bolt 'Budd' wheels (lug centered), and havent worked with the 8 bolt wheels & hubs - other than to unbolt wheels from the hubs, or bolt wheels onto a vehicle that was only going to sit. I though the center hole on the wheel was supposed to be a close fit over the 'raised ring' cast into the hub. Maybe that isnt a good fit after 3 decades of corrosion of wheel and hub? With automobile wheels that use the center hole for the 'centering' function, (hub centered) its common to have to fight the wheel to get it off that raised ring on the hub.



From: Coachmen1972
Sent: 8/19/2007 2:27 AM

NOW you tell me.......lol

Actually, I saw the old wheels on the spin balancer and there was some run out....tires wheels or both.

Picked up two new wheels with new tires on them the other day....haven't had a chance to mount them yet. Will report back soon.



From: 75Travco
Sent: 8/24/2007 5:36 AM

There is no raised ring to locate the center hole - the 8-bolt wheels rely on the coined holes for centering the wheel to the front hub.  The coined area fits into a matching counterbore around the base of each wheel stud.  In my case, it was difficult to get things precisely centered; the flanged lug nuts with their flat bearing surface will not locate the wheel like the coned lug nuts will.

Coachmen 1972 - how did you make out with the new wheels and tires?



From: denisondc
Sent: 8/24/2007 10:34 AM

Even with the 5 bolt wheels that have conical mating surfaces on the lug nuts and the wheel, you still have to be able to nudge the wheel a little to get them bolted on. First; to get the holes in the wheels so they let the lug nuts begin to move into the tapered sides of the holes in the wheel, (or the bottom of the nuts can just clamp the flat surface of the wheel). And afterward, to help get the nuts partly run-in on the stud. I like to turn the nuts by hand, and use my long tire iron working the wheel up and down - until all 5 nuts have been run in so the wheel is essentially seated. Then I torque the nuts - until they screech.



From: Chocoholic
Sent: 8/26/2007 10:16 AM

hi
well this may not help but past experiance similar with our 33' was violent shimmy and skaking at that speed range was later found out to be caused by the power steering pump was bad.. after that was replaced it was like a new coach again.
I had forgotten the stupid motor home salesman topped off the ps fluid with brake fluid but we had to get the rig home and as time went by the brain farts settled in.. hope this may be of a help.. by the way was a chevy chassis... 

happy camping alias Chocoholic 



From: Coachmen1972
Sent: 8/26/2007 11:25 AM

Sitting in the parts department.....haven't had time to put them on yet....