Bad shimmy at low to moderate speeds

[class87]

From: Boise_Chief1  (Original Message)
Sent: 4/5/2005 10:42 PM

I am having problems with a bad shimmy at low to moderate speeds.  This is normally brought on by crappy roads adn it starts small and seems to build unless I slow down or speed up.  I am really concerned as steering is nothing to fool with.
I'm supposed to take our maiden voyage on the 16th.  So I have this next weekend to diagnose and repair.  It feels as if the front wheel or wheels are not tracking correctly and the shimmy transfers through the steering wheel.
I am off to search the old messages but I don't have the knack of the search function.  I have been searching for the post that decodes DOT code to find out how old my tires are and am having no luck.
Thanks for any helo you might have.
Sean
 


From: Boise_Chief1
Sent: 4/5/2005 10:46 PM

I found this past post by the resident expert.  I thought I'd paste in anything that might be helpful for future generations.



From: denison
Sent: 4/28/2003 4:13 PM

If you have a shimmy on pavement, I would look at things like the amount of toe-in, the wheel bearing adjustments, the steering box adjustment, then the king pin wear, then the tire imbalance or out of roundness, that you wheels are not bent, the hub nuts are snug, and a few other factors. If you wanted I could send you a long long opinionated text that I sent to another guy with unlikeable steering.
denison denisondc@hotmail.com



From: Boise_Chief1
Sent: 4/5/2005 11:19 PM

Too all future fixers:
Search under front end there is much info to help you start finding the problem.
If anyone has anything to add feel free.   



From: cooneytunes
Sent: 4/5/2005 11:26 PM

Boise....Yes, Steering is not something to take lightly....First thing to Check.....Wheel tightness.... some of these old Winnies when a wheel is put back on, the lugs will not automaticlly center the wheel..if put on fast with a impact wrench....and the lug nuts will be loose after driving just a liitle way.....this will feel very much as you described....The will smooth out at a faster speed...The correct way to tighten the lug nut is, You have to center the wheel by hand (a helper is very helpful) put on at least two lugs (opposite each other) hand tight...then put the remaining lugs on hand tight...making sure the wheel is centered...Then crankem down with what ever leverage bar and tighten top one first then go to opposite side in other words, if you start at the 12 o'clock lug, go to 5 or 7 o'clock next and tighten in a criss cross pattern until tight  then repete...and never ever put any lubrication on the threads.....You can clean them with WD 40, a wire brush and a rag, but never lube them......If the wheels are tight......You'll just have to start, by looking at all the rods underneath and see if any has any play in them, they should not....Look on the left (drivers side) grab the steering collum shaft  ( just before it enters the steering box) and turn it lightly back & forth, only turn less than an inch in both direction...very light  and watch the pitman arm It's a little L shaped rod about 8 to 10 inches long that pulls on another rod, if this moves a little when you turn the shaft lightly back and forth that's good (the sooner it moves the better)....If you have to turn the collum more than an inch before the pitman arm moves, that's bad.....and your steering box will need adjustment...do a message search for steering box adjustment. If all passes or is good so far, Jack up one front wheel and pull on the top of the wheel, and then pull on the bottom of the wheel....if it moves (not turns) but moves in or out, then you've got a possible bad wheel bearing...Do the same on the other wheel...The problem you say your having though sounds like a loose wheel.....Remember on the old Dodges.....The drivers side lugs are..."LEFT HANDED THREADS"...That means, Lefty tighty.....Righty Loosey......Not the normal Lefty Loosey-Righty Tighty....Hope you find the problem....
Let us know how you make out....
Timmy



From: Boise_Chief1
Sent: 4/5/2005 11:39 PM

Another good search is kingpin.  More info available there.

I am going to cheat and take it by my friendly nieghborhood Les Schwab tire center.  I'll have them do a thorough front end check as well as front wheel bearings and brakes.  I'll probably have them do some of the work and treat them to a couple of pizzas.  Youd be surprised how food will motivate. 
Sean the Pizza Guy
 


From: denison
Sent: 4/6/2005 7:10 AM

Wow.....what a lot of coverage! I would repeat my former advice: Shimmy is based on 2 factors.
FIRST a wheel that isnt in perfect balance (but they shouldnt have to be perfect, just good enough), and
SECONDLY, some wear in the steering mechanism.
So, first I would check whether the wheel is bent, or the tire out of round, and get the front tires balanced.
Next I would get the toe-in checked/adjusted.
Third I would snug up the steering box,
Fourth I would have someone turn the steering wheel back and forth about 1/4 turn, and lie under the front of the vehicle and see if there was any "freedom" in the 4 steering ball/socket joints. Two joints on the drag link, two on the tie rod. If there is any, that part needs replaced. The joints also need greased every 2000 miles, along with the kingpins. And the axle has to be jacked up so the weight is off the tire to properly lube the kingpins. If you arent following the lubrication chart in the service manual, dont expect your Winny to stay problem free.
If you find a slightly bent wheel, or a tire that is out of round, or that cannot be balanced, you can try moving it to the rear axle, paired up with another tire of the same exact "standing height" - so both tires take the load equally.

There was a mention in one posting about a mechanic saying that "there should be no play at all" in the kingpins. This is incorrect for kingpins/bushing, but is true to a ball joint suspension. There would have been some tolerance when the axle was new. I have seen 2 published "limits" on that kingpin/bushing movement. After jacking the axle up so the wheel is just off the ground: pushing the wheel in and out at the top, and measuring how far the tire edge moves in and out - the two limits were 1/4 inch, and 3/8th inch. The two URLs were:
www.daytonparts.com/_pdf/PEP14_Steering.pdf
www.ncbussafety.org/download/NCInspectionManual.PDF

And I didnt need to remove the steering box to do a decent adjustment on it.



From: Derrek
Sent: 4/6/2005 9:34 AM   
 
Here is some info on Reading DOT tire codes:

One important thing to know is the age of the tires on your RV. This can be done by checking the DOT codes branded on the side of the tire. I modified a picture I found on the net using Microsoft paint to better explain how to find a decipher the code.

  The DOT code can be found on the sidewall of the tire near the rim. You will see the letters DOT followed by several sets of numbers branded inside of a series of oval shapes molded into the sidewall of the tire. The last set of digits will tell you the week and year the tires were produced. For tires made before the year 2000 the code will read like this example:

347 = 34th week of 1997

For tires made after 2000 the code will read like this:

3404 = 34th week of 2004

The latest issue of motor home magazine has an excellent article on tires. In the article it states that tires should be inspected when they reach 5 years old and replaced at 7 years regardless of the appearance.
                                                                                 
                                                                                      Derrek


From: Boise_Chief1
Sent: 4/6/2005 10:23 AM

King pin Question.  After looking through my chiltons there is no mention of the King pin.  I am assuming that it is the pin that essentially holds on the spindle.  Is this correct?  Also, how do you tell if you have split rims or not?
Thanks Guys
Sean



From: denison
Sent: 4/6/2005 2:44 PM

Yes, the king pins are what the front wheels pivot on when you are turning left or right.. You would be able to see their location, at the end of the axle, where the spindle is held in place, but they are completely enclosed inside the axle and spindle forgings. I was just greasing mine this afternoon.
Split rim wheels have a detachable rim piece that would be visible on a front wheel, not on a rear wheel that was facing “in”.. The detachable rim piece would have a slot in it, which allows it to be maneuvered off the base part of the wheel, for tire replacement or fixing a flat. They were the common type of wheel for trucks for half a century, and were used on some cars too. The improvement in tire technology and of wheel making technology made them un-necessary. If your wheels take a 16.5, 17.5 or 19.5 inch tire, they are a one piece wheel, with the dropped center; designed for tubeless tires.



From: Boise_Chief1
Sent: 4/7/2005 3:08 PM

Alright, 
I just returned from Les Schwab, and the culprit is most likely the front wheels being out of alighnment and worn spring bushings.  The kingpin is within limits .179 and all other front suspension parts look good.  The passengers side tire was quite misbalanced it took 14 oz to get it correct.  The drivers side took 4 oz. 

I think I'll replace the spring bushings this weekend.  Labor to have someone else do it is about 2 hundred dollars, parts are 30.00 through NAPA auto.  If you have any timesaving or tech tips on replacing these I'd appreciate your input. 
Off to the archives.
Sean
 


From: denison
Sent: 4/7/2005 3:53 PM

I am hoping you can give US the tips on doing it. My spring bushings, the rubber ones, are pretty well sagged. If your Chief is on the M400 chassis, there is a good chance it takes the same bushings as my 72 M400. I would be glad to know the NAPA part number, or the number of whoever the manufacturer is.
I can understand that you get the load off the spring, dismantle the shackle; and then magically somehow you press/push the new bushing into the spring "eye". I can imagine maybe using a long threaded rod to do this - I dont see the procedure described in the service manual.
Waiting to hear.....



From: Boise_Chief1
Sent: 4/7/2005 5:10 PM

In talking to the rep at NAPA he says the way to do it is to Jack up the coach until the tires are about to leave the ground block it and then remove the 4 u bolts holding the axle to the leaf springs.  then jack the coach up leaving the axle on the ground.  then finish removing the leaf springs from the coach.  He said that if I remove the whole leaf springs from the coach and bring them down he will press out the old bushings and press in the new ones.  then reassemble.

My worry is that I will mess up the alignment or drop a 10000 lb box on me. In your opinion will I be able to remove the axle in this way without removing any of the steering components.



From: denison
Sent: 4/7/2005 7:12 PM

Yes. The parts are just Heavy and the U-bolts will have rusty threads. The important thing will be to get the springs back in the same spot, relative to the rust patterns from the U-bolts and the axle, and with the tapered shim facing the proper direction so the “caster” of the kingpins is the same. You might want to undo the brake hoses, since they might get stretched with the axle being lowered further than it normally would be. If those brake hoses are original you might want the peace of mind of replacing them anyway. You want have to undo any steering linkage. Do you have the service manual? It gives the torque specs for reassembling each of the parts.
To support mine when I take off a front wheel, I use a supply of 6 by 6 lumber pieces, some 2 ft long and some 3 ft long. I make a pyramid of the things, laid crosswise to each other, with a 4 by 4 of 4 by 6 and a 2 by 6 for the top of the stack. I would chock the rear wheels before I started, fore and aft on both sides.
To get my wheels off (front and back) I have to jack the frame up, not the axle, so the wheel arch doesn’t interfere with the tire. I jack from the very front of the frame on each side. I would have my support stack behind the springs on each side, though the clearance to reach the frame rail can be tricky. Once the wheels are off the axle you can let the axle drop lower to the ground, and not have to raise the frame anymore.
I have never removed the springs or front axle on my Winny, but I have done it on my ‘29 Sterling and a friend’s 1925 Bulldog Mack. You might need to buy some a new socket wrench â€" I would think a 3/4 drive deep socket and breaker bar might be needed for the U-bolts. And lots of penetrating oil.



From: xsuperbgx
Sent: 4/14/2005 12:02 AM

I'm new to the forums and new owner of a '72 Indian.  I found that my winnie had a bad shimmy/shake when i first got it and when driving it home after purchase the shaking seemed to go away slowly (approx. 1 hr drive).  I think this was caused by flat spots on the tires from sitting so long(1-2 yrs) and went away due to tires getting warm and rounding themselves up.
As for spring bushings, I am a diesel mechanic by trade and have changed spring bushings before.  It seems to me that the front bushings don't wear as much as the rear ones, and if someone only wanted to change rear ones I've seen a guy just put a bottle jack in between the frame and the rear end of the spring to take the weight off of the rear shackles, bushings etc. so that bushings could be put in.  I am unfamiliar with the suspension of the winnebago and cant get to it now to look to see if this may work on it or not. But it could be an easy solution.

John



From: Boise_Chief1
Sent: 4/14/2005 3:57 AM

The shake you are describing is definately cold bias ply tires.  I have already replaced the spring bushings.  All in all it took 4 hrs to do.  You can find my post describing it using the search function and searching spring bushing.  While you are right about the backs being much worse, it would be difficult to get the old bushings out with a hammer and punch.  You might as well pull the whole spring and do both ends. the bushings are cheap and for peace of mind I would still do both.

Enjoy your new toy.  I am about 80% done for this year and am taking it out for it's true maiden voyage this weekend.
Sean



From: denison
Sent: 4/14/2005 7:14 AM

I am used to the flat-spotting from bias ply tires, so it doesnt bother me anymore, as I know its normal. If I havent moved the motorhome in the prior two weeks, I minimize the flat spotting by moving the RV forward about 3 ft the day before we are going to start on the long drive. Normally I am taking the RV for test drives in that period of time however.
After the first days drive, there will be some of that lumpy-effect the next morning when we leave a campground, but it doesnt last as long - maybe 5 minutes. And its normal anyway. Passenger cars had it for all of my childhood (before radials tires were common), though its hardly noticeable with 2 ply or 4 ply tires. It was slightly more noticeable with the 6 ply tires on my 52 Ford pickup. On my 54 Reo army deuce-and-a-half with its 12 ply tires, everything in the cab would rattle for the first few miles.



From: CLASSAWINN
Sent: 4/15/2005 11:44 AM

I have a 69 F-17 winny and I had some of the same problems. You said you had to put 14 oz. on driver side front tire. In my case ,and if the tires are old, the 6 or 10 ply tire will look good but they may have a broken cord in it or starting to seperate . It will vibrate on the motorhome and will not show up when on a tire balance machine. They will balance it but when you put it back on the motorhome it will still shake, and it will get worst the longer you drive it  till you can see the tire bulge or it blows out. Or it could be a bent or warped rim.. You can easily check that on a tire balance machine.. The way I found my problem was to get my friend to drive my motorhome and I drove beside it in my car and saw which tire was vibrateing and went from there . In my case it was a warped rim on the front. In another case I had it was a bad tire on the rear and I had had it checked several times and it look fine but and they would balance it and put it back on and it would still vibraite. It got a bulge on it and I got a new tire and then it was fine. I broken cord in a tire will tend to shake more a low speeds and will somewhat smooth out at higher speeds.



From: Boise_Chief1
Sent: 4/16/2005 1:46 AM

Class A,  My problem seems to be solved.  I had the front tires balanced and replaced the spring bushings and I haven't had a problem since.  The ride is tighter and I'm pleased.  I also lubed all zerts on the chassis which may be a part of it.  I used a full tube,  some of the joints were pretty dry.  I plan on re-greasing after this weekends trip.   We are going about 1 1/2 hrs one way for a trial run.   I bet I can re-grease and It'll need it after the grease is distributed around with movement.