Chevrolet C60s - Front Wheel "shimmy"

[Lynn Eades]

Wheel balance would generally be less of a problem with big old M.Vs. than the likes of modern vehicles with smaller dia. wheels traveling at higher speeds.

In saying that, I do not disagree with any of the above.

John If you have measured correctly then something is definately wrong (1" difference in camber??) were you on level ground to start with?

Jack it up and see if you have any play in the vertical plane (grab the tyre top and bottom and try to wobble the wheel)
If there is any movement get someone else to apply the brakes and try it again
If the movement has gone, it is wheel bearing adjustment. If it is still there, it is in the king pins.
You also need to deal with the toe in as well. 3/8" will be scrubbing the hell out of your tyres with each wheel trying to go in different directions.

If you disconnect the drag link (steering arm end)and then swing the wheel asemblies through their steering arc (left and right) you may be able to pick up any roughness in the king pins.

If you do have to do king pins, keep in mind that king pin bearing preload is normally set without the knuckle seals fitted.

[rob love]

Originally Posted by Lynn Eades

If you disconnect the drag link (steering arm end)and then swing the wheel assemblies through their steering arc (left and right) you may be able to pick up any roughness in the king pins.

Not sure one can swing a pair of 20" tires with the wheels still on the ground unless you have a pair of alignment plates underneath. If the axle is jacked up and the wheels are in the air, then the problem may not be evident as you have transferred the weight away from the kingpin normally under load to the kingpin that normally does not carry a load.

[cordenj]

Originally Posted by Lynn Eades

Wheel balance would generally be less of a problem with big old M.Vs. than the likes of modern vehicles with smaller dia. wheels traveling at higher speeds.

In saying that, I do not disagree with any of the above.

John If you have measured correctly then something is definately wrong (1" difference in camber??) were you on level ground to start with?

Jack it up and see if you have any play in the vertical plane (grab the tyre top and bottom and try to wobble the wheel)
If there is any movement get someone else to apply the brakes and try it again
If the movement has gone, it is wheel bearing adjustment. If it is still there, it is in the king pins.
You also need to deal with the toe in as well. 3/8" will be scrubbing the hell out of your tyres with each wheel trying to go in different directions.

If you disconnect the drag link (steering arm end)and then swing the wheel asemblies through their steering arc (left and right) you may be able to pick up any roughness in the king pins.

If you do have to do king pins, keep in mind that king pin bearing preload is normally set without the knuckle seals fitted.

Hi Lynn,
I rechecked the camber with wheels on level ground, the figures decreased slightly on both side with the weight of the truck on them, but still a difference between left and right hand side.
With the wheels jacked up, I tried shaking wheels to see if any play. There was no perceptible movement, even with a lever under the wheel, so that implies to me that the bearings are not too loose. The wheels rotate freely too, so no reason for possible "grabbing" being the cause.

[Dave Mills]

I am certainly no expert on the CMP and have watched with interest the conversation. I am delving into the unknown here but may I suggest that you check your shock absorbers. If you have checked everything else it seems like you may need to check these, if they are faulty they can cause a shimmy once you increase speed and hit any form of undulation in the road surface.

Dave.

[jake neville]

our marmon herrington gun tractor had this same problem when we first put it on the road. the entire front axle had been overhauled and the wheels balanced. when it got around 20mph it started shaking so violently it was dangerous and uncontrolable. we fitted castor wedges to the front which made a big difference. it now only comes in mildly when you hit a bump around 50mph.

robin mawson had similar problems with his white scout car. he played around with his for quite some time. tried a number of things and still had problems. eventually he tried ajusting the toe in more than what it said to in the book. no shimmy at all from zero to flat out.

we are planning to try the same on the marmon when we get time. this obviously increases tyre ware but for the amount we drive these old trucks waring out tyres is highly unlikely.

give it a try?

[Mike K]

Originally Posted by jake neville

we fitted castor wedges to the front which made a big difference. it now only comes in mildly when you hit a bump around 50mph.

50 mph in a M-H - YOUR KIDDING So what brand of turbo have you fitted on that flathead

[cordenj]

Thanks for advice everyone.
Now off to celebrate 70th Anniversary of the liberation of the Channel Islands (well Guernsey) for a week.

Sadly not in the Chev as planned until this wheel issue is resolved, so having to take the Jeep and one of my trailers.

I'll investigate the shimmy more on my return.

[Bob Carriere]

Based on all the work that has been done already .....

Start with the tie rod ends....... they can be disassembled to visually verify wear...... not unusual to see oval wear spots. Look at the tapered hole where the tie rod connects to the eggcup..... in some case the tapered hole has gone oval...... they can be machined larger and a new tapered insert manufactured.

Then move on the steering arms..... take them apart...again not unusual to find some round pins with significant wear spots..... then move on to tighten the steering box..... which you may need to remove and look at the innards .

If none of that improves the shimmy look at totally disassembling the front axle egg cups...... there are NO cone bearing in the CMP like the Dodge axle. You will be looking at the New Departure 928 bearings mounted on solid pins... they should be hard to remove as they are a tight fit..... any looseness or wear patterns should be visible to the naked eye...... when removing the end caps you will find small circular shims.... save them and keep track of how many which side.....when you reassemble you need to preload the bearing as per the manual. Dirk as the New Departure bearings and use to have spare shims..... other wise start buying front axles for spare parts. I have taken CMP front axles apart that the New Departure bearings where literally worn out and fell apart in my hands. Old bearing if good are usually a tight fit and and need to be pulled out and pressed back in place.

From my experience you need to start at the wheel bearings which has been addressed then move on to the next connection point one step at a time.

I know you can ruin the front axle of a Dodge M series in one Winter of driving with wheel chains..... the solution was to have the oval holes of the front axle flange drilled out and new tapered inserts pinned in place..... it would have been cheaper to buy a scrap M37 for parts. The tie rod ends were also replaced at the same time.

Good luck.

Bob C