Chevrolet C60s - Front Wheel "shimmy"

[cordenj]

Back from the Guernsey 70th Anniversary trip (in the Jeep) and now back to trying to resolve the Chev's Wheel Shimmy.

As two heads are better than one, I asked good friend, expert mechanic and fellow CMP owner, Andy to give me a hand to investigate further.

We spent all day yesterday working through the front axle.

Started by checking and slightly tightening the steering box. A test drive showed some improvement but a dose of major shimmy meant more investigation was required.

As some have said here, we think this is a combination of different factors that cumulatively cause the issue.

So logically it is a case of going through each possible cause and trying to eliminate it ,apart from what I've already listed earlier in the thread:

1. Steering Gear - checked, adjusted and ok
2. Front Axle tie rod - checked and in good condition
3. Wheel bearings - both sides are correctly set and in good condition
4. Pivot Pin bearings:
Near-side_steering knuckle binding slightly in the the chromed housing. Checked shimming and reset to avoid binding. Both bearings in good condition.
Off-side_steering knuckle binding in the the chromed housing. We think this side was overshimmed and had placed great pressure on the Pivot Bearings....unfortunately both need to be replaced....so will be trying to contact Dirk or Stefan on Monday for replacements.
We suspect that this wheel shimmy is not a new issue on this vehicle and that the bearings had been very tightly shimmed in an attempt to stop it.

5. Front springs - The photos below show the front springs, which have clearly sagged over the last 70 years......and as several posters on this thread have suggested, this is probably the a major contributor to the shimmy issue and the caster will be way out.
Close examination of the photos show some small wedges have been fitted in the past. My plan now is to try to get a pair of larger wedges machined a at a local engineering shop.

Once new Pivot bearings hopefully sourced and are fitted and the new wedges are placed between the spring and axle....and we'll see what happens.

Can't help feeling the real solution is a replacement set of good front C60S springs which can restore the correct caster. Anybody know of any in UK, Belgium or Netherlands?

[rob love]

You could take the springs to a good spring shop for re-arcing. Springs are "bull-work" and I have always generally found having this done to be very reasonably priced. The shop will dis-assemble the complete springs, re-arc each leaf, install slip pads and rebound clips as necessary, reassemble them, and you can do the spring bushings at the same time.

Just make sure they don't over do it. We used to have empty trucks leaving the shop looking like they were carrying tons of weight becaue the front ends would sit higher than the back.

[cordenj]

Thought I'd update on the continued frustrations of the wheel shimmy.

The parts arrived from Dirk very efficiently and we fitted the pivot bearings on the side where they had been over shimmed and damaged in the past.

I made up the special tool from the "Sept 43 Service Information Bulletin", to enable me to put tension on the Pivot Pin to correctly set the bearing tension.

While this was going on I had a pair of 3 degree and 6 degree wedges made at a local engineering shop

[cordenj]

I dropped the front axle and found that a previous owner had installed very small wedges....so clearly the castor angle has been a problem before.

I fitted the 3 degree wedges and then had to wait a month while a had the master cylinder rebuilt and brake hoses remade.

I've put up photos here, as while there is a lot of talk about wedges on the forum, I'd not found any photos of the job in progress.

So tonight was the first test drive with 3 degree wedges fitted.....and?

Made no difference at all! Bit disappointing, hit a small bump in road and got violent shimmy.

All I can do now is drop the axle again and try to 6 degree wedges to see if that works over the weekend.

It feels like I should be getting somewhere with this, especially as very small wedges had been fitted before

[Bob Carriere]

There has to be some looseness somewhere......

Reading back on previous postings......

There seemed to have been some improvements when the steering box was adjusted..... would it be worth while revisiting....or even doing a total disassembly of the gear box for a visual inspection of parts for unusual wear patterns.

Were the steering linkage taken appart for inspection.... I know I have taken some apart that had eggshape wear pattern on the round pivot balls or weak/collapsed springs.

Same could be said of the tie rods.... not sure if they are all meant to be taken apart but some I did and found some were good some were worn oval over the years of service.

Did you rotate the tires before your last road test. would it be possible to borrow a full set of wheels from a cooerative friend and do the road test again????
A bad set of already cupped tires could be a nasty composition to overcome.

Wishing you luck and will eagerly follow your trials and eventual tribulations in my search of knowledge.

Cheers

[Richard Farrant]

John,
Have you physically checked the shock absorbers for correct functioning? Not sure I have seen mention of them. I would borrow a pair of good known tyres and wheels to eliminate them also the road springs do look a bit flat. What is the condition of the spring shackle pins and bushes?

regards, Richard

[cordenj]

Thanks Bob/Richard,

I had suspected the replacement secondhand bar grips from the start, as I didn't get shimmy on the previous tyres that had a much "squarer" shoulder (but only did few miles on them before changing.

I can try to borrow a pair of wheels/tyres, but also have a pair of new modern 11x20s bar grips being delivered to W&P, so perhaps will fit them to see what happens.

The springs are definitely past their best and when the weight is on them, sit flat. Am trying to find a leaf spring refurbisher in south-east.

Will keep you posted on the 6-degree wedge test!