Stopping problem: WC-12

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Michael Keller
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Stopping problem: WC-12

Post by Michael Keller » Tue Oct 31, 2017 10:18 am

I have finished restoring my WC-12 and it seems to be seriously under-braked. I couldn't lock up the wheels if I stood on the pedal.

Brakes have been bled and have good pedal. Brakes have been adjusted. I do have 20" wheel for faster highway speeds.

I have been told that stopping power was always poor on these trucks. True?

Options that have been suggested: softer pads or bigger wheel cylinders. Are these the best and only options?
1943 M15A1 Autocar halftrack (restored)
1941 Chevy dump truck (restored and sold)
1978 M416A1 Quarter Ton Trailer (for sale)


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Re: Stopping problem: WC-12

Post by Tin Ear » Wed Nov 01, 2017 3:50 am

As no one has answered you yet I will offer my thoughts on driving a WWII WC. I have a WC7 and I can not lock the brakes at high speeds. I drive it frequently and feel safe if I remember that it is 75 years old and the design is from an era when vehicles were switching from mechanical to hydraulic brake systems. Do not drive out of a safe braking zone. I never drive faster than about 40 mph and leave plenty of room ahead to stop. If circumstances allow down shift and let the engine help slow you down when approaching a stop. Driving a WC is not like driving a modern car where you can take a corner at 45mph and stop in a few feet. Part of the problem may be that you upgraded the wheels to achieve higher speeds but did not upgrade the brake system to match. I hope you get some better answers. Stay Safe,
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Michael Keller
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Re: Stopping problem: WC-12

Post by Michael Keller » Thu Nov 09, 2017 10:26 am

It feels like either the front wheel cylinders or only the back wheel cylinders are applying the brakes. I'll jack it up and see. But most of my knowledgeable friends agree with you: they are just hard to stop. You have to be extremely vigilant.

Two suggestions I have received: use softer brake pads, or go to larger wheel cylinders. Any thoughts to these suggestions?
1943 M15A1 Autocar halftrack (restored)
1941 Chevy dump truck (restored and sold)
1978 M416A1 Quarter Ton Trailer (for sale)

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Re: Stopping problem: WC-12

Post by artificer » Thu Nov 09, 2017 11:09 am

All older vehicle brakes (I have not worked on these WC's) with fixed bottom anchor brake systems were not brilliant.

Here is what I would suggest:
1. Check the brake linings & drum diameters are matched....skimmed drums & standard linings will never be good.
2. Deglaze the brake linings & drums
3. Do a complete major adjustment using this method:
http://www.jeepdraw.com/images/BRAKES-101.pdf

If it were my vehicle I would be checking to see if later model Dodge Power Wagon that had self energizing (non fixed anchor & self adjusting) backing plates & shoes could be fitted.

Usually this type minor mod will be fantastic. Also sometimes 4x4 International of later models of similar size may work.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Stopping problem: WC-12

Post by dpcd67 » Fri Nov 10, 2017 3:29 pm

You have a Twenty inch wheel? No wonder you can't stop; these brakes work marginally well enough with 16 inches, but you have over matched the capability of them.
Have you replaced the wheel cylinders and have the big bores facing rear? I do not try to rebuild them; replace them.
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Michael Keller
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Re: Stopping problem: WC-12

Post by Michael Keller » Sat Nov 11, 2017 3:18 am

Easy things first: I'll de-glaze the drums and pads.

Other options: softer pads and bigger wheel cylinders.

I did not know that 1941 Dodge weapons carriers, even a half ton, had 16" wheels. It would cost a lot to replace wheels and tires.

'Hope there are no problems in today's parade.....
1943 M15A1 Autocar halftrack (restored)
1941 Chevy dump truck (restored and sold)
1978 M416A1 Quarter Ton Trailer (for sale)

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Re: Stopping problem: WC-12

Post by dpcd67 » Sat Nov 11, 2017 7:02 am

Half tonners came with 7.50x16 which are tiny little things compared even to the 900x16s on the 3/4 and 1.5 ton Dodges. And M37s. Basically they were Jeep tires. Putting a 20 inch tire on one puts a strain on the entire drive train; the 1/2 tons are not as rugged as the later Dodges. A good brake system will stop a stock vehicle well enough. Modified ones, not so much.
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Re: Stopping problem: WC-12

Post by Michael Keller » Sun Dec 24, 2017 1:24 am

Update FYI:

It was conveyed to me that this vehicle had 20" wheels. Not true. They are 16". They do have 900 tires with almost new tread. I get a little higher top speed and won't switch to the original 750 tires.

So I pulled the wheels and found the problem with braking power. Having sat for 5 years or so, all of the wheel cylinders had deteriorated and I found brake fluid on the pads. Lots of brake fluid. Worse, I found that all of the rear axle seals had also deteriorated and the rear pads were soaked in gear oil. Having thought the restoration complete, I actually drove this vehicle in the Veterans' Day parade. I'm lucky I didn't kill the entire high school band in front of me.

Pretty scary, huh? Well, the mystery is solved. I should be back on the road next week. And back on the road safely.

Thanks for all of the assistance.
1943 M15A1 Autocar halftrack (restored)
1941 Chevy dump truck (restored and sold)
1978 M416A1 Quarter Ton Trailer (for sale)


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