The Stovebolt Site Forums The Shop Area Driveline Strange Brake behaviour

Hi 61 C10 with stock standard brake system. All parts replaced including MC and wheel cylinders.

When stationary I have a good hard pedal with correct play. However as soon as the truck moves the pedal will drop nearly to the floor! It does not feel spongy then, but only catches when the pedal is nearly to the floor. Shouldnt the pedal feel the same when staionary or when moving? Should I suspect the MC or the wheel cylinders? No leaks and shoes are adjusted tight to the drums. Thanks for any ideas.

im no expert ...but i would check out the MC ...seems like your gettin a bypass of some sort ..have you checked the shoe adjustment now that it moves ?...they may need readjusted ?..just tossin out ideas.

I cant think that a bypass will only be happening when the truck is moving. The shoes are adjusted per description, tight first and then looser until there is just a slight drag. My shoes are religned , but I realised that they are both of the same size/length. Should there be a difference? Some guys say the leading shoe must be smaller and the trailing one larger or whatever. Will this be critical...the larger the better huh?!

Hy 61lorrie, are all eight of your shoes the same, could some short ones be installed together? In a self energizing system there should be a short [primary] shoe installed in the forward [front] position at all wheels, that being said, the installation of the shoes shouldn't cause the problem you describe. When you check your pedal when sitting still, is your parking brake applied? You should always adjust your brakes with your parking brake all the way off, hope that helps.

It sounds like you've backed the brakes off too much during the adjustment procedure. On a floating brake assembly like the Bendix system that year vehicle should have, tighten the brake until there is a firm drag, but NOT a total lockup, and back off 10 clicks if it has the coarse-tooth adjuster (without self-adjusters). Self-adjusting brakes with the fine-tooth star wheel get backed off 20 clicks, but the self-adjusting pawl must be released first.

If you back off until there is a slight, or no drag, the brakes are probably too loose. Free-floating brake shoes will drag a little as the adjuster is backed off, unless the brakes are applied after loosening the adjuster, to self-center the shoes again.
Jerry

I think the emergency brake adjustment may be too tight. Back off the adjustment on the cable & adjust the brakes like Hotrod says. Then tighten the cable to get the right feel onthe emergency brake. Test the master cyl. before you move it. Apply light pressure to the pedal & hold it awhile. If the pedal sinks the cyl. is bad. It,s doughtful if it,s a new one.

Thanks for all the ideas! I will definitely check the e-brake as it is not a standard setup. Cant find any parts for the original setup here locally.
The shoes are all the same...the shoe linings is of the longer type so no shorter linings on the leading edge. Could this cause the leading shoe to be pushed of the anchor bolt when moving as the friction is too high? thereby causing the wheel cylinder to expand a lot and having the pedal drop?

I have a 1960, should be simular although not positive. All my shoes are the same shoe. Front rear no difference.

I have a 1960, should be simular although not positive. All my shoes are the same shoe. Front rear no difference.

Also shoes here are very cheap $10. a pair.According to manual, raise vehicle,expand brake shoes until a light drag,on 1/2 ton turn adjusting screw oppisit direction 7 notches ( all other models back offf just enough to eliminate drum drag not to exceed 7 notches

Ken

Does it have power brakes?