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Car Forum / Antique and Collectibles / Studebaker / August 2005primary and secondary brake shoes
it is convention to have the primary (forward ) brake shoe to be the shorter lining shoe. On the 1939 President the brake cylinder has a 1 3/8" bore forward and a 1" bore to the rear for the front wheels. For the rear wheels the large bore is 1 1/4", also forward, and the rear bore of the cylinder is 1". The cylinders can only be mounted one way. The shoes are NOT "self energizing" with a floating star wheel at the bottom like later shoes. Instead each shoe has a pivot at the bottom (with a cam adjustable pivot center). Since the larger bore cyinder ends have more power, Force = Pressure X Area, it would seem to me that the longer shoe should be placed forward. I don't know why there is a difference in the shoe lining length since each is mechanically independent of its mate. But that's the way the car came to me. The parts manual does little to clarify the matter and the Thompson manual shows a long shoe with the larger cylinder bore. I don't have a Stude shop manual yet so manual owners are invited to look and advise. Help?  SignatureLark Parker I would make a guess that there is indeed a difference on the rear shoe (with the vehicle in forward motion). The rotation will try to 'push' the rear piston back into the wheel cylinder. Perhaps that is why they put the different sized piston in back. That would not happen on the front show if that shoe's anchor pin is solid and not passing the torque applied through to the other shoe. (unless backing up) Since most of the braking is done by the front shoes, perhaps they made the rear wheel setup less aggressive. Interesting engineering. I'd like to see their reasoning. Jeff > it is convention to have the primary (forward ) brake shoe to be the > shorter [quoted text clipped - 30 lines] > > Help? > I would make a guess that there is indeed a difference on the rear shoe > (with the vehicle in forward motion). > The rotation will try to 'push' the rear piston back into the wheel > cylinder. > Perhaps that is why they put the different sized piston in back. Won't the rear shoe actually be "stolen away" once it encounters the drum traveling away from the cylinder? Hence the need for the narrower bore? JT > That would not happen on the front show if that shoe's anchor pin is solid > and not passing the torque applied through to the other shoe. [quoted text clipped - 42 lines] > > -- > > Lark Parker Interesting term 'stolen away', I haven't seen that one before.. That would happen on the front shoe (with the wheel cylinder on top) and the rear show would be pushed toward the wheel cylinder. I'm no expert on this style of brake, which is why it is so interesting to me.. Jeff. "Grumpy AuContraire" wrote... >> I would make a guess that there is indeed a difference on the rear shoe >> (with the vehicle in forward motion). [quoted text clipped - 61 lines] >> > -- >> > Lark Parker My logic is the opposite of yours. I would think that the front shoe would be the one that has pressure to cylinder... Any brake experts here?? JT > Interesting term 'stolen away', I haven't seen that one before.. > That would happen on the front shoe (with the wheel cylinder on top) and the [quoted text clipped - 70 lines] > >> > -- > >> > Lark Parker > My logic is the opposite of yours. I would think that the front shoe > would be the one that has pressure to cylinder... > > Any brake experts here?? > > JT Heh, you called? I haven't read this whole thread, but let me just say that: > > >> > it is convention to have the primary (forward ) brake shoe to be the > > >> > shorter [quoted text clipped - 16 lines] > > >> > cam > > >> > adjustable pivot center). In fact they *ARE* self energizing (primary shoe in the forward direction, secondary shoe in reverse), what they are *NOT* is servo-action brakes. Since they are not servo action brakes (with a floating link of some type between the primary and secondary shoe) the primary shoe does most of the work in a forward stop. This is the opposite of servo action brakes where the secondary shoe provides most of the stopping power in the forward direction. Examples of non self-energizing brakes would be the disc brakes used on later Studes, and the externally contracting brakes used on earlier Studes. The Chrysler drum brakes with two hydraulic cylinders (one at the top for the primary shoe and one at the bottom for the secondary shoe) are an example of a two leading or primary shoe self energizing brake design - both shoes are primary shoes and are self energized in the forward direction (altho rear braking was reportedly not that great). -- wf. Your logic is opposite of most peoples' <lol> Jeff (and I am a (humble) brake expert...just not on this style) Rice "Grumpy AuContraire" wrote... > My logic is the opposite of yours. I would think that the front shoe > would be the one that has pressure to cylinder... > Any brake experts here?? > JT >> Interesting term 'stolen away', I haven't seen that one before.. >> That would happen on the front shoe (with the wheel cylinder on top) and [quoted text clipped - 4 lines] >> me.. >> Jeff. On the 36 that JP and I sold the long shoe was on the front with the large bore of the cyl. I don't know if it was right but that is the way it was so that is how I put it back. When done with the brakes it sure stopped good for an old car. SignatureJerry Kaiser (Studeblu) 64 One Ton 61 Champ pick up 53 Starlight Coupe ( pinky) 53 2R6 > it is convention to have the primary (forward ) brake shoe to be the > shorter [quoted text clipped - 30 lines] > > Help? >On the 36 that JP and I sold the long shoe was on the front with the large >bore of the cyl. I don't know if it was right but that is the way it was so >that is how I put it back. When done with the brakes it sure stopped good >for an old car. Sounds like the way to go. Thanks SignatureLark Parker Lark, According to the Motor's Manual the primary (front) shoe is the longer one. I can scan the pages and send them to you if that will help. Mike > it is convention to have the primary (forward ) brake shoe to be the shorter > lining shoe. [quoted text clipped - 24 lines] > -- > Lark Parker >Lark, >According to the Motor's Manual the primary (front) shoe is the longer one. >I can scan the pages and send them to you if that will help. >Mike No, that's fine. That is what I had decided to do if there was no advice. Thanks SignatureLark Parker |
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