Does anyone know why on front drum brakes that the "front" brake shoe is bigger than the "back" brake shoe? o No:
I think it has to do with the "self-energizing" feature of the brakes. The shorter shoe can wedge itself against the drum better than if it were longer. I don't know it for a fact, but it makes sense to me.
According to the Buick Chassis manual, the primary(front) shoe is shorter than the secondary(rear) shoe. They are of different composition also, so they are not interchangeable. I thought I heard that you can get more braking, if you use 2 secondary (longer) brake shoes instead of the primary and secondary shoes.
Just did a brake job on my front drum brakes. I have never done front drums, just front disks and rear drums. When I took the shoes off the front, the longer shoe was on the back (facing rear of car), and the short shoe facing the front. Thought this was kind of odd because my thinking is the long shoe should be facing the front. Just threw it back together like that but then thought maybe someone reversed the shoes on the last brake job that was done on it. It seems to be working fine. Haven't tried to take the shoes off and reverse them. What do ya think? Don't have another car with drum front brakes to look at.
Kind of makes sense. Just need another car with front drums to look at to make sure I've got it right.
Dee, The shorter primary shoe should be in front, according to the 70 Chassis manual. They don't explain why though.
The inquiring woman always wants to know WHY???!!! :rant: Thank you for the picture! Have a great New Year! :beer
Did a Google search on primary brake shoe, and came upon a site that explains it. Apparently the self energizing feature of drum brakes applies the secondary shoe with more force, so a larger lining would take better advantage of that force. Here's a Quote from the site: "The anchor pin on the brake backing plate keeps the shoe from turning with the drum. The frictional force tries to turn the shoe around the anchor pin. As a result, the shoe is pulled tighter against the drum with a force greater than the applied force that first moved the shoe against the drum. This is called self-energized action. When two shoes are connected by an adjusting link with some type of an anchor pin at the top, the applied force acts on one shoe, moving it into drum rotation and energizing the shoe through the action of the drum. Because this shoe starts the movement, we call it the primary shoe; the other shoe is called the secondary shoe. The greater pressure or force applied to the secondary shoe is again increased by the action of the drum if the shoe pivots on the anchor. Therefore, the braking efficiency of the secondary shoe is greater than that of the primary shoe through self-energized action. The action of both shoes has a tendency to force them tighter into the drum as they are both energized by drum rotation as shown below. " Hope that explains it
Adam, The short shoe is on the front, for sure. I came up with something, I posted right before you. Here's the whole text: http://www.autosite.com/garage/subsys/badrumbr.asp
ou: I deleted my post as it just confused things further. Larry, I did agree about the short in the front once you pointed it out. Thats what happens when you do brakes once every 5-years I guess. One thing useful maybe, while doing the search about brakes I learned how hangvers "work" on howstuffworks.com
Ahh, hangovers, just in time for New Years. The question is, knowing how they work, can you avoid them :laugh: I never seem to learn my lesson ou:
Okay, another question... There's a piece that fits under the brake cylinder, between the shoes, that fits into the notch on both shoes. My front brakes don't have this so it makes the little doogers (have not idea what they are called) on each end of the brake cylinder go in crooked. Front brakes are suppose to have this piece, right?
Dee, I know the piece you refer to, but I can't think of what it's called. It should have a spring over one end. It needs to be installed before you connenct the heavy duty springs which keeps everything together. I believe this item is stamped steel, and its function is to help the shoes aligned with the drums, thus they can apply equal force during braking. It is NOT pictured in Larry 70GS's picture. If the self adjuster fails, which I've seen happen, eventually, the entire brake system on the affected wheel could implode upon itself, resulting in NO BRAKING on the affected wheel. That is why you need the piece I referred to, darn, can't think of its name. :spank: The wheel cylinder does not keep the shoes aligned during braking, their action is solely to apply and release the brakes. The system requires the aligning bar (maybe that's what it's called) in order to work properly and safely.
Okay, so does anyone have a couple of extra front drum self adjuster thingys? I have none and the brake hardware kit that I bought didn't have a spring that would go on them either. Just to make it clear, I've attached the picture showing where the "thingy" I'm looking for goes in red. If anyone can tell me where I can get a couple of these, I'd appreciate it. :TU:
Hey Dee, This explains it. It's from an Eis Brake Service manual I have. It's a parking brake link, no parking brake on the front, leave it alone.
Thanks for clearing that up Larry. I was 100% certain that the front brakes had that link on them as well o No: It has been several years since I've had one apart though.
