Bendix brakes - leading/trailing shoes

[BillLee/Chandler TX]

I am installing Bendix brakes.

The leading shoe has the shorter lining, the trailing shoe has the longer lining.

Is there any "rule of thumb" about the ratio of the lengths of the lining of the leading and trailing shoes? Or perhaps a resource where a typical set of shoes might be dimensioned?

Thanks.

 

[51 MERC-CT]

I am installing Bendix brakes.

The leading shoe has the shorter lining, the trailing shoe has the longer lining.

Is there any "rule of thumb" about the ratio of the lengths of the lining of the leading and trailing shoes? Or perhaps a resource where a typical set of shoes might be dimensioned?

Thanks.

By actual measurement of a set of Bendix brake shoes, the ratio is 1.256:1

 

[V8 Bob]

I am installing Bendix brakes.

The leading shoe has the shorter lining, the trailing shoe has the longer lining.

Is there any "rule of thumb" about the ratio of the lengths of the lining of the leading and trailing shoes? Or perhaps a resource where a typical set of shoes might be dimensioned?

Thanks.

I'm not sure what value any ratio of lining lengths would have, as that can vary slightly, depending on the type and effectiveness of the lining material used, which is usually different on the primary and secondary shoes on most Bendix Duo-Servo brakes. (FYI, leading/trailing usually refers to non-servo brakes whose shoe/lining assemblies are exactally the same)
IMO, it's much more important to know the operation, proper assembly and adjustment of the brakes.

 

[BillLee/Chandler TX]

...(FYI, leading/trailing usually refers to non-servo brakes whose shoe/lining assemblies are exactally the same)
...

According to a LOT of reading on the 'net, the terminology "leading/trailing" applies to Bendix (i.e., self-actuating) brakes as much, perhaps more, than non-servo systems. Another terminology often found is "primary/secondary".

Agree to disagree.

 

[BillLee/Chandler TX]

By actual measurement of a set of Bendix brake shoes, the ratio is 1.256:1

Thanks. That's the kind of information I am needing.

Had shoes relined and they didn't distinguish. All were relined the same. Probably can use them that way but would rather have the shorter leading shoe.

 

[V8 Bob]

According to a LOT of reading on the 'net, the terminology "leading/trailing" applies to Bendix (i.e., self-actuating) brakes as much, perhaps more, than non-servo systems. Another terminology often found is "primary/secondary".

Agree to disagree.

According to the company that designed and built the Bendix Duo-Servo brakes, the front shoes are primary, and the rears are secondary, and always have been. This also applies to most/all other brands of similarly designed servo brakes.
Gota be careful what you read on the "net", and especially about brakes. For example, some companies that sell brake kits and related parts have very wrong information on their web sites about how some of the components function. One example that is a very common forum topic is residual valves.

 

[V8 Bob]

Thanks. That's the kind of information I am needing.

Had shoes relined and they didn't distinguish. All were relined the same. Probably can use them that way but would rather have the shorter leading shoe.

What year or vintage Bendix brakes are you using? I would get someone else to reline the shoes, because having both the pri. and sec. linings the same length most likely will result in aggressive or strange behavior, unless the lining material is 1937 fire hose.

 

[V12Bill]

My Lincoln Bendix brakes were originally lined the same length primary and secondary. When I sent them out to be relined they came back different lengths. The relining shop said that that is the way the lining kits are supplied to him. I felt better when I had the additional lining.

 

[Andy]

The primary shoe has short lining because it only sees the pressure from the wheel cylinder. The primary shoe tries to rotate around the drum and applies pressure to the secondary shoe. The secondary shoe therefore has both the wheel cylinder load plus the drag from the primary so it should be larger. The primary shoe should be smaller to have higher contact presure so it will grab.

 

[rotorwrench]

That's why they called them servo brakes. The front shoe was the main servo and the rear did most of the work of stopping the rotation in its secondary action. The Lockheed types both applied the same pressure with no leverage advantage at all. Lockheeds had no primary/secondary action just leading & trailing.

That leverage will apply much more stopping force to the one shoe than both shoes together on a Lockheed system. In a Bendix design, the full face of the linings makes contact. It's only partial on the Lockheed design so neither shoe makes full contact.

 

[BillLee/Chandler TX]

According to the company that designed and built the Bendix Duo-Servo brakes, the front shoes are primary, and the rears are secondary, and always have been. This also applies to most/all other brands of similarly designed servo brakes.
Gota be careful what you read on the "net", and especially about brakes. For example, some companies that sell brake kits and related parts have very wrong information on their web sites about how some of the components function. One example that is a very common forum topic is residual valves.

As I said: agree to disagree.

 

[V8 Bob]

As I said: agree to disagree.

OK, disagree on what?

 

[PeteVS]

Nobody has said anything about the shoe return springs. I replaced the self adjusters with manual adjusters in my Chevy brakes "back in the day." I recall that the springs that were provided with the kit specified that there were different springs for the front shoe and the rear shoe. I never understood why, and now, I don't know which is which.

 

[BillLee/Chandler TX]

Trying to get back on-topic: Thanks to 51 MERC-CT for his input. Does anybody else have additional information?

Thanks.

 

[rotorwrench]

Nobody has said anything about the shoe return springs. I replaced the self adjusters with manual adjusters in my Chevy brakes "back in the day." I recall that the springs that were provided with the kit specified that there were different springs for the front shoe and the rear shoe. I never understood why, and now, I don't know which is which.

The rear brakes include more equipment to operate the hand brake of emergency brake. This usually requires more spring action to move all the parts efficiently. In the Bendix system as a whole, the rear shoe usually takes a bit more pressure due to its size and amount of movement.

 

[rotorwrench]

Trying to get back on-topic: Thanks to 51 MERC-CT for his input. Does anybody else have additional information?

Thanks.

What 51 Merc Ct added is probably about as good as it gets. Different manufacturers vary somewhat. The original design Bendix system as used on the early Lincoln cars used linings that were the same basic size both primary and secondary. In service it was found that the rear secondary shoe would wear out but the front primary shoe was still serviceable. I think they changed the design to let them wear more evenly thoughout their service life. Customers ask a lot of questions when one part wears more than another.
Kerby

 

[51 MERC-CT]

Don't know if your shoes are bonded or riveted but if I had the same situation I would consider removing the necessary material from the existing long shoes.
Tried it in a used shoe and it appears that it might work.
Measure the circumference of the long shoe and multiply by ( .785 ).
This will give you the length of the short shoe.
Center that length on the shoe to be cut and remove excess material from each end by a saw cut almost all the way through the shoe and chip away material with a sharp chisel.

File down most of the remainig material. ( Should'nt make any differece if some is still left on )

 

[BillLee/Chandler TX]

Bonded, and your suggestion is what I have/had planned to do. Just needed some idea of "how much".

Thanks.

 

[41Fordor]

I'm confused now...I set my brakes up like in the Ford manual with the shorter shoe to the rear as in the picture:

Is this incorrect?

 

[BillLee/Chandler TX]

Different animal. The original question was for Bendix self-actuating brakes as found on 48 and later Ford pickups and 49 and later Ford cars. The brakes you are looking at in the diagram are late 30's and are not self-actuating. The front shoe (aka "forward" shoe) does most of the braking when moving forward, the rear shoe (aka the "reverse" shoe) is for braking when in reverse. Not much is needed in reverse, a lot is need when moving forward, hence the different sizes.