Floating brake shoes

[Phil C]

Could someone enlighten me please: what is the difference between floating and non-floating shoes?

Phil.

[DAVE BRADY]

Hi Phil,

As I understand it, a floating shoe is not held at one end by a pivot so that the shoe can centralise in the drum as it is applied.  This is supposed to make the brake better as more of the lining contacts the drum.  If you can imagine with a pivot one end of the shoe can never get anywhere near the drum.

Dave.

[MGI]

Interesting.. I have never heard of a floating brake shoe (till now) I wonder how it is supported in place and where the cam locates?  Do you have any further details please. I am aware of the TLS set up and the wrap round effect of a leading shoe, and I can see the advantages of having a shoe which automatically centralises, just never came across one. Which machines were fitted with floating shoes?

[JulianS]

Floating shoes on A10 full width hub. Lower shoe in photo is the leading shoe.

[Phil C]

I'm confused.  Julian, you say the photo you posted is of floating shoes. But on a separate thread recently, entitled Rear Brake, you said the rear brake was non-floating, linings not offset, and did not have steel pads. Attached again here is a photo of my rear brake (as attached on the Rear Brake discussion.) In terms of pivot pin and cam, it looks the same as yours. So what makes one floating and the other non-floating? Am I missing something? (probably)    Phil.

[JulianS]

The pivot pin and can dont change it is the shoe.

These photos might help.

First is a non floating 8 inch shoes from full width hub. Note the left hand end with the semi circular recess for the pivot.

Second a pair of floating shoes, note flatened end with steel pad on the left which is the pivot end. The flat allows the shoe to move slightly. Leading shoe at top here. You can also see the position of the linings. This is a from 7 inch full width iron hub.

Last a close up of the pivot end of floating shoe showing the pivot pad.

[Phil C]

So, with floating shoes, the pivot end slides along the pin, rather than just pivoting around it? Is that how it works? It pivots but also slides?   Phil

[MGI]

It apears that (to my unskilled eye)  as the cam is operating at the ends of both shoes the amount of self centralising taking place would be minimal given that the shoes are being pushed against hub at one end only? Is the benefit of this type of mechanism immediately apparent to a rider who is familiar with the conventional system?

[DAVE BRADY]

The idea is that the shoes move enough to give maximum contact with the drum.  As the end with the cam starts to touch the shoe 'floats' or slides slightly, to make better contact. The amount of movement is small but as the linings wear the contact is still good.  Sometimes linings on a non-floating shoe look like the pivot end has never touched the drum whereas floating ones have more even wear.
On some brakes like the A10 plunger rear, the hole in the brake plate for the pivot is either elongated or just oversize.  This so that the shoes can be centralised to some degree.  This is achieved by having the pivot nut backed off a bit and then applying the brake quite hard.  The pivot then centralises and the nut is tightened.  It may also be worth having the brake plate nut just backed off a bit when doing this so that the plate is centralised.  Usually this helps when the axel hole is a bit worn.  Again, tighten this while the brake is held on at the same time as the pivot nut.  The brake plate bit should be done with floating and non-floating shoes.
I hope this makes sense.

Dave.