My front brake was truly awful so I pulled the front wheel off and found this:



The shoes are too big, as in too long. They hang off the end of the cam and the alloy base has been dragging on the drum:



But one of them has the correct part number on it, 35-9235. They don't appear to be repos (although how does one tell?), they seem aged and have wear grooves from being operated by another cam on the steel face, ie in a different place from my cam now.

I measure the pivot centre to the cam centre at 5 9/16". The shoes measure about 5 3/4", judging where the centre of the cam faces are.
I'm wondering if I have the correct back plate. I doubt it's wrong but if someone could confirm the C to C 5 9/16" dimension that would be helpful.

Where to from here then? I've found 2 suppliers with repos, Cornucopia have one that looks right and British Only Austria have 'new replacement' that appears to be made from steel. Both are eye wateringly expensive.

This is a 1941 M20 (I assume M20 - it has a later M21 motor in it now), rigid tail and girder forks. I'm in Melbourne, Australia.

Thanks
Murray

email (option): murray [at] littlewoodmansion [dott] com

I have purchased some of the steel reproductions and wasn't impressed.

Mark

email (option): pes.sales@btconnect.com

Murray, I just took a couple of photos that may or may not help.

The centre to centre distance is pretty much 5 9/16" and the outside edges of a brake shoe are 6 9/16" at the very ends.





This is a photo of the front of the brake plate - pretty close to 8" edge to edge. The angle of the photo has some parallel error.




I'm in Melbourne so in your timezone. I can pull the pivot and cam out of this if you suspect something is out of whack with them?

Ray

PS. I was just looking closely last your photos and see that the actuator cam is different to what I have - I another one somewhere so I'll double-check that as well.




PPS. Yes, the brake from the second bike has the same sort of cam - not sure of this difference is relevant.
The flat face of the cam is 1" wide.

email (option): rays54(at)hotmail.com

Hi Murray
Modak can't help?
They used to have mountains of WM20 spares.

Thanks Ray, that confirms I probably have the correct plate, just wrong shoes even though they have the correct part number cast into them. Its a mystery.

And thanks Bob, I'll contact Modak. They're a surprise - I never thought there would be a BSA parts supplier here in Melbourne. Been there since the 1930s!

email (option): murray [at] littlewoodmansion [dott] com

Murray, if David at Modak doesn't have any then you might have luck with a second hand pair from Bill's Bits and bikes in Birdwood S.A.

I know he is still going as I was talking to him at the Bendigo swap on Saturday.

Ray

email (option): rays54(at)hotmail.com

Speaking of Bill's bikes, I live nearby & can ask him for you if you like. But I can't do it before Thursday, & I'm not sure which days he opens.

David at Mondak couldn't help me. He said he had boxes of them 20 years ago...

I couldn't find any web presence for Bill's Bikes so if you happen to talk to him Bob that'd be really helpful thanks. Give him my email address.

I filed some clearance where the shoe base was contacting the drum and tested them again. Still very poor. The center of the shoes must be offset from the drum axis so there just can't be good contact. I'm going to half to replace them.

Cheers
Murray

email (option): murray [at] littlewoodmansion [dott] com

I note the linings are riveted on but someone told me they had had distortion of shoes by heat fitting modern linings, a previous attempt perhaps?

Rob

email (option): robmiller11(a)yahoo.co.uk

Thats a thought Rob but I'd be surprised if they grew 1/4" longer. They still measure approx 7" dia all the way around. But that would explain the correct part number cast in. They'd need to be the high zinc version wouldn't they? That means they'd be heavier than usual. I've not got anything to compare them to although if I get some second hand good ones that might reveal something. I could also check the rear brake shoes but they're down the other end of the bike and I'm sort of working from the front. Trying not to have too many things in pieces at once!

Cheers
Murray

email (option): murray [at] littlewoodmansion [dott] com

Murray, Rob triggered a memory with that heat distortion suggestion and looking closely at your first photo it does look like one shoe is longer than the other?
That is is the same one with the rub marks - I didn't notice it initially because my eye was deceived by the shape of the backing plate behind.

Are they physically different lengths if you put them side by side?

They don't have a website but this is the address and phone number for Bills Bikes and Bits.

Address: 26 Shannon St, Birdwood SA 5234
Hours:
Closed ⋅ Opens 9 am Wed
Phone: (08) 8568 5756

I just took some photos of a shoe to use as a comparison - the 3" measurement is taken with the steel ruler sitting against the inside of the shoe casting.






Ray

email (option): rays54(at)hotmail.com

Thanks Ray, its quite possible (that one is longer than the other). I've just put the front wheel back on for the moment as I have to move the bike. The new workshop is getting wired today. I'll pull it off next week and compare the shoes to your measurements.

I'll also call Bill today. Thanks for that.

I seem to remember there was someone in Qld that had a large collection of parts, mainly later twins I think, but I can't find my note of his name or contact.

Cheers
Murray

email (option): murray [at] littlewoodmansion [dott] com

So Bill at Bill's Bits & Bikes in South Australia has found a pair of second hand shoes. I didn't even ask what condition they were in, I just bought them on the spot. I'll find out when the arrive in a few days. If they need relining I'll cross that bridge later.

Thanks everyone for your help. I'm going to look at the slipping clutch next.

Cheers
Murray

email (option): murray [at] littlewoodmansion [dott] com

M20 brake shoes were made in aluminum, mazak metal and steel. The mazak ones you can't glue the linings on as it will warp the shoe from the heat to cure the glue.

It is surprising for a bike of which 126,000 were made, that no one makes new brake shoes? For other BSA bikes which did not sell anywhere near this number, you can get new shoes!

I've never had or seen steel shoes so far (other than for pre war models)....It seems it takes a lifetime to come across all the variations of different parts!!...:smile: ...Ian

email (option): ian@wright52.plus.com

I have looked at making M20 Brake shoes, but new old stock ones still keep turning up.
The shoe will need to be cast to keep costs down, but still, I expect it will be more than most of you will pay.

Mark

email (option): pes.sales@btconnect.com