front drum brake

L.A.B. · May 6, 2016

frankdamp said:
The earliest front drum brakes on the Commando were completely ineffective.

I don't know how many bikes were delivered with that problem.

Possibly none, as you said before, you only rode the prototypes and have "never ridden any production Commandos". A stiffening plate was introduced in 1972 which apparently improved the brake but I don't think the brake was regarded as completely ineffective before that?

DogT · May 6, 2016

Actually, after I worked on mine it was night and day. Now I can really stop with the front brake where before I'd drag my feet first or most likely I just planned about 2 miles ahead and used the gears. I didn't install the extra plate either. But it's only good for one fast stop.

acotrel · May 6, 2016

When you compare a drum brake with a disc brake, perhaps you should ask yourself how many ways can you get it wrong. Almost every racing crash I have ever had has been due to a drum front brake. I still carry the injuries. Large drum front brakes look beautiful, however 'looks right, IS right' is not always a safe approach. When push comes to shove, you can always safely grab a big handful of a disc brake - not so with a drum brake.
Over the years there have been many things tried to get drum brakes to work. One is to fit the first two inches of the leading shoe with a harder friction material, so it does not heat up and become sticky. In Australia our period 3 Historic racing only allows drum brakes. That is why I don't own a Period 3 bike.

Bernhard · May 9, 2016

madass140 said:
I posted a few years ago
"Before I started manufacturing a replica Commando 2LS front brake I purchased new sets of front brake shoes from different suppliers, Ferodo, Norton etc , when fitted to the brake plate the diameter of the shoes
was less than 200mm, 8" = 203.2mm, so these shoes are as described to me by a buyer of my shoes "half worn
out before I start" he was impressed with mine that had minimal clearance just under 8"
when I originally had my shoes manufactured, same problem the manufacturer and no doubt the manufacturer of the shoes for the other suppliers assumed that the brake diameter was 200mm.
check the pic in this Ferodo set Ebay item No. 390565869228 and you see Ferodo advertise them as 200mm.
I never sold any of mine before rebonding them, I rebond mine with 1/4" linings then radius grind them to
7.960"-7.980" much better than about 7.800", I'm not trying to push my own cart as I rarely advertise my shoes
on their own, I prefer to sell my brakes complete, Just be careful when buying brake shoes"

Re; “"half worn out before I start"
yes’ this was a common problem for practically ALL the British bikes of the 1960/70s period , which is one of the reasons I went to a racing brake fitter, I was pi**ed off of having the whole of the brake adjuster taken up from new brake shoes brought over the shop counter, the other method is to “space out” the brake shoes which I use on worn shoes, or badly worn brake drums, but this should not be necessary on brand new shoes, surely :?:

frankdamp · May 9, 2016

L.A.B:

Completely ineffective was a bit of an exaggeration, perhaps. "Bloody useless POS" may have been more appropriate. IIRC, those early brakes were Italian manufactured, by Campagnolo, I think.

The disk set-up, once it was designed by someone who knew how a sliding caliper works, is fine. Initially, management didn't want assymetric front forks, and tried to make the disk move axially to accomodate a fixed caliper. Trying to get a steel disk, being pushed sideways close to its outer edge by the caliper, to move smoothly on an aluminum hub with splines (later, steel dowels) close to its inside diameter wasted a lot of design and test effort.

L.A.B. · May 9, 2016

frankdamp said:
The disk set-up, once it was designed by someone who knew how a sliding caliper works, is fine. Initially, management didn't want assymetric front forks, and tried to make the disk move axially to accomodate a fixed caliper. Trying to get a steel disk, being pushed sideways close to its outer edge by the caliper, to move smoothly on an aluminum hub with splines (later, steel dowels) close to its inside diameter wasted a lot of design and test effort.

The sliding caliper design must have been another idea that eventually ended up in the bin!

Bernhard · May 10, 2016

frankdamp said:
L.A.B:
The disk set-up, once it was designed by someone who knew how a sliding caliper works, is fine. Initially, management didn't want assymetric front forks, and tried to make the disk move axially to accomodate a fixed caliper. Trying to get a steel disk, being pushed sideways close to its outer edge by the caliper, to move smoothly on an aluminum hub with splines (later, steel dowels) close to its inside diameter wasted a lot of design and test effort.

Re; "The disk set-up, once it was designed by someone who knew how a sliding caliper works, is fine."

I must answer your statement regarding the sliding calipers, this was used by the big four from Japan and I can tell you they were a constant source of trouble, what with the road dirt constantly getting into the sliders, even with protective rubber bellows fitted, they also wear out as the soft alloy is no match for the steel sliding bolts rubbing against them –I have had to drill out and fit steel brushes on a worn set of calipers –overall more trouble than they are worth, all because the people who made the bike /brake calipers didn’t want to pay any royalty copyright fees to the firm who made the opposed piston calipers.

frankdamp · May 10, 2016

Opposed piston calipers wouldn't fit without a major redesign of the front forks, as the type available in 1967/68 were too long axially. I thought the production disk brake sold towards the end of the Commando program was the single piston sliding version. As you can tell, I didn't keep in touch after I went to Boeing.

L.A.B. · May 10, 2016

frankdamp said:
Opposed piston calipers wouldn't fit without a major redesign of the front forks, as the type available in 1967/68 were too long axially. I thought the production disk brake sold towards the end of the Commando program was the single piston sliding version.

It seems they managed it without a major fork redesign by using their own twin piston Norton-Lockheed caliper, the disc fork legs being no further apart than the drum brake forks.

acotrel · May 10, 2016

Use of 'rubber lubricant' on the seals helps solve some of the dragging problems of disc brakes.

front drum brake

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