Drum to Disc brake (2019)

Yes I understand what you are saying, but it comes a time in any system that has been working great when new but as they aged they weren't as good from being new, my MC had been rebuilt a few times replacing leaking seals etc, same as the calipa and pads to repacing dics, putting the RGM reducer kit in it, but there comes a time when a full upgrade is better than just rebuilding.
My Norton had done a lot of miles and like I say it was a everyday rider till I retired and brought a new bike yes its been rebuilt and I had other bikes while it was off the road, but the first 15 years of its life it was my only transport and it done a lot of long distant travels, I ride it hard as I do all my bikes.
I still have all my old brake parts will never sell them as don't want to put someone else's life in danger, I never did go back into it to find out what the problem was I just changed everything new with a better system, at the time Brimbo system was out of my price range, but the Grimica system works just fine with me and a lot cheaper.
You are doing a great job on your rebuild and doing the right things with it, but its no good if one day your old front brake lets you down as mind did without warning, first time I thought it was me but when it did it the second time and got hurt, it make you think.
38 years on my bike, I think it was time for a full upgrade and it wasn't that expensive at the time, my Joe Hunt cost more than my full brake upgrade.

Ashley

When I first got the Seeley, the rubber bellows in the master cylinder had a split in it, so I threw it away. It keeps the fluid level above the holes which feed to where the piston is doing it job. So the piston took a gulp of air while I was riding the bike. That created an exciting moment - NOT !

When I was racing my 500cc Triton, it had 7R AJS drum brakes front and rear. I had a lot of difficulty finding linings which would work sensibly. I ended up with a soft lining on the front shoe and a hard one on the rear. This meant that when I raced, I had good brakes from start to finish. I had also extended the lever on the backing plate. While I raced regularly, it was excellent. Then came the year when I raced early in the rear, then not for 10 months. I rode at a club meeting and my friend was there riding the Seeley I now own, but with a 750SFC Laverda engine in it. I hosed him off down the main straight, then when I applied the bike, the brake came on too hard. So the guy behind me saw the bike coming back at him. He rode around me into the first corner, then popped in front of me as we approached the next corner. He then grabbed a handful of disc brake in some form of bloody stupid reprisal. I over-reacted the slightest amount simply because I was out of practice. I locked the brake at about 70 MPH and got launched. I went down the road on the top of my head, with my legs in the air. I could see the other bikes coming up behind me. By the time I reached the ripple in the bitumen I was on my side, so my injury was a dislocated chromo-clavicular joint in my shoulder - not a broken neck. It is the only time when racing, that I actually believed I could have been killed. Disc brakes are a much safer option. However the single chromed disc on the front of a Commando is not enough. I found that out the first time I raced the Seeley 850 and got into the death-dive in a corner. I got around - JUST !

Why do these threads always end up reminding me of A Christmas Story?

I might sound pedantic, but drum brakes ARE NOT the way to go. They might have been good in the 1950s, but back then we also thought that pudding-basin helmets were good.

My rgm reserve worked a treat compared to the standard, then 2 years later the brakes started sticking. Oh yes I thought, caliper pistons. Stripped, no problems there. Master cylinder sleeve was binding ??? Honed it and no issues since ! Mechanical snugness making the brake grab at a blistering 55mph. 42 years and still rattling.

Al, this is a drum brake on Norton Forks on one of my bikes, I've set up many of these brakes for Nortons.
I spent some time carefully setting this one up and I can tell you its as good as one of my 6 piston 320mm rotor
brake kits. People still race using the Norton 2LS brake, they can be made to work quite well

Many years ago, I watched an A grade race at Calder Raceway in which most guys were using those brakes. John Maher had fitted a disc brake front end from a road-going Yamaha, to his TR3. Three guy crashed from trying to brake with him into the corner at the end of the front straight. You probably need to race with a TZ front brake against guys who have disc brakes. Judging subjectively from what happens on public roads, probably does not tell you much. The comparisons are not two guys trying to outride each other.

ahh, ok Al

Disc brakes have no self-servo, so to lock them you need to either do it intentionally or be very insensitive. The Yamaha drum brake is a copy of a Fontana which were amongst the best in their day. However in Australian historic racing, Period 3 requires the use of drum brakes - no discs, because running the two types of brake together on various bikes in the one race is dangerous.

If you are ever racing and somebody pops in front of you and grabs the brake, never try to avoid them - just knock them off their bike. The result is the same for you, but not for them.

acotrel said:

Disc brakes have no self-servo, so to lock them you need to either do it intentionally or be very insensitive. The Yamaha drum brake is a copy of a Fontana which were amongst the best in their day. However in Australian historic racing, Period 3 requires the use of drum brakes - no discs, because running the two types of brake together on various bikes in the one race is dangerous.

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Re; “Disc brakes have no self-servo”

Depends on the piston setup, opposed pistons like the Lockeed –No.
However a brake calliper with four Opposed pots there is a servo effect!
Even with two pistons like above but on a slider has half the servo effect as above.

Re; “requires the use of drum brakes - no discs, because running the two types of brake together on various bikes in the one race is dangerous”
Absolute Bo*****s!!!

When you race with disc brakes, the one thing you should never do is take a corner off somebody who has drum brakes and brake hard in front of them. A bike with drum brakes cannot be stopped as quickly and their front brake is almost certain to lock and launch the rider. I only ever had it done to me once and it almost ended my life. It is very dangerous. I usually never worry about road racing, but that incident gave me worries and an extremely painful injury, which I still carry. If all the riders are sane and experienced, such a thing should never happen. The guy who did it me has a big ego problem - he's a f*cking idiot. One day he even ran me straight off the end of the front straight at Calder Raceway when he decided he'd had enough racing for the day.. I was taking the corner off him by going around him at high speed and he just sat up and went straight.

The trouble is that a lot of the kids who do historic racing, have never raced against modern bikes. They get out there with drum brakes without knowing what can be done to them by other riders. In our Historic Period 4, disc brakes are prohibited -only drum brakes are allowed. Bits off TZ Yamahas are also prohibited. So a TZ brake would not get a look-in. Personally, I believe a single disc should be allowed. But twin discs on any bike would make a Manx with a double-sided drum front brake look stupid. With my Seeley 850, I could ride up to a guy on one of those and literally murder him.

Back to the original post. I like this caliper to replace my Lockheed/Norton. I have a '71 750 that will be put back together soon that has Kimtab alloy rims front & rear with Yamaha 750/850/ 1100 XS vintage '70's rotors. About the same thickness as a Norton rotor. A set of EBC floating rotors is also in house to have the modern look. They just don't fit with a Norton caliper. Hoping there's enough space between the pads of these Nissan calipers to squeeze in the older thicker rotors in. I had to experiment with pads with the Norton calipers as the Yamaha rotors were stainless. Nonetheless, braking was impressive with both front & rear discs and sleeved front m/c. I've just read a few posts that the stock caliper will boil the fluid from very hard use on hot days. That will probably never happen to me as I don't ever push myself that hard on the street these days. Still, modern technology is more desirable to me.

Deckard said:

They just don't fit with a Norton caliper.

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I adapted a yamaha wheel to norton forks and combined the yamaha disc and the Lockheed caliper. I made an offset bracket for the caliper, I also ground a tiny bit off the caliper casting to move the pads where I wanted the contact to be on the disc. I use one of Don Pender's master cylinder with it which I think is a 13mm diameter master. It works good enough, but no doubt a multipot modern caliper would work better... Here's a picture below. That's the old brake hose, not the new braided one, but you can see what I've done here with caliper and disk. At the time I did it, I wasn't looking for more headaches by introducing even more non-stock parts, but in the long run I could have used a better caliper without much more cost.

Even if that brake is inadequate, it is extremely unlikely that it would ever heat up and lock as you braked. With drum brakes, the linings usually either fade during operation or they become sticky. The worst situation with drum brakes, occurs when you brake from very high speed and the brake is not stopping you quickly enough. Then you tend to hold the brake on very hard. The leader sometimes suddenly becomes effective and can launch you. When I was using drum brakes, I used different linings on the two shoes - a soft and a hard. The soft worked for the first few laps of a race, then faded, then the hard started to work. It meant that in any race, I always had SOME brakes. With two-strokes, the motor is fastest when it is cold and the drum brakes are often more effective when cold - as you race the motor slows and the brakes get worse.

These days, I would never attempt to race with a drum brake. It is too much like hard work.

The linings I used in my drum brakes were ME36 and MZ41 - both contained asbestos. These days, finding the right linings would be even more difficult. Would you wear a ten dollar helmet ?

Deckard said:

Back to the original post. I like this caliper to replace my Lockheed/Norton. I have a '71 750 that will be put back together soon that has Kimtab alloy rims front & rear with Yamaha 750/850/ 1100 XS vintage '70's rotors. About the same thickness as a Norton rotor. A set of EBC floating rotors is also in house to have the modern look. They just don't fit with a Norton caliper. Hoping there's enough space between the pads of these Nissan calipers to squeeze in the older thicker rotors in. I had to experiment with pads with the Norton calipers as the Yamaha rotors were stainless. Nonetheless, braking was impressive with both front & rear discs and sleeved front m/c. I've just read a few posts that the stock caliper will boil the fluid from very hard use on hot days. That will probably never happen to me as I don't ever push myself that hard on the street these days. Still, modern technology is more desirable to me.

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There is adequate clearance to use the original disc rotor with the Nissin caliper. About 1mm each side.

acotrel said:

The trouble is that a lot of the kids who do historic racing, have never raced against modern bikes. They get out there with drum brakes without knowing what can be done to them by other riders. In our Historic Period 4, disc brakes are prohibited -only drum brakes are allowed. Bits off TZ Yamahas are also prohibited. So a TZ brake would not get a look-in. Personally, I believe a single disc should be allowed. But twin discs on any bike would make a Manx with a double-sided drum front brake look stupid. With my Seeley 850, I could ride up to a guy on one of those and literally murder him.

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In the UK we have a different set of race rules where earlier Manx’s are not allowed to have disc front brakes (Except the Arter Matchless that PW rode) the later period machines the rules are not so rigid so disc is OK.