Norton P11 Disc Brake Front Option

That's a very good point, Baz, although the achievable friction force depends on a number of factors, such as tire (rubber compound), friction force at the brakes, bike weight, weight distribution, and
wandering of CoG during braking. Please take into account that maximum rolling friction is considerably higher than sliding friction, where molten rubber serves as a lubricant.

Damage to structural members of the frame / chassis depends on the maximum friction force between tyre and tarmac at a certain speed. The Retardation Work performed over a certain distance, equal to the change in kinetic energy, is the governing factor. This work is absorbed in the frame or chassis as deformation work (= a volume integral of stress and strain) which may be elastic or plastic. The latter would be particularly damaging to the frame. Without going into details, we may conclude that disc brakes may inflict a frame damage where a drum brake doesn't.

- Knut

baz said:

And braking hard from a 3 figure speed on a regular basis

Click to expand...

3 figure speed on a P11 is kind of frantic. I did try riding my P11 fast a couple of times in my 40's. Frame is not built for the G forces. Starts feeling like it is hinged in the middle. Shortly after that phase I started buying modern motorcycles to ride and parked the Norton in the corner of the garage for somewhere between 27 and 30 years.

Only reason I put a bigger brake on the P11 is 1) I'm riding it again, and 2) I have run out of front brake a couple of times. Last time was last summer behind a truck. I got my front tire just to the left and 6 inches ahead of the rear bumper before coming to a stop. I thought for sure I was going to hit the bumper. I was thinking everybody was going to go through the light when it tuned yellow. Nope she stopped.

I put a 230mm 4LS on, and although I'm having a little QA issue with it, it is a big improvement. If the frame breaks due to the larger brake, I'll be sure to report back from the dead on what actually busted.

I use stick on emery for the drum trueing operation.
Get some stick on 7 or 8" discs at an auto supply. Ill check but from memory it is 100 grit.
Cut the discs into strips the same width as your brake shoes.
Stick them onto the shoes , put it all together and start grinding.
You might have to change the paper a couple of times. I just clamped the wheel down flat and rotated the brake plate by hand. Use a C clamp on the brake arm to slowly advance the shoes outward.
You might do better with Baz's drill chuck on tire method as it sounds like you have a lot to cut
You could try the manual rotation method first and see if you make progress. Take a little bite just contacting the high spots then take another little bite. Eventually the high spots are gone, the drag is even all of the way around. It might take an hour or so with this method.
I have fixed two front brakes with this method. Both had horrid pulsation. I didn't measure the actual runout amount.
Both are smooth and powerful now.
Once the drum is round, stick some emery strips onto it and arc the shoes to the drum.
Careful on this step as the linings cut very fast, don't overdo it

Glen

The real moral here is to NOT buy a brake from these CRS guys.

A drum brake is actually quite an engineering exercise, it’s very easy to get things wrong, even without the blindingly obvious things like ensuring the drum is actually round!

Good products tend to be expensive for a reason. Especially good products that require a lot of work, and only have a tiny market. When a similar looking product is offered much cheaper than the rest, this is usually for a reason too.

I have a 4LS front brake supplied by a firm fastidious about quality (Godet), of course this was reflected in the price, but the performance and feel really is better than any period disc set up and it’s a fabulous thing in its own right.

The price is what drives me away from any of the very nice looking high performance drum brake setups. For the price I can buy dozens of 2nd hand early 1970's Japanese stainless steel discs and calipers, and these will work better than just about any stock drum brake, especially if you drill the disc and fit modern, high friction brake pads.

I do, however, regret not keeping the quad leading shoe front brake off of a Suz GT750 I scrapped years ago. They just weren't cool yet at the time.