disc front brake question

seattle##gs · Aug 9, 2020

I am working on an 850 front brake ...12" disc and a lockheed caliper. A braided stainless line. I put a rebuild kit in the master cylinder, no leaks whatsoever. It stops well but not much better than the stock setup. Pulling on the lever and it is solid as a rock about 1/3rd of the way. Pads have lots of lining left, I have not inspected them. I THINK it should be braking better, what gives? I am sure a better MC would improve the braking by quite a bit.
On the other hand, I worked on a stock 750 with stock brakes and it braked better than any other Norton. Grab the lever and brace yourself. Couldn't figure out why on that one either.

Peavey Jeltz · Aug 9, 2020

Tell us more about the 850. You didn't say stock 850. Which caliper and M/C? The wrong combination will give you that "rock hard" feel you describe. Sounds like the "racing setup" with AP CP2696 caliper, adapter plate and a 5/8" M/C. Even stock, 5/8 M/C is too big. If you haven't already looked at https://www.vintagebrake.com/mastercylinder.htm

seattle##gs · Aug 9, 2020

It is the stock M/C, it is the racing caliper. So all it needs is the proper M/C?

gortnipper · Aug 9, 2020

11mm or 12mm bore mc as I think the AP CP2696 has 41.3mm pistons.

ashman · Aug 9, 2020

If you want good brakes then replace the old 46 year system to a better system, I went with a full Grimica set up over 8 years ago now and my front brake is as good as my late model Triumphs one finger stopping if you want without any fade, there are better systems around but it depends on how deep your pockets are, if you replaced your caliper, disc and SS line why didn't you replace the MC as the stock MC the bore was to big, you can resleeve the stock one to reduce it but there are better MC on the market. my life is more important than doing half a job and my stock front brake failed without warning when I needed it and I got injured.

Ashley

lazyeye6 · Aug 9, 2020

Real brakes require real money. Deal with it.

MichaelB · Aug 9, 2020

Stock MC is the problem. It's 5/8 or 16mm.
Sleeve it or replace with stock looking 13mm.
Or source a 1/2" or 13, 12, or 11.. Probably doing stoppies with 11mm.

acotrel · Aug 9, 2020

If you are using a chromium plated disc, you will always have problems. High speed steel discs give better friction. I use two Suzuki discs, both with Lockheed callipers and a master cylinder which is designed for one calliper. The old type asbestos pads are better than most. If the 750 Commando you mentioned had a drum brake, you are talking about something which is entirely different and more dangerous.
Do not use cast iron discs.
When I race, I keep 4 digits wrapped around the throttle with one on the brake. It has to be like that. - Stoppies only take a finger tip. You usually have not got enough time to change your grip when silly things happen.

acotrel · Aug 9, 2020

Is there anyone in the UK who supplies the second fork slider for twin discs on a Norton and the fork brace ?

SteveA · Aug 10, 2020

acotrel said:
Is there anyone in the UK who supplies the second fork slider for twin discs on a Norton and the fork brace ?

There is someone thousands of miles closer to you that supplies twin disc fork sliders!

peter12 · Aug 10, 2020

Ive gone down the upgrade route.
RGM 13mm master cylinder upgrade
Stainless braided pipe
Standard disc and calliper
Upgraded pads.

Brakes are good, too much lever travel which I could possibly tune out.

Have decided to take the plunge. Madass single disc upgrade complete with new master cylinder and modern calliper is on its way, supplied by Don Pender from the Phillapines.

I ride with groups of modern bikes and after much consideration have decided this is best for me.
Will report back when fitted!

Unfortunately seems to be great value but postage was a big hit to France!

baz · Aug 10, 2020

lazyeye6 said:
Real brakes require real money. Deal with it.

Not quite true,it's the choice of components that really counts
The front brake on my commando is superb, 320mm disc,nissin 4 pot and 12mm master cylinder
The disc was the only brand new component
The nissin caliper came from fleabay
The grimeca 12mm m/cylinder came from a burnt out scooter I found in the local brook!

Gadge · Aug 10, 2020

peter12 said:
Ive gone down the upgrade route.
RGM 13mm master cylinder upgrade
Stainless braided pipe
Standard disc and calliper
Upgraded pads.

Brakes are good, too much lever travel which I could possibly tune out.

Have decided to take the plunge. Madass single disc upgrade complete with new master cylinder and modern calliper is on its way, supplied by Don Pender from the Phillapines.

I ride with groups of modern bikes and after much consideration have decided this is best for me.
Will report back when fitted!

Unfortunately seems to be great value but postage was a big hit to France!

Don's master cylinder is a great improvement, you won't regret it.

jaydee75 · Aug 10, 2020

seattle##gs said:
It is the stock M/C, it is the racing caliper. So all it needs is the proper M/C?

Yes, I went down to 1/2" m/c piston with 12" Kawa disc and stock caliper, and it makes a HUGE difference.
Jaydee

maylar · Aug 10, 2020

You can exchange your stock M/C with a 13 mm upgraded one through Old Britts (here in the US). I think Al Miles is still doing it for them. I've had one for years and it's excellent.
http://www.oldbritts.com/14_061939.html

JimNH · Aug 10, 2020

13mm MC, AP clone caliper, new brake lines but not braided SS, and 12" disc here. Good stopping now. Bleeding MC is a challenge for sure but worth the time and effort as feel is just right compared to the block of wood feel and some deceleration of the stock brake.

Dukepaul · Feb 21, 2021

peter12 said:
Ive gone down the upgrade route.
RGM 13mm master cylinder upgrade
Stainless braided pipe
Standard disc and calliper
Upgraded pads.

Brakes are good, too much lever travel which I could possibly tune out.

Have decided to take the plunge. Madass single disc upgrade complete with new master cylinder and modern calliper is on its way, supplied by Don Pender from the Phillapines.

I ride with groups of modern bikes and after much consideration have decided this is best for me.
Will report back when fitted!

Unfortunately seems to be great value but postage was a big hit to France!

Hi,
could you tell me the RGM part numbers for this kit you fitted because I am looking to upgrade mine

thanks
Paul

TomU · Feb 23, 2021

It should be easy to find on their website. AN sells a 13mm MC also as well as Madass140 on this site (both a MC and a refit)

disc front brake question

seattle##gs

Peavey Jeltz

seattle##gs

gortnipper

ashman

lazyeye6

MichaelB

"Sons of Arthritus"

acotrel

acotrel

SteveA

peter12

baz

Gadge

jaydee75

maylar

JimNH

Dukepaul

TomU

1972 Roadster

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