Advice on front brake

Andrew:

The photo in your previous posting did not make it thru the electronic netherworld and this posting did not state whether your front brake is drum or disc.

If it is drum there is an ongoing discussion now posted about the drum brakes.

If it is a disc, the best fix is to have your brake master cylinder sleeved which re4sults in much more pressure on the disc.

The early disc brakes fitted on most bikes weren't so hot in the whoa department. One theory I've heard was that manufacturers feared that riders would lock their front wheels and crash, if the brakes worked too well. Sleeving the standard master cylinder will definitely help if originality is desired. If not, then either RGM or Norvil will happily sell you brakes to your hearts desire or wallet's flattening, which ever comes first.

In addition to the otherexcellentcomments, I would also suggestreplacingthe 40 year old rubberhydraulicbrake hose with a braided s/s one, I had a '74 850 that had spongy brakes due to the hose expanding when the front brake was applied.

Just a thought, while things are apart anyway doing the re-sleeve.

Skip

You may wish toconsider replacing the master cylinder with the upgraded one from Andover Norton. I have triedon two occasionsto get RGM to sleeve my original, and each time they were 'waiting to have a batch done.' in other words, you send them your m/cyl, and when they have enough of them, they send them off somewhere for modification.

Last time I asked, I got the impression that these batches are only worked-on every few months, so you could have a long wait.

Also, is sleeving-down the best way to go? I'm saving for the Andover upgrade instead.

Previously wrote:

Woooaaaahhhh! It doesn't stop like my Honda CBR!! I hear that I can have the front brake modified by RGM(?). Any idea how much? Is there a Japanese/Triumph one I can use instead? What do you suggest apart from ride slowly?

Andy

I had a similar issue - the original disk brake was very 'wooden' and not very powerful thus about 15 years ago I fitted the RGM disc brake upgrade kit (Grimeca etc.) - it was circa £200.00 in those days - I see it is now £335.00 + VAT. It is very good though (comes with braided hose etc.) and certainly powerful enough for most requirements. Fitting was a doddle and retains the existing master cylinder (without reboring etc.). The previous owner had moved the original disk to the 'Mk3' position i.e. on the left fork in front of the leg thus I fitted the new system in the same place. £335.00 + VAT seems a lot but it still seems competitive with all the other offerings.

Cheers

The master cylinder kit to RGM it is a very good improvement.

The original disk to the 850 MK3 was set up by the factory NORTON on the left fork.

Francis

Regards

andrew, i experienced exactly the same feeling when i bought my commando. i had been used to riding modern bikes and agree the original norton disc brake is frightening.

i went down the route of having the rgm master cylinder sleeving and it has improved the brake dramatically in conjuntion with a new lockheed caliper. the sleeving mod was £80 and as stated by alan walker, yes you do have to be patient. i sent mine off over the winter period when i wasn't using the bike and it was 3 months before i got it back, deffinetly ring them first.

see my thread on page 2 (front disc brake upgrade) there are some excellent replies on it

regards

Previously wrote:

The master cylinder kit to RGM it is a very good improvement.

The original disk to the 850 MK3 was set up by the factory NORTON on the left fork.

Francis

Regards

Sorry - I should have said that mine's a Mk2A 850 - i.e. originally disk on the right behind the fork leg

Hi Andrew For some reason (probably mine) I can't seem to respond on the quick reply at the bottom of your forum query, so I've sent it to someone at the club and hope he/she will add my reply. So here goes with what I was hoping to say on the forum. At the bottom of the page I have copied a very useful website link which helped me understand what the issues are with early motorcycle disc brakes. To cut a not too long story short it recommends that the ratio of master cylinder piston size to wheel cylinder piston(s) size should be a ratio of 27:1. Any greater than that and you will have a spongy set up and less than than that and it will tend towards a wooden feeling. I'm sure any owner of an original Commando front disc (for instance my fastback) will agree that to call it wooden would be a great compliment. It appears that the ratio of the original Commando cylinders are around 14:1 and with the lockheed caliper on your bike it is even worse. However in support of your caliper it does have a larger brake pad area and of course the larger diameter disc on which it operates helps with the old Archimedes principle of give me a lever long enough and I'll move the earth (or in this case, bring it to a standstill). So the conventional wisdom is to reduce the size of the master cylinder piston from 5/8ths to something less. The RGM sleeving solution seems to work well especially as it allows you to use the original brake cylinder and hence keep the original look, I do have friends who are very pleased with the modification and having tried it myself it does improve matters. I have heard that MZ did a brake cylinder of 1/2" and also some 1990's CBRs. Personally I have used a 1990's Suzuki 600 1/2" brake on one bike and that worked well but doesn't have a mirror mounting. However on my current Interstate I was planning a 15000 mile trip of the a country that I'm not allowed to mention because all my mates will take the piss if I mention it one more time (but the country name has 3 letters starting with an "U", ending with an "A" and has an "S" in the middle). My set up is a 14" Norvil disc with a lockheed calliper (like yours) and a triumph master cylinder, which I believe has a slightly better lever ratio from the pivot to the piston. On my 15,000 mile tour I was at a classic bike dealer in a town that starts with San and ends in Fr***sico in the previously mentioned unmentionable country. I was sold a reduced sized master cylinder and piston and in my favourite stainless steel. I do have to say that while, marginally, it isn't quite as good as a modern bike, it isn't far off and it is a two finger brake (by that I mean your fingers on the brake lever not those of the pedestrian that you nearly hit). Not being a Triumph expert â ooh that makes it sound like I'm claiming to be a Norton expert, which I'm not either â anyhow I don't know if the reduced size cylinder is readily available in the UK but I'm sure I could sort out the contact details of where I bought it if you need them. The 14" disc on my bike does look a bit of overkill and I'm sure the 13" would work just as well and look more aesthetically correct but it works for me. From the photo of your bike I imagine that you are not looking for originality and so the most cost effective route would be to buy a 1/2" front brake master cylinder off a CBR or Suzuki from a breaker. Finally of course a good quality modern sports bike brake pad material will add to brake efficiency, I like the EBC double H (from Norvil) but the soft green pad is also good but being soft doesn't last too long. If you need any further info, I'm happy to discuss it with you. Regards Bob Johnson

http://www.vintagebrake.com/mastercylinder.htm

I have not tried any of the front master cylinder mods, however I have a Brembo master cylinder and brake lever on my MK3 ES. This works very well and a vast improvement from the standard set up and this is with the original caliper and pads, although I have a braided brake line. On a previous MK3 ES I owned I fitted a Honda Master cylinder/brake lever from a Fireblade which also gave excellent results.

I have had a few Norton Commando's over the last 40 years andnon of the standard front disc's worked very well without modification. That is with the exception of a Norvil Commando Proddy racer and my current 961(which has Brembo twin set up disc anyway!!!) BTW my first Commandoa 750 S had drum brakes front and rear which were excellent.

There is not much to be achieved by sticking with the original master cylinder. I went with RGM's grimeca master and lockheed caliper while retaining the disc. It's good enough.The original 2LS drum was pretty poor unless it had been soaked and then held on to dry it out then it was lethal.

I converted the rear to 2LS hydraulic operation using a Mini (proper leyland mini that is) brake plate and a Triumph Herald master cylinder. That gives you some idea of the type of scrap cars that were lying around when I did it. If I put a modern master cylinder on it, it would be even better. Hydraulic operation ensures that both shoes are brought to bear at the same time rather than relying on a poor linkage mechanism.

I bought my Commando in 1975 for £350, when I totted up the cost of bits to convert to disc front brake, I think it came to about £450 I was gutted by the poor performance of the standard disc setup and had to spend more on caliper and M/cyl, pads etc. total about £600!!!! Such is life