Brake upgrade

We have installed and sold a lot of these kits- my son and all my friends have it on their Commandos (I ride a drum-brake model as everyday Commando). The hoses have a smaller internal diameter than the old rubber hoses, hence air bubbles tend to stay where they are rather than float up as in the normal system.

The system needs to either be vacuum-bled to get the bubbles out, or to be filled up from the lowest point.

I have this kit with a Norvil single disc kit at the other end. I found that very quick, sharp activation of the brake lever tended to shift air bubbles and they could be seen rising into the reservoir. Even when you do get all the air out you will find that the lever comes back to the handlebar much further than you are used to, and it feels rather disconcertingly soft instead of the previous firm feel, however the improvement to the braking amazed me!

I have the kit fitted too, and had similar troubles gettting all the air out. Just by coincidence I tilted the bike over to theright, in order to inspect the underside of the bike, When the bike was back upright, the air had escaped, and brake action was superb. Admitted the lever does go back a bit further than other setups, but a great improvement overall.

It may help to move the handlebars to the left and so the master cylinder is on a high point and flick along the length of the hose, leave it and repest in an hour or so. This should agitate the air bubbles in the hose allowing them to move to where they can be bled.

I have the same problem with the Grimeca master cylinder and original calliper set up in use for two years. Recently stripped calliper down to clean and check seals whilst front wheel was out for repair. Had difficulty getting a good brake when origionally fitting the Grimeca kit and same again after this rebuild. Did all the tricks which are mentioned on this and other forums as well as much swearing. Never had such a problem with a lifetime of brake bleeding on most types of vehicle both old and modern. I have found that when bleeding in the traditional way there is very little fluid expelled from the caliper nipple so reverse bleeding with a syringe is more effective pushing a greater volume of fluid upwards to take air bubbles out in natural direction. Normally I start with pistons fully retracted to minimise quantity of air in system but have succeded this time with the pistons pulled out so the brake pads are skimming the disc. Once the brake lever can produce some resistance things start to improve with further bleeding. Finally i bleed by levering the pad/piston away from the disc and achieve an effective brake with progressive feel.

Good luck, I sympathise with your frustration over what should be a simple task.

Gentlemen,

Had several different "Classic" brake retrofits and even the most stubborn AP racing calliper, Goodrich lines and M/C bled 100% once I removed the furthest (from M/C) bleed nipple and CAREFULLY wound with some PTFE thread tape, avoiding bleed holes and leaving no chance of stray Teflon tape shards getting into the system. Refit nipple less ~ 3/4 turn from bottoming out, then bled via syringe.

This way no air can be 'venturied' into system via a loose bleed screw and works first time.

Good luck!

Steve

Previously richard_mills wrote:

I have this kit with a Norvil single disc kit at the other end. I found that very quick, sharp activation of the brake lever tended to shift air bubbles and they could be seen rising into the reservoir. Even when you do get all the air out you will find that the lever comes back to the handlebar much further than you are used to, and it feels rather disconcertingly soft instead of the previous firm feel, however the improvement to the braking amazed me!

I bought the kit too, to go with a Norvil single disc and AP caliper. I ordered from Mick Hemmings one lunchtime last week and it arrived the next morning! Install was easy and no trouble with bleeding. I just topped up the master cylinder and pumped the lever several times to release the air. Then turned the bars to the left and used a bungee to hold back the lever overnight. It was completly bubble free next morning.

One observation with this kit though. I have what I believe to be standard UK bars and found the brake lever too far off the end of the bars. The kit wouldn't go far enough to the left because of the bend in the bars. I ended up filing the mounting to get a better fit (see picture). Apart from that, a superb kit that really makes a difference.

I had to do the exact same thing to the mounting as you did, David! I have what I believe to be the Interpol bars.