Discs brake upgrade

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scim77

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I was interested in improving the front disc brake performance of my 850 but retaining the original caliper. I have already fitted a braided hose and re-sleeved the original master cylinder down to 13mm, both of which have made a great improvement in feel and grip. It is always nice to have more in reserve and I found a company that make a 13" rotor which bolts directly on to the original fork leg and yet still retains the original caliper. No mods to stays or hydraulics are required.
I know there are better kits and calipers around but to retain most of the original appearance, this mod is worth a look.
Check out http://www.britishbikeconnection.com/im ... y_thmb.png
Has anyone got opinions on this or the company?
 
I went with a Brembo conversion form coloradonortonworks.com but it is using a different caliper and is kind of pricey. I actually just ordered it so I have not even really seen it yet, so I guess this doesn't really help you.

I did check out that BBC site and they have some nice stuff. I would like to find a new, drilled and plated rear disc to replace the stock, ratty looking one on my Mk III.
 
I also fitted the Lockheed racing lever, another slight improvement but it all adds up.
 
If you want to retain original looks then a more conventional disc could also be used, but of course with a weight penalty. The parts to make a larger floating disc using your old centre are readily available.

I think that a major failing with the standard caliper is it's one-piece construction. it lacks the through bolts close to the rotor o/d which would seem to improve rigidity in other designs ( the Lockheed Racing calipers for instance).

If you pull hard on the lever of a system with a modified master cylinder and steel lines, you can see the standard caliper flexing and trying to open outwards. Those heavy fins are presumably to aid stiffness. I don't think they are needed for cooling !
 
I have also got a Lockheed racing lever on the modified master cylinder and it adds even more leverage to the hydraulics. Worth the money. I think the Collorado kit is probably the best I have seen and feel that Brembo is hard to beat. Expensive, but arguably not as costly as shunting the bike into something due to inadequate brakes.
Perhaps I am misguided in trying to preserve original appearance. I, too, have noticed the original caliper flex under load. But I would not want to replace it with a caliper whose piston diameters were smaller, since this would reduce the line pressure and offset the gains I have made with the master cylinder and lever mods etc. (see http://www.vintagebrake.com/mastercylinder.htm )
Does anyone know what the diameter of the original caliper piston is?
 
scim77 said:
I think the Collorado kit is probably the best I have seen and feel that Brembo is hard to beat. Expensive, but arguably not as costly as shunting the bike into something due to inadequate brakes.
Click to expand...

That was my logic behind the decision to go with the Brembo kit.
 
scim77 said:
Does anyone know what the diameter of the original caliper piston is?
Click to expand...

I've just measured an old one at 1.75 " ( 44.45mm according to the handy button on the digital vernier :) )
 
The classic Lockheed Racing caliper is 41.3mm. The old "six fin" CP2195s are available again (although twice the price).

In my opinion, the only way to retain a real mid-seventies period look.
 
Thanks 79 x 100. By using a Lockheed racing caliper with 41.3 mm pistons rather than the original calipers with 44.4mm it would seem that I could suffer a reduction in hydraulic line pressure for any given input at the lever, thus making for a more wooden feel. Or would the greater rigidity of the racing caliper offset this?
The racing caliper has much bigger pads and would be capable of better heat dissipation but, if my schoolday memory serves me correctly, friction itself does not depend on area. So the tiny pads in the original caliper theoretically could bite better than the racing caliper, ignoring rigidity issues.
Any feedback from riders who have actually tried both systems would be interesting.
 
Scim, I have used both calipers but with the CP3125-4 "variable ratio" master cylinder. This has an actual bore of 15.9mm but at full adjustment gives an equivalent to 12.5mm according to the tech specs.

The Racing Caliper is certainly more effective, especially two-up and loaded and in my opinion doesn't need to be run with the master cylinder at full adjustment or lever travel becomes excessive. The set-up doesn't have the "bite" of, for instance, twin Brembos but it's not a white knuckle job either.

The site you quoted suggests that smaller than 12.5mm would be better but as he says, disc and wheel diameters make a difference and a 10.7" disc in a 19" wheel is always going to have it's work cut out.
 
The BBC unit looks very clean. I am sure the added leverage of the 13" rotor would help.
I am interested also in how well this system works.

Clubman has a nice 12" floater. But using the Grimeca caliper, you loose the front fender stay which is my complaint on the Brembo.

It would be nice if the stock caliper could be used on the 12" Clubman.
 
MichaelB said:
But using the Grimeca caliper, you loose the front fender stay which is my complaint on the Brembo.
Click to expand...

CNW sells a bent fender bracket to fit around the Brembo caliper.
 
New rear disc for MkIII

I don't want to hijack this thread, but my question is relevant to the original topic. I am looking for a new rotor for the rear disc brake of my MkIII. I want to keep the stock caliper but upgrade the rotor to a nice, new, drilled two piece variety. Any suggestions where I can buy one in N. America? I want the rear to sort of match the nice floating Brembo unit I am putting on the front.
 
The problem is the 10" diameter of the original.
I don't anyone who makes a 10" floater.

As I have said earlier, Clubman has a nice 12". An adapter or new bracket would need to be formed.
 
MichaelB said:
I don't anyone who makes a 10" floater..
Click to expand...

You just need to eat lots of fibre :oops:

The "buttons" to make floating discs are available and the conversion is quite possible by parting the standard disc from it's centre.

If you want something ready made, I think that you should be able to find a firm supplying conversions who will make a smaller OD version for you.
 
Captain said:
maybe this is what you and coco are looking for.. http://www.nithburgcycle.com/brit/commando.html

scroll down to brakes
Click to expand...

I looked at that, but I am pretty sure that disc id for the front. Excuse my ignorance in the matter, but I assume the original front and back rotors for the commando were the same????

That one does look nice, but I don't want a cast iron rotor since it will rust. The replacement I want for the rear has to look pretty :D so it matches the front Brembo I'm putting on. I could probably get it CAD plated maybe but I think that is a gold colour and not silver.
 
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