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Discussion Starter · #1 · (Edited)
Hi everyone,

After rebuilding the F05 calipers (keeping the pistons and all screw fittings), getting new locally made braided ss hoses made and buying a new copy 12mm master cylinder off fleabay (don't ask me why) I'm still put off by the long travel of the brake lever before it seriously grips the wheel. Is this normal for the Brembo F05 twin disc set up?

It only locks the wheel squeezed almost to the twistgrip. It's not what I'm used to from a single F08 anyway. The only thing I haven't rebuilt or replaced from the set up it came with are the brake pads, which are still plenty thick. Rebuilding the original Brembo m/cyl and calipers didn't improve much. So it's never really had a good tight brake lever.

Any thoughts or suggestions would be gratefully appreciated.

Thanks
 

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I would say that it is not normal; I've never found that. Do the brakes pump up? IE, if you pull the lever several times, does the travel reduce? I'm wondering if their is still air in the system or whether the discs are running out of true so as to push the pads back into the caliper as they rotate.
 

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As per Colin. No, it's not right. Twin FO5s with a 12mm master make a perfectly effective stopping combination - I know, I have them on my Vento, and they'd throw me over the top if I jammed them on hard enough.

Given the work you've done, long lever travel is pointing a very big finger at still having air in the system. Small amounts can get trapped in the most irritating places, and you will get as many opinions as you like on how to release it. The main thing to remember is that the air will always try to rise up thru the column of brake fluid. So make sure you have no high spots or knarley junctions where it's getting trapped.

It's normally easiest to bleed thru the m/c - don't forget the old trick of turning the bars to the left, pulling in the lever and strapping it in that position with a bungee or similar and leaving it like that overnight. And also try tapping all the joints with something metallic - can help get any trapped air moving

In extremis, take the whole installation of lines and calipers off - and suspend the whole lot from somewhere up high in as a straight a column as you can manage. And then bleed thru the calipers.

One further thought: a new 12mm m/c, you say? You sure its seals are still ok?
 

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Discussion Starter · #4 ·
Thanks for the tips and advice. Pleased to say that bleeding through the m/c overnight holding the brake lever squeezed has solved the spongy lever! Such a simple fix thanks Ventodue ;) glad to know that one and surprised I hadn't heard of it already.

Cheers boys.
 
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