riversbikes Posted April 17, 2009 Report Share Posted April 17, 2009 The allsorts ducati is rolling. Not stopping too well, however. New pads, but I am wondering if I haven't lost the plot with the master cylinder ratio. Single front brake caliper: 1 brand new 6-piston discaccc whatever caliper. Steel braided lines, bled properly Master: MV Agusta from an F4/Brutale (non-radial) My (likely flawed) logic was that a master from a 2x4 piston brake system would be "close"/OK when used on a 1x6 piston caliper -- as in the total number of pistons on an MV is 8 (4 per side) whereas my system has 6. Of course, might be the new pads that haven't bedded in yet, but does anyone have any thoughts? The feel is "wooden" at the lever. Weigh in, everyone! Link to comment Share on other sites More sharing options...
tootall Posted April 17, 2009 Report Share Posted April 17, 2009 Would imagine that the surface areas of the pistons is quite different though. 8 x fairly large pistons versus 6 x fairly small pistons. = quite a difference. Plus two hoses versus a single hose. Symptoms very little lever travel and buggerall feel? Link to comment Share on other sites More sharing options...
Evilchicken0 Posted April 17, 2009 Report Share Posted April 17, 2009 It's down to the ratio of the master cylinder - This is off a Brembo suppliers website http://www.iane.co.uk/brembo_home.html 16 = The least popular although can be good for Supermoto and 125cc to increase feel. Easiest to pull with most feel 18 = Used by almost every works rider using Brembo brake calipers. Best combination of feel and travel 20 = Most popular for bikes without Brembo race calipers. Hardest to pull with least travel Link to comment Share on other sites More sharing options...
thefatman Posted April 17, 2009 Report Share Posted April 17, 2009 If the lever feel is 'wooden' then you either need to increase the area or number of caliper pistons or decrease the area of the master cylinder. 16mm wooden, 18mm spongy? Help my brains a mess! When I fitted a brembo radial 16mm m/c to my supermoto it had a beringer 4 piston front caliper and the lever had fuck all movment, was very 'wooden' and lacked stopping power. Tried and 18mm m/c and the lever cam back to the bar before any stopping power could be felt. Link to comment Share on other sites More sharing options...
lorenzo Posted April 17, 2009 Report Share Posted April 17, 2009 I've got a small selection of aprilia rs125 master cylinders sat here in my garage, many are just the empty bodies of them but I'm sure that among them there's on with a full set of insides. Some of the bodies are a bit crusty, others are really nice, if you were patient you could build yourself a good one up no problem. Pay me the postage and a fiver towards the bors fund (which really 'owns' these bits) and you can have the lot of them to do as you please. Link to comment Share on other sites More sharing options...
thefatman Posted April 17, 2009 Report Share Posted April 17, 2009 Sorry, got the order of events wrong.. Me going to 18mm m/c was at the same time as fitting the 6 pot caliper and it was too spongy with the new caliper. So went back to the 16mm m/c that had been to hard with the 4 pot caliper but was fine with the 6 pot. If I could have got a brembo radial m/c that was smaller dia than 16mm I could have stuck with the 4 pot caliper, but Brembo don't make one so went with the larger caliper and I guessed, wrongly, that i would also need a larger bore m/c. If the lever is too hard you need a smaller bore m/c or larger piston bore in the calipers... All clear now, thanks millemille Link to comment Share on other sites More sharing options...
riversbikes Posted April 19, 2009 Author Report Share Posted April 19, 2009 I've got a small selection of aprilia rs125 master cylinders sat here in my garage, many are just the empty bodies of them but I'm sure that among them there's on with a full set of insides. Some of the bodies are a bit crusty, others are really nice, if you were patient you could build yourself a good one up no problem. Pay me the postage and a fiver towards the bors fund (which really 'owns' these bits) and you can have the lot of them to do as you please. Fair deal, Lorenzo... but I'm in Canada... any idea on the shipping cost? Link to comment Share on other sites More sharing options...
lorenzo Posted April 19, 2009 Report Share Posted April 19, 2009 Gawd only knows, but I'll do some research and get back to you. I assume you're not interested in the hoses and banjo bolts etc, just to save on the shipping weight? I'll have a root about and make sure what I've got is what you're interested in and go fromt here. Link to comment Share on other sites More sharing options...
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