newbie front brake problem

Corvus · Post by **Corvus** » Wed May 01, 2013 6:17 pm

[quote="Dai wiskers"]I'm liking Corvus more and more

Ha. Thanks Dai W. I just hope pauls can sort his problem.

Another couple of points, which are definitely long shots but what the heck.

Is the new master cylinder the correct piston size?

The second hole into the reservoir. The one in between the two cup seals. If this were partially blocked would it hold the master cyl piston in partial position, leaving a very free lever until the oil in between the seals has returned to reservoir?

Just floating ideas.

Merecat · Post by **Merecat** » Wed May 01, 2013 8:47 pm

pauls wrote:I then go down to my favourite bends at speed a 800 metre long straight hard on brakes sharp right brake spot on 600metre straight sharp left brake ok 800metre long straight very sharp right brake comes back to bars? go along bout 800metres sharp left no brake 1000metres more and a steady left brake spot on again?

Go a different way?

sorry, had to be done

Mick

McBoxer · Post by **McBoxer** » Wed May 01, 2013 9:42 pm

Merecat wrote: Go a different way?

There you go! That's what we need in a situation like this - a bit of 'blue sky thinking'.

pauls · Post by **pauls** » Wed May 01, 2013 10:18 pm

Been going that way for years my favourite set of corners done it on at least 30 different bikes without any problems. When I get back will try again but def not losing fluid? Funny tho

Corvus · Post by **Corvus** » Thu May 02, 2013 6:03 am

[quote="pauls"]?.......def not losing fluid?

A problem with the main "pressure" master cyl seal wouldn't show itself as a leak. Well, not a leak that you would see anyway!

ianbcr · Post by **ianbcr** » Thu May 02, 2013 7:04 am

scrap it.

pauls · Post by **pauls** » Thu May 02, 2013 8:47 am

Yeah or sell it? Nice bike tho 05 with schnitzer wheels/exhausts and carbon fibre belly pan and heel plates.cheers looks like I will try the single line theory first then go from there? The BMW mechanic says he has never ever changed one? Are they a common failure? Mines only done 18k

Corvus · Post by **Corvus** » Fri May 03, 2013 6:15 am

Does the bike have the EVO brake system?

pauls · Post by **pauls** » Fri May 03, 2013 6:36 am

Yes I think so BMW on the calipers?

Corvus · Post by **Corvus** » Fri May 03, 2013 4:10 pm

Does that mean they are servo assisted?

If so, doesn't that put a whole new complexion on things?

slparry · Post by **slparry** » Fri May 03, 2013 4:12 pm

I could be wrong but I didn't think the R1100S models ever had servo's? As far as I understand it BMW's can have EVO brakes or EVO servo brakes.

The EVO was I think supposed to mean there was 20% higher brake power from having larger discs and better calipers.

The servo version was supposed to add to that I think, and I think they were only fitted to the GS and RT models, not sure about the naked R or the RS versions tho'

pauls · Post by **pauls** » Fri May 03, 2013 4:27 pm

No servo just Evo calipers I think?

Corvus · Post by **Corvus** » Fri May 03, 2013 4:29 pm

slparry wrote:I could be wrong but I didn't think the R1100S models ever had servo's? As far as I understand it BMW's can have EVO brakes or EVO servo brakes.

The EVO was I think supposed to mean there was 20% higher brake power from having larger discs and better calipers.

The servo version was supposed to add to that I think, and I think they were only fitted to the GS and RT models, not sure about the naked R or the RS versions tho'

It is far more likely that I am wrong. I've never owned an r1100s. It was just a thought. I wondered (if they are servo) if it could be intermittently going into fail safe mode. Probably a red herring, and if so, I apologise.

Cheers

pauls · Post by **pauls** » Fri May 03, 2013 5:07 pm

That's ok any suggestions welcome as I am off to nurburg ring in June so need brakes sorting for then? Cheers

Merecat · Post by **Merecat** » Fri May 03, 2013 5:48 pm

Go with your original idea and disable one caliper at a time to determine if its one or the other of them. You said you've changed the master and the hoses, so its unlikley to be those, and as i understand those were changed because of these problems. Next in line are disks, calipers, and pads. Wheel bearings etc.
Still sounds like the pistons are being forced back in to the caliper for some reason. If this is on twisties it strengthens the argument for wheel bearing play. Have you had the front end off the floor and pushed and pulled it?
Is there excessive play in the disk mounting posts? Are the disks true?

Mick