Bleeding brakes

RiceBurner · Post by **RiceBurner** » Wed May 19, 2004 11:13 am

I know how to do it (before everyone chimes in with detailed explanations...

), but I have two questions :

On the Rockster the brakes currently do not bite until about a third of the lever movement is taken up (on the largest span). To me this is not good enough - I want finger tip precision and bite immediately.

First question : is this possible with the BMW master cylinder? (I know that 'Blade brakes always have a bit of "slack" - it's designed into the master cylinder, but I also know that the M/c on the ZXR400 allows this). I think it is - reasoning : if I grab the brakes, then release and take a second grab - the bite point is MUCH earlier in the lever travel - in my experience this means the brakes have a small air bubble somewhere.

I mentioned that I thought the brakes could use a bleed to the shop before the first service and they alledgedly checked the brakes over and I was told that they're fine. Alledgedly the senior mechanic was the one who checked em.

Now - bear in mind that he service manager is new (although he's worked there for several years on a previous occasion), and I don't have a "customer relationship" with him.

Second Question : Should I make more of an issue out of this? If I say to the service manager "I think these brakes could be better" and he effectively says "No they can't", should I start to take whatever he says with a pinch of salt?

I'm not particularly happy about this - especially since I had a good (although brief) customer relationship with the previous service manager (couldn't do enough for me!) and I have a good customer relationship with other members of the staff at this dealership. I got the impression that the new service manager could be a bit "overbearing" and "always right".

I've always looked after my bikes myself (and will be bleeding the brakes properly before long), I don't like giving them to possibly inexperienced / uncaring mechanics who won't treat them right, so the trust issue is important to me.

How can I improve my customer relationship so that I can rebuild the level of trust between us to the level I enjoyed previously?

Alternatively : How do I take him down a peg or two?

Rob B · Post by **Rob B** » Wed May 19, 2004 4:11 pm

Are you sure you are not suffering from a little pad knock off, or the seals are sucking the pistons back a little. It won't be very much, but when you're tuned into it, as you clearly are, you'll be able to feel a difference.

It's the same in my car, never actually have a problem, but I can feel the difference if I do a dab before a real application of force.

Rgds,

Rob

bigblackfalco · Post by **bigblackfalco** » Wed May 19, 2004 5:52 pm

Son,if your brakes are bleeding,you have put the wrong stuff in the master cylinder.You need brake fluid.
Always keep blood in your own system where it belongs.
Bailey.

Gromit · Post by **Gromit** » Wed May 19, 2004 6:16 pm

bigblackfalco wrote: Always keep blood in your own system where it belongs.
Bailey.

Just as long as it doesn't dilute the alcohol stream too much.

bigblackfalco · Post by **bigblackfalco** » Wed May 19, 2004 6:34 pm

Gromit wrote:
bigblackfalco wrote: Always keep blood in your own system where it belongs.
Bailey.
Just as long as it doesn't dilute the alcohol stream too much.

Right on brother!Hic.
Bailey.

mdouglas · Post by **mdouglas** » Wed May 19, 2004 9:16 pm

2 points:

1)there is a loctited screw that determines the relationship between the lever and the master cylinder piston - adjustment of this would make the piston move earlier in the lever's range of movement

2)any slight run out in the disks will push the pads back such that the first application moves the pads into contact with the disk - a rapid second application would benefit from the pads not having been pushed back. The amount of caliper piston movement for any one squeeze of the lever is pretty small so even a small amount of take up will manifest itself as a large(ish) lever movement.

Darth_1100S · Post by **Darth_1100S** » Thu May 20, 2004 12:10 am

Bleedin' brakes......and Feckin' Clutches

Jason M · Post by **Jason M** » Thu May 20, 2004 9:30 am

RB - what were the brakes like on your previous Rocker? Surely if they were as tight as you would like and these are not then surely you have a good point to argue your case with the mechanics. Alternatively have another spin on their demonstrator to compare and contrast?

I'm not happy with any 'superflous' movement either cos I'm scared that even the hint of fade will exacerbate the problem and scare me shitless!

Jason

RiceBurner · Post by **RiceBurner** » Thu May 20, 2004 10:18 am

Jason M wrote:RB - what were the brakes like on your previous Rocker? Surely if they were as tight as you would like and these are not then surely you have a good point to argue your case with the mechanics. Alternatively have another spin on their demonstrator to compare and contrast?

I'm not happy with any 'superflous' movement either cos I'm scared that even the hint of fade will exacerbate the problem and scare me shitless!

Jason

Interestingly enough the First Rockster had the same problem - until the first service. I had intended to mention it - but forgot and when I got it back they were good - just how I like them.

But this time I asked about it and they came back the same as they were before.

anyway - it's all a bit academic now - I've found a superb way to pump brakes up: overbalance on a hill and virtually bend the lever in your super-human efforts to stop the bike falling over.

MDouglas - I'll have a look for that little screw.

jltownshend · Post by **jltownshend** » Wed Jan 31, 2007 2:41 pm

mdouglas wrote:2 points:

1)there is a loctited screw that determines the relationship between the lever and the master cylinder piston - adjustment of this would make the piston move earlier in the lever's range of movement

2)any slight run out in the disks will push the pads back such that the first application moves the pads into contact with the disk - a rapid second application would benefit from the pads not having been pushed back. The amount of caliper piston movement for any one squeeze of the lever is pretty small so even a small amount of take up will manifest itself as a large(ish) lever movement.

Erm...

I have these symptoms (second squeeze requires less lever travel) as well as a squeak at low speed with very light braking, but don't quite understand the above...

Is it just that the disk(s)/wheel are slighly out...and if so what's to be done, if anything. Am servicing it tomorrow...

Thanks,

John

oyster · Post by **oyster** » Wed Jan 31, 2007 6:39 pm

When I changed hoses, I found the bubble at the master cylinder banjo. Cleared it by removing the complete bar (easiest way) located above yoke, with resovoir cap firmly screwed into place!! hold the bar vertical, lever end pointing up, and activate lever. By moving the bar about while repeating the brake action, the bubble gets sucked back into the resovior and into the air space. If you have under yoke bars, it means either removing the brake lever assembly to do the above, or opening the banjo jointto bleed it - not always successful.
I can imagine some of the other responses this may prompt, lay the bike on it's side; try braking when scratching into a bend on the left side....

Boxadog 2000 · Post by **Boxadog 2000** » Wed Jan 31, 2007 6:58 pm

I found the same problem when I had my S, i changed to a full braided system which helped a bit.

The old trick of cable tying the lever back to the bars overnite worked quite well.

You could always check the crinkle washers under the disc bolt as well if they get full of crud the disc does not float as it should.

I found a couple of these had fractured and on replacing them all the brakes improved by 100%.

Bob

Backmarker · Post by **Backmarker** » Wed Jan 31, 2007 7:29 pm

Dunno where you live, nor where you got your bike serviced, but...
I was down at Brian Giles' (BGM) place a couple of months ago, there was a guy with a Rockster having it checked over. Despite apparent assurances from the 'main dealer' he bought it from that it was fine, Brian pointed out that every single washer was missing from the disk bolts, leaving the disks moving about under braking - ie intial pressure pulls disk back against the bolts, subsequent pressure slows bike.

Unlikely you have the same problem, but might be worth getting a second opinion anyway.

My GS was serviced by 3 main dealers before I found BGM, each subsequent one found/sorted problems that the previous dealers had missed/denied was a problem.

For the record of all the main dealers used, CWs are the only ones I trust.

Backmarker · Post by **Backmarker** » Wed Jan 31, 2007 7:30 pm

Dunno where you live, nor where you got your bike serviced, but...
I was down at Brian Giles' (BGM) place a couple of months ago, there was a guy with a Rockster having it checked over. Despite apparent assurances from the 'main dealer' he bought it from that it was fine, Brian pointed out that every single washer was missing from the disk bolts, leaving the disks moving about under braking - ie intial pressure pulls disk back against the bolts, subsequent pressure slows bike.

Unlikely you have the same problem, but might be worth getting a second opinion anyway.

My GS was serviced by 3 main dealers before I found BGM, each subsequent one found/sorted problems that the previous dealers had missed/denied was a problem.

For the record of all the main dealers used, CWs are the only ones I trust.

jltownshend · Post by **jltownshend** » Sun Mar 04, 2007 2:50 pm

FWIW, all seems fixed in changing tyres...so maybe just pads...