Rear brake service.

Post by **nugget** » Fri Aug 16, 2019 7:37 pm

With me finally getting the blue spots sorted.

I decided to give the rear brake caliper the same treatment and I ordered the new seal kit and some new brake pads. The rear pads were also binding on the disc slightly.

Today with the weather being crap I set to and stripped them down and as you can see the seals and the seal grooves in the caliper were full of crud so after a good scrub and clean up it's all put back together and the pistons glide in and out smoothly now and the binding as gone altogether.

I haven't fitted the rear caliper yet because after bleeding the system I've chocked the rear brake lever up so it puts the fluid under pressure and it should force any trapped air bubbles up to the caliper and I'll crack open the nipples tomorrow just in case there is any.

Teego · Post by **Teego** » Sun Aug 25, 2019 10:17 pm

Warped disc John? Or you forgot to take your foot off the brake.

Post by **nugget** » Mon Aug 26, 2019 9:21 am

Like you say Kurt it only seems to do it while the bike is moving so heat as something to do with it.

I have a newish disc on the bike it's the same as the one you bought and to the best of my eyesight and knowledge the disc is running true. There is always a bit of run off with a disc so it enables the disc to push the pads slightly away from the disc.

When I came to bleed the system I used a brand new unopened bottle of brake fluid so I don't think that's the problem. One thing that has come to mind when I did the bleeding of the system, the weather that day was very hot and humid so unless it's picked moisture up from the atmosphere I'm not sure??

So now we are on to thinking it's got air trapped somewhere in the system.
When I came to bleed the system before I do anything I always take out the old fluid in the reservoir with a small shringe so that I'm not pumping old fluid through the brake lines, I know there's old fluid in the lines already but that can't be helped. When I bled the system I went through half a bottle (400ml) of brake fluid so I know it's got good clean fluid in there and there wasn't a trace of any air coming through the tubes.

After cleaning everything up I raised the rear caliper up higher than the reservoir and MC and chocked the brake lever down with a block of wood so the fluid was under pressure all night long, so if there was any air in the lines it would/should float up to the the highest point being the nipples and banjo bolts. The next day I cracked open the banjo bolt and all I got was brake fluid and no air, when I came to crack open both of the nipples a very small puff of air came out of them both.

My plan today is seeing has it's far too hot to put my 30 year romper suit on. I'm going to bleed the system through again with another brand new bottle and while I'm at it, to finish the bottle off I'll do the clutch line also.

Hang about lads because there could be a post coming up saying I have a clutch problem now.

Post by **nugget** » Mon Aug 26, 2019 9:26 am

Teego wrote:Warped disc John? Or you forgot to take your foot off the brake.

The disc is a newish one and as for leaving my foot on the brake. Well I know I'm a bit senile at times but I don't think I'm fully there yet or am I??? How would one know?

Teego · Post by **Teego** » Mon Aug 26, 2019 11:58 am

nuggitt wrote:
Teego wrote:Warped disc John? Or you forgot to take your foot off the brake.
The disc is a newish one and as for leaving my foot on the brake. Well I know I'm a bit senile at times but I don't think I'm fully there yet or am I??? How would one know?

Ask Matron.

Post by **nugget** » Mon Aug 26, 2019 1:51 pm

I've just come in from the garage and when I cracked open one of the two nipples (the one nearest the wheel) not a single air bubble appeared so I did the outer nipple and that was the same, not one single bubble. I bled the system once again using new fluid just for peace of mind so that is all working correct.

After bleeding the lines again, what I did notice was I took the caliper off the hanger and removed the pads etc and pumped the brake lever to see if the pistons were coming out evenly and they were. When it came to push the pistons back in by hand it took a quite a lot of pressure from my fingers to get them back in to being flush with the caliper body. Made me huff & puff a bit.

Something is telling me, should there be that much pressure and is it that pressure that's holding the pads onto the disc after braking causing the disc to get hot? How can you ease that pressure off a bit, because I don't think you can?? When I fitted the pads back back in etc I pumped the brake lever to push the pads back out on to the disc to take the play up, I had good braking pressure and the wheel was spinning freely without any binding at all.

I'm getting more bamboozled by the minute

PS: I've bled the clutch line and that's good to go. No problems there.

itsnotagenesis · Post by **itsnotagenesis** » Mon Aug 26, 2019 7:01 pm

You said you adjusted the brake lever to suit you. Is the plunger pushing the master cylinder slightly stopping the fluid returning to the reservoir, basically causing hydraulic lock which can be quite dangerous if it locks the brake completely.

Teego · Post by **Teego** » Mon Aug 26, 2019 8:34 pm

http://www.exup1000.co.uk/meets/matlock_300406.htm

Post by **Stig** » Mon Aug 26, 2019 9:19 pm

Teego wrote:http://www.exup1000.co.uk/meets/matlock_300406.htm

Wow that was a while ago

I've not forgotten about the bike, it's just I have to get the Twincam roadworthy so have moth balled the bike to give me chance to get the car sorted.
Luckily things are progressing well so hope to have it back on its wheels before winter. All the hard work is done now. Just got the underneath to Paint then I can start bolting all the refurbished bits back on.

Post by **nugget** » Wed Aug 28, 2019 9:25 am

Chris,

On my last inspection I did take the pads out and I pumped the pistons out slightly just to see if they were coming out ok and they were. like I mentioned in my last post above when it came to push them back in it took a lot of pressure. It's looking like the MC could be the problem. I do remember a few years back taking the MC off and giving it a good clean up and I think there's either 2 or 3 little holes in there (fading memory) and I'm sure there was a bit of dirt in one of them. I might as well order a new kit for that, then I've done the job lot.

I've just had a look in my bike history book to see when I last changed the gubbins in the master cylinder and for some reason I don't seem to have it. Very odd because I'm a bit of an anorak when comes to writing stuff in the book with the jobs I do.

Thank God the clutch is fine. Ooops should I have said that?

As for the pads they are brand new see photos on page 1.