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1Back to top Go down   changind disc pads Empty changind disc pads Mon Sep 13, 2010 8:15 am

RT

RT
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It's warming up and I'm itching to go, as long as I can stop. So, I put new pads in all round, after having bled my system. Then I found something that perturbs me. When I put the new much fatter pads in, I had to try and push the calipers back to fit over the disc, and to my surprise they just went really easily. I should have known. When I tried the front brakes, I got ntg at first, just a leak from the bottom of the master cylinder, then pressure built up again with pumping, and I have brakes again. Trouble is I don't trust them. They feel fine and stop well, but there shouldn't have been a leak.
Anyone see what I've done wrong, Should I re-bleed?. I might add I have replaced the piston and rubber boot in the master and all connections seem tight, just a line of fluid along the bottom of the master cylinder.
RT

    

2Back to top Go down   changind disc pads Empty Re: changind disc pads Mon Sep 13, 2010 2:20 pm

Avenger GT

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When you push the pistons back into the callipers it is better to open the bleed nipple to give the fluid somewhere to go. If you don't do this then it is possible to turn the seal on the master cylinder piston, thus causing a leak. If this happened the brakes would not pump up again, you would loose all the brake fluid. There are a couple of possible reasons for the fluid leak.
1. The master cylinder seal is worn.
2. The reservoir was full, and the returning fluid overflowed.
I have had a seal turn on me on a car once, and I have had a reservoir on a car overflow. I do not know if a bike reservoir can overflow like that, as I always open the bleed nipple on any calliper I am working on now when I push back the pistons.
It is normal for a brake pedal or lever to require a few pumps to push the pistons back out after fitting pads.



Last edited by Avenger GT on Tue Sep 14, 2010 7:46 am; edited 2 times in total (Reason for editing : Forgot to add last line.)

    

3Back to top Go down   changind disc pads Empty Re: changind disc pads Mon Sep 13, 2010 8:03 pm

RT

RT
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Excellent, sounds so logical, why didn't I think of that beforehand. Oh yeah, I'm an idiot, I forgot.
Definitely had a full cylinder, it seems ok now, full stopping power but there s that nagging though as you approach that 17 year old girl in a Hyundai texting and about to u-turn, and you can see it coming, she gives you the finger as you slide past on your side with only back brake working.
Thanks Avenger GT.

    

4Back to top Go down   changind disc pads Empty Re: changind disc pads Mon Sep 13, 2010 11:44 pm

phil_mars

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Hydraulics are pretty bulletproof and generally work or not. If you are worried what you can do is put some pressure on the front brake lever using some fairly serious rubber bands so they hold the pressure on and any leaks etc will reveal themselves over a period of time.

If not all should be well other than the aforementioned texting 17 year old for which there is probably no cure.


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Regards,
Phil
    

5Back to top Go down   changind disc pads Empty Re: changind disc pads Tue Sep 14, 2010 12:31 am

RT

RT
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Will do, also just found a leak in clutch cup/boot aaarrgh it never ends.
Tks for advice mate, one I'll get down your way on it.

    

6Back to top Go down   changind disc pads Empty Re: changind disc pads Tue Sep 14, 2010 4:54 am

Crazy Frog

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@RT wrote:When I put the new much fatter pads in, I had to try and push the calipers back to fit over the disc, and to my surprise they just went really easily. RT

If the pistons and chambers are nice and clean, it should not require too much force to push them in. When you release the brake lever, nothing pushes the pads back.
The only restriction when pushing the pistons is the size of the return hole in the master cylinder. If you push the pistons slowly, they will steadily go back without applying a lot of pressure.


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7Back to top Go down   changind disc pads Empty Re: changind disc pads Wed Sep 15, 2010 9:07 am

RT

RT
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Thanks my good man, of course it goes without saying I applied maximum force thinking it was going to be hard. The brakes seem to be working fine and no further fluid leaks, I am about 2 weeks away from becoming road worthy, then I shall be able to test everything out fully. What was the phone number of that bike rescue place again. HA.

    

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