BRAKES!!!

[popeye72]

Morning guys and girls, firstly i need to appologise to the london foccers as couldnt make sunday due to the above :'(

i recently changed my front brake lines ( braided ) and piston seals, after cleaning my rear brake pistons and found they needed changing i thought i would look at the front and clean them up. on piston would not retract, i could get it to push out but really struggled to push it back in. I removed the piston cleaned everything thouroughly and yet it still is ALMOST impossible to push all the way home. it will go passed the dust seal but when it gets to the oil seal stops. so inspected again and the only thing i can see is the seal looks as if it is not seated properly but it is very hard to tell. removed seal and reseated but still looks the same as if back edge is slightly raised. anyway new seal ordered, but has anyone had this before. i have renewed master cylinder seals and all other pistons move freely.
also how much pressure would you expect to use to push the piston back?????

thanks in advance

[red98]

they are a snug fit and when pushing back in you need to be spot on square,try smearing the piston with brake fluid,little bit of lubrication works every time for me  :lol

[wezdavo]

It has to go in dead square mate, try turning it as it goes in, much easier with the caliper halved...

[popeye72]

cheers guys i have had it in and out lots of time  :b  pretty sure its square i think its the oil seal but not entirely sure

[darrsi]

Smear the seals with red rubber grease.
You should be able to push the piston in with just your fingers if it's functioning properly.
Out of curiosity are they Yamaha seals?

[popeye72]

got them from wemoto cant remember if they were yam ones

[darrsi]

got them from wemoto cant remember if they were yam ones

I think they are Yamaha one's from Wemoto, there are cheaper brands out there that are not as good, i've already learnt that lesson myself before!

[popeye72]

cheers im having another look today i recon one of the seals may not be seating correctly

[robby boy]

Is the groove the oil seal sits in clean, I have seen a built up of aluminium corrosion in this groove on some calipers, a good scrape out with a cocktail stick and a rub with a tooth brush should do the trick.

[popeye72]

ok all sorted, it was crud sitting in the seal channel, you wouldnt believe the amount of crap within theses channels, anyway brakes all good now :b  thanks guys on another note i think i can hear a metalic knocking noise eminating from the exhaust hoping its not a valve but i may be being a little over sensative :o

[edc]

So what's the deal with seals?!?
Yamaha ones work out at sh1t loads.  Can rubber rings really be that expensive????

[Chris]

Is you being able to stop your bike by using your brakes worth the price of the rubber rings? Yes it is... I hope is your answer...

They have a pretty hard life and don't need replaced very often if kept clean etc so worth the extra for ones that work 

Chris

[darrsi]

So what's the deal with seals?!?
Yamaha ones work out at sh1t loads.  Can rubber rings really be that expensive????

Not a matter of cost, more the fact that they're made exactly for the job!
They simply just fit with no issues, whereas the copies don't fit as good, and can be a bit randomly sized in comparison!
No point in finding out the hard way (been there, done that) and then having to pay out again 'cos you've got a leak!