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Tight pistons in caliper

Posted: 03 Jun 2011, 02:59
by oldbaz
Any help on this appreciated :D

I have removed the pistons from front and rear brakes (with extreme difficulty), cleaned up caliper recess and grooves (with small Dremel brush), fitted new seals and tried to push the pistons back in (smeared with silicone grease). So bloody tight!

(also carefully cleaned up the pistons with 1000 paper)

Now, if I slip the seals onto a piston (the "plastic" piston), they are tight. so what do I do, force pistons in and see what happens when I reassemble, bleed,etc??

Re: Tight pistons in caliper

Posted: 03 Jun 2011, 09:08
by twistednuts
They shouldnt be that tight, you 100% sure you got the right seals?

Cant really be much else seein as youve cleaned the grooves up. I smear mine with just enough brake fluid to wet the seal an they go in lovely

Re: Tight pistons in caliper

Posted: 03 Jun 2011, 09:13
by twistednuts
Maybe worthwhile investin in new pistons aswell

Re: Tight pistons in caliper

Posted: 03 Jun 2011, 18:26
by back off road
wheres john when you need him ?

Re: Tight pistons in caliper

Posted: 03 Jun 2011, 20:09
by john7780
trying to avoid threads like this :lol:

Re: Tight pistons in caliper

Posted: 03 Jun 2011, 20:35
by voodookid37
back off road wrote:wheres john when you need him ?
some might have thought he was on a break..... :lol:

Re: Tight pistons in caliper

Posted: 03 Jun 2011, 20:59
by fallenmikethebike
Yes, brake fluids the best lubricant for brake parts.
If the pistons are nice and square to the barrel that's quite odd.
You might try popping the pistons in the freezer for a couple of hours prior to trying to fit them next time.
Some seals are directional,is this the case here?
Mike

Re: Tight pistons in caliper

Posted: 03 Jun 2011, 21:26
by john7780
voodookid37 wrote:
back off road wrote:wheres john when you need him ?
some might have thought he was on a break..... :lol:
you can pee off an all :lol:

Re: Tight pistons in caliper

Posted: 03 Jun 2011, 21:35
by twistednuts
I wasnt tempted to mention john this time, i thought id put a stop to it, unlike john.....

Re: Tight pistons in caliper

Posted: 03 Jun 2011, 21:42
by back off road
john sprung to mind as soon as i saw a brake related post due to the hard work he put in finding the problem and then resolveing it , many others would have given up and replaced the lot weeks earlier

Re: Tight pistons in caliper

Posted: 03 Jun 2011, 23:12
by Eddie Evans
If the groove that the seal sits in is corroded it will have the effect of making the internal diameter of the seal smaller and more difficult for the piston to pass through.
On a different bike I had to grind the width of a small flat screw driver down so that it would fit into the seal groove. I was then able to scrape the bottom of the groove out. Once this was clean I fitted the seals and the pistons went in.

Re: Tight pistons in caliper

Posted: 04 Jun 2011, 07:45
by oldbaz
Thanks for the comments/help.

Answering some points :-
Correct seals? Yes, in that they came in Honda packaging with the correct Part Number.

Grooves are clean

Will they go in after freezing? Yes I think they will, but I was unsure how they would retract in use.

Then I read this :- http://books.google.com/books?id=5rW-pp ... ct&f=false

Re: Tight pistons in caliper

Posted: 04 Jun 2011, 17:24
by voodookid37
Eddie Evans wrote:If the groove that the seal sits in is corroded it will have the effect of making the internal diameter of the seal smaller and more difficult for the piston to pass through.
On a different bike I had to grind the width of a small flat screw driver down so that it would fit into the seal groove. I was then able to scrape the bottom of the groove out. Once this was clean I fitted the seals and the pistons went in.

my take on this is similar.
i always use these http://cgi.ebay.co.uk/NEW-PRO-SET-DENTA ... 3cabfb1b92 or similar....useful also for many other bike related tasks....
useful for prising the seal out. then very gently scrape any crystalisation away (gets right into the corners no probs.)......blow with some compressed air or even the pc airduster ..sometimes i give the groove a polish out with the dremel......lube the seal(s) with some brake fluid and insert,light coat of fluid on clean polished piston and push it home...
never had any problem doing this and shock horror have even been able to re use the odd seal ( for the h+ s police i have replaced asap afterwards :o )....d
then new seal

Re: Tight pistons in caliper

Posted: 04 Jun 2011, 20:05
by fallenmikethebike
oldbaz wrote:Thanks for the comments/help.

Answering some points :-
Correct seals? Yes, in that they came in Honda packaging with the correct Part Number.

Grooves are clean

Will they go in after freezing? Yes I think they will, but I was unsure how they would retract in use.

Then I read this :- http://books.google.com/books?id=5rW-pp ... ct&f=false
In Brief would that be, yes :?:
Mike

Re: Tight pistons in caliper

Posted: 04 Jun 2011, 20:32
by john7780
back off road wrote:john sprung to mind as soon as i saw a brake related post due to the hard work he put in finding the problem and then resolveing it , many others would have given up and replaced the lot weeks earlier
sorry about the language but teeeeeeeewat :lol: perseverance always pays off in the end ;)