matt_the_blat Posted September 12, 2009 Report Share Posted September 12, 2009 I'm replacing the seals on my front brake calipers and I've got 3 of the 4 pistons out but the last one doesn't want to budge and I don't have access to a very high pressure compressor. It was moving freely enough with fluid in the system so it shouldn't be totally jammed, just a bit stubborn. Could I use grips just on the rim of the piston if I'm very careful? Even with brand new pads the pistons don't go all the way in so I'm reasonably confident any scoring that resulted wouldn't interfere with the seals, or is this really a major no-no? Cheers, Matt Link to comment Share on other sites More sharing options...
Grumpyduck Posted September 12, 2009 Report Share Posted September 12, 2009 Don't use grips on the recalcitrant piston. Service the other pistons and re-assemble the caliper. Attach it back to the master cylinder and fill and bleed the system. With the caliper still off the bike but attached to the mc place something between the opposed pair of serviced pistons that prevents them from moving. Then slowly pump the brake lever and the other pair that includes the unserviced one will start to push out. Use finger pressure to slow the serviced one of the pair and you will be able to pump the recalcitrant one out. Just go easy on the brake lever as it gets near to coming out. You don't want a face full of brake fluid! What he said... Link to comment Share on other sites More sharing options...
will#224 Posted September 12, 2009 Report Share Posted September 12, 2009 Or use a grease gun, you'll find it clips over the nipple quite nicely. The grease lubricates stuck pistons and prevents scoring. You just need to find an appropriate bolt to block the hole the banjo goes in. Link to comment Share on other sites More sharing options...
matt_the_blat Posted September 12, 2009 Author Report Share Posted September 12, 2009 Thanks guys, looks like I'll have to do it the hard way..... Out of interest does anyone know, if you have a decent compressor (such as you would have in a workshop) is that normally sufficient to blow all the pistons out of a 4 pot caliper? I recall having doen this some years ago with 2-pot calipers. Otherwise once you've removed the first piston you would need to block up the ports with your fingers I was trying this with my weedy compressor which is just about man-enough for pumping up tyres but not much more than that - after I got the first couple of pistons out I was running out of space, fingers and hands to hold the caliper, block up the ports and hold the compressor nozzle! LOL Link to comment Share on other sites More sharing options...
will#224 Posted September 12, 2009 Report Share Posted September 12, 2009 My compressor is a 2hp with a 30 litre tank. I placed the pads in the caliper and filled with air using a modified tyre inflater. The pistons will only come out so far and wont pop out. I then removed the air and lubricated them by pumping grease into the caliper. Applied air again and removed one of the pads. Let the pistons move in and out, in and out several times then removed the pads. I then used a screwdriver at an angle to wedge the pistons and let them out bit by bit eventually they all came out. Maybe borrow a compressor or hire one? Link to comment Share on other sites More sharing options...
Mr.Pigdog Posted September 12, 2009 Report Share Posted September 12, 2009 Ello mate,i bought a tool from sealey made for spreading the pads open on cars for under £10-its kind of like a pair of scissors with a large threaded bolt to open them.Anyways they are ideal for inserting into 90% of bike brake pistons and grabbing them internally and thus NOT damaging the outer piston surface or needing compressed air.Also cheap so no worries if you require grinding them to size or getting brutal etc-i shall go find a link thing now my friend Also theres a kit out there kind of like a slide hammer-it's more pricey and i havent come across a set of calipers i cannot do with the cheapies(although older bikes that dont have hollow pistons are excepted) Just edited to add i've serviced hundreds of brake calipers so im not a complete munson Link to comment Share on other sites More sharing options...
Mr.Pigdog Posted September 12, 2009 Report Share Posted September 12, 2009 http://www.justoffbase.co.uk/Disc-Brake-Pa...l-Sealey-AK7112 sorry--i'm a mechanic-these computers just make no sense to me Link to comment Share on other sites More sharing options...
spacemonkey Posted September 12, 2009 Report Share Posted September 12, 2009 http://www.justoffbase.co.uk/Disc-Brake-Pa...l-Sealey-AK7112 sorry--i'm a mechanic-these computers just make no sense to me Yeah, caution on using the air line to pop 'em out! You'll end up with a cloud of brake fluid mist in your workshop if it works and that can't be good! An expanding mandrel could be used on the inside of the piston to grip them and you could pull them, maybe use a slide hammer although I doubth that would be neccessary. You'd need the tooling for this though and it'd probably be loads simpler to just hook 'em back up to the master cylinder as suggested earlier....... Link to comment Share on other sites More sharing options...
ronenige Posted September 12, 2009 Report Share Posted September 12, 2009 what MM said , or these are pretty damn good , Link to comment Share on other sites More sharing options...
Mr.Pigdog Posted September 12, 2009 Report Share Posted September 12, 2009 Yup thats the one!!(pic above) Link to comment Share on other sites More sharing options...
alexp5 Posted September 12, 2009 Report Share Posted September 12, 2009 what MM said , or these are pretty damn good , Link to comment Share on other sites More sharing options...
Mr.Pigdog Posted September 13, 2009 Report Share Posted September 13, 2009 Trouble is that kit will not do all pistons as you're limited by the insert size-just off the top of my head i think you're quite restricted when it comes to moto-x bikes.Also its lots of faffing about assembling it-those 'pad spreaders'i mentioned earlier are universal and easy to insert into piston just to rotate-ensures you clean around the whole piston when you're cleaning it in a service-most don't Link to comment Share on other sites More sharing options...
matt_the_blat Posted September 13, 2009 Author Report Share Posted September 13, 2009 Thanks all for the advice and suggestions. If anyone is interested I reckon these would also do the job. Cheers, Matt Link to comment Share on other sites More sharing options...
Cibbersicks Posted September 13, 2009 Report Share Posted September 13, 2009 Used these (similar) for the last caliper service i did, and they are top drawer, dont be a cowboy and pull them out with grips etc, if it doesn't fuck the new seals up, your bike will forever bare the mark of a cack-handed spannerer... Link to comment Share on other sites More sharing options...
Mr.Pigdog Posted September 13, 2009 Report Share Posted September 13, 2009 Thanks all for the advice and suggestions. If anyone is interested I reckon these would also do the job. Cheers, Matt I bought a set of them a while back and to be honest if you want them to take any proper load you need to replace the bit of metal the clamp screw winds into(the thread is quite thin and weak and the actual metal is only fixed from one side-so it opens out when it has a proper load on it)easy to modify though-fix it from both sides and chuck a thicker thread in Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.