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Buggered Juicy 3
#1
OK, so the title might be an exaggeration, but my front brake is currently unusable, which is my fault.  After a ride around Oldbury yesterday I came home and did a bit of maintenance on my bike.  My front brake was rubbing, so I recentered the caliper.  I noticed my pads were just about toast, so I decided to swap them out.  I pulled the old pads out, pushed the pistons back (probably should've done this step first), and attempted to put the new pads in.  I couldn't get the new pads in, as it doesn't seem the pistons would retract all the way.

Now I made the seemingly fatal error of trying to cycle the pistons without pad in place, in an attempt to get them unstuck.  I pumped the lever several times to get the pistons to come out further, and went a bit too far, as some brake fluid dribbled out from behind the piston.  I immediately knew that they would now need to be bled, but I tried to see if I could salvage the situation.  I pushed the pistons back and tried to put the new pads in.  They still wouldn't fit, so I put the old ones back in.  However, now the old ones won't even make contact with the rotor, and there's a dodgy clicking noise that occurs many times with each rotation of the rotor within the caliper.

So I know I definitely need to get my brake bled, but I'm also concerned about the potential problem of caliper retraction.  They only need to retract another 1-2mm for me to be able to get the new pads in, but does it sound like there may be a problem with the pistons?

I rang my local shop, The Bike Warehouse in Sevenoaks, and they said they're booked up for a week and a half on service right now.  Can anyone recommend another shop nearby?  What's a bleed going to cost me?  If there's a piston problem, what will that run me?  Would it be more cost-effective to buy a replacement brake for £45?

Cheers.
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#2
Plenty of people on here are proficient at bleeding avids so as long as one can offer their services it shouldn't cost more than a box of beer, and it'll prob get done quicker than the shop time frame!
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#3
I don't have my bleed kit at the moment so can't really be of much help until I get it back, but that said, CyclesUK Maidstone can often do it on a walk in although be safer to ring them and they'll do a good job. Not sure what they'd charge to bleed the brakes though. Definitely not £45. Their pads however cost a feck load so takes your news ones with you.
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#4
I think Blackers may have left a bleed kit amongst his bike stuff at the house.  I'll have a look.  I watched the official SRAM bleeding video on Youtube, and it looks to be within my level of mechanical ability, so I might try to do it myself, knowing that I can't really make it any worse.  If he didn't leave one, I've found loads of unofficial bleed kits on ebay for £10-12, which could hopefully arrive quickly.

I'm still concerned about the piston retraction.  Maybe I can take my slightly worn rear pads and put them up front, and put the new ones in the back as a workaround.

If I need to take it to a shop, I may try CycleOps or CycleUK in Tonbridge.  Half the battle with the shop option is getting there within opening hours, as I leave for London before 8am, and don't get home until 7 most nights.
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#5
I'm sure the Juicy's have a little post thingy on each piston that engages with a hole in the pad backing plate.
If the pads are slightly out of alignment this arrangement prevents the pads going back fully to the pistons.

Pistons are often stiff to get back in.  This is because you're tyring to drive the fluid back through the system into the reservoir.  It often takes much longer & more persusion than you imagine.
The easiest way is usually to use a small (or big ;D) flat bladed screw driver between the old pads prior to removal.  Use a a kind of slow rocking motion the screw driver between the pads,applying pressure to 1 pad then the other & you'll find the pistons go back in stages as the system equalises.
I tend to put a larger driver in there & use a twisting motion, so using the with of the blade to push both pads at once.  This loads the pads more centrally, so provides less margin for problems & apply less force to the system, however it does take more effort from you as twisting is harder on the wrists tan levering.

Since you've popped one piston you need to be sure this goes back in square or it will stick & not retract.  You can use the system pressure to sqaure it up.  Use a strap or something to hold the other piston in place & then squeeze the lever slowly whilst watching the piston closely.  Since the pressure will act on the piston evenly, but the resistance will not be even if the piston is skewed the pressure will square it up.  Stop squeezing the lever as soon as the piston moves square & free, then use the screw driver to push both pistons back in.

The clicking noise is probably the badly located pads or the spreader catching the "spokes" of the disc.  Confirm this by either watching carefully as the wheel rotates or count the clicks & see if you get as many clicks as you have "spokes."

Sounds to me like the situation is perfectly retrievable, although you will need a bleed to remove the air probably entrained when the piston popped.  Having said that it may have done you a favour as sometimes a system is bled with old pads in place & there isn't enough room to push the pads back fully.  You've fixed that problem at least Wink

I'm happy to help, but I'm along way from you Sad
There must be someone closer........
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#6
"Tinc" Wrote:I'm sure the Juicy's have a little post thingy on each piston that engages with a hole in the pad backing plate.
If the pads are slightly out of alignment this arrangement prevents the pads going back fully to the pistons.

Pistons are often stiff to get back in.  This is because you're tyring to drive the fluid back through the system into the reservoir.  It often takes much longer & more persusion than you imagine.
The easiest way is usually to use a small (or big ;D) flat bladed screw driver between the old pads prior to removal.  Use a a kind of slow rocking motion the screw driver between the pads,applying pressure to 1 pad then the other & you'll find the pistons go back in stages as the system equalises.
I tend to put a larger driver in there & use a twisting motion, so using the with of the blade to push both pads at once.  This loads the pads more centrally, so provides less margin for problems & apply less force to the system, however it does take more effort from you as twisting is harder on the wrists tan levering.

Since you've popped one piston you need to be sure this goes back in square or it will stick & not retract.  You can use the system pressure to sqaure it up.  Use a strap or something to hold the other piston in place & then squeeze the lever slowly whilst watching the piston closely.  Since the pressure will act on the piston evenly, but the resistance will not be even if the piston is skewed the pressure will square it up.  Stop squeezing the lever as soon as the piston moves square & free, then use the screw driver to push both pistons back in.

The clicking noise is probably the badly located pads or the spreader catching the "spokes" of the disc.  Confirm this by either watching carefully as the wheel rotates or count the clicks & see if you get as many clicks as you have "spokes."

Sounds to me like the situation is perfectly retrievable, although you will need a bleed to remove the air probably entrained when the piston popped.  Having said that it may have done you a favour as sometimes a system is bled with old pads in place & there isn't enough room to push the pads back fully.  You've fixed that problem at least Wink

I'm happy to help, but I'm along way from you Sad
There must be someone closer........

Cheers Tinc.  Your assessment seems spot on.  The pads won't get past the "post thingy."  When the pistons are fully retracted, should they be flush with the caliper body, or will they still protrude a few mm?  Mine are not flush currently.

Regarding the "popped" piston, I did manage to get it to retract to put the old pads in place.  Is it possible that it went back in without being square?  If it is square, I assume I still need to perform the equalization procedure as you described?

Lastly, I'm sure you're right about the clicking noise.  It sounds like wheel spokes hitting something, but it is clearly not that.  I thought it might be the rotor hitting something, but I couldn't see what it was.

EDIT: Since I have to bleed the system anyway, would it be easier/possible to push the pistons back with the system open?
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#7
"Yankee" Wrote:Cheers Tinc.  Your assessment seems spot on.  The pads won't get past the "post thingy."  When the pistons are fully retracted, should they be flush with the caliper body, or will they still protrude a few mm?  Mine are not flush currently.

Regarding the "popped" piston, I did manage to get it to retract to put the old pads in place.  Is it possible that it went back in without being square?  If it is square, I assume I still need to perform the equalization procedure as you described?

Lastly, I'm sure you're right about the clicking noise.  It sounds like wheel spokes hitting something, but it is clearly not that.  I thought it might be the rotor hitting something, but I couldn't see what it was.

EDIT: Since I have to bleed the system anyway, would it be easier/possible to push the pistons back with the system open?

A little yeah. pop your brake levers forward (mine click forward further than normal operating distance from the bars) if possible to ensure the reservoirs are 100% open.
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#8
"Yankee" Wrote:Cheers Tinc.  Your assessment seems spot on.  The pads won't get past the "post thingy."  When the pistons are fully retracted, should they be flush with the caliper body, or will they still protrude a few mm?  Mine are not flush currently.

You have to squeeze the pads together against the spreder to get them in - apologies if I'm missing the point there, but you'll never get them in without squeezing them almost far enough for the pad faces to contact in your fingers.
The pads should be flush with the psiton face, that is to say the socket in the rear of the pads should completely house the piston post.  The positioing is critical as there's no much room in there.
The piston face should be flush with the caliper, but the little post protrudes.

Quote:Regarding the "popped" piston, I did manage to get it to retract to put the old pads in place.  Is it possible that it went back in without being square?  If it is square, I assume I still need to perform the equalization procedure as you described?

If it's gone all the way in you can assume it's sqaure.  If it's not it should square up the first time you brake & it contacts the pad.

Quote:Lastly, I'm sure you're right about the clicking noise.  It sounds like wheel spokes hitting something, but it is clearly not that.  I thought it might be the rotor hitting something, but I couldn't see what it was.
EDIT: Since I have to bleed the system anyway, would it be easier/possible to push the pistons back with the system open?

It is, but not much TBH.  On top of that if you do it with a closed system you assist the entrained air in travelling to the lever, so you can get it out easier.  There's loads of potential for mess if you do it open, you're better off just applying pressure.  Remember that under normal operation the fluid doesn't move very far if at all, the system works on pressure.  You're asking a fairly viscous fluid to move through small appertures under pressure - it's not instant.  Your suspension uses exactly the same system to keep you off your bump stops - there we call it damping Wink
Use the lever technique & apply pressure to each piston in turn in they're both out.  If you can't get the old pads back in try a couple of bits of card or wrap the screwdriver in tape, just so you don't damage the pistons.
If you can get the old pads in then you'll not damage anything as long as you don't let the screwdriver slip.  The last couple of mm's is always the tricky bit as that's the bit that spends to longest out in the crap.  You could try applying a drop or two of brake fluid to the piston to lubriacate it.  Dip a small screwdriver into brake fluid & then touch the screwdriver to the piston & give a second or two to run round the seal.
NOTE: DON'T get brake fluid on anything else & if you do clean it off straight away with soapy water or isopropal alcohol.
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#9
I think I managed to fix my brake last night.  I watched the Avid Youtube video a couple of times in preparation, and then just went for it.  The brake seemed to work in a short test ride around the garden.  Hopefully it will hold up well in trail riding.  I guess if there are bubbles I will feel fade?  

Anyway, the procedure was easy enough, but I don't know how anyone can do it without dripping brake fluid all over the place.  The second I opened up the bleed screw on the caliper, loads of fluid dripped out.  Luckily I put some newspaper down below it in anticipation of that happening.  

The lever feel is much firmer than the factory bleed on the rear brake, so now I need to do the rear.  I would've done it last night, but my wife was bugging me to help get our son into bed.  I had been hoping that I could improve the lever feel with a bleed, so I'm happy to discover that this seems to be the case.
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#10
"Yankee" Wrote:I guess if there are bubbles I will feel fade?
If there are bubbles/air in the fluid the lever would feel spongy.  You mentioned it feels firmer than when it was new.  That was my experience of Juicy 3's too.  Seems they don't store the fluid too well at the factory :Smile
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