These brakes came on my 07 Stumpjumper. I have never really been impressed with the stopping power.
I cannot get the front brake to lock up no matter how hard i pull the lever, I only weigh 9.5 stone!!
I have bled them but this makes no difference. The pads are only coming into contact with the middle part of the rotors, this means i am only using 50% of the available braking surface.
The calipers are aligined well, and i get no rotor drag.
Firstly, check for contamination, especially if you've bled them as dot fluid will find it's way anywhere, it does sound like a contamination issue more than 'owt else, grease on rotor and or pads even in the slightest will drastically reduce power.
You say you've bled them, but have you BLED them?? Juicy's are b*stards to bleed correctly in most instances, and are very sensitive. My front one was an absolute bag of pants from new, it took three bleeds to sort out, then Bam! serious bite, good feel, strong power, firm lever, etc. To begin with it had no bite, little power, lazy pad return, excessive lever travel before bite and a slightly 'elastic' feel, not like the spongyness associated with requiring a bleed, just like as though the hoses were made of rubber not whatever they are made of.
Key points to the bleed are, Take the time to degas the fluid until you have to put a lot of time and effort into getting a small 1/8" (3mm) air bubble to expel. Then remove the caliper syringe first before the lever syringe (opposite to instructions) and lay bike on side before removing caliper syringe so no fluid can run out and air enter the system. Before removing lever syringe, push the plunger in to pressurise the system and let it return slowly on its own, remove syringe just before plunger has stopped moving, you should get a slight purge of fluid as you remove it then quickly screw in the grub screw. (And immediately wash away any fluid before it eats your paint)
Also useful is when it says to pump the lever blade, only pump gently until you feel resistance, if you squeeze it you will blow fluid out between the caliper syringe pipe and brass union, at the least this is messy, at worst it could cock up the whole bleed.
Before you begin, thoroughly clean and degrease the rotor with isopropryl alchohol (ipa) or some such like that will leave no residue and fit brand new pads (using worn ones will reuslt in the system being overfilled when you push pistons back for new) If the pads you have are new, chack for contamination as this will also result in no power.
As for the pads only touching centre of rotor, I suspect this is simply a bedding in issue with pads and or rotor.
Hope this helps, and if owt seems patronising, sorry! I don't know what you do or don't know.
GOT AVID 3,S and theres little stopping power ,seems too be a fault,with the design, as for isopropyl alchol, antiseptic wipes from the chemist work well and are good for the rucksack incase of injury.
Try bleeding them as above sadbloke, my fives are the best brakes I've had now, but initially I hated them as they were poor performers until sheer determination made me persist as I was sure it was bleed related, and it was! They seem to get a vacuum in the sytem somehow which is part of the problem, and hence why the pressurisation technique with the lever syringe. Works a treat.
mine have been fine since i got them. I once seized the pistons in the front and had to have then bled, but as for stopping power , never had any issues. Good luck with the rebleed.
"I cannot get the front brake to lock up no matter how hard i pull the lever"
Just why anyone would want to lock up their front wheel is beyond me
And as for the "pads are only coming into contact with the middle part of the rotors" I wouldn't worry, my J7 G2 rotors are still more polished in the center than at the edges over a year since I fitted them.
The only reason i mentioned the bit about the front wheel locking up is I have an old 04 Hardrock with crappy Tektro V-brakes on it, and it stops loads better, obviously I wouldn't want to lock the front wheel up on the trail, i was meerly trying to express how sh1t they are.
My brother has Juicy 3's on his bike and the pads contact all of the rotor (they are much more powerful), that is why I mentioned this.
But thanks for the advice on the bleed Clocky, i will give it another go when i get chance.
I have exactly the same problem with the rear brake, do you think the shop could have cut the lines when they built the bike and never bled them properly?
Unless the lever is going all the way to the bars bleeding brakes has no influence on power*. Brakes that lack bite lack friction. Friction can be influenced by caliper alignment, rotor material and condition, pad material and condition but not fluid condition.
Ridng the bike in truly horrible conditions, a hose down then a couple of bedding in stops is a good way to improve bite. The mud cleans up the pads, roughs up the rotor and removes any contamination. A few stops after the clean puts the necessary trace of pad material back on the disc and you have great brakes.
* mechanical advantage often increases through the lever movement so a bit of air resulting in a bit more lever movement will increase power rather than reduce it.
Juicys are funny buggers john, they seem to get a vacuum in them as I mentioned above, and just don't behave right at all. I'm not the only one to discover this btw.
My juicys went from very poor indeed, to very good indeed after the final bleed, the pads were the same ones and so was the rotor, and I had already changed both previously trying to rectify the situation, to little avail. It was do or die, I tried one last bleed, being very meticulous, and doing the alterations mentioned above which I had come up with after far too many sleepless nights perusing why the brakes were sh!t, and that, fortunately, was that, otherwise they were going, no question.
I have also had very similar issues with my k18 which came bled from new, not touched in any way, shite, very similar to how the juicy's were, so guess what? two bleeds later and it's a completely different brake, now behaving as folk say k18's do. More than coincidence. (Not that I'm in any doubt that would ever be coincidence, I'm no fool when it comes to anything mechanical)
I do know what you're saying, and in principle yes, but don't forget that they are a sealed system, a vacuum inside will cause a negative pressure (obviously!) which keeps the pistons back and requires excessive lever travel to get the pads to touch the rotor, and thus goes past the optimum leverage part of the lever stroke, reducing the mechanical advantage, amongst other things which I cannot work out, but I don't have a masters in hydraulics, just a general mechanical aptitude, so I'm not gonna know! (It's a bit like 'pumping up' brakes that need bleeding, they feel and work shit, but pump tham rapidly a few times to increase the pressure in hose and caliper and they significantly improve for that singular application, then go shit again immediately after. Though pumping juicy's doesn't make any odds (I suppose if there is a vacuum you can't pump them up?))
haven't read the whole thread but will just add that have just fitted set of juicy fives and prior to bedding them in properly was not impressed.
betting in consisted of going for a road ride and every time i hit 20mph locking everything up until i came to a stand still then quickly dousing the brakes in water from a bottle.
did about 20 -30 stops and now they are awsome.
the proof. rode whites levels at afan last weekend and they would stop me on a dime. i weigh 19 st.
what i would suggest is new set of pads.
get the disc off and clean it throughly, there are various methods which i can see some people have mentioned.
then bed the pads in.
if you then still have a problem at least you'll know its not the pads and disc so then move on to getting them bled. just remember to take the pads and the disc out when bleeding as you dont want them contaminted.
That's just it, eliminate the pads and rotor first (as I did) then bleed.
Juicy's dont have a spacer for bleeding, only a plastic wedge that fits between the pads, so may as well leave the rotor in and bleed the system as it is in operation on the bike, this gives the best result. You just have to be super careful not to contaminate, which is quite easy if you pay attention to what you're doing and repeatedly check for any fluid going where it shouldn't be.
If you have any air in the system, when you pull the lever you will move the pads against the disc, then you will just start compressing the air as you squeeze more. That's my understanding as to why brakes lack power when there is air in them.
Your brake fluid is just the method of transmitting a squeeze at the lever to a squeeze at the pad. 100% brake fluid is as near as dammit incompressible so as soon as you squeeze the lever, you will start to press pad against disc. With air in the system though, you will move the pads initially, but then any additional pressure you apply through the lever will just go into compressing the gas and the pads won't grip the disc any harder (unless you have enough lever travel to compress the air until it becomes virtually incompressible and then it will start to bite more again).
As suggested already I would start with the easy bits like clean rotor thoroughly and whack some new pads in. Bed them in and see where you are. If they are still pony, then bleed them.
Amazingly enough, i bought my GF Juicy 3's about 18 months ago, from set up they have been fine for her, perfect stopping power, and they havent been touched since, not even new pads! Why my 5's take such tinkering all the time is beyond me!
i am having similar problems with my juicy 5's.except it seems , the caliper doesn't retract away from the pad after braking. it actually feels as if the brake is on,even when pushing the bike.
how much is a bleed kit?or is it worth just getting my LBS to do it ?
