Bicycle Mechanics - 'Mushyness' with XT dual control discs
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09-04-07, 11:36 AM
I am trying to get my 06 model XT discs to feel stronger and more snappy. They seem to be dialed in correctly since they are not rubbing in anyway, but they are feeling mushy and not giving much stopping power. A friend of mine said that this is a design flaw with the dual control, and was the reason that shimano redesigned the levers. Was wondering if anyone had any experienced opinions of what can be done for improvement.
09-04-07, 04:58 PM
The brake lines can expand when you squeeze the lever, which can be part of the mushiness. If the brake lines are plain old rubber you can eliminate some of the mushiness by replacing them with steel braid line. If you're interested I saw some at jensonUSA.com. Of course if you already have steel braid hose the point is moot.
09-05-07, 06:53 AM
Caveat: I own no bikes with disk brakes and have never worked on one in my life. However, from car experience, I know mushy brakes often = water in brake fluid. Thought I'd suggest replacing that.
09-05-07, 07:37 AM
Maybe a stupid question, but when is the last time you bled them? You need to bleed them about once a year or so. Its a pain in the butt, but doable especially if you pick up Shimano's kit. Its allot easier if you are #1 an octopus and have four or more hands, or #2 you get someone to help you out.
09-05-07, 01:39 PM
They have less then a hundred miles on them, and have been feeling mushy straight from the box. I was thinking either the stock pads needed replacing or it is poor engineering by shimano.
I noticed that they are not hitting the disc square, maybe >1mm off center. However, I don't think it is possible to manually set them to be perfect.
09-05-07, 10:43 PM
#1 it is totally possible to set them up so the pads his the rotor squarely. the mushy feeling could very well be because of them being off center.
#2 if setting them up properly (so the pads contact the rotor squarely) does not solve it, one trick i've learned is to use a toe strap to hold the lever against the bar for an hour or so. this compresses the fluid, allows any large air bubble in the system to float up the line to the lever/reservoir and as soon as you release the lever, is sucks the air bubbles into the reservoir, which eliminates the possibility of the air getting back into the line.
IMHO, shimano brakes are the easiest brakes to work on and set up. a VERY close second would be avid juicy 7s. the XTR calipers can be a bit finicky to set up, but everything else is ridiculously easy compared with, say, a hayes, or magura. the other nice thing about shimanos is that they use mineral oil, rather than DOT fluid, which isn't nearly as nasty on paint, or for your nervous system, given long-term exposure. as a consumer, you may not care as much about that last fact as a mechanic, but it's an important factor to consider.
09-06-07, 06:21 AM
IMHO, shimano brakes are the easiest brakes to work on and set up. a VERY close second would be avid juicy 7s. the XTR calipers can be a bit finicky to set up, but everything else is ridiculously easy compared with, say, a hayes, or magura.
Really? My Juicy 7's are mad easy to work on... never got the chance to work on a Shimano. If you don't mind, I'd like to know whats easier about a Shimano setup.
09-06-07, 11:01 AM
the shimanos don't have the spherical washers of the avids, which means you only have to line them up on one axis. unless the frame disc tabs are totally jacked up, that's usually all you need. the spherical washers can sometimes stick and make it more difficult to line up the pads.
the other thing i like about them is the bleed process. with shimanos, you just need their bleed kit, or a bottle of their mineral oil and a typical syringe with a plastic/rubber tube to connect to the bleed nipple. (the bottle of mineral oil can be used in lieu of a syringe) just hook up the supplied hose and squeeze the oil in with the reservoir cap off. it's basically a one step bleed. the avids add about three steps for bleeding, all of which make sense for their system, and require their special syringes with the fittings. the avid bleed process takes about as long as the shimano does, but if you don't have their fittings, you can't do it. at the shop, we've had to bleed about 10 avids for every shimano brake that comes in. my other beef is that you can't pressurize an avid brake while bleeding. with shimanos (and hayes) you can put the res. cap back on and pump fluid in to pressurize and set the pistons, then close the bleeder valve with the hose still connected and you're done. the avids don't allow this, as the bleed fittings thread into the caliper port and lever ports, so you end up losing a tiny bit of fluid ever time you remove the syringe to replace the screw in the bleed port. this can make life difficult on a juicy 5 or 3 if you're trying to get the lever throws even.
my personal juicy 7s have failed twice on me due to a leaky reservoir. SRAM replaced the levers both times, but the second failure was with the brand new lever right out of the box, during installation. i've never had that happen with a shimano brake.
don't get me wrong, i love my juicy 7s, and i've gotten very good at bleeding them, and the process goes very quickly now, i just happen to prefer working on the shimanos. if i was so inclined, i'd get a set of the new XTs, but for now, the avids are working well enough.
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