Disks: XTR vs. Juicy 7 vs. Hays HFX Mag +
What's the lowdown on these disk brakes? Are the XTR's really that hard to keep from rubbing? I'm no mechanic whiz, but I am decently competent (can overhaul a fork, hubs, ect). I'd appreciate any help- they're going on a 2004 C-dale Team edition Scalple if it matters.
Of the brakes you are interested in, I've only used the XTR/XTs. For the first 4-6 weeks, they were fantastic...excellent power and modulation with a very firm lever. Just I look for in brakes. Then, the front brake started to rub. One of the pistons would not fully retract after the lever was released. I tried everything to fix it, but nothing worked. Eventually, the rear started to exhibit the same sticky piston syndrome. Once I had some downtime (i.e., weather was -48F), I pulled the brakes off and warrantied them with Shimano USA. They just arrived back at my LBS after 4 weeks. I'm not yet sure what the warranty consisted of -- hopefully, new calipers.
Originally Posted by xcgeek
First generation XTR calipers had piston bores that were actually too smooth. As the pistons extend, a seal pulls the pistons back after the lever is released. Since the surface was too smooth, the seal could not grab onto anything. So, the piston remained extended causing pad rub.
Newer XTR calipers are said to have rougher surfaces to allow the seals to grab.
As for the other brakes, I like the ideas behind the Juicy 7, but I'm always leary about 1st generation products.
The Hayes Mag + looks nice, too. But, I've never been a fan of Hayes' off/on feel. I prefer a much more modulated brake....Formula B4 SLs and XTR/XTs are some of the best, closely followed by the Hope Mini.
I've been running the XTR disc setup for almost a year. Having worked in a shop with all the different brands, I must say that the XTR is the nicest setup yet. Very clean and well designed.
I have had a couple minor incidents of brake rub/drag like you have mentioned. Here's what I have noticed seems to be the cause and what can be done to fix it:
1. Make sure the brake mounts on your frame/fork are perfectly perpendicular to the axle. The advent of MTB disc brakes has brought the invention of a facing tool designed to shave off excess paint & just enough metal from the inside of an I.S. brake mount to make everything square. If you can't get a shop to perfom this service, you can "substitute" by mixing and matching shims (XTR). These are .25mm and .50mm thicknesses. Get the caliper as centered and straight as possible over the disc rotor.
2. If you don't mind a little noise, run your brakes with the little X-shaped silver anti- rattle spring removed. All this does is keep the pads up against the pistons so they won't rattle when the brake is not applied. The spring is the culprit of most XTR brake drag problems. Sometimes it can hinder the brake's self adjusting operation and can also lead to uneven pad wear (pads may wear in a tapered manner). The problems will be alleiviated if you remove the spring. The brakes may also have an ever so slightly firmer feel as well. But you will now have a bike that rattles.
3. Keep the bike clean. Accumulated brake dust and other dirt in the caliper, on the exposed piston surface, and other brake surfaces may hinder the brakes ability to self adjust and retract. Degrease periodically with a mild degreaser and hose off with clean water.
.....XTR discs rock. There are other good brakes, but I wouldn't think of using anything else.
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