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Old 07-05-2012, 09:05 AM
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Default mtn bike disk brake maintenance

Hey, anyone have a bleed kit? Do I need that? My Hayes brakes (about 8 years old?) have never been bled.. I am running halfway through my travel before I make contact. I guess I could look at the pads, huh.. but in all honesty I'm still on the original tires, once our kids came on line the bikes have done more hanging in the garage than anything. My pads are likely fine.

But I realized yesterday that I've got bleeders on my calipers, so hey I should learn how to bleed these things. Found this video from Leonard Zinn http://www.5min.com/Video/How-to-Ble...akes-509768730 (side note: we actually have a Zinn in our collection). curious though as it seems like he's doing it upside-down, squeezing it in down at the caliper then it oozes out at the lever? Maybe that's how you do mountain bikes though.

Also interesting he's using DOT 4, I thought that was the evil compared to 3 or 5? anyway, open up the chatter on brake maintenance..
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Old 07-05-2012, 09:42 AM
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DaveInDenver DaveInDenver is offline
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I have the Hayes bleed kit. You do not strictly need their kit, although they have the right fittings to adapt to the levers which makes it easier. Otherwise it's just plastic bottles and tubing, nothing fancy.

I replace my pads typically twice a year normally, sometimes just one. I use the cheapest Hayes OE pads, they work best and are the most quiet for me. They cheap ones are organic and don't tear up the rotors as much. I deviated on my current pads and went with EBC green. I hate them, squeal like crazy, dirty with brake dust, glaze the rotors awfully.

Yes, catch bottle at the master (handle) and fresh in through the caliper. It's a closed system and so you want the air bubbles to rise, which is why you tip the bike up and flip the levers up. Inside the levers is the master cylinder and it's got a diaphragm to compensate for expansion, but no reservoir like your truck brakes.

Yes, DOT3 or DOT4 is fine. It's DOT5 that is bad. I couldn't tell you if DOT5.1 is OK in Hayes, but DOT4 is preferred because of it's higher boiling point. There's not a lot of fluid in the system and they do get very hot. I've had DOT3 get mushy on my bike and I am far, far, far from gonzo. Nice thing is the small bottle at Autozone is a pint and you can bleed half a dozen MTB systems with it, so get your riding buds, a 12'er and do all your bikes at the same time.

And yes, there is a good chance you will spill some, do it in the garage and have rags ready to keep from striping the paint off your bike. Otherwise, it ain't rocket surgery and after fumbling through the first time it'll only take you a few minutes to do after.
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Old 07-05-2012, 09:51 AM
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I've never bled Hayes, but Allison has had Avid's on her last 2 bikes and so do her friends so I have bled them lots.

they have a procedure with two syringes (one in caliper, one in master) and you push fluid from the caliper to the master. We probably bleed her brakes 3 times a year just because it is easy bike maintenance. Her friends take much worse care of their bikes and we bleed them at trail heads and stuff when it's been over a year that they did it last. we all ride probably every day so it may be a more extreme case.

As far as pad wear it has a lot to do with how you ride and what terrain. muddy, kills pads.
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Old 07-05-2012, 10:05 AM
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Oh, important to point out that some brakes use mineral oil and NOT DOT BRAKE FLUID! Shimano does I know, I think maybe Magura, too. The process might be the same but you cannot mix them up.
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Old 07-05-2012, 10:13 AM
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That's a great point! My Shimanos (just got hydraulic brakes for my bike!!) use mineral oil, but the Avids use Brake fluid. Specifically the Avids call for the 5.1 stuff.
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Old 07-05-2012, 10:18 AM
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is Wikipedia correct here?

It states that 5.1 has a higher boiling point than 4. I thought that was true and why motorcycles spec it.

http://en.wikipedia.org/wiki/Brake_fluid

Also, I have been able to find it at some car parts stores.. but not in Boulder. I haven't seen that NAPA carry it in a while. Anybody know of any stores that carries it? I guess any motorcycle shop huh..
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Old 07-05-2012, 01:27 PM
J Kimmel J Kimmel is offline
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5 bucks says your pads are almost done. I've got Hayes on my Yeti and had the same thing going on, and also thought it was an air bubble. It was the brake pads almost gone.

just a thing to check
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Old 07-05-2012, 01:47 PM
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Alright I'll post a pic later...
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Old 07-05-2012, 09:12 PM
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Ok I have .075" of pad on each side.. I have run trucks with less, how thick are new ones even?

Also on the lever I don't see the little bleeder screw that's in the video... where is it?
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Old 07-06-2012, 05:46 AM
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This it in on your HFX-9. He's demonstrating on brakes a few years newer than yours.

Yours still have a little meat on them it seems (I'd guess about 50% of new), but why don't you just spend the $30 to replace them and remove any question? The spec for the min pad thickness is 3mm (the friction material would be 1mm), if you want to measure them. New they are supposed to be 4mm total, so you're working with 1mm of material over its life. I replace them at around 0.135" on my micrometer and new they usually fall between 0.155" and 0.16". This is overall thickness, not friction material thickness.
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