school me on bleeding mtb disc brakes

[semlin]

so i need to bleed my disc brakes. they are hayes mag g1's. the rear one recently went to the "floorboards" when i went to ride it and then i was able to work it back to about half the old braking power. i can't find any leaking fluid anywhere and the hayes manual says to bleed if that happens. i'll start there anyway.

my local lbs has no bleed kits or adaptors for sale. plus i have read a bunch of horrible reviews of the hayes bleed kit online. i pulled out my vacuum pump car brake bleed kit which works by drawing fluid out of the brakes. it has an adaptor that fits the hayes caliper so i am thinking of buying just the master cylinder adaptor online and using the car kit. it looks something like this...



do you think this would work by pulling fluid throught the system and out the master cylinder? i guess i would need to start a siphon from the brake fluid container to the caliper somehow so i don't introduce air?

if not, what is best way to bleed these brakes? would a syringe work to force the fluid into the caliper?

 

[Dirtgypsy]

I used a 10cc syringe to push the fluid from the caliper to the lever. Just made sure that all the air was out of the tube. Just crack the nipple (haha I said nipple) and push it through. Having a extra person to close the bleeder is helpful. I also se the lever flat with set screw as level as possible.

Yes the hayes bleeders suck.

Clint

 

[Red Herring]

It might be like my motorcycle MC, which, after bleeding the lines needs the brake lever tickled repeatedly with very light, shallow pulls and the MC itself tapped with a screw driver end to knock all the air out.Those little air bubbles that cling to the inside of the MC and line take offs are a nuisance.

 

[RHINO]

dont use the vacuum pump, use a syringe or squeeze bottle and push new fluid from the caliper up through the master. you can buy bleed kits online, or, make yours like i did for mine.

 

[LukeZero]

When I've done mine (I have Hayes something or others). It's been pretty easy. Just flip the levers upside down so that the little reservoir [tip] is the high point. Then go slowly with a syringe. I got some huge-as* syringes at the veterinarians that work great. Those and a little piece of tubing from the Mity-Vac kit works.

Luke

 

[scottm]

Did mine a while ago, still feels tight and responsive.
https://forum.ih8mud.com/bicycling/221195-bleeding-shimano-hydraulic-brakes.html

 

[Red Herring]

I was wondering about retro bleeding, and I know it's popular with some folk, but I was wondering how you avoid pushing sediment, which always settles in the calipers, back into the MC, thus causing durability issues?

 

[Fast Eddy]

I was wondering about retro bleeding, and I know it's popular with some folk, but I was wondering how you avoid pushing sediment, which always settles in the calipers, back into the MC, thus causing durability issues?

Push it all the way through until the fluid coming out is clear.

 

[scottm]

I wouldn't bleed backward in a car, but a bike is simpler, and just as likely to have contaminants at either end. But it was simple enough to bleed mine from top to bottom, seems like it'd be more complicated the other way.

 

[SamETullsworth]

about the only thing the hayes bleed kit is useful for is the small plastic fitting that goes from the bleed plug on the lever.

with the mags, turn the lever 90 degrees to the bar, and pump with a syringe or squeeze bottle from the caliper.

while you are there, check the pistons. often they stay set out, and will cause you problems if you replace the pads. place a small amount of brake fluid around the piston and ease it back in with a 10mm box end.

just make sure to clean up well after with alcohol.

 

[Ozdunc]

Early Hayes brakes are a biatch to get right. It's easier to bleed from top to bottom, but you do need a syringe and little bit of tube to slot in the lever, and a nice long bit of hose to go over the caliper nipple. Fill the syringe and prime the tube so there's no air, remove the wee screw, insert the tube. Crack the nipple, and start squeezing. Stop when there's no air or ugly looking fluid coming out.
Tighten the nipple. And remove the syringe. Don't be tempted to pressurise the lever as it just makes the lever bite to early in the stroke and you'll get finger pump on the big descents.

I adjust my bite point by squeezing the lever with the nipple open to where I want it to bite then close the lever. Its not exact but in the absence of proper adjustment like later levers its the best you can do.

Hope this helps

 

[General Sherman]

Early Hayes brakes are a biatch to get right. It's easier to bleed from top to bottom, but you do need a syringe and little bit of tube to slot in the lever, and a nice long bit of hose to go over the caliper nipple. Fill the syringe and prime the tube so there's no air, remove the wee screw, insert the tube. Crack the nipple, and start squeezing. Stop when there's no air or ugly looking fluid coming out.
Tighten the nipple. And remove the syringe. Don't be tempted to pressurise the lever as it just makes the lever bite to early in the stroke and you'll get finger pump on the big descents.

I adjust my bite point by squeezing the lever with the nipple open to where I want it to bite then close the lever. Its not exact but in the absence of proper adjustment like later levers its the best you can do.

Hope this helps

The reason you find Hayes difficult is your bleeding them wrong. I will repeat earlier posts by re-explaining. By using a syringe or bottle push new brake fluid fro the caliper up to the lever. The Hayes kit has a small plastic insert that fits perfectly into the bleed hole. You rotate the lever up with the bleed at the highest point. The plastic piece is inserted into the bleed hole with a tube to keep the brake fluid from spilling every where. I have an old water bottle that i use as a catch can.
Clean the bleed screw so no debris can get in the system. Open the bleed screw and push fluid through to the caliper. The Caliper has a bladder in it that allows for the fluid to expand when heated up. You can tap the caliper as you bleed to ensure the air comes out but you should't need to mess with the lever itself. If you do, you should push extra fluid through to ensure the right amount of fluid is in the lever. There is a lever adjustment on the earlier levers but it only adjusts the lever closer or further from the bars. The "amount" of lever pull it take to apply the brakes is fixed when bleed properly. If you push fluid out of the lever when bleeding to increase the pull amount, the bladder will probably be collapsed and be harder if not impossible to get all the air out.

 

[semlin]

just to clarify, is there a special fitting for the mc/lever end or is it a tube? i thought i needed a threaded fitting like this. i am putting together an order of several things from jenson and was just about to order this piece. it says it is for the hfx-9 but jenson says it also fits the mags.

HAYES MASTER CYL. BLEED KIT FITTING at JensonUSA.com

 

[Ozdunc]

Semlin, the old Hayes brakes certainly pre-2000 just use tube

Here's a great piccy using General Sherman's method
Home Mechanics - How to bleed hydraulic disc brakes

GS, the reason I do top to bottom is to tune the brake bite point as the stock Hayes setting is to far away from the bar for me even with the lever fully adjusted in.
You are right though about the bladder, I'd forgotten about that.

Hooray for Avid Elixers they are so much better and easier to bleed these days

 

[semlin]

thanks. those are my brakes so that should work!