Bleeding Disk Brakes

Adam-NLV

Adam-NLV

Well-Known Member
Got these Trail Buddy 30mm shock & disk brakes. They are in need of adjustment because the lever feels spongy and bottoms out. The tire isn't stopping like it should either.
I think it may of got air in the system from the reservoir moving up & down from the installation.

I don't even see a bleeder screw or bleeder Nut. Which one is that? Is that the one my finger is pointing to? The level of fluid seems all right. I'm sure all it needs is to bleed the brakes but I do not know how for this system and I just don't want to start taking things apart...

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adam the screw you're pointing to is the bleeder. attach a hose (preferably clear) to it with the appropriate (8mm?) wrench on this nut. keep the reservoir open so you can add fluid.squeeze your spongy front brake lever, hold pressure on it, then crack this screw until fluid begins to run through the hose. when no more fluid runs, close it, pump the lever 3 or 4 more times, then hold the lever down, crack it again…. repeat until the lever has good feedback. maybe even a few times after that to ensure there's NO air in there. be sure to add fluid when the reservoir gets low or you'll be putting air back into the system. also i recommend putting the little hose you attached to the bleeder screw into an old 20oz coke bottle or the like.

PS brake fluid is nasty don't touch painted stuff with it and clean it off QUICKLY with a clean rag and brake cleaner or thinner alike. also be sure to use the correct fluid. i assume DOT3, but if it is DOT3, you can use DOT4. if it's DOT 4, use ONLY DOT4. if it's DOT5, use only DOT5.

hope that helps
 
Hey thanks Eng Dr. That makes sense, It's a odd looking bleed/nut kinda looks like it was meant for air or something but it's shaped like that to accept a bleed hose DuH!

There's gotta be a lot of air in there. When i had the tire off I pushed the lever and the brake calipers stayed shut and the disk wouldn't go in. I pried it and it opened back up so I could get the wheel back on.

wish they had a instruction sheet on the whole unit, including fork oil capacity and viscosity... it would help us Newbies. I'll try bleeding it first thing tomorrow.
Thanks again Dude :)
 
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In a case as this, with a small amount of fluid required, has anyone ever emptied a WD40 can into a container and used it for brake fluid? I'm sure that WD40 would boil easily in an automotive or big motorcycle application, but what about a small bike as this? Since brake fluid draws moisture, wouldn't it be cool to use a fluid that displaces it? ....just wonderin'
 
Well with this set-up runnin at 3 Bills, I aint gonna experiment with it!... I'm gonna use the fluid they recommend; Dot 3 or Dot 4. Kinda funny but that's what it reads on the reservoir. You can use either one.
 
Adam-NLV said:
Well with this set-up runnin at 3 Bills, I aint gonna experiment with it!... I'm gonna use the fluid they recommend; Dot 3 or Dot 4. Kinda funny but that's what it reads on the reservoir. You can use either one.
Click to expand...

I didn't mean you should Adam.lol. Was just wondering if anyone had ever tried. Just another bizarre thought going through my abused brain.
 
ummm….

okay guys
CJ: Brake fluid DOES absorb moisture, that's why it comes in a sealed contained, has a limited shelf life (so they say), but as it absorbs moisture, the boiling point LOWERS, which is bad, because gasses are compressible, whereas fluids aren't. And, it would be advantageous to have a fluid that absorbs moisture, as opposed to displacing it, that way it's mixed in solution. in a sealed system, where is the displaced water to go? probably only going to cause corrosion or wearing of the seals at that point. Whats more is WD-40 is a very LIGHT, non viscous fluid. therefore, in almost any brake application, it's liable to boil down at the caliper pistons, which heat up TREMENDOUSLY from the friction of braking. Plus, the difference in price is probably negligible.

Adam, Dot 3 and 4 are compatible, glycol based fluids, whereas dot 5, is a silicon based fluid. therefore, 5 don't go down, and 4 don't go up… there's a realy confusing one in there somewhere ( i think it's 5.1) that works with 4 but not 5…… yes, dumb i know, but i didn't make the types. they might as well be A, B, and G… or g.1…. either way

so, in summation, stick with brake fluid. if you have dot 3, dot 4 is an upgrade, but don't go higher than that...
 
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