rear brakes

[Pooh]

i thought i had a great idea to try get my rear brakes to firm up, they were kinda soft. i was wrong. now the rear is so soft they hardly work.

i blead them like a car, pump pedal, open the bleader, close bleader, repeat


what did i do, and how can i fix it?

[slowbird]

From threads that I am reading it seems that bleeding bikes aren't like bleeding cars. Though I can't see why it'd be different.

[mello dude]

Originally Posted by Pooh

i thought i had a great idea to try get my rear brakes to firm up, they were kinda soft. i was wrong. now the rear is so soft they hardly work.

i blead them like a car, pump pedal, open the bleader, close bleader, repeat


what did i do, and how can i fix it?

Replace the rear bleed valve with speed bleeders. It makes the job much simpler.

Link
Speed Bleeder

MD

[mello dude]

Originally Posted by Pooh

i thought i had a great idea to try get my rear brakes to firm up, they were kinda soft. i was wrong. now the rear is so soft they hardly work.

i blead them like a car, pump pedal, open the bleader, close bleader, repeat


what did i do, and how can i fix it?

I forgot to mention that you can over stroke the pedal when you bleed. You want to avoid moving the piston past the fluid feed on your master cylinder. If you do, you get brake fluid on the backside of the piston and your S.O.L. - You aint gonna get full pressure from the piston after that. The only fix then is to take the master cylinder apart and clean it out, put it back together. If its super old like yours, you might as well rebuild it.

BTW - you can also over-stroke a front master cylinder with the same effect and then have the same fun playing mechanix.

MD

[saf]

A much easier and effective way (IMO) to bleed calipers on those bikes is to connect a fuel line (or any other rubber pipe that can take gas) to the bleeder. Open the bleeder and dip the line into a cup with brake fluid. That's it, then you just pump the pedal and watch bubbles coming out (don't let the brake fluid level to drop too low or the line to get out of the brake fluid). Once bubbles have stopped coming out close the bleeder (while holding the line dipped). You are done!

[Yonan]

Originally Posted by saf

A much easier and effective way (IMO) to bleed calipers on those bikes is to connect a fuel line (or any other rubber pipe that can take gas) to the bleeder. Open the bleeder and dip the line into a cup with brake fluid. That's it, then you just pump the pedal and watch bubbles coming out (don't let the brake fluid level to drop too low or the line to get out of the brake fluid). Once bubbles have stopped coming out close the bleeder (while holding the line dipped). You are done!

I second this method. Use it everytime and no problems.

[DANIMAL]

I third, my grandfather taught me to do it that way.
he passed away in 1980. I miss him.
He was the coolest old dude.

[slowbird]

That sounds like a neat method.

My guess is that the rubber line/hose to the bleeder screw needs to be air/fluid "tight"?

...and then just pump away until no more bubbles come out of the submerged end of the hose?

[Yonan]

Originally Posted by slowbird

That sounds like a neat method.

My guess is that the rubber line/hose to the bleeder screw needs to be air/fluid "tight"?

...and then just pump away until no more bubbles come out of the submerged end of the hose?

You got it!!!!

[Pooh]

what does it take to rebuild the brake? take apart, clean and put back together?

like i said the brakes were spongy when i tried to do the bleading so maybe the cylender needs cleaning

i like the sound of the rubber line, ill try it

[mello dude]

Originally Posted by Pooh

what does it take to rebuild the brake? take apart, clean and put back together?

like i said the brakes were spongy when i tried to do the bleading so maybe the cylender needs cleaning

i like the sound of the rubber line, ill try it

Um - you werent doing the plastic line on the bleeder to the jar in the first place like above? Sorry -- I assumed you were already doing that. Hope your fluid is fresh too?

Back up start there. A little automotive vacuum spring hose clamp over the hose on the bleed valve will save great agravation. Buy 'em at any autoparts store.

If you need a rebuild, you will need to buy a rebuild kit. See if you can find a manual too.

MD

[slowbird]

EBAY has plenty of VF500 Master cylinder rebuilt kits.

I don't think they come with instructions though.

Is it difficult? Complicated?

[saf]

I've rebuild all 3 calipers on my bike and no, it is not complicated. The most difficult part (at least in my case) was forcing pistons out of calipers. You can do it either with a compressor or just by pumping breaks with break pads removed. The latter method is easier but results in massive break fluid spillage. The former method is probably the one that you should use but be careful, those pistons will shoot out of calipers with substantial force...

At least in my experience though rebuilding calipers did not have any effect on break firmness. If bleeding your lines again does not help I'd recommend replacing break lines (unless you already replaced them). Old lines tend to become stretchy with time and don't hold pressure well anymore.

One consistent problem that I observed with all of my calipers is moisture penetrating under boots and causing the caliper to be frozen (it is supposed to move sideways to allow for even break pad and disk ware). One of them was so bad that I had to cut out the slider cylinder out of it because it completely rust-welded to the caliper. If you cannot move your caliper sideways when the disk is out of it you should consider rebuilding it. Otherwise, I doubt it will help your problem (IMHO).

[mello dude]

Originally Posted by slowbird

EBAY has plenty of VF500 Master cylinder rebuilt kits.

I don't think they come with instructions though.

Is it difficult? Complicated?

MC - not all that tough, a little patience and your ok.

MD

[slowbird]

Yea...I meant the MC not the calipers.

Thanks Mello.