Lost back brakes

[Boog]

Problem solved, air in the line somehow. I bleed the back brakes and the darn thing feels like new. Gotta get used to it all over again. Thanks guys!

 

[Mhboldt]

On the way to Ridercoach prep today, my back brake went all the way done with no useful rear brake. I found my master cylinder very low, I believe air got into the system but there's no leakage anywhere. The brake pads are just about at the end of their useful life, perhaps the reservoir is not big enough to accommodate the difference in fluid from new pads to worn? I've never had this happen before, where brake fluid is low with no leaks anywhere in the system.

 

[Gregger]

perhaps the reservoir is not big enough to accommodate the difference in fluid from new pads to worn?

Think you just answered your own question....

Were you pulling any wheelies recently, or involved in some heavy braking. Really low reservoir will allow air to get ingested into the master cylinder.

 

[cootertwo]

I've also heard that if your caliper pistons are nice and free, and the boots are stuck on them, the boots will pull the pistons back away from the disc, instead of leaving them, just touching, and being worn, creates a gap that must be filled before they start to make contact.

 

[Rick Morris]

I put rear brakes on recently, took the bike out yesterday absolutely no rear brakes. Pumped the hell out of them and nothing. When I replaced the pads I bleed all the old fluid out and replaced it with new DOT 5 fluid. I had awesome brakes in December. Bike sits and no brakes. WHY?

 

[Gregger]

I put rear brakes on recently, took the bike out yesterday absolutely no rear brakes. Pumped the hell out of them and nothing. When I replaced the pads I bleed all the old fluid out and replaced it with new DOT 5 fluid. I had awesome brakes in December. Bike sits and no brakes. WHY?

DOT 5 silicone based brake fluid is not supposed to be compatible with DOT 4 glycol based stuff. From what I've read, it shouldn't be used in ABS systems also, designed for DOT 3 or 4. Not sure if this would have caused an issue.

There is a DOT 5.1 which is glyol based that can be used though.

 

[sonny]

Guys look at the rear brake bleeder. Mentioned it early in the post. You can go off into all the science and technical sh%t but simple says simple do. Stock bleeder is a joke and leaks air. Replace and have had no issues since. Back brakes have worked fine since then.

 

[Rick Morris]

DOT 5 silicone based brake fluid is not supposed to be compatible with DOT 4 glycol based stuff. From what I've read, it shouldn't be used in ABS systems also, designed for DOT 3 or 4. Not sure if this would have caused an issue.

There is a DOT 5.1 which is glyol based that can be used though.

I will bleed off that fluid and replace with DOT 4 or 5.1. I will keep you posted. I will also replace the bleeder screw to see if Sonny is onto something

 

[Jag]

I will bleed off that fluid and replace with DOT 4 or 5.1. I will keep you posted. I will also replace the bleeder screw to see if Sonny is onto something

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Here is the ones I used.

 

[Journeyman]

I've also heard that if your caliper pistons are nice and free, and the boots are stuck on them, the boots will pull the pistons back away from the disc, instead of leaving them, just touching, and being worn, creates a gap that must be filled before they start to make contact.

Some good advice out there. Maybe keep this in mind if all else fails. On my Thunderbird Sport I had spongy brakes- replaced the lines, rebuilt MC, new pads, multiple bleeds.... still spongy. Finally, I rebuilt the caliper. Now I use one finger for braking, lest I accidentally lockup the wheel. It's firm like "cold blue steel, cat can't scratch it."