Brake tech

[nattybumppo]

So my bike brakes great, but after a few miles the front disc sticks on and it drags progressively worse until I pop the bleeder screw and shed a little fluid. Then it works great for a few miles until the whole thing starts over again. I have rebuilt the calipers, replaced the pads, and flushed out the system several times. There do not appear to be any kinks or restrictions in the brake line. Any ideas? I havn't rebuilt the front brake master yet, so I guess that's next. What about the disc itself? It looks OK, but could it be a source of this problem?

 

[60wag]

If it were a car, I'd say you have a brake booster problem. You don't have power brakes on the bike do you? Sorry, no help here.

 

[MDH33]

Even a tiny amount of corrosion in the caliper or on the piston will cause the brakes to not release 100%.

 

[nattybumppo]

Even a tiny amount of corrosion in the caliper or on the piston will cause the brakes to not release 100%.

Hmmm. The caliper was quite clean after I removed all the gunk, but there was a little scoring on one of the pistons. Although I polished it some, maybe that is the problem. I can still get a new caliper housing unit, and maybe even some pistons. I guess that will be my next step if the MC rebuild dosn't do it. Thanks, Martin!

 

[farnhamstj]

If it sticks when it's hot it sounds like an air bubble in the system somewhere. What are you running for fluid? Dot 5.1 is the norm these days and is not compatible with Dot 3,4,5 or anything else as I understand. Not available at Napa or Autozone. Motorcycle specific. Could be a mix of fluids that's giving you a problem too.

 

[nattybumppo]

If it sticks when it's hot it sounds like an air bubble in the system somewhere. What are you running for fluid? Dot 5.1 is the norm these days and is not compatible with Dot 3,4,5 or anything else as I understand. Not available at Napa or Autozone. Motorcycle specific. Could be a mix of fluids that's giving you a problem too.

I have flushed it three times, but always used the same stuff I use in my cruisers...Synthetic DOT3/4 (I think Valvolene). DOT 5.1 is a different kind of fluid completely, isn't it (which explains why it's incompatible)? Isn't it the stuff that is completely hydrophilic and more compatible with high temps, but not as good at rtransmitting the force?

 

[farnhamstj]

I just know I had to go to a motorcycle shop to buy it. I'd guess that is your problem. Rebuild for the MC is usually like $13 and can be done in 15 minutes. How straight is your disk? If it rubs too much it'll cause problems too. Just bend it with an adjustable wrench.

 

[nattybumppo]

I just know I had to go to a motorcycle shop to buy it. I'd guess that is your problem. Rebuild for the MC is usually like $13 and can be done in 15 minutes. How straight is your disk? If it rubs too much it'll cause problems too. Just bend it with an adjustable wrench.

Thanks for the tips Farnham. I'll rebuild the MC and switch fluids before I go anywhere else with this!