What causes brake calipers to tighten up while riding?

[rdlsz24]

I was on a short ride today on a flat old railroad bed, really no need to even use brakes, especially the rears. I went to turn around to head home and noticed some severe resistance at the rear wheels. The brake pads were clamped down hard on the rear rotor. I couldn't even move the rear tires by hand. The weird thing is these brakes don't even work that great normally. I have to stand on the lever to get them to work.

I still had to get home and unfortunately didn't even have a small crescent wrench with me to release the pressure (lesson learned there), so I had to ride it. I couldn't even get out of first gear and by the time I got home the rotor was smoking. The brake hose eventually blew from the extreme heat. The smell of smoked brake fluid still haunts my nose. The hose blowing caused the pads to release their death grip on the rotor and I was able to roll it in to the garage.

What would cause this? It's a caliper from a 2000's CR80 so it's not like it's a 25 year old piece of junk. It looks like new.

On a side note the 250R I recently bought had this same issue when I bought it; the rear pads were clamped down on the rotor so hard I could barely push it by hand. I undid the hose to release the pressure so I could roll it into the garage after buying it. I haven't ridden it yet so I am not sure if it they will tighten back up the first time I ride it.

Any thoughts? I now have to get a new hose but I don't want this to happen again

Rob

[dougspcs]

Two things possible..brake hose collapsed internally and formed a check valve not letting pressure return to the master or the master piston is stuck in the cylinder.

Since you have to replace the pressure hose, also get yourself a master cylinder rebuild kit and do it also..

Done and done!!

[muthey]

also make sure you bleed them , air in brake lines can do all kinds of things, might want to check the rubber breathing grommet in the cap as well can do weird things when they go bad

[tx200m]

^ Ya , what they said. If the slides had frozen, it would still have been stuck even after the hose blew.

[atc007]

Orrrr,,none of the above : ). Your caliper slide pins are dirty,,stuck. More than likely. One is a 5.5 mm allen,it will come out VERY hard,polish it and clean the caliper where it slides thru and the other one also,,regrease,replace the rubbers if they rip,job done. Let us know what you find,,your R is probably the same problem.

[bobotech]

Could water in the brake fluid cause something like that? Since water would boil as the brakes get used, it would create steam which would then clamp down on the rotor and heat up even more making the problem even worse.

Just wondering out loud.

[dougspcs]

Could water in the brake fluid cause something like that? Since water would boil as the brakes get used, it would create steam which would then clamp down on the rotor and heat up even more making the problem even worse.

Just wondering out loud.

No, water in the fluid has an opposite effect. When it gets hot and boils it creates an air(steam) bubble..then the pedal goes soft as if your brakes were not air-bled properly..then when they cool down the pedal comes back.

[just ben]

bent rotor will do it. causes the fluid in the caliper to heat up and expand eventually engaging the brake. may need service clutch now too

[pantera1975]

I had it where there was all kinds of corrision in the groovers when the piston seal oring go and made it real tight. I cleaned it out with a dremel wire wheel and its fine.

[cbx1170]

Wow never heard of a brake hose getting hot and blowing. you sure its the hose? Bent disc if obvious #1 check. then-1 of 2 things that normally causes brakes to lock would be bypass port on the rear master cylinder plugged rendering it a one way valve. Cause: old dirty fluid in the cavity underneath the black plastic fitting on hose from reservoir to master cylinder connection. the pressure from stomping on brake pedal causes pressure to build up in hose to rear caliper and constantly forcing pads to clamp onto disc. normally when you let off the pedal the last bit of upward travel uncovers this bypass port to release all the pressure inside master cylinder from when you stomp down. Solution: clean this area blow out and/or push a small 0.0010in wire thru this hole to unblock -do not move master cylinder & have it in the "un pressurized position" while doing this and do not press on the pedal while wire is thru hole as your piston and seal and m/c wil be damaged. DO NOT drill it bigger. both will cause you to have to possibly repair or replace master cylinder. 2nd thing is the rear caliper is dirty or filled with old brake fluid that "cakes" under the piston seal causing them to become a one way thing also. the pistons come out of the caliper to push pads onto disc but won't work normally and "release" their push on the pads. the seals in normal operation are slightly loose fitting in their groove they "rock" in their groove under normal operation "ON-OFF". this "grip" under pressure makes the seal grip the piston and when pressure is release it pulls the piston back just a little bit and brake pads release their grip on disc. Cause: contaminated or semi dried "cake" or old brake fluid that is underneath the seals in their operating groove. Solution: take caliper off disc, leave hose attached and fluid in system slowly pump pressure up in system and pistons will "walk" out. get both out together, if one comes out first you lost the way to remove the second one. you can pull the whole caliper off the hose and use air but its hard to evenly control them - pieces of thin wood help. pistons can go flying and hurt. pull out seals & now look into the fluid seal and dust seals groove area. Remove the crud using a scribe or small spiral wire brush to clean groove. prolly a good amount of white crap in this groove-keep cleaning-manually as not much else works. Neat thing is the pressure seals are very reuseable in either direction when reinstalled. Yes i have done this hundreds of times not ONE has leaked or worked improperly. But the dust seals (outer thinner ones) 50% time are swolen/damaged/toast and will still make pistons stick and not release. Lube with new fluid and reassy. Bleed and be happy. You got brakes again.
Sorry for long reply but I did bike/tryke/4whlr/PWC/snowm/power products for 25 years its very accurate.