Hot Weather = Front Brake Drag

[zayanteman]

An ongoing problem I have had (six months now) has to do with weather affecting the front 82 brake.  Cold weather means the brake works great.  Warm weather means that after sitting in the sun for a bit (an hour?) the front brake starts to drag really heavily.  It gets so bad I can't push the bike in neutral, and when riding will be like I am grabbing brake while just going along normally.  Then, when the brake system decides to try something new to piss me off, it gets all super-mushy and takes almost full lever movement to actuate.

Is this the caliper piston / master cylinder piston rebuild problem, or would a stainless line change it?  I'm guessing heat expansion is causing it, but what is the heat expanding, exactly?

[Lucky]

First of all, some of us up hear are freezing our ball bearings off! heat problems?! no sympathy...

Just playing with 'ya.

sseveral possabilitys:
-- brake fluid is having a hard time getting back into the master
--  The caliper seal is swollen or otherwise damaged
-- The brake line has collapsed internaly. (rare, but old lines are prone to it)

What you can do is the next time it happens, crack the banjo bolt at the master, and see if the brakes free up.  if so clean and/rebuild the master.
if that doesn't help, crack the banjo at the caliper, if this helps, replace the line (with stainless, in fact, replace it with SS anyway, it makes a big difference)
if cracking the line at the caliper doesn't help, then rebuild the caliper.

-be sure to hold a rag under whever you crack the line, so you don't get it on your paint or pads.
--Lucky

[RobTx]

My guess is that the fluid is boiling from the heat generated by the brake dragging.  That's what's causing the mushy feeling.  You should rebuild the caliper and flush the master cylinder and brake line.  I bet the fluid is old and loaded with water (brake fluid is hygroscopic, in other words it can absorb water out of the atmosphere).  This can cause problems in the caliper as well.  They are fairly simple to rebuild.
Rob

[bikeseamus]

 Zay    Lucky's first sentence is your most likely suspect. The fluid return in the master cylinder can garf up in systems that haven't been flushed out about every other year. You can watch the fluid return if you remove the top of the reservoir. It should come back with enough pressure to be visible. I would urge you to get on this problem like a dog on a bone. A locking front brake will place you directly into the graveyard, and may take someone else with you. Even a dragging front brake in a corner with a little sand in the apex...... graveyards are full of people that ignored brake problems. You're in the danger zone, buddy. Get on outa there!