sudden increase in rear brake pedal travel

[HarryHornby]

Hi All,
 
I left work yesterday and it was instantly noticeable that there was an increase in the amount of rear brake pedal travel before the pads would bite.  I commute every day and use the rear brake everyday so know how it normally feels.
 
It was fine going into work and the bike just sat undercover all day, what could cause this?  Before my journey to work today I had a little play and  I managed to lock up the back wheel while manoeuvring down the drive, so the brake is working, just with excessive pedal movement.
 
I thought maybe it was air in the system but I've not touched the brakes, I looked for a leak, but couldn't find one.  The amount of excessive free play has stayed constant throughout my ride home last night and ride into work this morning.
 
I had the calliper seals replaced about 8 months ago (pads about 6 months before that) and all has been lovely since that point, that's what makes me think it's not air in the system, surely that would have presented itself sooner.
 
Cheers in advance.
 

[YamFazMan]

Hi
The same thing happend to me I was heading for a MOT started out with a normal pedal went to brake and pedal stroke doubled
Blagged the MOT he had me opperating the brakes
When I got home I bleed the brakes and found  huge airlock on the inside caliper. ???
ATB YFM 

[HarryHornby]

I bled the brakes over the weekend and a big glob of air came straight out of the outside caliper.  Never bled the brakes before, turned out to be a nice easy job and another one I can add to my list of things I can do.
 
Strange how they had been fine for about a year before the air showed itself, is this a sign of something that needs attention, or just something that can happen now and again.
 
Cheers for pointing me in the right direction.

[Major Rant]

Just an observation ... but it must have come from somewhere.  Is the reservoir full?
 
On the other hand... it could be one of these 'long term' things.
Fluid starts out dry.
Gradually absorbs water so that in Year3 there are ting droplets of water in the fluid.
Water reacts slowly with the metal so that in year 5 there is 2cc of hydrogen gas in there.
Pads wear down a bit and suddenly you press the pedal and it gets admitted to the 'business end' of the brake.
 
Just speculating ... could be one reason you're supposed to change the brake fluid every 2 years but few people actually do.