XT M775 Disc Brake problems
 

Yesterday I went out to ride and by the second half of the ride, my rear disc brake lever was acting up. Normally it doesn't engage till I pull the lever about a cm but it became Instant brake. Braking power wasn't effected though.

I don't know, maybe it is the Temperature. It was 25F yesterday but when I rode a few days earlier, it was no more than 20F. Yesterday there was a bit more fluffy snow on the trail though.

Any thoughts?

One of my co-workers commented the other day about how his (Shimano hydraulic) disc brakes were acting kind of strange when he was riding in sub-freezing temps. I remember he said they had a different feel, but I don't remember exactly what he said the difference was. Based on that, I would say it's quite possible the temperature was the cause of your brakes' different feel.

We don't ride too much in subfreezing temps around here, so this isn't something we deal with very often.

Now that I've thought about it, my friend said his brake calipers/levers didn't seem to rebound normally in the cold temps, in other words, they felt sluggish in this way. I wonder if your brakes feel as if they're engaging much more quickly at the lever because they're not rebounding much from the last time you engaged them.