I've got some shimano xtr disc brakes, which are being sent back to madison for a warranty claim. Was trying to disconnect the rear brake, but the head of the bolt that attaches the brake hose to the caliper rounded when I tried to unscrew it.

Any suggestions on how to undo this bolt now?

Cheers

Hacksaw a slot & use screwdriver.
Or find a drill bit & carefully drill till head pops off.

I would tap an equivelent torx head with a hammer into the hole that has been made… and undo the bolt with that.

get a screw extractor set, only about £5 , drill a small hole in bolt head and insert exstractor, it worked for me.

neverfastenuff – Member
I would tap an equivelent torx head with a hammer into the hole that has been made… and undo the bolt with that.

+ 1

This works really well and is the easiest and quickest way to do it.

Are you talking about the older ones – with the banjo style connector?
If so then working the banjo bit back and forth with some pliers will walk the bolt out.
If its the straight connector then get going with the molegrips

the head of the bolt that attaches the brake hose to the caliper

molegrips

moles or torx. with the bango method if pos.