I replaced the front brake pads following a youtube video as I went.

Everything seemed to go well but when I tighten the allen key bolt back into the calliper it seems to cause the brakes to stay engaged. If I back this bolt out abit everything seems to work fine.

I'm just concerned now that the bolt isn't tight tight it might unthread during a bumpy ride.

Should this bolt be really tight or it supposed to be left a little loose? What could be preventing me from tightening it down?

Many thanks!

 

My only guess is to go back over your doings and check if you installed properly.did you take break lines a loose while doing this ?

 

The small hex head socket screw on the caliper is just to make pad removal/installation easier by removing it which allows the caliper bracket end to move a bit further back. When both calipers are done,new pads installed and the system pumped up,just install the screws. While turning the rotor slowly(with the tire off), turn the screw in until you feel a slight drag on the brake rotor,then back off 1/8 turn on the socket screw. Then do the other caliper. What this does is to help align the caliper with the rotor and sets the distance between the inner brake pad and rotor.