 You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
which type do I need??
Its for my Boardman Comp Racing bike (about 6 years old)
I cant work out what type of brake they are but the rest of the groupset is Tiagra. The pads attach to the mount via a single allan key bolt in the back which screws into the pad. Any ideas?
Chainreaction seem to do hundreds of different types - im not sure about standards with road bike stuff.
Sounds like Cartridge brake pads.
The metal casing holds the pad evenly against the rim and in theory makes it easier to reset the brakes when you change the pads, because you might not need to adjust the pads position, just the cable. Usually you only need to remove a small retaining screw to allow the pad to slide out - the closed end of the backing should clearly be facing forward, so the pad is retained NOT by that pin, but by the casing.
Usually they look like this
[img] 
[/img]
and In my experience they are the same fitting for several companies.
I suggest you take yours out, pop in to a shop with it and get some Shimano pads that fit from them. Then armed with the name of the Shimano brakes that those pads will fit [check the pack] I'd buy Swisstop ones in the future, as IMHO Swisstop are the best quality for rim-brake pads.
http://www.swissstop.ch/road.aspx
Swiss stops are good, Ultegra 6700 are the best I've used, think current Ultegra is the same compound. Not as ultimately powerful as Swiss stop maybe but the modulation and way the power comes on is superb, no grab but a huge amount of control.
Definately get Swiss Stop pads - well worth the expense and your braking will be miles better.