Ok need a hope HBSM20H to run an IS caliper on a post mount fork but what size disk will I need 180mm or bigger.

Cheers, Geoff.

Whatever size disc the caliper is for, +20mm…

I got a hope caliper for 180 ish and now run 200 ish with that adaptor..

And to make life easy setting it, you need ball end allen keys, its doable without but its a pain in the arris.

HBSM20H is that this one? –
http://www.hopegb.com/voir_ADAPTMANAV.html

be careful not to mix it up with a Hope 'H' adapter as that is 183 post to post

you will need a 20mm bigger disc, so on front 74mm post mount forks I think[/i] that means a 180mm disc (based on the fact that I have a post mount Hope caliper mounted direct on my post mount forks and it runs a 160 disc)

I've got a HBSM20H adaptor going spare if you need one

What forks are they…ended up having to take a dremel to both forks and adapter to a pair of DTs recently…if you were running a 183mm disc you will need a 203mm now