most likely you have two options, eitehr a +20mm IS to IS adaptor, or a replacement 180mm PM to IS adaptor. From memory the reba forks are IS mount and the XT brakes are PM, and come with a 160mm PM to IS adaptor as standard from Merlin.
Won't be a +20mm IS to IS. Most likely is a 180mm post caliper to IS mount adaptor like [url= http://www.madison.co.uk/searchresults.aspx?vertical=Cycling&style=0&kw=SMMAF180PS ]THIS[/url]
well he could use a +20mm IS to IS, wouldn't be neat though, but would do the job if it was cheap.
Try finding a Shimano +20mm IS to IS adaptor and why would you buy an adapator to adapt your existing adaptor when for the same price you could buy one part to do a much neater job?
Mister P is right, it is just a shimano front 180 I.S. bracket.
I like neat so mister p is your link what you think i need?
One of these front 180mm IS ?
http://www.merlincycles.co.uk/mountain-bike-disc-brake-spares/shimano-disc-brake-spares/shimano-disc-brake-brackets.html
I don't dispute that mister P, however I was giving him options in case he had a +20mm iS lying around, or knew someone who did, or in fact those were XTR calipers, as I can't tell 100% from the picture, in which case he would need a +20mm IS adaptor as XTR brakes are IS mount unlike XT which are PM. Point taken though, neatest and best solution is a 180mm PM to IS adaptor if the brakes are XT.
Mister P's link is exactly the part you need.
Yes they are xt brakes
Thanks for the help guys
and it is sometimes better to know all options but yes simplest/neatest is good in this case
The merlin one is also correct, the second one down.