Brake mounts!!

I need new brakes for my Xc bike, the fork is Post mount but the brakes I'm looking at have IS mounts, so do I need a IS to Post mount or a Post to IS mount?? Also as I need an adaptor will I be able to run a 160mm disc or do I need to go up to a 180mm. The brakes are XTR, cheers for any help.

IS to Post and yes you need to go to 180mm - I'm 90% sure but would be glad to hear confirmation from Al, Stu, Gerry etc!

http://www.chainreactioncycles.com/M...?ModelID=13735

That's what I thought but wanted confirmation too, cheers Richard. Merlin have a sale on at the moment which Ive been trying to ignore but the Xtr brakes work out at a very good price, unfortunatley they only have the IS caliper and not the Post caliper so might have to settle for bracket and bigger disc option!

ya 10% off on Merlin, Im getting a pair of Avid Elixer 5's for €136.

yeah you need to go to a bigger rotor as with adaptor. Although given the reason for going for xtr is to have lightweight the difference over xt will be ruined by the adaptor two xtra bolts and bigger disk. I'd get xts as they'd end up about the same weight. Xts have a bigger oil reservior in the lever than xtrs so the oil doesn't over heat as easily so they are less prone to fading on long descents and are a better performing brake.

Sorry Al but i don't get that, the oil isn't pumped around the braking system when you break (meaning like a cooling system in a car, it flows in a one way system to keep cool) so how can a bigger reservior be any better? The oil is pushed down and doesn't flow. Also by adding a bigger reservior your adding weight, not only because the reservior is obviously bigger but the oil that has to fill it.
Break cooling is all down to how the disc's are vented and what the calipers/pads are made from and what design they have, it's how it's dispersed under pressure, not by the size of the reservior.
Also the bigger the disc the less pressure you need to apply to create sufficient stopping power thus less heat generated and less fade.

Take big cars and big bikes for example, they all have big vented discs and 6 or 8 pot + caliper brakes.

You'd also need rear adaptor, or a 140mm disc (not supplied) with that offer.

I know the oil isn't pumped around like cooling but having more oil in the system helps with stopping the brake overheating. More oil does mean more weight. Given that to get the IS xtr calipers to work with post mount your going to have to add a adaptors and a bigger disk etc adding weight bringing it closer to the weight of the heavier xts. Im suggesting it may be better to get post mount xts that will perform better and probably be cheaper. The xts have numberous advantages over the xtrs. The only advantage of the xtrs is that there lighter which is being taken away by adding adaptors etc to make them work so why bother.

Thanks for all the help guys. Doesn't seem to be much point in getting IS front caliper and then adding weight of bracket and bigger disc, also I didn't really want to go bigger than 160mm. Might just wait till CRC get back in Post mount calipers. Al could you PM a price for a set of XTR s with post front caliper and the new 6 bolt Floating xt discs, cheers.

The reason more fluid helps cooling is that heat is transfered back up hoses from caliper into a large reservoir with cool fluid in it .This cool fluid absorbes the heat from hot fluid in hoses. Next please .Coach Byrne says Stay off the brakes yez benders so no worries.