I purchased a Cube LTD a few months ago and decided to upgrade the chainset for one that had 48 teeth on the outer ring because 42 was just not enough.The crank I took of was a FC-M780 and I replaced it with a FC-T781;

http://www.bike-discount.de/index.ph...ils&pdid=47443

I realised I would also need to replace the front mech so I purchased a FD-T781 thinking that this would be compatible;

http://www.bike-discount.de/index.ph...ils&pdid=47442

I could not set it up and I put it down to being crap with gears so I took it to a LBS. They could not set it up either and said that that it looks like it is incompatible even though they looked it up on shimano website and shimano says it is compatible.

So, they recommended a XT-M770 with states it goes up to 48T;

http://www.chainreactioncycles.com/M...?ModelID=52285

Today, when I have gone to set it up, I can shift into all 3 front ring but I get rubbing when at either the biggest 3-4 biggest cogs on the cassette. If I adjust to eliminate this, I get rubbing on the 3-4 smallest cogs. This happens in all three front rings. Also, the H limit screw does not allow the FD to go far enough past to stop the chain rubbing the outer plate on the FD when in the biggest ring up front. This is similar to the problem they had at my LBS, they could only set up the other FD in the middle and out or the middle and inner as it would not even shift into the inner when the outer and middle where set up.

This front crank is only available in Germany and the USA, no shops in the UK stock T780 components which is making it harder to find completable components.

The shifters I have are SL-M780 which are also used for trekking components according to Shimano website as I though this could be a compatibility problem regarding the shifters but it does not seem so because the FD-T781 should be compatible.

What do you think the problem could be ? This is giving me such a headache and the LBS are going to be confused when I go back with the recommend much but still having a similar problem.

If you need to know what other conponets I have relating to the drive train I can post them too but please recommend me a front mech that will fit a FC-781 chainset.