SRAM Rear Derallieur Puzzle!!

erasmus1

Hi all.....some much needed advice please - I am going mad. :?

Rear Derailleur - SRAM X-0
Front Derailleur - M770 XT
Front Crankset - M770 XT

I have replaced the stock 'custom for specialized' front derailleur and crank (actually last year LX and XT respectively) with the above. I did not replace the existing BB however (XT M762) with the new M770 XT one that came with the cranks as my understanding is that these will be the same in dimensions - and removing the non drive side part is a real bind on the 08 Stumpy FSR Expert due to the hydraulic hoze for the rear FSR Brain being routed directly above the BB non drive side cup - and this is almost completely inflexible. So I opted as I say. to use what is last years XT BB already in situ - and not worry about what would be a small weight difference.

Now all is set up and adjusted as far as I can see - (I am not a novice I dont think ). Here is my problem ladies and gents - Now when my chain is on the smallest front chain ring and one of the smallest three cogs on the rear, the rear derailleur cage is basically horizontal and the chain is obviously rubbing on itself effectively folded over on the top jockey wheel.

Can someone give me sone advice - is there something I am missing on the SRAM X-0 (all previous experience is Shimano) - is last year XT BB different in size to this year's XT M770?? Am I missing a trick?

I generally hate to take my bikes to bike shops to get work done - and I am sure I am missing something quite obvious....can the collective help?

Thanks

E

nicklouse

sounds like either the chain is too long or the mech cage is too short or both.

erasmus1

Yeah thanks N - that was my first instinct - but it didnt do this before I changed the front components?

nicklouse

well if everything is the same size (cog size) then there should be no adjusting to do.
so the issue must have been there before but as they are gear positions you should not use you may not have noticed

cee

nicklouse wrote:

well if everything is the same size (cog size) then there should be no adjusting to do.
so the issue must have been there before but as they are gear positions you should not use you may not have noticed

I get a similar thing in the smallest front and smallest back cogs. Its like the chain is rubbing on itself due to the foldednessnesnesness of the rear mech. As nick subtly suggested, I get round this by ahem not using them....

I also get some mech rub luvin in the biggest fron and biggest back....again ahem i dont use em.

erasmus1

Thanks guys - and yes absolutely right I may simply not have noticed this before - as you rightly say - these are not gear combos I would use 8) . I guess this might just be a case of this being the first time I have gotten the rig up on my stand and really worked on it gear wise.

As a bit of a perfectionist I am I think just worries about messing up my chain alignment - although naturally I checked this and middle cog front and back it looks straight and true in line.