Narrowed down the noise to the BB (I think), it's a SM-BB70, old model XT?
Looking at current XT, MT800, the cups look smaller overall. Is the tool the same? If not, is it worth changing to new standard or should I buy a third party version from Uberbike or somebody?
it is a different size but when I bought a new BB I got the adapter with it to fit the old tool to the new cups
As above, the later road and MTB higher end bottom brackets are supplied with a plastic adapter that fits inside the original tool - if from a reputable dealer!
Shimano now have 3 "standard" hollow tech BB cup sizes;
16 notch 44mm Older hollowtech
16 notch 41mm "New" Ultegra 6800, MT-800
16 notch 39mm "New" XTR, Dura Ace
Some of them also fit mid drive lockrings, some STEPS etc
Its annoying.
You get an adaptor with them so it doesn't really matter
Watch out if you are hamfisted and the bottom bracket is very tight in the frame as they are made of plastic and can split. Yes I am hamfisted.
Was looking for a bottom bracket myself a couple of weeks back looked at the XT 8000 but most didn't supply the adaptor you had to buy separate (£5 for a piece of plastic) so just got one from Uberbike & you can replace the bearings...
