Ratadog – how tight was the chainstay clearance with 113 and is a square taper BB fairly simple to fit?
It looks like somebody else got here with the answer before I did and good on them. My square taper is now on a standard inbred not a 456, but as far as I remember the clearance is much the same and it is as illustrated above. I have never had any problems with it.
Square taper/cartridge BBs are easy to fit provided you have a bottom bracket tool that fits, you take care to get your lefts and rights sorted and check the threads, and you grease the metal threads as instructed. I tend to use antiseize on the threads rather than grease but except on the Ti bike that is probably overkill.
Essentially, the main body is inserted and screwed in till the flange on the cartridge seats against the frame and you then insert the threaded adaptor in the opposite side (shimano says grease it if it's metal but not if it's plastic) and screw that up until it's tight. Then add crank. If I remember rightly you grease the crank bolts but not the square taper itself or the square socket in the crank as the two parts deform each other slightly to produce a decent interface and if you grease the joint you may be able to get the crank on further than shimano wishes.
Park tools page on bottom bracket insertion is here
with lots of links to other relevant pages and lots of insistence that the job can only be performed with their own tools – not unsurprisingly
The product page for shimano's square taper BB is here
and a nightmare to find in their website now they see it as less than mainstream. The pdf files top right are the product info and the fitting instructions.
Personally, I have invested in a copy of Zinn and the Art of Mountainbike maintenance which makes all these jobs seem straightforward and remains the book I have open when I am getting my fingers oily.
Hope this helps.