My new, and so far unused, bike came with a push fit bottom bracket and SRAM double chainset but I would like to convert to my old SLX chainset with single ring only. I understand my SRAM bottom bracket is not compatible with my SLX cranks so would ideally like to convert to an external bottom bracket. I understand there is an adaptor for this purpose, is that correct? I know I could get a push fit bottom bracket to accommodate the SLX cranks but by moving to external bottom bracket if gives me an easy way of attaching a chain guide. The bike has a direct mount front mech and the direct mount chain guides are not only ugly but also very rare. Any advice would be greatly appreciated.
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You won't be able to fit a BB mounted chain guide on a press fit frame, it would spin!!
Also you cannot convert a GXP push fit BB to an external BB, you will either have to buy a shimano, raceface or superstar press fit BB or convert your SRAM cranket to single.
Only the larger BB30 can be converted to a normal BB by using something like this;-
http://www.evanscycles.com/products/race-face/pf30-bottom-bracket-to-24mm-spindle-converter-ec045222?utm_source=froogle&utm_medium=froogle&utm_campaign=froogle&utm_content=mkwid__pcrid_17321847296_kword__match__plid_