Chainset and BB help please

wishitwasallflat
wishitwasallflat Posts: 2,927
edited November 2013 in Workshop
looking for help and advice once again folks ...

I currently run the 175mm Compact 50/34 chainset that came with my 2011 Specialized Sectuer. It's labelled SRAM but its not series (i.e. its not marked Apex, Rival, Force or Red etc) and it works with a 68/108 Power Spline BB. At a recent fit the fitter recommended I change to 170mm cranks because of a knee problem.

Now I have read the many many threads where many say you can't tell the difference while some others say you can and cite the one published article. I reckon it looks like some can tell a difference and some can't and so I won't know till I try. I fancy trying but if possible I want to do so cheaply. I spotted this today -

http://www.ebay.co.uk/itm/BRAND-NEW-unu ... 33872196c2

and wondered if I was correct in thinking I could transfer my current chainrings onto this cranks arm set and also use the same BB I have and get the same chainline and an ok set up? Would that work or is there some compatibility issue I don't know about? Would the chainline be ok its standard road at 43.5mm.

Comments

  • Thanks madas... It was Peacocks in Newcastle and the fitter is a podiatrist called David Eardley. I know there's doubt and controversy about cranks and leg length but I reckon it worth a try if costs allow. My inside leg is 30.5 on both sides but my femur and tibia are different lengths so he reckoned 170mm was the best compromise. It feels to me like less flex at top of stroke would be good but who knows for sure until you try?

    Thanks for the info and seller has replied to say he thinks the crank is FSA Powerdrive not Powerspline as listed. FSA Powedrive and Truvativ Powerspline are apparently not compatible so as you say it would need a new BB as well to make this work. That still may work out cheaper for me though as I cannot find anything Powerspline anyway.

    Thanks again for the reply.