Crank Spin

timbo_tim

Hi

A bit of a strange question but on a normal 20-22 speed road bike, if you spin the cranks backwards does it make it past one complete revolution? I borrowed a bike recently and it felt like it spun almost twice suggesting to a novice bike mechanic like me that my bike(s) may not be in the best shape in some way? If that is the case, can anyone shed any light on what I can do, if indeed there is something worth doing, to improve my steeds. It may be psychological but a freely spinning drivetrain feels / sounds like it is well looked after without any bad resistance somewhere in the set up? Am I way off the mark here?

Thanks

fenix

Why would you pedal backwards ?

Theres lots of things that could affect that factor - how hard you pushed - what gear you were in - wear on the chain or sprockets.

I'd not waste any time thinking about it - there's nothing to be gained thats measurable.

timbo_tim

Thanks, it was more a "test" when off the bike - spin the pedal / crank and see how freely it spins. I seem to recall reading somewhere that a pro-bike spins more / better. On the assumption that it goes well one way, then presumably the important, going forward motion is equally free and therefore more efficient.

Not going to lose sleep over it, just wondered if there was any consensual perceived wisdom...

slowbike

ok - you're checking for drag ...

check the crank separately - remove the chain and see how well they turn - there shouldn't be any (well perhaps a little bit) resistance. If that's not turning right then you need to look at the bottom bracket.

Whilst the chain is off you can check the jockey wheels on the rear mech - they should turn freely - if not, take them apart and clean them up.

Still without a chain attached - try the cassette - it won't spin so much as there are pawls that will cause it to click - but it shouldn't drag hugely.

Finally - whilst you've got that dirty chain off - put it in a pot and give it a clean up ...

Job done

keef66

You can get a crank to spin very freely by removing the bearing seals and lubricating them with light oil. They won't last very long like that though. Ceramic bearings you can allegedly run without any lubricant at all...

I'm happy to accept a tiny amount of drag from the seals on my HT2 bearings because I know they are keeping the water out and the grease in.