Hi everyone
i need a bit of advice, im doing up a hotrock 20″ for my little girl
ive noticed that there is alot of play in the cranks coming from the bb
ive looked up the bb size and its 68 shell x 128 axle square taper
thing is i can only find 1 bb like this at £17 but i can get a 68 x 122.5 for £8 will this be ok ? and what diffence will it make
im trying to keep the cost to a minimumand its only a kids bike so not much wear
all advice greatfully received
thanks pete

A lot of hotrocks use an old style adjustable bb

As for changing bb length what size hot rock is it

ebay?
http://www.ebay.co.uk/itm/Sealed-Bottom-Bracket-English-Thread-RRP-19-99-/350354724489?pt=UK_sportsleisure_cycling_bikeparts_SR&var=&hash=item5192c4d689

It’ll move the chain line in by 3mm, so long as there’s enough clearance between the chain ring/crank arms and stays the shorter bb axle will work out just fine.

It will move each crank arm in towards the rear chainstays by 2.5mm, this may cause a problem with chainline to the rear cassette and with the cranks hitting the rear chainstays but in all honesty i seriously doubt it will make that much difference, you may have to check you have enough clearance at the chainstays to allow you to lose 2.5mm but i’m sure it will be fine. You will also have to adjust the front mech stop screws, if in fact there is a front mech fitted, otherwise bash on.