i need to replace the non sealed bb in my sons 700c wheeled commuter bike.i will fit a cartridge as a replacement but how do i know what axle length to buy? do i i just measure the old non sealed axle length and get the same?
what if i had bought a bare frame and chainset seperatly? how do you then know what length you need?
please explain!!
measure the old axle length.
for new builds, can be a bit hit and miss depending on compoments and frames.
how do you then know what length you need?
The manufacturer of the cranks should provide you with the correct axle length to buy.
"can be a bit hit and miss depending on compoments and frames"
my LBS told me this or simular and said i would be best to take it there as they had all the sizes and so it was a case of trial and error...
seemed a bit inacurate to me and i thought there must be a more precise way of doing it?
"The manufacturer of the cranks should provide you with the correct axle length to buy."
this is probably true but this is me we are taking about, the tightfisted skint optimist, i havent and prob never will buy NEW cranks!
What cranks are they?
Is it a single ring or double/triple?
triple.unknown brand (cheapo)
p.s. if i was to remove the granny ring, as he doesnt need it, would/could/should i change the chain line or leave as it was?
In terms of operation I don't think changing the chainline if you remove the granny ring will make that much difference.
Double's tend to have a shorter bottom bracket axle than triples (Taking Stronglight road chainsets as an example recommended lengths for a double = 107mm, triple = 110mm). So you could measure the old one and then go slightly smaller for a better chainline but there is a risk that your chainset will be too close to the chainstay.
so if i measure the distance from tube to middle ring on the old one i can get an idea of spacing and then work out the length needed for the new one?
presume the axle sits exactly central and protrudes each side equally (sorry if thats obvious!)