Bottom Bracket Spindle Length ?

hairy_boy

Hi,

Need a little advice on spindle length on a new bottom bracket.

Here is what I am doing:

Taking a square taper chainset off a used Felt frame I have bought to fit it onto a Specialised hardrock sport to sell the Specialised. I will be taking the Hollowtech Deore BB and chainset off the Specialised to fit to the Felt frame.

The Felt frame has a 78mm wide BB shell whilst the Specialised has a 68mm wide BB shell so need to get a cheap square taper BB in 68mm shell width.

The question is, the old (78mm) bottom bracket had a 122.5mm spindle length, but I was wondering should I get a 113mm spindle length on the new BB (68mm) to fit to the specialised. There was around 8-10mm spare space on the left side of the spindle when the crank arms where fitted on the Felt ?

Does a longer spindle basically just give extra length on the left side - I assume on the right (drive) side everything is how it should be to give the right chain line regardless of spindle length ?

If it helps the deore hollowtech chainset fitted to the Specialised currently has the normal 2 spacers drive side and 1 spacer left side and everything works fine - would this indicate a 113mm square taper spindle length should be ok for the Specialised ?

nicklouse

the spindle length will be the same as before.

so a 68 BB with a 122.5 axle presuming you have not typoed that.

73mm not 78mm

hairy_boy

Thanks Nicklouse,

I did typo, the Felt had a 73mm (not 78mm) BB fitted with 122.5mm spindle.

I will order up a 68mm x 122.5 square taper bottom bracket for the Specialised.

Thanks again.

treadzmac

Hi, was just wondering what felt frame model you have. Ive currently got a felt q520 and want to replace the bb but ive no idea what size or type it is. Or will i just have to remove the old one to find that out.

nicklouse

treadzmac wrote:

Hi, was just wondering what felt frame model you have. Ive currently got a felt q520 and want to replace the bb but ive no idea what size or type it is. Or will i just have to remove the old one to find that out.

Frame and year are don't matter other than for the shell width.

The cranks determine the axel length unless it is ISIS which s covered in the FAQs or external.