Bottom bracket spindle length selection

[Grebel]

Please help....

 

I am in the process of putting together a MTB for my son. We have been collecting parts for a while. The box of bits has grown substantially over the last few months and we are almost ready to roll. I am in the process of buying cranks and a BB. The shell width is 68mm but I am not sure how to select spindle width.

 

It is going to be a 1x9 setup with the possibility of a bash ring and a chain device being added at a later stage. The spindle length options available are 110mm, 113mm and 122,5mm. I understand that the spindle width will determine the chain line which will have to suit the FD position which is dictated by the seat tube diameter.

 

On a 1x9 setup, is the spindle width important seeing as there is no FD or will a middle of the road approach be fine. I was heading towards the 113mm spindle.

 

Thanks in advance.

[Johan Bornman]

Trial and error.

 

Go for the 113 and then tune the chainline by moving the rear sprocket around with the use of spacers.

 

You don't say if it is a converted 3x10 crank and where the chainring will be situated. If you use the granny position, go even shorter.

[Grebel]

Hi Johan,

 

I am looking at a Shimano m442 (?) 3x9 crankset on a square taper 63mm bb. Will be running 9 speed casette with a single shifter and will probably fit a chain device if I have trouble. My reasoning was that the 113 was somewhere in the middle so it would give the best compromise with the chainline.

 

I am planning to take the granny ring off and use the 32 middle ring with a bash guard in place of the big ring.