TA 314/344 bottom bracket chainline question

[sawston_vulcan]

Would a 344 axle be a total disaster for the chainline?..I know getting a 314 is best but they are difficult to find.

A 314 axle=111.5mm and a 344 axle=116mm. A total of 4.5mm difference which equates to 2.25mm on the drive side. Could i use a washer to move the sprocket out 2.25mm as a counterbalance to the extra width of the 344 axle? Alternatively, will 2.25mm make that much of a difference? Its just that 344 are much easier to source than the 314 BB/axle.

 

[daccordimark]

Would the extra length be split equally or would it be mainly on the drive side seeing as that's where you need the extra length to accommodate the double chain rings?

Mark.

 

[one-eyed_jim]

Would the extra length be split equally or would it be mainly on the drive side seeing as that's where you need the extra length to accommodate the double chain rings?

Sheldon gives this table of dimensions:

http://sheldonbrown.com/harris/images/ta-bb-axles.gif

i.e. 3mm more on the drive side for the 344. It looks as though reversing the spindle would improve matters by 1mm.


sawston_vulcan:

Assuming the 314 would give perfect chainline with the hub you're using, 2mm discrepancy is more than is ideal, but normally within workable limits. A steel Sturmey spacer under a fixed sprocket works well for chainline adjustment, or axle spacers can often be arranged to adjust the chainline.

I have a set of TA Pro track cranks and various bottom brackets lying around. If there's anything I can measure for you, let me know.

 

[sawston_vulcan]

Would the extra length be split equally or would it be mainly on the drive side seeing as that's where you need the extra length to accommodate the double chain rings?

Mark.

Mark...it is for a fixed gear bike...so single chainring...ideal BB is the 314 but are hard to find....according to SB....for a 314 drive side is 2mm longer than non-drive side and 344 is 3mm longer on the drive side than the non-drive side

 

[sawston_vulcan]

Would the extra length be split equally or would it be mainly on the drive side seeing as that's where you need the extra length to accommodate the double chain rings?

Sheldon gives this table of dimensions:

http://sheldonbrown.com/harris/images/ta-bb-axles.gif

i.e. 3mm more on the drive side for the 344. It looks as though reversing the spindle would improve matters by 1mm.


sawston_vulcan:

Assuming the 314 would give perfect chainline with the hub you're using, 2mm discrepancy is more than is ideal, but normally within workable limits. A steel Sturmey spacer under a fixed sprocket works well for chainline adjustment, or axle spacers can often be arranged to adjust the chainline.

I have a set of TA Pro track cranks and various bottom brackets lying around. If there's anything I can measure for you, let me know.

PM sent....it will be easier!