Space_doodle

Hello, I recently bought new crank arms because I wanted them shorter. Original pair that came with be Ike are pictured on left and new ones the right. They are different in more ways than length. What does the td vs vl mean? I might not care except that the originals (on Giant from lbs) had 3mm spacers on each side but when installed spacers on new cranks the left arm would not go on all the way. I took them out and everything looks good. The Shimano dealer's manual says that some models of cranks don't need spacers but how do I know what I have? M7100, m7120 and m7130 are listed on these arms! As is the this td or vl business that I can't find information on anywhere. Many thanks in advance for your help. P.s. just replaced the arms and not the chainring.

RCMoeur 

TD: manufactured in April 2021.
VL: manufactured in December 2023.

Space_doodle

That's awesome, thanks for image. Doesn't explain why the 175s came with spacers that won't fit on the 170s, though.

KCT1986

Is the picture of the left arm? Is the right arm marked in the same manner, with multiple model numbers?

Shimano sometimes mark crank arms with specific model numbers on the right, but multiple model #s on the left side when the part is common.

maddog34

spacers cost money to make. the new arms don't need the spacers and are therefore less expensive to produce, offsetting material cost inflation.

Space_doodle

Thanks everybody, for the version codes and suggestion to look at the right crank arm (duh). Mystery solved. Thanks.

KCT1986

So, did you find that the model # is different between your cranks?

The different models of the crank varies in the length of the spindle and has a small effect on the chainline & thread width (Q factor). This allows options, depending on the frame specification and chainring(s).

The selection is based on the rear dropout spacings, configuration of the chainstay or other factors.

Space_doodle

My new cranks are m7100 whereas the originals were m7120. My understanding is that the old ones are boost only but the new ones can do either, the downside being tight frame clearance and narrower tire choice. The more inboard chainline might help shifting in lower gears but I don't know yet. Correct me if I'm wrong.

KCT1986

Yes, that is exactly what I expected was happening.

The chainline difference would be 3mm, a little less than 1 sprocket inboard, usually not really noticeable. Just something to remember if you change chainrings and currently have tight clearance there. The change in crankarms width is 6mm, only possibly effecting the items you mentioned.