I have a Shimano Tiagra Triple 30/39/50 and I want to find out what is compatible in terms of smaller chainrings for touring. Ideally, I’d like to be able to go down to a 26 or even a 24 for the smallest. Thinking in term of 26/36/46 or 48. This is a 4 bolt crank and it seems there’s little to no compatibility with other sets.

  • It's a bit more expensive, but since it's a wear item anyway, have you thought about getting a freewheel with a larger range?
    – DavidW
    Apr 19 at 20:22

Unfortunately the asymmetric four bolt pattern that Shimano switched to for these cranks is a new patttern and so far there are no small inner rings available. The best advice I can give is to switch to the older five bolt style crank, for which many small rings are available. I use 26-39-50 on the previous generation of Tiagra with no trouble.


Do you know what BCD is used for the smallest ring? 4 bolt holes could be 65mm or some other size.

https://cdn.shopify.com/s/files/1/0230/9291/files/Measure_BCD_5ad6ccfa-f146-4048-ac0f-e2279602c9e1.pdf is one way to measure it

Assuming your crankset is a FC-4703 then the specs are at https://bike.shimano.com/en-EU/product/component/tiagra-4700/FC-4703.html and suggest its 74mm BCD.

Sheldon says that a 74mm BCD will take a 24 tooth chainring, or 26 and 28 options as well. He also suggests a "deflector" to help the chain make the big jump down from the 39 without missing, to prevent damage to the frame.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.