Tiagra 4500 with 4600 compatibility?

rflynnr

Stripped the interior threads on the left hand (non drive side) Tiagra 4500 crank on my hybrid last week. I want to replace the crank but have experienced some uncertainty from shops as to whether I can buy a left hand crank separately (i.e. without getting an entirely new crankset). A new Tiagra crankset on Rosebikes is €67 inc. postage. However, the new crankset will be Tiagra 4600. Is there any reason to think that won't work with the 4500 front derailleur and shifters? I've done some research looking at forums elsewhere and Shimano's own techdoc site. The forums haven't addressed the problem and the techdoc for the 4600 crank only lists post-2011 Tiagra (i.e. 4600), 105 and Ultegra parts as compatible. I guess what I'm asking is whether anyone knows whether there has been a fundamental difference introduced in the 4600 chainset (different spacing between chain-rings?) that might require changing the existing 4500 shifters and chain?

Cee-Jay-Cee

Not sure if this is any help to you but my 9spd Tiagra bike has a 10spd crankset and chain.

cython

I have an 8 speed setup with a 9 speed crankset, so I wouldn't think you'll have much in the line of issues. Potentially if you were looking at a triple you might have issues in fine tuning the shifting, but for a 2 chainring setup I'd say you'll be fine. Worst case scenario if the spacing is slightly closer you might have to take in your lower limit on the derailleur and have some slack in the cable in the small ring, but even that seems unlikely.

rflynnr

I ended up contacting Cycleways for some advice/pricing on a triple and they seem confident that the spacing between the rings on a 4500 and 4600 is identical. Given this I have to assume that the Shimano Tech Doc's failure to list 4500 series shifters as compatible with 4600 series cranks is either a) simply an innocent omission or b) an attempt to encourage purchases of complete groupsets rather than upgrading in a piecemeal fashion. Either way, thanks for the replies guys.

rflynnr

Just to complete this thread - having replaced my Tiagra 4500 crank with a 4600 at the weekend I can definitively confirm that the latter is compatible with all the existing bits of the 4500 groupset (shifters, front derailleur etc.). Just in case anyone else faces the same issue at later date.