Short Cage / Cassette / Crank Question

mottone

Hi All,

Quick Techy question. I have a Trek Madone, set up is as follows;

Cassette - Shimano Tiagra 12-30, 10 speed
Crank - SRAM S350, 50/34 (compact)

Im running this with a short cage Shimano 105 rear derailleur, is that correct? This is how it came direct from the dealer. I had to take it to my local bike shop for something else and had a lengthy conversation in which the head mechanic was adament I should have a long cage with the above set-up. I checked with Trek direct and they assured me that the short cage is the right set-up / standard issue. I'm no mechanic myself, but I stuck with the short cage. Am I foolish in doing so?

Just wondered what people in the know thought?

Any help at all is much appreciated.

Cheers.

rolf_f

I think recently Shimano recommended that the maximum size cassette for a short cage on a 50-34 setup was 28 teeth. I think this is now 30 but even the older mechs might be fine for 30 depending on the specifics of the frame design. If you can select big-big without exploding your chainstay, then you should be fine.

I sometimes run a 29 tooth cassette on my Ribble with Campag 2010 10 speed short cage which isn't supposed to work but is actually fine.

mottone

Cheers Rolf, much appreciated.
The chap was clearly unimpressed when i stuck with the short cage. More fool me when it all goes wrong!

smidsy

You do not say which version of 105 but the 5700a rear mech can certainly go to 30t with a short cage.

http://techdocs.shimano.com/media/techd ... 746860.pdf