sapeacock

I apologize if this question has been asked before, but i didn't want to sort through 500+ threads for the answer.

I currently have a compact 50/34 crankset, with 116 link chain, with 12-30 cassette and a shimano 105 short cage. I would like to change my cassette to a sram 1070 11-32. Will my 105 short cage beable handle this or will i need to change it out with something else?

I have read 105 specs that say and quote "30t max capability" then other specs "30t max for triple and 32t max for double" Which is true?

Thanks in advance. I am a weak climber and my goal is to climb this 16% grade 3-mile climb. - Steve

trailangel

On the outside of the box it says
30 max with short cage (SS)
30 max triple and 32 max double with long cage. (GS)

FBinNY 

There's a bit of fudge room beyond the rated capacity. Part of the issue relates to the crankset and the total chain take needs. You have 16 teeth spread up front, and 18t in the rear for a total of 34 teeth now, and will be going to 36.

I'm not going to look up the published capacity, you can do that for yourself and see how far you're pushing it.

IMO, the odds greatly favor this working if you set it up carefully, but make sure the chain is long enough to wrap the larger sprocket (large/large + 1" slack). I don't think it's come to this but you might need to measure the chain long, and not be able to run the small/small combinations.

sapeacock

Thanks for the replies. I'm gonna play it safe and get the 105 rear derailleur - RD-5701-GS - long cage for the larger cog and change to a 12-32 cassette for the small to small chain combo slack.
This will be the route i take, unless i hear otherwise.

Thanks Much!!! - Steven

drdave943

There is a good link to help. If you are using a Shimano 105 5700 this page

https://techdocs.shimano.com/media/te...9830702204.PDF

gives the specs.

You can find other derailleur specs for Shimano at the techdocs.shimano.com by just searching RD5600 or RD6700 etc.

FYI this doc says both the SS and the GS will only handle 11-28 cassette. The GS will handle a wider range on the front.
As a newbie, I can't say if you can go with a 12-32 even with the GS.

Another link that might help with compatibility is
Celebrazio: Bicycling - Shimano Road Bike Parts Compatibility

It has all the cross compatible choices and shows which cassettes (Shimano only) can be used with which derailleurs.

Gnosis

If it were me, I’d forego the purchase of a Shimano 105 GS rear derailleur and instead purchase a far more capable Shimano mountain bike 9-speed rear derailleur.

The Shimano 105 GS rear derailleur can only handle (officially) a max rear cog size of 28 teeth and has a chain wrap capacity of 39.

Conversely, all Shimano mountain bike 9-speed rear derailleurs can handle a max rear cog size of 34 teeth (36 teeth on certain models) and have a chain wrap capacity of at least 43 to 45.

A Shimano 105 GS rear derailleur came on my Trek 2.1 road bike triple and I’d replace it with a Shimano 9-speed mountain bike rear derailleur in a heartbeat if I needed to install an 11-32 or 12-32 10-speed cassette in place of my 11-28 10-speed cassette. I’m not impressed in the least of ways by the Shimano 105 group.