I have a 53-39 chainring and 9sp Shimano drivetrain, and I’m looking for lower gears for climbing the hills in my area. I have a 12-27 cassette now. I’ve read about a 13-30 rear cassettes. There is a Century Special from Harris cyclery, for example.
Has anyone tried this? Do I need to change the chain and cage going from the 12-27 to the 13-30?
Thanks!

I have a 53-39 chainring and 9sp Shimano drivetrain, and I’m looking for lower gears for climbing the hills in my area. I have a 12-27 cassette now. I’ve read about a 13-30 rear cassettes. There is a Century Special from Harris cyclery, for example.
Has anyone tried this? Do I need to change the chain and cage going from the 12-27 to the 13-30?
Thanks!

The first is the largest cog issue. Shimano road derailleurs are indicated to handle a 27tooth maximum large rear cog. Most likely, if you simple install a cassette with a 30, the upper pulley will rub the 30 tooth cog. The way around that is to dial the "B" adjustment screw in the back of the derailleur all of the way in. That will pull the derailleur back so that the pulley is behind the cog and won't rub. You may have to substitute a longer B screw or install it backward in the derailleur to get it to work.

The second is chain wrap. It's important to have a chain that is long enough to safely cover the big/big combination. If your chain is too short and you accidentally shift into that combination, it will pull your derailleur into the spokes and wreck lots of expensive stuff, maybe even your whole frame. As long as your chain is long enough you'll be OK. If your chain is a little too long for the derailleur to take up all of the slack in the little/little combination, it's still probably OK because your not likely to use that combination anyway.

You'll probably need to add a link or two to the chain to make it work (though perhaps you should change the chain anyway for the new cassette), but I think that Sheldon assembled that combination specifically to be compatible with existing non-MTB derailleurs.

Trent

Thanks for the quick reply. OK, so I definitely don't want to wreck my rims or drivetrain, so I will need to have enough chain - and ensure clearance. I'm less concerned about the small-small combo since I won't use it and even if I accidentally get into that range it sounds like I won't wreck anything, just have a loose chain that may drop.

Thanks

Why not find yourself a smaller chainring than the 39? I have a 36 I use for centuries that are hilly. It goes on and off in a flash...and no need to change cassettes or chains.

Why not find yourself a smaller chainring than the 39? I have a 36 I use for centuries that are hilly. It goes on and off in a flash...and no need to change cassettes or chains.
38 is the smallest you can stick on a shimano 130BCD crank.

Compact crankset would be the answer to get down to 36 or even lower. A super-wide range rear cassette would have alot of large jumps, IMHO.

Putting a smaller chainring isn't a bad idea, instead of replacing the cassette with 13-30. I think the FSA compact crank is a 50-34 and should just be able to replace the 53-39 with same bottom bracket, and leave the 12-27 rear. Doing the calculations, that would actually give a lower ratio with 34 chainring and 27 cassette (1.26) than the 39 with the 30 cassette (1.3). On the high ratio, the 50 with the 12 would be a higher ratio also (4.167) than a 53 with a 13 (4.0). So that means that with the compact FSA crankset I'd get both lower low and higher high with the 12-27 than the standard crankset with the Harris 13-30 cassette.
Anyone see anything wrong with this FSA compact combo?
Thanks

I run FSA's carbon pro compact 50/34 with a 12/27. Standard front derailleur shifts it fine. FSA makes an alloy version, Energy, I think Bulltek sports carries them, as well as the carbon version. ISIS bb's seem to have somewhat of a poor reputation on this board, but I've run the FSA Platinum Pro Ti ISIS for 2plus years on mtb, and a year now on my road bike with zero problem FWIW.

Putting a smaller chainring isn't a bad idea, instead of replacing the cassette with 13-30. I think the FSA compact crank is a 50-34 and should just be able to replace the 53-39 with same bottom bracket, and leave the 12-27 rear. Doing the calculations, that would actually give a lower ratio with 34 chainring and 27 cassette (1.26) than the 39 with the 30 cassette (1.3). On the high ratio, the 50 with the 12 would be a higher ratio also (4.167) than a 53 with a 13 (4.0). So that means that with the compact FSA crankset I'd get both lower low and higher high with the 12-27 than the standard crankset with the Harris 13-30 cassette.
Anyone see anything wrong with this FSA compact combo?
Thanks

I also run the FSA compact 50-34 crank with a DA 12-27 and can climb just about anything. However, if cost is the main consideration for Bwong88, then perhaps the 13-30 cassette and chain swap would be the ticket.

and it worked fine. I experimented with the 13x30 cassette from Harris Cyclery to use at Six Gap, specifically for Hogpen Gap. Like another poster stated, all I had to do was run the b-screw in until the upper pulley cleared the 30t cog. I also installed a chain with a Sram connector link to use for this cassette. The front and rear der. shifted fine.

As it turned out, I prefer to grind up Hogpen with a 27 so I sold the cassette, chain and connector to a friend who also used it with no problems.

Frankdl and lithiapark: When you used the compact FSA did you have to shorten the chain - or change the rear cage? Or is it a straight swap of crankset?
The carbon FSA compact is expensive, but I have a carbon FSA now.
Thanks
bwong88

Frankdl and lithiapark: When you used the compact FSA did you have to shorten the chain - or change the rear cage? Or is it a straight swap of crankset?
The carbon FSA compact is expensive, but I have a carbon FSA now.
Thanks
bwong88

I installed a new DA chain and had to remove 3 links. Hope that helps. Good luck!

Frank

You probably would want to lower the FD on the Seat tube a little to help the front shifting, but I agree, its simple.