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Front and rear chain ring combination for climbing(10 posts)

Front and rear chain ring combination for climbingBanky
Jun 2, 2003 9:21 AM
I am a FLorida boy who rides in the flats,in addition I weigh 205 lbs. This September I am going to a ride in the Northern Georgia Mountains called the Six Gap Century. The grade at some points is 14%. Can someone give me some Ideas as to what would be the best combination of front and rear chain ring setups for a double. I am thinking of a 39/53 w/ a 12-27. Are there other options availabe? Thanks
re: Front and rear chain ring combination for climbingChen2
Jun 2, 2003 10:32 AM
It really depends on how strong you are. A 14% grade on a century ride sounds tough to me. A lot of riders will tell you that a 39/27 combination will be fine, but I would have problems if that 14% grade is very long. You could replace the 39 with a 38 or you could make or buy a custom cassette with a big cog up to 30t. I converted my wife's 12-25 D-A cassette to a 14-28 using cogs from www.sheldonbrown.com. Just remember that the smallest cog must have a "built-in" spacer to work with the lock ring. Good luck with the ride.
re: Front and rear chain ring combination for climbingBanky
Jun 2, 2003 11:50 AM
Is the conversion difficult, How much was the custom cassette, will sheldon be able to assist. Also where can I locate a 38 front?
re: Front and rear chain ring combination for climbingxcmntgeek
Jun 2, 2003 12:19 PM
A one tooth difference (38 vs. 39) in the front chainrings won't make that big of a change. I know people who have put a mountain bike cassette on for situations such as yours and they have been very happy. Try a 12-30 XT or, of you run Campy, they make a 12-29 that would be perfect.
re: Front and rear chain ring combination for climbingBanky
Jun 2, 2003 1:57 PM
forgot to mention I have shimano, Campy may not be the ticket, the XT is shimano? If so that may work.
re: Front and rear chain ring combination for climbingChen2
Jun 2, 2003 2:51 PM
Don't try to run Campy with Shimano, it's possible but the shifting performance probably won't be acceptible. If you want to build a custom cassette try www.sheldonbrown.com. Yes he can help you. As you go to larger cogs, 28, 29, or 30, you need to check to make sure your chain is long enough and you may need to adjust the "B" screw on the rear derailleur. If you want to go larger than a 30 you really need to run a mountain type rear derailleur. A mountain cassette and rear derailleur will be completely compatible with your 9-speed shifters and chain but you will need to add some chain. The only problem with going to a mountain cassette is the large ratio jumps between cogs. This will give you some cadence problems on flat rides. But you could switch to the mountain rear set-up for the big hills and then switch back when you return to Florida. Mountain cassettes have either a 32 or 34 large cog. If the 14% grades are long, the mountain cassette may be the best choice. If you are unsure how to make the conversion, let your LBS do it.
~Al
re: Front and rear chain ring combination for climbingBanky
Jun 3, 2003 8:27 AM
Thanks, I think if I go with a 12-27 Rear and change the front to a 38 that will be just enough improvement and not require to much change over. What do you think? Also where can I get the 38 front?
re: 38 ringChen2
Jun 3, 2003 7:02 PM
A 38 should not be too hard to find. Try Brandford Bike on the net. Or check with your LBS. TA rings seem to have a good reputation. I've never tried this, but you might lose some shifting performance due to the bigger difference between the 38 and the 53. A 52 might work better with the 38. I question that changing from a 39 to a 38 will make those 14% grades easy. But only you know the answer. If it was me, I'd pull off the 12 and 13 cogs, add a 13 with built-in spacer on the front and a 29 on the back. I've never tried a cog bigger than a 28 on a road derailleur, but several folks have reported running a 30 successfully. I just got back from a tour of Andalucia (Spain). The touring bikes were equiped with Shimano 9-sp 105 shifters and cranks and Deore XT 12-34 cassettes and rear derailleurs. There were lots of long grades in the 10% to 15% range, and I used every gear on the bike.
~Al
re: Front and rear chain ring combination for climbingKeeponTrekkin
Jun 3, 2003 7:10 AM
Custom cassette through Sheldon Brown is a great solution when you don't have a triple. Sheldon sells pre-made custom cassettes or, as stated above, you can convert the one you already have.

I did it and found I preferred what Sheldon calls an "Alpine" style (not an MTB style) cassette. The Alpine style has closer ratios through the smaller cogs and big jumps to the big cogs. The MTB style has more even jumps so you have larger gaps between the road ratios you use a lot and smaller gaps as you move up to big cogs. I removed the stock 12 and 13 rings from an S12-27 and replaced them with the custom 13 (with built in spacer) and added a big 34. It's a big jump from 27 to 34 but the XTR derailleur handles it, I don't miss the 12 cog and I still have close ratios in my working range (14 - 19). An MTB cassette would have a 30 cog between the 27 and 34; I prefer that extra cog in the working range to keep the ratio changes smaller where I use them the most.

Other posters say you can use a 30T cog with a Shimano road derailleur (even though "S" says 27 is the limit. I think Sheldon says 28T is the max (I have 28T on a D/A der and it works beautifully). Check that 30T advice carefully. If correct, it might save you from buying the XT or XTR derailleur if 30T is enough for you.

I was in Fl last month and did a little riding; talk about FLAT!!!. I don't know where you can go to get any hill practice. All I have where I live are hills.

Good luck...
re: Front and rear chain ring combination for climbingBanky
Jun 3, 2003 8:35 AM
I checked Sheldon out, he seems a little pricey, his cassette went on without any problems? Also what are your thoughts on the 38 front?