Different Cassette?

[OakLeaf]

Does a smaller puppy gear (with no change in the middle and big rings) increase the risk of dropping the chain? Or make shifting rougher?

[SadieKate]

You never want the difference in ring size to get too large - I think it's pretty universal that you never should go larger than 14. 50-34 compact cranks have the greatest differential at 16 and they've had their challenges with quick shifting and dropped chains though this is improving over the years. You can always add a Deda Dogtooth on the seat tube near the bottom bracket. A lot of the pros run these because they don't ever want to chance a dropped chain, no never.

The larger the gap, the longer to shift up and the greater chance of dropping when shifting down. This doesn't matter whether it is a double or triple crank.

[violette]

I changed my cassette and Ultegra derailler to a Mtn bike cassette. The difference is amazing, but I lost my higher end derailler. The gear shifting is not as smooth as with the Ultegra, they changed my chain and it works like a charm. I would seriously consider changing if you do steep climbs. The LBS told me that some of his customers go to France to try the Tour the France route and they change their deraillers and cassettes, because the mountains are so steep, they could never do it with their regular gears and they have the high end bikes.

[aicabsolut]

I wouldn't put a 32 or 34t cog on the back with a little 30T chainring. A 1:1 ratio of gears (e.g., 30 and 30) means that you get one wheel revolution per revolution of your pedals. This definitely takes little force to accomplish, but you start having to spin like mad to keep enough momentum to keep yourself upright, particularly when gravity is working against you as well. I would most definitely NOT go greater than 1:1 (the 32 or 34 rear cog), because that will mean more than one revolution of the pedals to get a complete revolution of the rear wheel. You just won't be able to go fast enough. I'd advocate sticking with your normal 10sp derailleur and putting something like a 12-27 (shimao or sram) or 12-28 (sram) on the back. That will get you close to a 1:1 and still be pretty easy while allowing you to keep your momentum up such that you don't tip over. If you're running campy, then the current rear derailleur can accommodate a larger cassette (I forget if it's 29 or 32..i think 32), but I still wouldn't go past 1:1.

Basically, you're going to get to the point where you have to see if you can make things easy enough that you can manage to go a little farther without putting yourself in a situation where you will be pedaling your heart out and going at a pace that you could probably beat by walking.

[SadieKate]

Does a smaller puppy gear (with no change in the middle and big rings) increase the risk of dropping the chain? Or make shifting rougher?

Oakleaf, can you clarify whether you were asking about the difference in chain rings sizes (number of teeth difference between each chain ring) or the difference in size between the small chainring and the largest cog. My answer had to do with the shifting performance pros/cons of the gap between chain ring sizes. It had nothing to do with cassettes.

aicabsolut, Northern CA has plenty of hills where a smaller chainring than the largest cog is appropriate. Tourers use small rings. Mtnbikers use a 22x34 all the time and manage to stay upright. It all depends on the demands of a specific person's terrain and her body.

From Peter White: "My most popular chainrings are 48 - 38 - 26 and 24 tooth replacements for Shimano's Ultegra and 105 triple cranks."

[Melalvai]

I absolutely love my 22T chainring. It made a world of difference in my life. One mechanic argued for a larger ring in back, and the other told him he didn't know what he was talking about and that I needed the smaller one in front. I know who is the better bike mechanic so now I have a 22T up front!

[aicabsolut]

I know what 17% looks like. I think I hit around 3-3.5mph once on a 22.5% grade. I thought I was going to fall over. I would've liked a granny gear then, but I still think a bigger cog than ring is overkill on a road bike for most people, even those who climb mountains.

[boy in a kilt]

I run a 30/40/50 12-27 combo. It started out as an experiment but after a while, I fell in love with it. A 17% climb will still suck, but you'll have a great combination of gears for almost everything else.

[Veronica]

I wouldn't put a 32 or 34t cog on the back with a little 30T chainring. A 1:1 ratio of gears (e.g., 30 and 30) means that you get one wheel revolution per revolution of your pedals. This definitely takes little force to accomplish, but you start having to spin like mad to keep enough momentum to keep yourself upright, particularly when gravity is working against you as well. I would most definitely NOT go greater than 1:1 (the 32 or 34 rear cog), because that will mean more than one revolution of the pedals to get a complete revolution of the rear wheel. You just won't be able to go fast enough. I'd advocate sticking with your normal 10sp derailleur and putting something like a 12-27 (shimao or sram) or 12-28 (sram) on the back. That will get you close to a 1:1 and still be pretty easy while allowing you to keep your momentum up such that you don't tip over. If you're running campy, then the current rear derailleur can accommodate a larger cassette (I forget if it's 29 or 32..i think 32), but I still wouldn't go past 1:1.

I have to disagree here. It all depends on where you ride.
When you ride stuff like this regularly, you need little gears. Or at least I do.


Borrowed from DiabloScott

My smallest gear is a 33 - 34. Yes in that order. I ride stuff with long sections of upwards of 12% and some nearing 20%.

Here's what 17% looks like, the Summit Wall.

http://bp3.blogger.com/_hSZo5vjiPmQ/...h/P6140128.JPG

I can climb this at about 4 mph, with my little gears, seated the entire way. I've also been able to stop in the middle of this and start again.

On some other climbs I've seen less than 3 mph on my speedometer. I did not fall over.

For the easier section, North Gate Rd to the Junction I average just under 8 miles an hour and I am not spinning madly. My average cadence is in the high 70s, low 80s. I'd probably go faster with taller gears, but my knees would hate me. Therefore I focus on spinning faster in my easier gears.

Does Aggie_Ama need such low gearing? I don't know. I haven't ridden in the Texas hill country. But low gearing does work and you don't fall over or spin out of control.

V.