Take the 2-minute tour ×
Bicycles Stack Exchange is a question and answer site for people who build and repair bicycles, people who train cycling, or commute on bicycles. It's 100% free, no registration required.

I currently have a touring bike, with fenders, rack, panniers, and so on. I currently run a triple crankset 28/38/48 and 9sp 11-34 cassette. I mostly commute and tour with this bike. And with a fair load, I mostly ride on my 48 in front and 14-ish and around in the back. I can climb most climbs with the 38 and sometimes as high as the 26 (rarely the 30 and 34t)

As I want to go more on the workout/sport/exercise type of riding I am considering the purchase of a road bike (more of a racing type).

I prefer a compact 50/34 crankset but am wondering for the cassette, do I need to go as high as a 10sp 12-30 to climb all I need? Because I also like the idea of closer gears, so is 12-28 or 12-25 too tough?

share|improve this question

5 Answers 5

up vote 4 down vote accepted

First, about the big steps between gears: you should really go on a test ride to see how you like shifting on a bike with such big steps between gears. For some people it's not a big deal, for others, it's a major annoyance. I don't think anyone else can make that kind of qualitative decision for you.

Using Sheldon Brown's Gear Calculator, I calculated some approximate ratios for the gears you use most commonly. I don't have the exact wheelbase or BCD for your bike, but here are the approximate ratios for the gears you mentioned using most often:

48 / 14: 6.9

38 / 26: 2.9

38 / 34: 2.3

There's some decent range that you use there. FWIW, my 1970's Motobecane Nomade with a 52/40 crankset and a 14x28 rear cluster covers a range down from 7.5 down to 2.8. That's good for your average commute, but leaves you without the bailout gear for when you have a really tough climb. It's back to the problem you originally stated -- it's all about whether you want the bailout gears or not. From a purely functional standpoint, however, the compact crank is not a bad idea.

If you're really interested in getting a bike with the gearing range that you have one your current touring model, you should run the numbers through the aforementioned gear calculator. Note that the calculator also shows the percentage increase/decrease between gears (as stated earlier, lower % increase typically makes for a smoother riding experience).

share|improve this answer

If you're looking to expand into some workout/exercise riding, you don't necessarily need to go as high as 30 or 28. When I run a 50/34 crankset with just a 12-23 cassette, I find that I can still make it up just about any hill, and you probably already put in more miles than I do on your touring bike. So I think you'll find great success with a 12-25.

share|improve this answer

The difference between 28 and 30 is only about 8%. If you climbed a hill at 70 RPM on a 28, you would only be riding at 75% on a 30, and your force would only go down a little bit.

share|improve this answer

If you can, find the approximate gradient of hills you want to climb/train on and estimate your power to weight ratio. For 7% climb 34/25 (front/back) is good combination if you have power weight ratio >= 4. With less power, or more weight/load, just get the biggest cassette allowed by the rear derailleur.

This way you can maintain about 60 rpm or higher on long 7% climb and that's good for training. Just upshift when you want to train at lower rpm. http://cycle2max.com/ can help giving some ideas how a climb like.

share|improve this answer

I run a 50/34 with a 12-25 and I absolutely love it. My sweet spot for normal training on flats is around 20 mph and the 12-25 gives me a 16 right where I need it, while an 11-25 or 11-28 omits the 16 leaving a big gap. For me, I care more about even gear spacing near my normal speed than I do about having a very high or very low gear that I will rarely use. For example, 50 x 11 at 90 rpm on 700x23 tires = 31.6 mph, which I only do down a big hill or a huge tailwind. So I gave up the 11 to get the 16, giving me a nice evenly spaced range.

To answer the original question, I have not yet encountered a hill where 34 x 25 wasn't low enough. But... I mostly ride in central Illinois. If I lived in Colorado I'm sure it would be a different story!

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.