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Ben C. sent in the following question:
“I have a 2003 Giant Boulder SE I converted to a commuter bike by slapping on some 26 x 1.6 slick continentals. I have also made a rear bike rack for my luggage.
Anyhow, my problem is that I would like to get more speed out of it. When I leave for work, I go down the hill and coast around 25mph. If I really try, I hit 36mph but I run out of gears and am pedaling very fast. I have to climb the same hill on the way home. My bike is a 21 speed. 3 rings on the crank and 7 on the cassette. I do have a granny gear. I used to mountain bike with RL.
What can I do to increase my speed without sacrificing my ability to ride uphill? I ride 9 miles one way and takes me about 35-40minutes. If I get lots of green light, then it takes me about 30 to 35 minutes. My goal is to be able to shorten my ride to 25 to 30 minutes.”
Here is the bike in question:
This bike was featured on our site a while back, and is also featured on PVC Plans.
Anyhow, there are a few things you could do to wring out more speed from your commuter bike. There are some fairly cheap methods, and others that may require a bit more money.
First, the cheap method: find some narrower tires. 26″ x 1.6″ tires are nice and cushy, but they’re just too porky for road use. If you can, find some 1″ or 1.25″ tires and decrease your rolling resistance. An additional benefit of narrower tires is that they tend to be able to hold a higher pressure, allowing you to really pump those tires until they’re hard — thus reducing rolling resistance even more (with the sacrifice of a little comfort).
Second, let’s play with the gearing: after talking with Ben, I learned that he is running a 14-34 7 speed cassette with a triple mountain crank (46T-34T-23T). He also indicated that the cassette’s freehub is slipping — a PERFECT time for an upgrade! I asked Ben about his gearing uses, and he mentioned that he rarely uses the little ring up front. There are several methods to changing up the gearing on this bike. The first could be as simple as finding a bigger big ring…perhaps a 49 or 50 tooth ring for the outermost position. Alternatively, since the little inner ring isn’t used so much, switching to a double like a compact road crankset might make sense. Traditionally, compact road doubles come with a 50T outer and a 36T inner. This kills two birds with one stone — a bigger gear for mashing at high speed, and a smaller ring for hillclimbing.
Now, there are also several methods to tinkering with the gearing in back. Since the freehub has gone bad, might as well buy an 8-speed model…it will bolt right onto that existing hub with no other modification. Then, you can choose from a wide variety of pre-made cassettes with 11 or 12 tooth first-position cogs going up to 32 or 34 tooth 8th-position cogs. This will also give a bit more speed on the low end and still leave plenty of ratios for climbing hills. My favorite is to create a “custom” cassette by grinding/punching out the rivets that hold a cassette together and rearranging the stack with cogs of my own choosing…you might even be able to salvage a couple used cassettes from your LBS so that you’ve got plenty of cogs to select from.
The only drawback to upping the cog count in back is that you’ll also have to find another shifter. In this case, Ben is using a 7-speed thumb shifter. I’m not sure if it can be switched to friction-mode…if so, a 7 speed thumb shifter should be able to handle 8 cogs in back. If not, an alternative shift controller might be needed — and there are plenty available like twist shifters, trigger shifters and others.
Playing with your gearing can be fun — there’s no reason why you shouldn’t be able to get some more speed out of your rig and still have gear ratios available for climbing. If you’re interested in tackling something like this, visualizing the gearing choices and ratios on paper can be a good start. Sheldon Brown has an easy-to-use calculator on his site — just plug in the tooth counts front and rear and hit the “calculate” button! Ben, thanks for sending in your question…good luck and have fun out there!
Have a cycling-related question? Just Ask Jack! Click on the link in the right-hand column to send me your questions.