Shifting strategies for hills

How should I be shifting gears on the front chainring and the rear cogs to cope with hills?

Member Question from Belted

When climbing a challenging hill,  as I move from the largest front chainring down to the medium and the small "granny gear" chainring, I find myself with a problem. By the time I move from the medium chainring down to the small one, I am already in the easiest gear on my back cogs/cassette.  That means once I shift down to the smallest chainring in front, I slow down somewhat and the hill gets harder, but I can't shift to an easier gear because I am already in the easiest gear. What is the best technique to avoid this? How do I end up in the smallest chainring in front, but a medium or hard gear on the rear cassette, so I can still shift to an easier gear in the back a few times?

Answer from Dean Phillips
Fitwerx

When you’re forced to shift to a smaller chainring while climbing a hill, it’s best to combine that shift in the front with two shifts harder on your rear cassette immediately after the chainring shifts. This will effectively get you to an overall easier gear, while also better maintaining your momentum and leaving you a couple extra gears to shift to on the cassette.

Shifting 101

Let's back up a little for those with not much experience shifting. As everyone probably knows, there are two shifters on the bike. One is for gross adjustments and one is for fine adjustments. The front chainring on most bikes has either two or three rings. The biggest one makes it hard to push the pedals if you are going slow or starting up from a stop, but if you are going fast, you can create a lot of power by cranking the pedals in your hardest gear and you can fly. The smaller chainrings are great for getting started or for climbing hills. It doesn't take as much force to push the pedals when you are in the smaller chainrings, but your bike also doesn't go as far each time you pedal.

The gears in the back, called cogs or the cassette, work in a similar way, but the change from one gear to another in the back is much more subtle--almost imperceptible sometimes. In the back, the larger gear is easier to push, and the smaller one is harder. With both sets of gears, when the chain moves closer to the bike frame, it feels easier to pedal, and when it moves away, it feels harder. Also, you probably already know that you can shift all the way up and down the gears in the back and get one result, and then move to a different chainring in the front and move through all the gears in the back with a different result. That's because the gear ratio is calculated taking both the front and rear into account. There is some overlap. That is, if you are in the hardest gear in front (your big chainring) and your easiest gear in back, it will feel about the same as being in your medium gear in front (your middle or smaller chainring) and your hardest gear in back. This gives you some flexibility you will come to appreciate, and allows you to avoid having the chain in a position that causes rubbing and noise (called cross-chaining) while still riding in a comfortable gear ratio.

Gear ratio success

To further explain the answer to the rider's question, let’s assume your triple crankset has chainring sizes of 52, 39, and 30 in the front. (Those numbers are the number of teeth on the chainring. You can count them or look to see if it's written on the chainring.) Let's also assume you’re running a 10-speed cassette in the back ranging from 12 to 25 tooth cogs (12, 13, 14, 15, 16, 17, 19, 21, 23, 25). The smaller the ratio is from chainring to cog, the lower the gear.  Lower gear ratios make the hills easier. In the situation you describe, you’re riding up the hill in the 39/25 gear and then shifting to the 30/25 gear when you drop to the smallest chainring in front. When you divide the chainring by cog size in your case, you’ve shifted from a 1.56 ratio to a 1.20 ratio, which is 23 percent lower, or 23 percent easier. If you maintain the same pedal cadence, your speed will eventually slow by that same amount – 23 percent. But if instead you followed your front chainring change (from 39 to 30) with two clicks harder on the rear cassette (from 25 to 23 to 21), you’re now riding in the 30/21 gear which has a ratio of 1.42. This gear is only about 9 percent easier and will allow you to eventually shift easier one cog to the 30/23 gear which has a 1.30 ratio, then finally one more shift easier to the 30/25 gear and its 1.20 ratio. Stated another way, when the going gets tougher on that hill, you will be able to shift to an easier gear two more times before you run out of gears and have to grit your teeth.

Instead of shifting from the 1.56 ratio down to the 1.20 ratio like you’ve been doing, now you’ve found a sequence where you shift from 1.56, to 1.42, to 1.30, and finally 1.20. There are a number of benefits to following this more effective (and less drastic) shifting pattern:

• You’ll maintain a more consistent effort level on the hill
    
• You’ll avoid that big drop in momentum when simply shifting to the smallest ring up front
     
• You’ll get up the hill faster!

This same shifting pattern can be used when you’re coming off a big downhill and shifting from your big to medium chainring (52 to 39) when the road starts to flatten. Riders using double cranksets instead of triple have 53/39 chainring sizes or the compact 50/34 version, but they should also follow this shifting routine.

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Dean Phillips is a co-owner of Fit Werx²in Peabody, MA.  Dean frequently writes tech articles for BeginnerTriathlete.com and is humble enough that he would likely never tell you (so we'll tell you for him) just how fast he is on a bike.  Dean holds multiple TT course records in New England, having broken records previously held by some of America's best pro cyclists, and he set these while being a father of three young children and owning his own business.  Dean knows speed and how to get the most out of his training time.