Posted by: Ian | August 1, 2010

More on gears

A couple of posts ago I wrote that I was leaning towards standard road race gearing for my new training bike. My concerns that a 39t chainring with a 25t or 26t sprocket on the cassette might not give me enough gearing for steep hills were alleviated by the fact that I can get up Swains Lane, with its 20% maximum gradient, on my fixie riding 48×16. Then, in an exchange of comments with Ant, it struck me that doing this once on a short ride is one thing but doing it repeatedly is something else.

I was thinking about this yesterday while preparing the wheel that Emily gave me, which I’ll be using on my Felt once I switch my wheel with the CycleOps hub to my training bike. I took the Ultegra cassette off and cleaned the sprockets. There are individual sprockets with 12, 13, 14, 15, 16, 17 and 19 teeth and a combined unit that has 21, 23 and 25 tooth sprockets on at the low end. In Tim Krabbe’s book, The Rider, he describes how before every race he would take a box of sprockets and choose the ones he’d need for the ride at hand. That seems ideal in a way, though I can see why we ended up with preassembled cassettes.

Today I tested my gearing on a different type of hill. I rode for 15 miles towards Taunton as a warmer-upper and then turned up the hill that rises through Corfe. It doesn’t have Swains Lane’s steepness but it runs for 5 miles and it’s busier, which is one reason I’ve never done it before. Up to Corfe itself the gradient is gentle, mostly 6% or less. For this, and indeed for all of the preceding miles, I’d avoided using my lowest three gears. I guessed that these stepped down as 28-26-24 and that the next one down – the lowest gear I allowed myself – was a 22t. This gave me a ratio front to back of 34/22, which is the closest I can get to the 39/26 or 39/25 lowest gear on a standard road racing set.

Leaving Corfe the gradient steepened to 13%. This is still very moderate by Somerset standards but it became much harder and it seemed to me I had three choices: suffer (which is what I should have done); stop (which I was never going to do); or flick down to a bigger sprocket (which I did). If I had been riding an actual road racing config rather than simulating it on a bike that had the big gears in reserve I would have managed to get up the hill. If I did it a second time on my Felt I’m sure I could get up there on the 22t ring (just as I only got up Swains Lane in one go on my second attempt) – knowledge helps. But it’s not an especially hard climb and the difficulty I had is enough to seal my choice of a compact groupset on my new bike.

For the record, here’s the Swains Lane profile, together with my heart rate, taken from my Garmin:

It’s notorious for being steep but it’s not long. And here’s the ride I did today, with the hill through Corfe coming at 15 miles:

Obviously the slopes on the chart do not reflect the relative gradients of the climbs. The blip in my heart rate at the start is strange but I get it quite a lot. Leaving Hill Farm House and riding on the sweeping downhill of St Rayn’s Lane I show a rate of over 220 bpm, which doesn’t correspond at all to how I feel. I ascribe it to a quirk of the Garmin, or the fluttering of my jersey.

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