Comparison: Singlespeed vs Geared

Last week I had ridden the singletrack at the Northern Kettles using a 9 speed (1x9) setup. Yesterday, I switched to a singlespeed setup using a 34x19 gear. I wanted to get a good comparison between the geared setup and the singlespeed. I also had data from last August when I had set my fastest times ever over the same trails.

The bottom line is that I was faster with the singlespeed. However, just being faster doesn't mean alot as course conditions can affect times dramatically. So I also compared the power readings from my PowerTap. Over the same trails, I averaged about 10 Watts more power with the singlespeed than with the geared bike. This is approximately the amount of power needed to pull the chain through the derailleur as measured on my bike about a month ago. I had measured 12 Watts as the power needed to pull the chain through the derailleur.

Because the power needed to pull the chain through the derailleur is not power that reaches the rear hub the PowerTap does not measure it as part of the power data. The PowerTap only measures power to the hub. If you can eliminate losses before the hub, then the power will pass on to the hub and be recorded by the PowerTap. In otherwords, that power is now available to move the bike instead of just pull the chain through the derailleur. More power should translate to quicker times and more speed.

When all the frictional losses are considered on a bike, a 1% increase in Power should translate to about 0.5% increase in speed. My overall power increase with the singlespeed was 8% while my speed increase was 4%. Excellent agreement.

Of course this is just one example and relates to just this course. The Kettles trails do not have big climbs although there are many very short uphill parts. I plan to do some more runs at the Kettles and try other areas also. I also want to try with a slight gearing change as I think I can do better with a 33x19 instead of the 34x19 gear.

As I collect more data I will give you more specifics.

Mike

Is a Single Speed Slower?

Each year I try to compare my training with where I was at the same time last year. In the past, I have used such things as time over a certain route or average speed for the same route. However, these are not a very good indicators as they are highly dependent on weather conditions.

Last year I purchased a CycleOps PowerTap hub for my MTB and now I can compare power over a ride, course, or part of a course such as a certain climb or sprint. So when I switched to a single speed I was very curious if the single speed was slower than a geared bike under various conditions.

So far I have only been able to compare various road rides, as here in Wisconsin the ground has not completely thawed and dried and so the trails are not yet open. Right now I am using a 2:1 gear ratio that seems to work well on the short but moderately steep hills in the area. This ratio gives me a top speed of about 20-21 mph before I "spin out" on flats and downhills.

So what is my overall finding so far? On the average I'm slightly faster on my single speed compared to my geared bike rides from last year. The average power output is slightly higher. That may mean I'm just in better condition than last year at this time, but it is interesting.

One worry I had about the single speed was in climbing, but when I compared specific climbs to the geared bike I have found that I'm just as fast on the single speed and have a similar power output. How about sprints? In a short sprint, 10 seconds, it appears that I am slightly faster on the single speed. On longer sprints I am slightly slower as I spin out after 10 seconds or so. It is encouraging and leads me to think I can compete with the geared bikes in my age group.

In a couple of weeks the trails should be open and I can test the single speed on single track, so keep checking back.

Mike