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

I'm Back

Sorry for the lack of posts, but I've been out of town. At the end of May I retired from teaching physics at the University of Wisconsin-Manitowoc. Then my wife and I went to Texas to pick up our travel trailer which we had left there in January. We took our time returing, stopping in Tulsa, Oklahoma for two weeks. Tulsa has a great bike trail system along the Arkansas river called the River Parks trail system. The trail is blacktop and is about 30 miles in length. Parts of it have separate paths for walkers and bikers.

One of the neatest things is that the trail goes past Turkey Mountain which has some of the best technical singletrack in Oklahoma. Probably a good 15-20 miles of trail. We always stay at Cherry Creek Mobile Home Park which has spots for RV's. The River Parks system passes right by the trailer park and Turkey Mountain is just 2 miles down the trail. You can't get better than that.

I tried some singlespeeding at Turkey Mountain but just didn't have the gearing. The trails are very technical, lots of rocks, and for me slow, so I went back to the 1x9 setup. I tried a 34x19 but that was just too tall. For me I think a 32x20 would work but didn't have one.

Now I'm back in Wisconsin. Two days ago I went to the Northern Kettles and rode with the 1x9 setup. I plan on going back tomorrow with that setup again then switch to a singlespeed setup this weekend. I want to get some base data as a 1x9 then compare performance to the singlespeed. I think at the Kettles the singlespeed will be faster.

Mike