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Impressions on road bike efficiency after night at the track(8 posts)

Impressions on road bike efficiency after night at the trackAlexR
Jun 22, 2001 10:18 AM
A few weeks back, the day after a workout on the track, I hopped on my road bike for a nice training ride. The rear end of the road bike felt very soft and mushy, as if the wheel were out of true or misaligned in the dropouts. Basically, the feeling was that something back there was making me slower, less crisp and efficient. After an hour this feeling was gone, I had grown accustomed to the feel of the ride. I had the same experience the next week following a track night, and the week after that.

Point being, the transmission of a fixed gear is so unencumbered in comparison to a multi-speed, freewheel drivetrain that switching between the two makes me feel sluggish on the road bike every time.
Even though I now expect this feeling, I still stop and spin the wheel with an eye for misalignment.

Does anybody know just how much force (measure it as you see fit) is lost as a result of the freewheel, two pulleys, off-line chain, etc. of a road bike?

I would be curious to hear your hypotheses,

Alex
Forces at work...Cima Coppi
Jun 22, 2001 10:31 AM
Based on the physics of creating motion on a bicycle, I'd say there is not much difference between a track and a road bike...

Understand this, the force applied to the crankarm is transmitted to the chain on the section from the top of the cassette to the chainring creating tension. The chain at the bottom of the chainring heading back to the pulleys is relaxed (only under tension because of the spring in the derailleur). On the track bike, you will see minor slack on the bottom of the chain before it revolves aroung the cog again.

That being said, and I hope it makes sense, the sluggishness you are experiencing is most likely due to the road bike geometry being more relaxed than your track frame. Also, the rear axle on a track bike is narrower, allowing for less flex on the wheel.

Hope this helps!!

CC
AppendCima Coppi
Jun 22, 2001 10:34 AM
I forgot to conclude that the presence of the derailleur on the road bike is not why you're experiencing the sluggish feeling, but the wider road hub may affect this for different reasons.

CC
Horse dungnm
Jun 22, 2001 10:46 AM
nm
Really nm??Cima Coppi
Jun 22, 2001 11:02 AM
Let's hear you reasoning for this overly truncated statement!!
Thoughtsmuncher
Jun 22, 2001 10:51 AM
Not sure about the root causes - but I have single and 9 speed road bikes (inter alia). Can't say that I have noticed any differences of the sort to which you refer. Conclude therefore that it's a question of weight and/or geometry and/or wheel build & tyre differences?

Interesting though.
re: Impressions on road bike efficiency after night at the trackgrz mnky
Jun 22, 2001 6:54 PM
Well, besides there being the possibility of major differences between frame and wheel stiffness, the biggest variable is probably the tires and the inflation pressures used. Your line about feeling like everything was moving around on the back end made me think about getting a slow leak and how sluggish it makes the bike handle. What are you running for inflation pressures and are we talking tubulars vs. clinchers?

Also, lighter structures tend to feel more crisp and responsive, assuming that they aren't flimsy and weak. It's all a matter of momentum and inertia (depending upon how you like to view things).

Basically they're different animals. Ride a MTB on your normal road route for another view point and appreciation on tire compliance and F=ma.
re: Impressions on road bike efficiency after night at the trackSteeeve
Jun 23, 2001 6:48 AM
"Ride a MTB on your normal road route for another view point and appreciation on tire compliance and F=ma."

So what happens when the "m"'s are equal?