torque

I found this in the cyclingpeaks forum (by wwhiley....thanks) and this answer my question :

Torque is a measurement of rotational force over distance, typically measured in newton-meters. This can be expressed as T = N*m. Wattage is a measurement of this torque over a unit of time, so W = T/s, or N*m/s. The m/s here is a measure of rotational velocity, and is directly proportional to your cycling cadence. So, to simplify this, your wattage is a factor of the force you apply and your cadence - makes since, since turning a gear faster will generate more watts, and turning a harder gear at the same cadence as an easier gear will also generate more watts.

In terms of what this tells you about your ride, torque quite simply tells you how hard you were pushing on the pedals. When you analyze your data, pull up the power, torque, and cadence lines on your graph, and you will see the relationship. 300 Watts at a cadence of 60rpm requires more torque than 300 Watts at 90rpm, because the rotational distance traveled in 1 second at 90rpm is 1.5 times the distance traveled at 60rpm, and since W = N*m/s, if m increases, then N (the force component) must decrease if W is to stay constant. How this will look in your data is the torque line will generally run below the power line when cadence is higher, but above the power line when cadence is low. This could possibly help you determine your most efficient cadence, or perhaps determine what your cadence/force ratio was when you felt the strongest or weakest during a ride.

For example, I will look for sections of a ride where my power was highest in relation to my torque at my threshold heartrate, because this is where I'm being most economical with my strength, which is critical during a race, since high-torque efforts generally mean more muscular exertion and hence more buildup of the harfmul byproducts like lactate. At least, that's how it works for me - I always feel less muscle fatigue putting out 300W at 90rpm than I do at 60rpm.

spot1100 said:

I found this in the cyclingpeaks forum (by wwhiley....thanks) and this answer my question :

Torque is a measurement of rotational force over distance, typically measured in newton-meters. This can be expressed as T = N*m. Wattage is a measurement of this torque over a unit of time, so W = T/s, or N*m/s. The m/s here is a measure of rotational velocity, and is directly proportional to your cycling cadence. So, to simplify this, your wattage is a factor of the force you apply and your cadence - makes since, since turning a gear faster will generate more watts, and turning a harder gear at the same cadence as an easier gear will also generate more watts.

In terms of what this tells you about your ride, torque quite simply tells you how hard you were pushing on the pedals. When you analyze your data, pull up the power, torque, and cadence lines on your graph, and you will see the relationship. 300 Watts at a cadence of 60rpm requires more torque than 300 Watts at 90rpm, because the rotational distance traveled in 1 second at 90rpm is 1.5 times the distance traveled at 60rpm, and since W = N*m/s, if m increases, then N (the force component) must decrease if W is to stay constant. How this will look in your data is the torque line will generally run below the power line when cadence is higher, but above the power line when cadence is low. This could possibly help you determine your most efficient cadence, or perhaps determine what your cadence/force ratio was when you felt the strongest or weakest during a ride.

For example, I will look for sections of a ride where my power was highest in relation to my torque at my threshold heartrate, because this is where I'm being most economical with my strength, which is critical during a race, since high-torque efforts generally mean more muscular exertion and hence more buildup of the harfmul byproducts like lactate. At least, that's how it works for me - I always feel less muscle fatigue putting out 300W at 90rpm than I do at 60rpm.

Thank's for explaining that. no wonder 280W feels harder climbing then on the flats.

spot1100 said:

I found this in the cyclingpeaks forum (by wwhiley....thanks) and this answer my question :

Yes, but it is useful only if the torque is measured at the crank (i.e. by SRM or Ergomo). If you use PowerTap like I do, note the following comment:

acoggan said:

The torque values recorded by the PowerTap/displayed in the Link software are practically meaningless, since they are measured at the hub, not the crank. Consequently, they are gearing-dependent, i.e., for the same torque applied to the crank, the torque at the hub will be higher when the gear ratio is lower, and vice-versa. (As anybody who has ever tried to remove an old-fashioned freewheel with a large cog already knows!) It is possible to calculate the crank torque from power and cadence data, but doing so requires accurate cadence measurements, i.e., use of a PowerTap Pro with crank sensor, and not the original PowerTap with its "virtual cadence" feature.

(from thread http://www.cyclingforums.com/t229180.html )

Because of this, I don't show my torque data in the graph anymore.

Now I just wish CyclingPeaks had the ability to "calculate the crank torque from power and cadence data" built in...

Just in case you are using PowerTap...

Ken