Measuring Cadence

West Texas Jim said:

Any recommendations on what I should get to reliably measure cadence? If it comes with a computer that also measures speed, that measurement needs to trigger off the back wheel, since I spend most of my time on the trainer.

I'm pretty cheap, so less than $100 would be nice. :P

Thanks in advance

I use a Flight Deck computer. It is virtual cadence, but for me it is functionally equivalent to measured cadence. I believe the wiring harness for the speedo sensor is long enough to go to the rear wheel, but you'd have to check on that. Or you could go wireless for the speed sensor, and put it on the rear spoke + seat stay.

Many (most? all?) other computers that use measured cadence at the crank arm also measure speed at the rear wheel.

West Texas Jim said:

Any recommendations on what I should get to reliably measure cadence? If it comes with a computer that also measures speed, that measurement needs to trigger off the back wheel, since I spend most of my time on the trainer.

I'm pretty cheap, so less than $100 would be nice. :P

Thanks in advance

Cateye Astrale

Camilo,
Do you have to tell the device what your gear ratio is?

West Texas Jim said:

Camilo,
Do you have to tell the device what your gear ratio is?

Nope. It uses a magnet on your crank arm and a pick up to determine cadence.

West Texas Jim said:

Any recommendations on what I should get to reliably measure cadence? . . .

I'm pretty cheap, so less than $100 would be nice. :P

Count your strokes for 15 seconds against the sweep hand of your watch and multiply by 4.

Cadence measurement from cyclo computers uses the same principle as speed. A magnet attached to left crank arm passess thru the sensor attached to the frame which triggers the measurement.

Cadence is measured regardless of your gear. It is just the frequency of a repetitive activity such as pedaling.

How important is it to measure cadence on the bike? I still haven't forked out for the cadence sensor unit for my computer. Although I do ride to a cadence on the exercise bike, so have a good feel of the cadence range I am on.

Camilo said:

I use a Flight Deck computer. It is virtual cadence, but for me it is functionally equivalent to measured cadence.

What da heck is "virtual cadence"?

Bob Ross said:

What da heck is "virtual cadence"?

Virtual cadence is calculated cadence as opposed to measured cadence. With normal bike computers that give cadence, they have a magnet attached to the crank arm and a sensor (wired or wireless) attached to the chain stay. It tells the computer how many times per minute the crank arm goes around - which is pedaling cadence.

The virutual cadence of a Flight Deck computer is not measured, but it is calculated based on your speed and what gear you're in. Speed is measured in the conventional way - magnet on spoke, sensor on fork. The gear is sensed by the Flight Deck mechanism in the brifters. One of the unique features of Flight Deck computers is that it can tell you (visual display) what front and rear gear your in. I actually like that feature quite a bit.

West Texas Jim said:

Camilo,
Do you have to tell the device what your gear ratio is?

You program the Flight Deck computer with wheel size (for the speed reading) and the number of teeth on the front chain rings and rear sprockets. The Flight Deck mount has wires and connections that you hook into the brifters. The mechanism inside the brifters tells the computer which front and rear gear you're in, and the computer (programmed with teeth # by you) then knows what the gear ratio is, and combined with speed then can tell you what your cadence is.

The only "down side" is that if you're coasting, it will still give you a cadence reading because it doesn't know whether you're actually pedaling or not. But, I never look at the cadence when I'm not pedaling anyway!

Very interesting explanation on how a Flight Deck computer figures out cadence.

Another brand/model that does cadence measurement off of the crank is the VDO C3DS model, which has wireless pick-ups for both speed and cadence. The speed magnet and transmitter can be set up for either the front wheel or rear wheel, so you can use it when your bike is mounted on a trainer. (The cadence magnet goes on a crank arm.) A digital transmission technique is used - this way if there is a temporary glitch in the wireless transmission the accumulating wheel and crank revolution "counts" are saved up until the transmission link is restored.

(As an example, if I pass right under a high-voltage tower, I might get a temporary blank-out in the current speed and current cadence values - but once past the tower the readings come back with no loss of data in terms of distance traveled, average speed, average cadence, etc.)

It has all of the usual features and calculations, and can be set up to exchange between two bikes, with differing wheel sizes. What it doesn't have is an altimeter, or a heart-rate monitor (nor is it GPS-equipped). It's a model that's been around for a while, so the catalog places like Performance Bike and Nashbar have them marked down to $89 or $99.

West Texas Jim said:

Any recommendations on what I should get to reliably measure cadence? If it comes with a computer that also measures speed, that measurement needs to trigger off the back wheel, since I spend most of my time on the trainer.

I'm pretty cheap, so less than $100 would be nice. :P

Thanks in advance

I do it the free way. Count my rpm for one leg for 15 sec and mulitply by 4. Easy-especially on a trainer where you don't have to worry about variances in terrain.

If you do want a device, the suggested Cateye Astrale is probably the best value in a rear wheel pick-up speedo with cadence.