Shimano Flight Deck Cadence

[LONE RIDER]

Has anyone made a comparison of the Flight Deck virtual cadence with an actual cadence measuring device. I'm just wondering because rationally the FD cadence should be fairly close to actual when I'm pedaling at a constant speed (not accelerating) but it seems to change more than I would expect, maybe +/-5 rpm. Lately I've been using the cadence and HR monitor to keep the cadence up above 95 and the heart at a 80-85% of max. and this got me paying more attention to the rpm display. Thanks.

[TAW]

The problem with the virtual cadence feature on Flite Deck is that it doesn't take into account wind or terrain. Since it calculates cadence based on speed and gearing, in the real world it's not overly useful.

The only place I use it is on rollers, since it is accurate where there is no wind or hill resistance.

[benb]

I always found it worked just fine as long as you're actually pedaling against resistance.

It's most off when going downhill or with a massive tailwind. But it works plenty fine most of the time.

To me it works fine for the important things. e.x. slogging up a hill and making sure you're not pushing too big of a gear. It works pretty well in that situation.

[Sandy]

I have the flight deck computer, and would think that in most situations the cadence would be reasonably accurate, as it is a function of speed and the gearing. My problem is that my computer is almost always broken, and doesn't even show what gear the bike is in, thus making almost all data useless. I wish I never bought it.


Sandy

[Keith A]

The problem with the virtual cadence feature on Flite Deck is that it doesn't take into account wind or terrain. Since it calculates cadence based on speed and gearing, in the real world it's not overly useful.

The only place I use it is on rollers, since it is accurate where there is no wind or hill resistance.Maybe I'm missing something here, but cadence reporting has nothing to do with wind or terrain. Cadence is simply the rate that you are pedaling at and it doesn't matter if you have a 20 mph head wind or tail wind. Obviously if you are coasting (or not pedaling against resistance) then your real world cadence isn't going to match the virtual cadence, but if you are pedaling (and assuming the mathematics used by the FlightDeck are accurate), then the cadence reported by the virtual cadence should be very close to reality.

[mcgillicuddy_p]

Keith I think you are missing something-then again maybe I am. The virtual cadence is determined by your speed and the gear you are using. If an external force (terrain, wind, etc.) is causing you to increase or decrease in speed then the calculation will be flawed. For instance, you can stop pedaling down a hill and the FD will still calculate a virtual cadence for you (not zero which is the actual cadence).

[Keith A]

mcgillicuddy -- I understand you point, which is why I stated "Obviously if you are coasting (or not pedaling against resistance) then your real world cadence isn't going to match the virtual cadence". So as long as you are pedaling with some resistance, then the virtual and actual cadence should be very close.

[TAW]

Since Flite Deck calculates cadence based on your speed and your gearing, a tail wind means that you'd be going much faster in the same gear as you would if you were going into the wind, or even if it was calm. You could spin a gear very slowly with a tail wind, and because of the gearing and speed, Flite Deck will register your cadence much faster than what you are actually spinning, and the converse would be true if you're going against the wind. :)

[RPS]

Maybe I'm missing something here, but cadence reporting has nothing to do with wind or terrain. Cadence is simply the rate that you are pedaling at and it doesn't matter if you have a 20 mph head wind or tail wind.+1

If accuracy is off I'd check cassette and chainring sizes in program first.

[benb]

You know when it's not working. If you're going downhill and soft-pedaling, it's not working.

If you're going downhill and you've shifted up aggressively so there is still resistance, it's working.

If you've got a tailwind and you're soft-pedaling, it's not working, if you upshift to the point where you're working, it is.

I could generally care less about my cadence when I'm bombing down a hill, etc.. the point is to optimize power vs. messing up your knees, etc.. and the Flight deck's "virtual" cadence works fine for that.

It's not worth worrying about it unless you're the completely obsessive data collector who is uploading cadence logs to the computer after each ride.

I had incredible reliability out of my Flight Decks while using them. As long as you have a good electrical connection to the shifters it works great. I'd get maybe 18-24 months out of the batteries too.

I sold a Flight Deck with my old bike in February that was 7 years old and still working perfectly.

That said I won't be using one on my new bike since I went with SRAM shifters.

[Sandy]

Maybe I'm missing something here, but cadence reporting has nothing to do with wind or terrain. Cadence is simply the rate that you are pedaling at and it doesn't matter if you have a 20 mph head wind or tail wind. Obviously if you are coasting then your real world cadence isn't going to match the virtual cadence, but if you are pedaling (and assuming the mathematics used by the FlightDeck are accurate), then the cadence reported by the virtual cadence should be very close to reality.

Suppose you are going down a steep hill with a very large tailwind. Your speed is an astonishing 65 mph. Assume that you are pedaling. The computer only reads the speed and the gear that you are in, to extrapolate your cadence. Your pedal input and pedal speed (cadence) is trumped big time by the wind and gravity. You could stop pedaling, pedal at a slow cadence, or pedal at a faster cadence. The computer doesn't care. If the speed was maintained and the gear remained the same, the cadence, given by the computer, would remain constant. If you were pedaling at 25, 45, 75, or 95, the cadence given by the computer would be the same.




Sandy

[TAW]

For an example, say a person is on rollers, using their same bicycle with the
same Flite Deck, and he is going 24 mph in a 53x16, and the cadence reads 90. This would be the most accurate read out he could get.

Now this same person rides the exact same gear, with the exact same cadence, (same bike and computer) but he's riding on a road into a headwind, so he's only going 20mph. The virtual cadence is going to tell him that he's only spinning at 78, so this would be inaccurate.

[Keith A]

Sandy -- As I stated (as well as another poster), as long as you are pedaling against resistance (ie not soft-pedaling or coasting) then your virtual cadence and real world cadence will be the same -- unless if you haven't setup your computer correctly or if the computations by the computer are inaccurate.

[Bud_E]

I'm with benb on this one. I've gone through many a flaky computer and the flite deck has been by far the most reliable. The cadence function suits me because I have a tendency to push hard gears when my mind wanders.

But having said that I have now jinxed myself and it will break tomorrow. :rolleyes:

[Keith A]

TAW -- If you are in the same gears and same wheel size (you don't even have to be on the same bike) and at one point your going at 24 mph, then your cadence is going to be higher than if you are going 20 mph...this is simple mathematics. It doesn't matter why you are only going 20 mph, your legs are going to spinning at a slower rate than they would at 24 mph.

Yep..benb gets it.

[erikbrooks]

This software engineer is with Keith on this. It's a simple calculation. As long as the computer has been programmed with the correct tooth counts, and you are pedalling, not coasting, the cadence shown should be quite accurate - more so than MPH, which does not take tire size into account unless you've done a careful rollout.

Soft pedalling, wind, and hills won't affect the calculation any more than they do the MPH figures. As long as you aren't coasting at all, it's good.

BTW, I have played with the cadence feature WHILE coasting. I was going down a hill at maybe 30MPH, and just kept downshifting while coasting. When I got to my lowest gear, it read cadence of 220. This means nothing, of course. I did try spinning my fastest and upshifting til I stopped freewheeling, and that was at 160. I could only do that for a couple of seconds, and that was still downhill. Again, this means nothing, but it was kind of fun to play with.

[Keith A]

From one software engineer (with a strong background in math) to another, thank you Erik!

[mcgillicuddy_p]

These numbers are for arguments sake not actual. Assume I am spinning a 53 x 16 at 90 RPM (actual not virtual) on flat ground with no wind and travelling at a constant speed of 22 MPH. Flight Deck would calculate that as a cadence of 90 RPM.

Let us say that the next day I am riding the same flat road with the same bike in the same gear and the same actual cadence of 90 RPM. The only difference is a 40 MPH head wind. This would reduce my speed to 17 MPH and thus my Flight Deck would calculate my RPMs at something lower than the actual 90.

The cadence function only factors in 2 variables-speed and gear. All other external forces are not calculated.

[Sandy]

This software engineer is with Keith on this. It's a simple calculation. As long as the computer has been programmed with the correct tooth counts, and you are pedalling, not coasting, the cadence shown should be quite accurate - more so than MPH, which does not take tire size into account unless you've done a careful rollout.

Soft pedalling, wind, and hills won't affect the calculation any more than they do the MPH figures. As long as you aren't coasting at all, it's good.

BTW, I have played with the cadence feature WHILE coasting. I was going down a hill at maybe 30MPH, and just kept downshifting while coasting. When I got to my lowest gear, it read cadence of 220. This means nothing, of course. I did try spinning my fastest and upshifting til I stopped freewheeling, and that was at 160. I could only do that for a couple of seconds, and that was still downhill. Again, this means nothing, but it was kind of fun to play with.

I just don't understand your statements in your first paragraph. In certain situations (like down a hill with a steep tailwind, for instance) , I think that you could be pedalling and the virtual cadence could be significantly different than the actual cadence. I really don't follow you at all.


:banana: Sometimes Spinning Speedily Sometimes Spinning Slowly Seemingly Stupid Serotta Sandy :banana:

[benb]

Let us say that the next day I am riding the same flat road with the same bike in the same gear and the same actual cadence of 90 RPM. The only difference is a 40 MPH head wind. This would reduce my speed to 17 MPH and thus my Flight Deck would calculate my RPMs at something lower than the actual 90.


This would require your tire to have broken traction and be spinning like a car at the drag strip.

If you're riding the same cadence (not coasting or pedaling slower then possible) in the same gear with the same wheel/tire size you go the same speed, no matter what the conditions are. When you actually get out on the road in a 40mph headwind you will not be able to turn the pedals at the same cadence as on a day with no wind or a tailwind. That's why your speed will be lower.

[Bud_E]

As long as you are meeting resistance when you are pedalling,
virtual cadence = real cadence

(discounting tire slippage)

[benb]

I just don't understand your statements in your first paragraph. In certain situations (like down a hill with a steep tailwind, for instance) , I think that you could be pedalling and the virtual cadence could be significantly different than the actual cadence. I really don't follow you at all.


Yes your right...

At any speed you can pedal at the cadence which will apply drive to the bike in that given gear. If you are doing so the virtual cadence equals the actual cadence. If you are pedaling slower then that speed you're coasting and the real cadence is lower then the virtual cadence.

Here is an exercise for everyone who still doesn't get this:

- Get out on the road. Pedal the bike. Listen for the freewheel clicking.

- If you hear no freewheel clicking, you're not coasting, and the flight deck would show you the correct cadence.

- If you can hear your freewheel clicking, you're coasting at some % and your cadence is lower then the flight deck would report.

- If your freewheel is clicking you're not putting optimal power into the bike and/or you've got a dead spot in your pedal stroke. You're getting some sort of rest.

Go up a significant hill.. you will not hear the freewheel clicking. Go down a hill, you will hear it clicking unless you grab a big gear and pedal hard. Ride in a tailwind, you'll hear the freewheel unless you've got a big enough gear and are pedaling hard.

Here is another way of thinking about it. On a fixed gear bike the Virtual Cadence will always equal the real cadence.

[SoCalSteve]

Ive read through this entire posting and no one has really answered the op question....

I will:

I have Flightdecks on all my bikes, I also use a Polar 725 with the cadence sensor (so I can record my avg cadence). They are almost always identical when pedaling. When you are NOT pedaling, there is no cadence, so the reading (whatever it is) doesnt really matter.

So, the answer is: Yes, the Flightdeck is extremely accurate when it comes to cadence.

Steve

[superunleaded]

BTW, I have played with the cadence feature WHILE coasting.

Good one.
Have you played with 3 magnets on the wheel? That too is fun even when the bike is on a trainer or stand where you can spin the wheels.

I'm with you guys on this one btw. FD's cadence is accurate and useful if used properly.

-g

[TAW]

Ive read through this entire posting and no one has really answered the op question....

I will:

I have Flightdecks on all my bikes, I also use a Polar 725 with the cadence sensor (so I can record my avg cadence). They are almost always identical when pedaling. When you are NOT pedaling, there is no cadence, so the reading (whatever it is) doesnt really matter.

So, the answer is: Yes, the Flightdeck is extremely accurate when it comes to cadence.

Steve


Well, I have to admit that this is pretty good evidence for the accuracy of the Flite Deck. Maybe it's just my way of thinking, but would it not be true that a car would use more gas to maintain the same speed going against the wind as going with it? It uses more gas because it has to maintain a higher rpm in order to stay the same speed. Since the Flite Deck's variable in computing cadence is speed, it seems to me that a fluctuation in speed would have to affect the cadence. Going into the wind using the same gearing and cadence would have to be slower, IMO.

Where am I thinking wrong?

[Bill D]

The analogy to using more gas would be like measuring *power* and not *cadence* on a bicycle because you're also taking into account the energy required to turn the cranks at that RPM. As others have pointed out, as long as you're not coasting, a given RPM in a given gear produces one speed. True, it's a lot harder to achieve that RPM and speed into a headwind or up a hill; but that's saying that it takes more power.

The example of the fixed gear (from someone above) is a great one here. Pushing a fixed gear on the flats or downhill is easier than getting that same fixed gear up a hill. But that doesn't mean you go faster at the same RPM, just that it's harder (requires more power or energy) to achieve those RPM. Turning the cranks at x RPM turns the rear wheel at y RPM, which is a function of the gearing. The chain is fixed by the sprockets and doesn't slip, right? So the speeds of the crank and rear wheel are related only by the gear ratios. Speed, then, is a function of that RPM of the rear wheel and the circumference of that wheel.

This is one of those things that may be easier to visualize if you turn your bike upside down and turn the crank.

-bd

[LONE RIDER]

Thank you SoCalSteve! This is what I was looking for. This has all been very interesting. One mind experiment I would suggest for others is to replace the discussions of virtual cadence with an actual measurement of crank cadence. In this case if you are pedaling at a constant 90rpm in the same gear with or without a head wind (and not accel or decel - acceleration being the change in velocity over time) you would be going the same speed - correct? And in a head wind you would need more power to go the same speed - power being the energy expended over a unit of time and the extra energy is needed to overcome the additional wind drag. Cool stuff!

[tch]

If you are going in the same cadence in the same gear, you are going the same speed. Period. If you are going slower, you cannot be going in the same cadence in the same gear. All this discussion of headwind etc. is dumb (excuse me guys). If you are going 17 mph into a headwind instead of 20 mph, as posited above, you are not riding in the same gear at the same cadence. It's simple mechanics.

[RPS]

(snip.....)Maybe it's just my way of thinking, but would it not be true that a car would use more gas to maintain the same speed going against the wind as going with it? It uses more gas because it has to maintain a higher rpm in order to stay the same speed. (snip.....)

Where am I thinking wrong?TAW, the main reason a car uses more gas to go into the wind or climb a gradual grade is due to the throttle being open more, thereby charging each piston with more air and gasoline, hence the higher fuel rate (i.e. -- uses more gas). It is possible that RPM could vary a little with an automatic transmission if the load is increased enough to disengage the torque converter's lock-up, but that's minor and not the issue here. On a manual transmission car -- which is more like a bicycle in how it operates -- as long as you leave the transmission in the same gear and the clutch doesn't slip then the engine will run at the same exact RPM to hold the same speed. The car will use more fuel at the same RPM due to the pistons being charged at higher pressure with more fuel and gasoline, not because of higher RPM. That's where you are confusing issues IMHO. :argue:

[Brons2]

These numbers are for arguments sake not actual. Assume I am spinning a 53 x 16 at 90 RPM (actual not virtual) on flat ground with no wind and travelling at a constant speed of 22 MPH. Flight Deck would calculate that as a cadence of 90 RPM.

Let us say that the next day I am riding the same flat road with the same bike in the same gear and the same actual cadence of 90 RPM. The only difference is a 40 MPH head wind. This would reduce my speed to 17 MPH and thus my Flight Deck would calculate my RPMs at something lower than the actual 90.

The cadence function only factors in 2 variables-speed and gear. All other external forces are not calculated.

Impossible. So long as you have the freehub fully engaged (ie not coasting whatsoever), 53x16 at a certain cadence is going to yield the exact same speed regardless of external factors.

If you are going slower into the wind, you are pedaling at a lower cadence-period.

This is not like an aircraft where you have distinctions between true air speed and ground speed.

[Brons2]

If you are going in the same cadence in the same gear, you are going the same speed. Period. If you are going slower, you cannot be going in the same cadence in the same gear. All this discussion of headwind etc. is dumb (excuse me guys). If you are going 17 mph into a headwind instead of 20 mph, as posited above, you are not riding in the same gear at the same cadence. It's simple mechanics.

Yes. Thank you.

[Brons2]

On a manual transmission car -- which is more like a bicycle in how it operates -- as long as you leave the transmission in the same gear and the clutch doesn't slip then the engine will run at the same exact RPM to hold the same speed. The car will use more fuel at the same RPM due to the pistons being charged at higher pressure with more fuel and gasoline, not because of higher RPM. That's where you are confusing issues IMHO. :argue:

Yes, and I own a manual transmission car. The tachometer never varies at a set engine speed, say 70mph which I set often on my cruise control, the tach is always at 3100 RPM. It uses more gas into the wind because throttle is opened wider. But the engine speed (cadence) doesn't vary.

So too the same is true with the human body, you would expend more energy into the wind but at a given cadence at a given gear you would go the same speed as with a tailwind using the same gear and cadence.

[TAW]

I was wrong about this. Went for a ride today with the Flight Deck and checked the virtual cadence on the computer against actual cadence riding with the wind and against it, and in both instances the Flight Deck was accurate. I just couldn't get my mind to think in the right terms, but in any case, clearly I was incorrect.

Sorry for the misinformation. It appears that I'm a bad advertisement for Flight Deck computers.

[Keith A]

Now that we have this settled, maybe we can solve the problem of drugs in the peleton :rolleyes: