# How does Shimano Flight Deck measure cadence?



## Clevor (Sep 8, 2005)

I have the SM-SC70 harness kit and SC-6502 computer for 10-speed setups. Will be trying to install it soon on my 6600 Ultegra setup. From the instructions, I see only one sensor which fits on the fork. Does this read both speed and cadence???? Normally you'd need a separate sensor to fit on the chainstay to read cadence, but I only see one sensor in the harness kit and instructions.


----------



## RussellS (Feb 1, 2010)

It estimates cadence. Virtual cadence. The computer knows your speed and what gear you are in. It calculates your cadence from that information. Simple math. But you can be coasting down a mountain in your 39x27 gear going 50 mph and it will say you have a 200+ cadence. Virtual cadence. It always assumes you are pedaling at full force. Not coasting or soft pedaling.


----------



## Clevor (Sep 8, 2005)

RussellS said:


> It estimates cadence. Virtual cadence. The computer knows your speed and what gear you are in. It calculates your cadence from that information. Simple math. But you can be coasting down a mountain in your 39x27 gear going 50 mph and it will say you have a 200+ cadence. Virtual cadence. It always assumes you are pedaling at full force. Not coasting or soft pedaling.


Leave it to the Shimano engineers to use math rather than extraneous hardware :yesnod:. A good try to avoid having to use two sensors. I guess the drawback you mention is why manufacturers of standalone cycling computers shun this approach. I'll keep that in mind when I have mine installed.

Actually I do a lot of climbing and will be running a Rox 9.0 at the same time anyway, to give me slope information. The Flight Deck can do a lot (considering when it debuted), but I need the Rox for total feet climbed, heart rate, and calories burned .

I mainly want the Flight Deck for the gear indicator. I always wanted to know distance and speed in km/hr too so I will set my Flight Deck for that and set the Rox for miles. 

I like what Shimano did, because now my chainstay is clear for the Rox cadence sensor! :thumbsup:


----------



## RussellS (Feb 1, 2010)

http://techdocs.shimano.com/media/t...1_M500/SI-7AP1F-ENG_v1_m56577569830686508.pdf

From page 12 of the PDF: 

"Cadence is calculated from the F -R gear tooth numbers and current speed.
Note; Cadence always appears during bicycle movement regardless if the crankarms are rotating."


----------



## martinrjensen (Sep 23, 2007)

Other manufacturers did not shy away from this aproach because it always measures cadence regardless of pedal load, but because they couldn't do it. How are they going to know what gear you are in without a proprietary connection to the derailleurs? Also....Think about it, If you are coasting, you really don't care what your cadence is anyway, so that function is not really an issue. Saying all that, the flight deck is a little long in the tooth and there are other issues with it but they are mechanical.


Clevor said:


> Leave it to the Shimano engineers to use math rather than extraneous hardware :yesnod:. A good try to avoid having to use two sensors. I guess the drawback you mention is why manufacturers of standalone cycling computers shun this approach. I'll keep that in mind when I have mine installed.
> 
> Actually I do a lot of climbing and will be running a Rox 9.0 at the same time anyway, to give me slope information. The Flight Deck can do a lot (considering when it debuted), but I need the Rox for total feet climbed, heart rate, and calories burned .
> 
> ...


----------



## rochrunner (Jul 11, 2006)

What does "pedal load" have to do with it? If you know the exact circumference of the wheel and the gearing, you can calculate the cadence exactly and it doesn't matter how hard you're pressing on the pedals as long as you've got enough load on them that you're not coasting for any part of the revolution.

It's basically a solid mechanical connection from the pedal to the tire -- there's no slippage related to the force being applied to the pedal.


----------

