General Discussion Triathlon Talk » Cadence computer v. non cadence computer for trainer Rss Feed  
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2011-10-25 12:55 PM

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Subject: Cadence computer v. non cadence computer for trainer

Just got back from the LBS and am a bit confused.  I just started using an indoor trainer and my computer sensor is mounted on my front tire - since I don't feel like moving it from the front tire (have to cut zip cords, unwind wire etc.) I was thinking of just buying another inexpensive computer to track my indoor workouts.  So I ask the guy in the LBS about this situation and he starts suggesting I get a cadence computer(he admitted he has not installed or used one himself on a trainer).  I asked what the difference is between a cadence and non-cadence computer and he never gave me a good answer - he did mention something about having a sensor for the pedals in addition to the wheel itself but then he started talking in circles and confused himself...

So I just want to track the same info on the trainer that I normally do on outdoor rides - speed, average speed, distance, calories burned etc.  Can I do that will a regular Cat Eye computer like I currently have or having a sensor on a trainer (on the rear wheel) require a cadence or different type of computer?



2011-10-25 1:07 PM
in reply to: #3737587

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Subject: RE: Cadence computer v. non cadence computer for trainer

If the guy at the LBS can't do a good job of explaining a cadence sensor to you, then I think you need to be talking to somebody else. It's not rocket science. The cadence sensor simply tracks the number of pedal cycles per minute, using a small magnet on the crank that works pretty just the same as the speed sensor on the wheel. 

You can certainly get a rear speed sensor without the additional piece for cadence. I actually have the cadence sensor on my Cateye V3, which includes HR tracking. But the cadence part is not functioning, and frankly I don't miss it. I have a good idea of the relation between specific cadences and speeds in different gear ratios. 

(By the way, you can probably just ignore the calorie calculator on your current computer and just pay attention to speed. The calorie estimate is unlikely to bear much relation to reality.)

Enjoy your trainer workouts. They are hard, but they really do help.

2011-10-25 1:33 PM
in reply to: #3737605

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Subject: RE: Cadence computer v. non cadence computer for trainer

At a minimum you will want to put a wireless cateye or similar cyclo computer mounted on your bike with the speed sensor and magnet on the rear wheel.  Maintaining a measure speed is very important for riding on a trainer.

If you have a Garmin 310xt, Edge 500 or similar Garmin unit, you will benefit from adding a garmin speed and cadance sensor to your setup.  The SC10 attaches to the off-side chainstay, and uses two magnets.  One on the rear wheel that measures speed on the trainer and a seperate magnet on the crank arm that provides cadance by counting the number of times the crank passes by the front of speed/cadance sensor.

Regards.

 

2011-10-25 2:20 PM
in reply to: #3737587

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Subject: RE: Cadence computer v. non cadence computer for trainer

Most of my trainer dvd's are focused around cadence. When i first got my trainer i did not have a cadence computer so at times it was hard to follow the workout dvd. so i got a wired cat eye cadence computer.

 

 

 

2011-10-25 2:38 PM
in reply to: #3737587

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Subject: RE: Cadence computer v. non cadence computer for trainer

I have to 100% disagree with the previous answers.  Not trying to be a jerk about it, but here's my opinion.

I use the cadence reading almost the entire time I'm on the trainer.  Cadence, HR and power.  I don't look at the speed ever.  Keeping a high cadence is very important.  I use spinervals for a lot of my indoor workouts and they are based on gearing and cadence.  Troy will say if you can't keep up X cadence, then change gears so you can.  He never talks once about speed/distance. 

A good article here on BT regarding cadence can be found here.

2011-10-25 2:46 PM
in reply to: #3737587

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Subject: RE: Cadence computer v. non cadence computer for trainer
If your training specifically targets cadence, I can see the value in going with a cadence set-up, but  I just use a stop watch: 15 revolutions in 10 seconds = 90 RPM.


2011-10-25 3:00 PM
in reply to: #3737732

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Subject: RE: Cadence computer v. non cadence computer for trainer
dhwebb - 2011-10-25 3:38 PM

Keeping a high cadence is very important. 

No, it's not.  Power output is very important.  Cadence is just one piece of it and can vary from rider to rider.  The best advice on cadence is to ride a lot and you will find a 'comfortable' cadence.

To the OP, just be aware that your speed/distance on the trainer may or may not be similar to what you would do outdoors at the same effort.  If you set up your trainer the same each time, you can get reasonable comparability between trainer sessions so speed may still hold some value to you.  But, you can do all your riding on effort if you want and not worry about the 'data'.

2011-10-25 4:57 PM
in reply to: #3737587

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Subject: RE: Cadence computer v. non cadence computer for trainer

Used to train on my trainer with PE and than bought a cadence sensor. What a difference. I work much, much harder, keeping my cadence up. Trainer workouts have become much bigger sufferfests. On a trainer, dont worry about speed and distance. Its all about power output, HR and cadence

I would recommend one anytime. 

2011-10-25 5:36 PM
in reply to: #3737587

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Subject: RE: Cadence computer v. non cadence computer for trainer

Cadence x Gearing yields Speed.
Speed maps directly onto Power for most good trainers.
(though it has no relation to speed on the road). 
Power is what matters in the end. 

So if you already have a power meter, then speed and gearing are not terribly useful. But if you don't have a power meter, then a consistent set-up plus speed are the most informative sources of information, as they can predict power. Neither cadence nor gearing alone can predict power. Jointly they can predict power -- but jointly they are equivalent to speed.

2011-10-26 8:11 AM
in reply to: #3737975

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Subject: RE: Cadence computer v. non cadence computer for trainer
colinphillips - 2011-10-25 6:36 PM

Cadence x Gearing yields Speed.
Speed maps directly onto Power for most good trainers.
(though it has no relation to speed on the road). 
Power is what matters in the end. 

So if you already have a power meter, then speed and gearing are not terribly useful. But if you don't have a power meter, then a consistent set-up plus speed are the most informative sources of information, as they can predict power. Neither cadence nor gearing alone can predict power. Jointly they can predict power -- but jointly they are equivalent to speed.

Good explanation.  Thanks.

Cadence, by itself, is NOT important--be it "high" or "low".  I do not ever think about my cadence rate when I ride other than deciding if I feel comfortable riding at whatever cadence I am spinning at the moment.  If I am not, I switch gears.

2011-10-27 4:29 AM
in reply to: #3737587

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Subject: RE: Cadence computer v. non cadence computer for trainer

Since I'm also in the position of looking at a computer to track my trainer time (my GPS-based Polar isn't going to do much good I suspect Tongue out) I want to make sure I understand how these things work a bit:

A bike computer uses something like a magnet on the wheel to trigger a sensor on one of the stays - so the more times per minute the magnet passes the sensor the faster you're going.... Is that right?

And based on wheelsize and rpm, the distance can be calculated, and speed as well?

And a cadence add-on does something similar, except it counts revolutions of the crankset rather than the wheels?

And without a power meter, any computer that offers power (like the KK computer) is merely calculating it based on some formula using the above inputs?

Since I don't yet have a power meter, I figure a simple computer that can tell me speed and distance will still help - I can still track progress that way, right?

Thanks!



2011-10-27 6:35 AM
in reply to: #3739970

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Subject: RE: Cadence computer v. non cadence computer for trainer
wannanorseman - 2011-10-27 5:29 AM

A bike computer uses something like a magnet on the wheel to trigger a sensor on one of the stays - so the more times per minute the magnet passes the sensor the faster you're going.... Is that right?

And based on wheelsize and rpm, the distance can be calculated, and speed as well?

And a cadence add-on does something similar, except it counts revolutions of the crankset rather than the wheels?

And without a power meter, any computer that offers power (like the KK computer) is merely calculating it based on some formula using the above inputs?

Since I don't yet have a power meter, I figure a simple computer that can tell me speed and distance will still help - I can still track progress that way, right?

Yes, this is exactly right.

If the trainer is stable over time (not all trainers are alike in this regard), then you can use speed as a replacement for power. The key thing is to make sure that your set-up is consistent from one workout to the next, i.e., rear wheel resistance, tire pressure. As long as you do this, the same speed will always correspond to the same wattage. A good way to test for consistency in the set-up is to measure the coast-down time from some fixed speed. E.g., after warming up a bit, pedal up to 20 mph, then stop pedaling and time how long it takes for the wheel to come to a stop. You want that time to be the same across workouts. 

If you want to get a bit fancier, then you could explore piping this data to trainerroad.com, which can do all kinds of clever stuff with it.

2011-10-27 7:57 AM
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Subject: RE: Cadence computer v. non cadence computer for trainer
How are you planning on using your trainer? Are you following a particular training plan? Using bike training videos? Just getting on and riding? How you plan to use the trainer may dictate what you need. I agree with most that after some time riding, you'll find a comfortable cadence, and what that cadence is isn't particularly important - unless you're using a training tool that directs you to pedal in a certain cadence range (like some Spinervals DVDs do).

If you're training by heart rate - no need for a cadence computer.

Training RPE - no need for a cadence computer.

Training with power - no need for a cadence computer. However, a rear wheel speed sensor can be useful for if your trainer has a known power curve and you want to train with "virtual power". This is what I'm planning to do over the winter. I hope to pick up a real power meter at some point, but virtual/simulated power plus heart rate will work well for me for now, I think. I picked up a cheap Garmin Ant+ Speed/Cadence sensor, and I plan to use that with the new Trainer Road application to train on the trainer over the winter. Pretty inexpensive way to begin training with "power" for now...

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