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I've recently heard of these power measuring computers that Kurt makes to connect to they're Kinetic model trainers. They make out they're an accurate power measuring tool and they're pretty inexpensive when compared to other power measuring devices around. Has anybody got any experience or comment on these? I'm in the market for a new trainer and if these things work I'd probably buy one.
 

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I have a friend with one who thinks it was worth the money. With a road bike hooked into his Kurt trainer running a Powertap, the wattage was within 5 watts at 200 watts. Kurt trainers are calibrated pretty consistently but a number of things come into play when measuring wattage on a trainer that a 50 dollar cyclo-computer cannot take into account like how tight the roller is on the tire, actual rolling resistance of your tire and tire pressure just to name a few.

Basically what you need for indoor training is something that is repeatable but not necessarily 100% accurate which the Kurt power computer will do if you make sure the variables are always the same.

Good Luck
 

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PMC said:
Basically what you need for indoor training is something that is repeatable but not necessarily 100% accurate which the Kurt power computer will do if you make sure the variables are always the same.
What PMC said. I bought the Roadmaster and power computer last winter. When my wife bought me a HRM a couple years ago, that and Friel's MTB Training Bible were the best things for helping me train better. Now, reading Morris' Peformance Cycling and getting a Kinetic trainer/power computer has given me another breakthrough in training. I highly recommend Kinetic trainer/power computer for getting your feet wet in power training. The trainer by itself was a vast improvement over my magnetic trainer, providing a much more realistic power load.

Only negative note is that occassionally, on longer workouts of 1-2 hours, the computer stopped picking up the signal. After 20 minutes or so, it started working again. Originally fixed the problem with realigning the sensor/magnet combo. After a couple weeks, it occurred a couple more times. For SMSP (short) intervals and sets, this hasn't been a problem.

The real-time power number jumps around 20 watts or so, I think because of the time slices not taking into account partial rotation of the tire. What I do is put it on scan so I can see the average power along with current and max. After awhile, you get to know the gearing and cadence (measured with a cateye computer) needed to produce a ballpark power output.
 

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I've used an older version for several years now. When it works, it seems to work pretty well, but I've found it to be a little flakey. The battery life is not particularly long, and sometimes the unit doesn't respond when you push the buttons. If you want to use it as a regular bike computer, be warned that it doesn't work well in cold conditions.

All that said, I do like having some indication of power on the trainer, and I've learned not to take it out in the cold and to have extra batteries on hand.

It looks like the new model also has a cadence sensor, which is a nice feature. Maybe they've also improved the button and battery issues?
 

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I just ordered mine. I am hoping it is all what I expect it to be. The main thing I want to be able to do is test my FTP and then develop a training plan based upon those results. Next spring I hope to retest at a higher FTP. ;)

The main clincher for me was that feedback seemed to indicate the power option was consistent. I don't so much care if it is a 100% match with a power tap, (although I guess that would be nice) my main concern is that:

  • I can objectively measure my current fitness
  • develop a training plan based upon that measurement
  • objectively test for fitness gains - measure the success or failure of my plan

I will follow up with this thread or another one after riding the trainer for a while.
 

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Bummer on the wired cadence. If it was also wireless, I would consider it.


I do have the wired $50 one. It works for use on the trainer. Its kind of a pain to take on and off.
 

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A few suggestions to maintain consistency. Try to always keep the same tension between the roller and tire. I release mine when not in use so when I reset I always turn it back the same number of turns as I used to back it off. I found that I need to go 4.5 turns after contacting the tire to get no slippage between tire and roller, which is two more turns than my manual recommended. To test for slippage, push the tire in one direction then suddenly reverse direction - their should be very little slip. Also check the consistency of your set-up by measuring coast-down times at the end of your workout. One other note, if you are using the KK in a cold setting (i.e. garage), it takes about 10 minutes of warm-up for the fluid to warm up and reach a static temperature and produce consistent power readings.
 

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Just to avoid confusion, this unit is not measuring torque (as I understand it); it is taking wheel speed (and maybe cadence?) and then using formulas (based on the known resistance curve of the resistance unit) to calculate power. That's not necessarily a bad thing--just clarifying. Kinetic explains it all here: http://www.kurtkinetic.com/powercurve.php and on that page is a link to a chart that shows your power at any given speed. With that chart, you don't need to by the power unit--you can simply know that 18mph is somewhere around 206 watts on the road machine version (subject to the caveats about tire to trainer interface inconsistencies that I mention below).

Also, as others have said, consistency of power readings from ride to ride will be skewed if the pressure/resistance between tire and trainer is not consistent from ride to ride, or even within a ride. This is a huge issue, in my experience. I've had a Tacx trainer that calculates power for years, along with a powertap, and tire pressure on the trainer can swing power dramatically. It seems that tire temperature (based on how long your riding and the speed of the tire during that riding) changes the power quit a bit (when measured with power tap). It seems that tire temperature is a big factor, and for me it's hard to predict how it will be. The rubber of a tire seems to change tackiness with tire temperature, and the tire pressure will obviously change with tire temperature. I could never seem to predict my power based on wheel speed--I always had to rely on the power tap.

So, based on my experiences, I would not rely on this trainer, or any trainer, to give me consistent power readings from ride to ride--making it hard to track progress (except when your progress has changed dramatically). In my experience, the tire/trainer interface is just too unpredictable, even when trying control it carefully. And, for me, the whole purpose of measuring power is to be more precise with intervals than HR would allow. If my trainer says I'm doing 250 watts, but I'm really doing 225 watts (a 10% difference--which in my experience is common with trainer readings), then I'm losing some of the benefit of training with power.

Bottom line for me: take the power readings with a huge grain of salt.
 

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millennium said:
Just to avoid confusion, this unit is not measuring torque (as I understand it); it is taking wheel speed (and maybe cadence?) and then using formulas (based on the known resistance curve of the resistance unit) to calculate power. That's not necessarily a bad thing--just clarifying. Kinetic explains it all here: http://www.kurtkinetic.com/powercurve.php and on that page is a link to a chart that shows your power at any given speed. With that chart, you don't need to by the power unit--you can simply know that 18mph is somewhere around 206 watts on the road machine version (subject to the caveats about tire to trainer interface inconsistencies that I mention below).

Also, as others have said, consistency of power readings from ride to ride will be skewed if the pressure/resistance between tire and trainer is not consistent from ride to ride, or even within a ride. This is a huge issue, in my experience. I've had a Tacx trainer that calculates power for years, along with a powertap, and tire pressure on the trainer can swing power dramatically. It seems that tire temperature (based on how long your riding and the speed of the tire during that riding) changes the power quit a bit (when measured with power tap). It seems that tire temperature is a big factor, and for me it's hard to predict how it will be. The rubber of a tire seems to change tackiness with tire temperature, and the tire pressure will obviously change with tire temperature. I could never seem to predict my power based on wheel speed--I always had to rely on the power tap.

So, based on my experiences, I would not rely on this trainer, or any trainer, to give me consistent power readings from ride to ride--making it hard to track progress (except when your progress has changed dramatically). In my experience, the tire/trainer interface is just too unpredictable, even when trying control it carefully. And, for me, the whole purpose of measuring power is to be more precise with intervals than HR would allow. If my trainer says I'm doing 250 watts, but I'm really doing 225 watts (a 10% difference--which in my experience is common with trainer readings), then I'm losing some of the benefit of training with power.

Bottom line for me: take the power readings with a huge grain of salt.
I agree that the Power readings cannot be taken as gospel, but the unit offers much more then just the Power readings. I think it is just icing on the cake if you will. I know other units do similar things but the pricing is the same and the Kinetic still does the Power rating. I cannot afford to purchase a good computer and a Power meter and I truly believe even it is, and I do think 10% is a bit steep, but if it is that far off I am still better off then training with out it.

I don't know about you but if I am doing 20 mph on the road and I drop down 10% 2 mph to 18 I can defiantly tell the difference. I just think it's the poor mans toy and I will use it to it's full advantage
 

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My first "FTP" test:

Background:

Age = 41
Weight = 215lbs
Level = Cat 3
Exp = Less then 1 yr ( 5 XC races and 2 time trials)
Best Finish = 2nd Citizen Clyde. Avg finish 7th....70th overall
Avg training week = 6hrs lots of base miles and at least once a week a race pace 50% longer then my races. And once a month a long distance 80% of race pace (30 miles). Also once a week I do hill intervals.

So here are my numbers:

:30 with a :12 warm up
9.26 mi
Avg 18.5 mph
Heart Rate avg = 150 Max 178
RPM avg = 75 Max = 107
Watts = 190 avg Max = 745 :)030 sprint at the end)
 

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What do you need cadence for? You can do fast pedaling drills - just pedal as fast as you can in whatever gear you need to use.

Other than that, having a good estimate of power vs speed based on a repeatable power curve would be pretty nice.
 

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What do you need cadence for? You can do fast pedaling drills - just pedal as fast as you can in whatever gear you need to use.

Other than that, having a good estimate of power vs speed based on a repeatable power curve would be pretty nice.
 

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Belkin34 said:
My first "FTP" test:

Background:

Age = 41
Weight = 215lbs
Level = Cat 3
Exp = Less then 1 yr ( 5 XC races and 2 time trials)
Best Finish = 2nd Citizen Clyde. Avg finish 7th....70th overall
Avg training week = 6hrs lots of base miles and at least once a week a race pace 50% longer then my races. And once a month a long distance 80% of race pace (30 miles). Also once a week I do hill intervals.

So here are my numbers:

:30 with a :12 warm up
9.26 mi
Avg 18.5 mph
Heart Rate avg = 150 Max 178
RPM avg = 75 Max = 107
Watts = 190 avg Max = 745 :)030 sprint at the end)
Thanks for posting this Belkin!
 
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