A bicycle power meter is a serious training tool.
with a bicycle power meter will greatly improve your results."
Wikipedia, a power meter is "a
device on a bicycle that allows measuring of the power output of the
rider." While this may seem like a pretty simple
explanation, the physics and engineering behind the power meter is not
The most common of these is the Power Tap SL. This hub has been around for many years and is well known in the bicycle power meter community. These are made with both a Shimano compatible hub body and a Campy compatible hub body.
A less expensive version, the Power Tap Pro, offers the ability to measure power but weighs a little more.
Available in both a wired and wireless model the PowerTap is simple to interchange between bikes as long as the drive trains are compatible. Here is what a built up wheel looks like with the Power Tap hub installed.
strain gauges in the rear hub transmit the data to the head unit where
it is viewed by the cyclist as well as stored for downloading to any
number of software products. You can even upload your data to
coaching software for self-analysis or review by a coach.
The battery in the computer and the hub both last a long time. The manual says 400 hours of riding time and I can say that is pretty accurate. The use of the Power Tap in the really cold weather will sap the batteries faster than riding in warm weather.
Check out eBay if you are interested in a good used Power Tap bicycle power meter.
I purchased the S710 Heart rate monitor and the Polar power output sensor kit as an add-on.
The Polar power output sensor kit use chain vibration to measure power. It works with the Polar S710, S720i,S725X , S625X, and CS600
You can buy the power meter kit with these or as an add on.
How does it do it? Think of it like an electric guitar. When you strum the strings of an electric guitar you are putting energy into the string. The frequency of the vibration has an equivalent energy signature. The power kit for the polar works in very much the same way. There are some parts placed on different areas of the bike. Take a look at the picture below to get an idea of what I am talking about.
The parts are starting from top left:
One big thing I learned about using this bicycle power meter is it helped me train at a consistent power output rather than a consistent heart rate, which is really tough and both are way better than a perceived exertion style of training.
After some initial fiddling with the meter, I got it on the bike and it worked, sort of. I noticed that when the chain was in the big ring on the front and first gear in the back (yes, I know you shouldn't cross like this but I was using a compact crank), the power readings were not very accurate. However, in the rest of the gears, this thing was really accurate. I even tested it against my Computrainer Pro and it was within 1-2% all the time.
Take a look at these on eBay if you don't want to buy a new bicycle power meter. I sold mine on eBay. There wasn't anything wrong with it, I just wanted to try something different.
Rumors abound about another manufacturer bringing out a bottom bracket power meter and I'll try to find out about it and post it here.
One of the riders in my club has gone through three of them. They kept failing. He is buying them pretty cheaply on eBay now.
If you are brave, you could try one. Here is a listing of the current Ergomo bottom bracket bicycle power meters on eBay:
SRM Training Systems is very well known throughout the cycling community. Among cyclists, it is a well respected power measuring device that is used by many, many pros in both training and races. If you watch stages of the Giro d'Italia or the Tour de France, you can see SRM power meters on many of them.
The three main component suppliers, Shimano, Campagnolo and SRAM have versions available to work with virtually anyone's bike.
The system is comprised of the following pieces:
Inside the crank spider, there is a strain gauge. This measures the power applied to the crank arm and calculates the wattage the rider is generating from the force applied. Along with power, these systems measure altitude, heart rate, distance, cadence.SRM released a full wireless system in 2008 that uses the ANT+ standard for wireless data transmission. Now you can have wireless power, speed and heartrate pickup with the SRM system.
One of the biggest drawbacks to putting any bicycle power meter system on a bike is the running of wires. Now that more and more manufacturers are getting on-board with the ANT+ standard, I don't think it will be long before we see everyone release a wireless version of their bicycle power meter.
The other player in the crank based power meter is newcomer Quarq. They are offering the Cinqo power system.
The Cinqo power system replaces the spider on your existing crank, if it is one of these listed below:
They are working on bringing more options to market, just give them a
little time. This will be the next power system on my bike.
I like the idea of using your existing cranks and keeping a
more "stock" look to the bike.
I started using this type of power meter in 2007 when I saw the ad in Velonews for the iBike power meter. I thought: "Now here is a great idea. A power meter that you can just put on your bars without all of the complicated setup, wiring and special do-dads that the other types of power meters required."
For the most part I was right. The iBike has outstanding customer support. I spent a good amount of time on the phone with the developer and owner of the company. He was very helpful in getting many of my problems solved. I have even visited the factory. Made in the USA is a plus.
I had a problem on a trip in Italy and one of the designers spent 40 minutes on the phone with me to help me solve the problem. I can't say I have had service like that (with no fee mind you) from anything other than a small local company. These guys know their customers and how to treat them.
Now on to how it works:
The iBike goes on your handlebars. If you get the wireless version you only have to put the wireless mount on your bars and do the calibration to set it up for your bike. Calibration is three different choices. Fast Setup, Advanced (called USER) and Racer setup. The fast setup will work for about 95% of the riders out there. The User and Racer setups just get you that last little bit closer to perfect.
Before every ride the system will auto calibrate the wind speed sensor. This gives you a zero line for wind hitting the power meter
During the fast setup, you will have to do this one time:
I have been using this for several years. The firmware updates that come out make these units more and more advanced. For the money, I feel they are a great deal!
The data I have seen is very accurate. There is even data from racers using several power meters at once to compare back and forth. I used the iBike with a Power Tap and I can say the data was very close.
The only downside I have found to this bicycle power meter is that it eats batteries in the cold weather. The latest version of the firmware, 4.0 is supposed to have changed this quite a bit. It hasn't been cold yet so I'll have to report back later. I find it necessary to replace one every month in the cold months. The good thing is they are still good to put in during the summer they recover when they warm up.
Here are some iBikes currently available on eBay:
There is a new product out now from a company called Metrigear. They have a power meter that is integrated into the hollow shaft of a standard bicycle pedal. It will be available the first quarter of 2010 from the company. After the release I will do a review of the product.
You can get more information here from their website.
An in development project is also in the works from is from an Irish company called Brim Brothers. They don't have a product on the market yet. It is still in development and they aren't saying much about it. You can see their site here if you would like.
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