A Guide to Powermeters

A Guide to Powermeters

Power meters are great. They offer an objective number to determine how much force you are putting into your bike. In very simple terms, the more power you create, the faster you go. Having a tool to help determine how much force you are putting into your bike can assist you with how you train, race and recover.


Power meters are not a cheap upgrade but are arguably one of the most valuable. They won’t make you go faster, they will almost always add weight to your bike and are an extra thing to charge. Unlike purchasing a new set of wheels where there is a clear benefit on the first ride, a power meter won’t make a difference. So why bother buying one?


Heart Rate and Perceived Effort

Traditionally cyclists have relied on heart rate and perceived effort. Again, in very simple terms, the higher the heart rate or perceived effort the faster you are likely to be going. Both of which are great because perceived effort costs nothing and every single cyclist can use it. Secondly, a heart rate monitor is so common in most people’s watches now that you don’t even need to go out and buy a dedicated heart rate strap, and if you do they are incredibly cheap. However, they are both affected by your sleep, caffeine intake, diet, stress and so on. There is very little consistency with these two figures which means creating a consistent training plan is very difficult and therefore your ability to develop as a cyclist can be slightly hampered.


What does a power meter offer?


A power meter provides a number that is consistent regardless of how you are feeling, the weather or your speed. This number is provided in Watts and is the amount of force that you as the rider are generating. The number that is generated remains the same day after day and means there is a constant to base all riding around. This means that you can see clear developments in your training if you can hold a certain power for longer.

 

A power meter can also help make informed decisions on how to pace an event. If you know how long you can hold a certain power then you have something to try and hold for a whole ride. If you try going too hard and fast then you may use up too much energy and struggle to make it through the event. Alternatively, you may be following a training programme that sets you certain power zones to try and spend time in. Being able to train in those zones regularly without any variance like perceived effort or heart rate provides means you can develop quicker as an athlete. 

 


Quite simply, as a training tool, a power meter is one of the most useful items you can purchase.


What types of power meters are there?


Power meters can fitted to your bike in a variety of ways which include:

  • Pedals;
  • Crank arms;
  • Spider based; and
  • Rear hub.

The first three are the most common and there are some other types which include a chest strap, on the crank spindle and a gauge on your inner tube valve, however these are much less common and so I will stick with the main types.


Power meters also are either single sided or double/dual sided. 

A single sided power meter measures just one leg and doubles the figure to create your overall power reading. This is usually the cheaper option however it does create more inaccuracies. If one leg is significantly stronger than the other then the number will be a long way off a true reading. However, if you are relatively balanced then it provides a figure pretty close to the true value. 

A double/dual sided power meter detects power from both legs and provides a very true and accurate power reading. But, these usually cost more and do pose so different challenges which I will discuss later.


Pedals


Pedals are one of the best options for their simplicity of putting on and taking off a bike. Even for the most mechanically challenged, changing a set of pedals should be a task every cyclist can do. Additionally, if you have multiple bikes it is very easy to swap pedals between bikes which means you only need to invest in one power meter, saving you a fair bit of money.


Pedal based power meters are also great because they are the first piece of equipment which come into contact with the cyclist. As soon as you put force through the pedals that is immediately detected by the pedals. There is no delay for the force to be passed down through the cranks and into the spider, or through the chain into the hub. This means that they should in theory be the most accurate destination of measuring how much power you can generate.


Examples include:


  • Favero Assioma
    • UNO
      • These are single sided power meter and provide a power accuracy of +/- 1% which is very impressive. At £400 these are a very good option
    • DUO
      • The dual sided version of this power meter costs £600 which marks a significant increase in cost. However the added accuracy will be a really useful 
  • Garmin Vector
    • Double sided power meter
      • A slightly more expensive option at £665 the dual sided pedals come from the well known brand  and have an impressive 120 hour battery life

A single sided power meter can connect pretty easily with your cycling head unit. However, a dual side power meter has two separate items which need to connect and this can sometimes create issues. An example is where only one pedal connects and the other doesn’t. It isn’t that common issue but it is worth noting the simplicity of single sided power meter does have its benefits.



Crank Arms


Power meters based in the crank arms offer a broader range and can provide a very cheap option to entering the power meter game. Usually there is a small sensor fitted to the inside of the crank which detects the riders output and sends a signal to your head unit showing power. Stages and 4iiii are the big names here with these options:


  • 4iiii
    • Precision
      • Within the Precision range there are multiple options to fit all levels of Shimano and Sram cranks. These are all left crank only and canm be found as cheap as £250. With a suggested 1% accuracy these really are one of the best options
  • Stages
    • G3 Power
      • Like the Precision offers above, there are options to fit all levels of groupsets and they are priced very similarly to 4iiii
      • At £669 you can purchase a Shimano Ultegra dual sided version 

One consideration with crank arm based power meters is the clearance with your frame. Due to the small sensor on the inside of the crank arm it may not be possible for the crank arm to move freely past the frame. It is worth checking this before purchasing.


Spider Based


Spider based power meters are arguably one of the best options. They are incredibly accurate, they are unlikely to be damaged if you crash and are the favourite amongst the pro peloton. Quarq and Rotor provide some fantastic offerings and it is difficult to go against spide based options given their reliability and accuracy. If pure precision day in, day out is what you are after, then I would suggest going no further than these.


  • Quarq
    • Dzero 
      • These options start at £355 and provide dual sided readings. With a battery life of 200 hours this really is a great option
  • Rotor
    • Inpower
      • At a slightly higher price, the Rotor Inpower power meter can be purchased for £529. The added bonus of this is that they will work properly with oval chainrings which is not the case with all power meters.

For all of these options, you are still going to need to purchase crank arms and possibly a bottom bracket as well. This is not a cheap option, but it is the most accurate. 


Conclusion


Whichever power meter you decide to go with, over time it will provide you with the consistency to develop your training. If you choose to go for a cheaper single sided option which may not be as accurate as the top end versions, it will provide consistency over time. If you are switching between power meters then this may add to some complications and so I would suggest sticking to one style. 


There are some cheap options out there, and the second hand market is often filled with old ones. Think about your mechanical skills and whether you can fit it to your bike, or whether you want to be able to switch it between bikes.

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