Magene P505 Power Meter Review: Affordable but with Flaws

Magene P505 Review

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This is my Magene P505 spider power meter review.

I’ve been using and testing it for the last couple of weeks. I compared its data with Saris H3 smart trainer and Favero Assioma DUO pedal power meter.

P505 is a decent spider power meter considering its price. You can buy it here. However, it has some minor flaws.

Learn more about them below.


Magene P505 Summary

Here is a summary of the main features, my findings, and tech specs of the Magene P505 spider power meter.

Main Features

  • P505 can measure left and right balance and pedaling smoothness
  • Auto zero-offset
  • Multiple colored stickers included
  • Affordable price
  • Pairing with the Magene app doesn’t always work
  • 2-year warranty

Technical Specifications

  • Claimed accuracy: ±1.5%
  • Claimed battery life: 200h (rechargeable)
  • Compatibility: 4-arm or 5-arm chainrings
  • Active temperature compensation: Yes
  • Connectivity: ANT+, BLE
  • Weight: 110g

Who Is Magene P505 for?

Magene P505 spider power meter is for riders looking for an affordable spider power meter without sacrificing too much data accuracy*.

*Skip to the accuracy tests section for more info.

It’s suitable for beginners and average cyclists who look for advanced features like L/R leg balance or pedal smoothness.


Magene P505 Unboxing

P505 is sold in multiple options. The compatible chainrings are:

  1. P505-S1108/R110X/S1103: Shimano 110BCD 4-arm chainrings, and 5-arm chainrings of SRAM, ROTOR, FSA, etc.
  2. P505-S1078: SRAM 107BCD chainring

And the compatible crank arms:

  1. P505-S1108 / S1078: SRAM 8-bolt crank arm (with SRAM Red AXS, Force AXS, Red 22, Quarq, etc.)
  2. P505-S1103: SRAM 3-bolt crank arm (with SRAM Force 22, Rival 22, S-900, etc.)
  3. P505-R110X: ROTOR Aldhu, Vegast etc. 45-tooth crank arm

Because I have a Shimano groupset, I opted for the S1108 version.

The power meter comes in a bright orange box. It includes the spider, charger, and colored stickers.


Magene P505 Installation

The biggest downside of spider power meters is their compatibility and installation. It’s not as straightforward as the installation of power meter pedals.

You also need a compatible crankset that I didn’t have. I had to buy SRAM Force D1 DUB, SRAM DUB BB386 bottom bracket, and an SRAM 8-screw set.

Parts needed for P505 assembly
Parts needed for P505 assembly – bottom bracket, crankset, and bolts

I visited my friend who runs a bike store to help me replace the BB and install the power meter. I also needed free hands to take some pictures, haha.

Throughout the installation, we (luckily) didn’t experience any issues. Everything went smoothly. We just had to adjust the front derailleur to ensure smooth shifting.

Once we installed the power meter, I paired it with my phone using the Magene app.

The Magene app showed the power meter almost immediately. Then I had to fill out my email address where I received the activation code. Finally, I completed the pairing process by submitting it.

However, during further use of the power meter, I noticed that the app doesn’t always connect to it. Even when I followed the instructions like turn off/on Bluetooth, the app showed it as not connected.

Screenshot from the Magene app - Search Unsuccessful
Magene P505 Search Unsuccessful

The interesting thing is that I experienced no issues with connecting it to indoor cycling apps like TrainerRoad, Wahoo RGT, etc.


Magene P505 Features & Benefits

One of the things that surprised me about Magene P505 was the auto zero-offset. It is pretty handy because you don’t have to think about it, and the power meter will set it automatically once you start pedaling.

Data geeks will appreciate the advanced measurements like the L/R leg balance. I was pretty surprised when I found out my L/R balance was 55/45. My left leg is about 1 cm longer than the right leg, so I guess this explains the disbalance.

Screenshot from ELEMNT app (L/R balance)
My L/R balance, according to the Magene P505

The pedal smoothness data are interesting and valuable if you plan to improve your pedaling technique. However, I don’t have ambitions to pedal smoothly as pros, so they are “just” interesting for me.

Like most of today’s power meters, P505 offers ANT+ and BLE connectivity so that you can connect it with indoor cycling apps and head units. I tried to connect it with Zwift, TrainerRoad, ROUVY, and Wahoo ELEMNT ROAM, and everything worked without issues.


Magene P505 Accuracy Tests

To get a better idea of the P505 accuracy, I did multiple tests indoors and outdoors.

I compared my indoor ride data from this power meter with the data from the Saris H3 smart trainer and the Favero Assioma DUO pedal power meter.

For outdoors testing, I compared them with the Favero Assioma DUO pedal power meter. I use them as a benchmark for most of my accuracy tests.

Indoor Tests

I used Wahoo ELEMNT ROAM for recording data from Favero Assioma DUO, Wahoo ELEMNT BOLT for Magene P505, and indoor cycling apps for Saris H3.

Indoor Test #1 (ERG Mode)

Here are the results from testing the ERG mode of the Saris H3 that are also valid for this test. As you can see, all three power sources are almost on point with each other.

Magene P505 - Indoor Test 1 - power
Magene P505 – Indoor Test 1 – power

And here is the cadence. Also accurate from all sources.

Magene P505 - Indoor Test 1 - cadence
Magene P505 – Indoor Test 1 – cadence

Indoor Test #2 (Freeride)

Below is the indoor freeride of the Pienza route from Wahoo RGT. Assioma DUO and P505 are close to each other (except for the maximum power). H3 spiked at the beginning of the ride.

Magene P505 - Indoor Test 2 - power
Magene P505 – Indoor Test 2 – power

The cadence chart shows multiple drops of the Saris H3 cadence readings. P505 is again on pair with Assiomas.

Magene P505 - Indoor Test 2 - cadence
Magene P505 – Indoor Test 2 – cadence

Indoor Test #3 (Race)

And the last one is a Zwift race. Unfortunately, I had to crop the first 30 seconds because my connection dropped right at the beginning of the race. Therefore, Zwift didn’t capture the data from Saris H3. The lack of data from the trainer would cause larger average deviations.

Magene P505 - Indoor Test 3 - power
Magene P505 – Indoor Test 3 – power

The cadence was, again, on point.

Magene P505 - Indoor Test 3 - cadence
Magene P505 – Indoor Test 3 – cadence

Indoors, Magene P505 performed pretty well. So what about the outdoors?

Outdoor Tests

For outside tests, I didn’t create any specific workouts. Instead, I used two head units (Wahoo ELEMNT ROAM and Wahoo ELEMNT BOLT) to record the data of a few rides.

Outdoor Test #1 (Long Group Ride)

Here are the results of the first group ride. Note that the empty spaces are breaks for food and enjoying nice views.

The average power was within 1% of accuracy. P505 struggled with maximum power and read about 35W higher power.

Magene P505 - Outdoor Test 1 - power
Magene P505 – Outdoor Test 1 – power

The following cadence chart doesn’t show cadence drops caused by the connection or power meter but drops when I stop pedaling.

Magene P505 - Outdoor Test 1 - cadence
Magene P505 – Outdoor Test 1 – cadence

Outdoor Test #2 (Short Solo Ride)

The following picture shows the data from my solo ride where I made multiple 30×30s high/low power efforts. Again, P505 overcalculated my maximum power. The deviation from the average power was also higher (almost 2%), but we are talking a few watts here.

Magene P505 - Outdoor Test 2 - power
Magene P505 – Outdoor Test 2 – power

Again, no problems with cadence.

Magene P505 - Outdoor Test 2 - cadence
Magene P505 – Outdoor Test 2 – cadence

P505 is pretty accurate during lower and mid-range power efforts. However, it struggles with estimating the maximum efforts and usually overestimates my power.


Other Things to Consider Before Purchase

Magene is a relatively young brand that has not as much experience with power meter development as established power meter brands.

I read in a few reviews that they sometimes struggle with releasing firmware updates to fix bugs and other issues.

But, they seem to be pretty responsive to customers’ feedback and take things seriously. They want to make their products more accessible to average cyclists, but sometimes they struggle to ensure their products are on point (you can watch this video from GPLama for more details on Magene P325 CS).

I’ve been using the P505 power meter for a few weeks, so I can’t comment on its long-term reliability. Will it stand out the test of time? We will see. If you have the P505 for a longer period, share your experience in the comments.


Magene Fitness FAQ


My Verdict

Magene P505 is a relatively affordable spider power meter suitable for beginners or people on a tight budget.

Except for the standard power + cadence, you also get advanced data like your L/R balance and pedal smoothness measurements.

Based on my testing, P505 is accurate and consistent in low to mid-range power. However, high power efforts like sprints are not too accurate and deviate by about 5% from Assioma DUO.

It also often struggles to connect with the Magene mobile app. Hopefully, they will sort it out with future updates.

In short, if you are looking for an affordable spider power meter with minor flaws, Magene P505 is worth your consideration.


The product for this review was kindly provided by the manufacturer. This did not influence my overall verdict or my opinion about the product.

About The Author

8 thoughts on “Magene P505 Power Meter Review: Affordable but with Flaws”

  1. I hope the durability is better than the P325 CS. I was in on the Kickstarter campaign, and had a battery failure last October/November. They eventually replaced it under the 1 yr warranty, but made me ship the crank with the PM to them ($$). Now the replacement seems to have failed. Hopefully, they have changed the design of that part for the 505. But I also have the complaint about poor shifting b/c of the chainring design. I actually got the Stone Spider so I could switch in my SRAM chainrings, but this latest failure is making me wonder if it’s worth it, even if Magene come through with a replacement.

    1. Hello Matt,
      I am sorry to hear about these issues. Unfortunately, it seems you are not alone. The P325 CS was not reliable and people experienced all sorts of issues.
      The issues you mention really make you consider pedal power meters that are super easy to instal.
      The P505 on my bike still works fine, but I will need to go back to Ultegra Di2 cranks because of reviews of other power meters.
      – Petr

  2. Hey!
    Interesting to read your P505 power meter review, and it’s really impressing how you are comparing those different PMs. It’s only the long-term use that tells us the individual calibration, does the same PM do the same measurement, today tomorrow and next year.
    I’m considering buying a P505. I’m thinking cheap because watts are just watts, gadget, a gadget that tells us how hard we are pressing down through our legs into the pedal, but it’s not telling us the exact performance the body must perform, anyway it may show us the power increase at the same HR.
    I’m happy with my Xcadey xpower and Sigay rx power meters, they tell me that I tread 10 more watts home from work than to work. When I exercise, ie threshold training and oxygen uptake training, I validate the training effect with lactate measurement, and compare to HR and PM.

    I want to challenge you on a question.
    Why and how is it obvious that the Assioma who is the one that is 100% correct at high power efforts ?

    1. HiTorben,
      Thank you! Yes, I tried to do a data-based review that has some added value. 🙂
      You are right that the long-term use tells more, but it’s not a very sustainable model.
      I think these cheap power meters are ok if you are looking for a tool that helps you pace or provides you with some data. But they are not too reliable/consistent and, therefore, suitable for serious cyclists.

      Favero Assioma (are considered one of the most accurate power meters out there (based on dozens of reviews). I use them for all power meter tests – they are the baseline. To find their inaccuracies, I would need to compare them with other power meters like SRM, or Quarq. Unfortunately, I don’t have these power meters yet. 🙁
      Hopefully, I answered your question.
      – Petr

      1. Yes, but “highest added value possible”, would never defend 1000 $ / € use, in mind of the utility value.
        The wattmeter objectively measures how hard you push into the pedal, but not the insert behind. It does not tell you if you are tired or about the full recovery parameter.
        Pulse tells how hard the heart must work, to serve the body’s efforts. Lactate tells the amount of lactic acid in the blood. My advice is a cheap/middle wattmeter and a Lactate meter for 200 €. Then making a lactate profile, to control the actual intensity of the workout, by comparing it to watts and HR during training.

    1. Hi Clint,
      Well, sort of… You can use Ultegra chainrings, but you need SRAM cranks (and BB). As you can see from the pictures, I use it this way. 🙂
      Let me know if you have any questions.
      – Petr

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