Verdict: Accurate enough despite a LR balance issue. Great price offsets the assembly time.
83%
Summary
The Magene P505 is an affordable spider power meter with a solid base of features suited for mainstream cyclists.
Compatibility for your Shimano bottom bracket and existing Shimano chainrings might make PES P505 an appealing option for those wishing to retain dual-sided power and change crank lengths as cheaply and easily as possible.
The accuracy levels are probably usable, but not the solid 1% I’m looking for. I’d also consider the crankset weight a hundred grams over what performance-grade cyclists expect from Ultegra/DuraAce equivalents.
The connectivity options and cycling dynamics data are also good enough for most people.
For casual cyclists looking for dual-sided power and those on a budget, Magene is a reasonable choice. However, if precision is paramount, established brands like Favero or Quarq may be worth the extra cash.
Pros
Supports key metrics
BLE and ANT+ connectivity
Excellent claimed battery life
Decent range of options
Good aesthetics
Cons
Slight faff with assembly/installation
One BLE channel
My tests show total accuracy slightly below the claims
Power meters have been in the mainstream for ten years, so some of you will be here to upgrade, and others will buy their first power meter. Unless you want something highly specific, the P505s are a decent option for mainstream road cycling needs, especially if you already have Shimano cranks.
You might want to upgrade to a more accurate power meter or follow the recent trend toward shorter cranks.
What to watch out for
Perhaps you want extra connectivity options with Bluetooth to link a smartphone, computer or TVOS apps. You can do any of those individually, but you are limited to only one Bluetooth channel, so simultaneously connecting to an app and your apple Watch might prove tricky, although there are workarounds.
While this power meter could, for example, be a source of power for Zwift, you will also need a smart trainer if you want Zwift to control the resistance/power. A smart trainer plus your regular power meter can make sense and keep your gaming data separate from your other training data. Thus, you would use your P505 and bike computer to record a duplicate set of indoor data with the same sensor you use outdoors, making your training numbers consistent (don’t link data from Zwift anywhere else in that scenario).
Power meters can vary in accuracy from one device to the next – just because an online reviewer says the data is accurate or not might not be reflected in the device you buy.
Magene PES P505 – Alternatives
I recommend a single-sided (left) power meter as the cheapest option to get power. However, these Magenes are not much more expensive and give you dual-sided power, which should be as consistent but more accurate overall.
If you have multiple bikes and have a reasonable budget, consider the Assioma dual-sided power meter pedals. If budget isn’t much of an issue, getting the same-branded power meter for all your bikes can be a good idea.
For now, avoid options like cheaper models shipped from overseas and Stages’ power meters – the company went bankrupt. You must consider what happens if you need a warranty replacement or repair.
Assembly & Installation
Shimano compatible – check your BB if you do not have Shimano cranks
You can quickly assemble and install this if you are DIY-minded. If you’ve never changed a crank, this task is not trivial, and you will need specialist tools. You will need to read the manual.
It comes ‘flat-packed’. You need to attach the spider to the spindle using the adapter provider to tighten a lock nut, but you’ll probably need a special tool to tighten it to the correct torque- in technical terms, it needs to be VERY tight. You’ll also need the torque wrench to properly attach the chainrings and left-side crank.
Removing and replacing your old Shimano crankset with this one should be easy enough unless your old crankset has bonded to the bearings.
It was an odd experience to attach the left-side crank with a strange bolt that had a dual purpose, each requiring a different hex wrench to set the precise LR distance and secure it to the inner of the spindle. Finally, unlike Shimano’s two, the crank is secured with one bolt. It would be best to add a torque wrench to do everything correctly.
I needed to adjust the Ultegra 11-speed Di2 front derailleur by +3 adjustment points.
Charge it up with the proprietary cable, pair it to your head unit, and you’ll be ready after a quick calibration.
Aesthetics
I think they look pretty decent, and extra stickers tweak the colours.
I suspect using the latest Shimano-branded chain rings would not be a good idea aesthetically, even though they should fit.
Magene P505 – Key Specifications & Features
These are the main features
ANT+, Bluetooth
Unlimited ANT+ connections, 1x Bluetooth connection
SRAM DUB spindle compatibility with the QED P505 model
Active Temperature Compensation: Not stated
Spindle: 24mm
Data range: 0~2500W, 20~200RPM
Q-factor: 147mm
Waterproof: IP67
Weight: 650g excluding chainrings
Oval chainring compatibility: No. Consider ASSIOMA or ROTOR
There is a spider-only alternative and the QED P505 (DUB spindle, 110BCD), both claiming higher accuracy at +/-1%
Magene P505 Accuracy Test Results
I performed a variety of tests, indoors and out
Warmup
This chart seems OK to me with 5-sec smoothing. I’ve highlighted some slight unders/overs.
After another manual calibration, ASSIOMA and P505 track each other nicely in terms of cadence and total power. LR power has some variances, giving more of a skew on the left side than expected.
total Power
LR Power
Cadence
A few minutes later, with some harder repeated sprints, you can see a few-second delay in the data recorded by Magene. These are NOT time stamp differences, as they didn’t exist a few minutes earlier. So, the delay is either in the processing/transmission from the P505 or the receiving and writing from the Magene head unit.
Again, there is a possible skew to the left side from Magene.
Total Power
LR Power
Cadence
Slightly harder, shorter reps with a high declining cadence and bigger range tricked the KICKR MOVE into missing one interval entirely.
Again, there is a possible skew to the left side from Magene, but with similar totals.
Cadence
LR Power
total Power
These are similar reps in the same test conditions on a different day.
The lag with the Magene data is not visible in the charts shown, but when zooming in, there is still a delay, albeit much reduced from before. However, on HR data (not shown), there is a lag on the Magene data, suggesting that the lag problem might lie with the Magene bike computer rather than systemic to the cranks.
Again, there is a skew on the Magene’s left side. I do have a LR imbalance, but it is not this much. Mine is often 52:48.
Cadence
LR Power
Power
This data is from the road with a Sunday group ride on often flat but POOR quality surfaces; Magene overestimates and still skews to the left.
Cadence
LR Power
Power
This data is recorded with a Garmin Edge 540 and appears much better. The road surfaces were smoother than in the previous example.
LR Power
Power
Another day recording on the road with an Edge 540. The total power lines are separated, and there is still a left-side issue
Cadence
LR Power
Power
It was another day recording a long ride on the road with an Edge 540. The total power shows more variation from Assioma than I would expect.
cadence
LR Power
Power
Accuracy and Other Notes
I flicked through some of the other Magene PES P505 reviews. There are a few, as the product has been around for a while. GPLAMA was happy with the accuracy of his crankset, and others noted connectivity issues I didn’t experience, presumably because the product has matured since those early reviews. Tariq at SMART Bike Trainers also generally got accurate matches to his comparator power meters, including a Wahoo Powrlink Zero pedal set.
When asked, Magene didn’t comment on the left/right balance but did suggest the lag resulted from “the timing of the recording device.”
I would point out that a spider power meter does NOT measure left and right power. Instead, it measures total powerand then estimates the LR split. This is NOT the same as measuring one side and doubling it. Most people rarely look at LR split, so as long as you are happy with the total, all is good.
Magene’s QEDP505 range is more performance-orientated, with a higher claimed accuracy and minor improvements to other features.
Calibration
I always manually calibrated the P505 before a ride despite no apparent need due to autocalibration. A further option is to backpedal 5x whilst riding to trigger a calibration.
Charging
At 200 hours, the battery life is excellent, and I do not need to charge it with the custom cable.
Take out
This is a decent power meter solution, considering the caveats I mentioned.
From a market perspective, Magene seems to focus on selling full cranksets, unlike competitors such as Sigeye, XCADEY and power2max, which have a spider-based power meter that will fit most cranksets. This limits sales opportunities, in my opinion. Perhaps Magene will see higher absolute profits from selling a higher-value complete crankset?
A flat-packed crankset requiring user assembly reduces Magene’s assembly and distribution costs. However, it adds an unnecessary burden on the consumer to have the right tools to complete the assembly themselves – I doubt anyone has all the tools to 100% correctly assemble and fit a crankset – for example, I only had the tools to do the latter. Then, having to rely on friends or the local bike shop (LBS) to complete the installation somewhat negates the benefit of a relatively cheap crankset, as the LBS will inevitably charge for helping out (fair enough).
Buy Magene PES P505
You can get these directly from Magene or trusted power meter companies like Power Meter City (USA).
Longer cranks and bigger chainrings are slightly more expensive (+50Eu/S/£).
