Idea: Zwift Trainer Verification Programme

There is a significant problem with trainer accuracy for serious racing. This does not just affect the very top level, but also racing for many who still take it seriously at lower levels, for example the ZRL.

Over time Zwift racing will become a bigger part of the racing lexicon, and the ‘it’s just a game’ rhetoric will become less and less valid. This of course is a huge opportunity for Zwift and the validity of racing on the platform needs to be taken seriously.

Currently power number validation is primarily proven by dual recording - using a second power meter (nearly always pedals or cranks) to show that the numbers match to a certain percentage.

This approach is fundamentally flawed for a number of reasons:

  • pedal and crank PMs can usually be configured to match the trainer numbers with little effort, therefore just proving something that is already false
  • a second power meter purely to prove the accuracy of a trainer is extremely cost prohibitive, particularly now more and more riders are using smart bikes
  • newer trainers and smart bikes are usually factory calibrated. The onus should therefore be on the manufacturer for accuracy and not a significant cost to the rider

Personal example : I have a Tacx Neobike. I have power meters on my IRL TT bike and road bike. The neobike is factory calibrated. There is no way I am spending over £400 for hardware that proves the accuracy of another piece of hardware I have bought, where part of its sales pitch is its accuracy. Its non-sensical.

Second personal example: I know riders performing at a high level with matching dual recordings with inaccurate power numbers.

What I propose is a Zwift Trainer Verification Programme. For those newer factory calibrated trainers and smart bikes, manufacturers would need to certify these to Zwift standards. The certificate should last for an appropriate period of time.

For other trainers, you should be able to take the trainer to a local bike shop or mechanic, and have the trainer certified for accuracy. This would cost say £20-£30 and be valid for a year. Providers should quite quickly become available locally as it proves a nice business opportunity.

What Zwift would need to do is produce a protocol for proving the accuracy (maybe with Favero Assiomas or other proven accurate hardware), and a database of service providers. Certificates could be uploaded to zwift power (or zwift itself post-ZwiftPower)

This approach opens up a validation process for Zwift riders that want to take racing seriously, and of courses races not requiring validation can still take place.


Apart from manufacturers are never going to buy into this due to the onslaught of issues it brings them, how do you plan to get your 50kg neo bike to a shop and back to have it approved. (When I say you, apply that to the variety of people who might own one)

Then if it fails, you have to find a way of fixing it, remotely or return to vendor? Then back to the shop to re-approve it etc…


If it’s zwift certified versus not zwift certified, which trainer are you going to buy?

Zwift own the smart trainer economy and can dictate the terms.

Of course you don’t take your smart trainer to a bike shop, but there are options. All smart bikes are factory calibrated I believe, and if the certification needs to expire you can arrange a remote visit if you need to (like already happens with WattBikes).

dual recording is more like a fingerprint than an accuracy test, it’s very easy to spot a sloped power meter or a trainer that has been tampered with or is unacceptably miscalibrated, particularly if the rider has done a baseline zada test or has a long history of uploading duals.

as far as the stated and actual accuracy of even the most reputable power units and trainers themselves go, well… that’s a can of worms and as you say the onus is on manufacturers to get that part right in the first place. my direto x tends to read slightly higher than my 4iiii in sprints, and low at sub threshold watts. which unit is correct? who knows, probably neither. not much i can do about it other than keep them calibrated.


Isn’t this addressed quite a long way already in Zwift Certified FAQ ?

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Does calibration really last for a year?

I don’t think it’s a problem for restricted cats anyway, at least if you’re categorised by performance :slight_smile: if your trainer is generou you just end up racing against slightly better people.

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Totally makes sense!
Why would riders endure the whole cost of this transparency process while it could be easily reduced if certain rules and regulations will be applied on manufacturers of smart trainers !
In a way , riders are doing more efforts to come clear while Zwift could help by uniting all manufacturers to use some certified testing to get the validation of calibrated and accurate smart trainers.

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I think your description of the problem is spot on. What started as a relatively low entry activity shouldn’t become unnecessarily “for the few”. I’m not sure if the solution would work in practice, but it doesn’t harm to raise and discuss the problem nonetheless.

My line of thinking would maybe be more something like an external test you can do - a bit like a bikefit? You already have your own supported trainer with data through which you qualified for certain high profile races. Then to confirm that the numbers are genuine you could go somewhere to do a pre-determined test program on qualified equipment e.g. at a bike store.

I am probably overlooking something here, but I suppose that if you can produce matching figures on an independent piece of equipment you have no control over then this might suffice for approval?


I recently upgraded from a Suito (2.5%) to a Direto XR (1.5%) because I wanted a little heavier flywheel. The Suito matched my Rotor InPower (Crank based left side only 1%) to within a couple of percent. However, the Direto XR reads about 10-13 percent higher. I think the heavier flywheel weight is affecting the readings of the Inpower, but I don’t know how to prove it.

I guess it does partially yes, although those criteria are micky mouse, and it makes no difference to your dual-recording requirements.

That’s a good idea too, although it validates that you can put out close to the power rather than the accuracy of your equipment. 5% is probably close enough to show you can hit that power, but quite a big discrepancy in accuracy for a race.

I did a 20 min ftp test with direto and it was only a 7 watt gain over the Suito. 226 to 233, about three percent. Rolling with the Direto