It has been my experience that the TACX Bushido Smart is a bit of a Wattage Vampire. This isn’t just me, this is other people who also ride the TACX Bushido Smart. I look at their data and it does seem to under report wattage from 30 to 40 watts. This is important to anyone who is racing on Zwift or wants to stay consistent with their indoor and outdoor training. I have been able to validate the baseline power curve and the differences in wattages reported by this trainer versus a power meter. I did a bunch of testing to show everyone how to hack the Bushido Smart so it starts reporting closer to real power. This will be especially helpful to your Zwifters out there getting your butts kicked in Watopia.
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The TACX Bushido Smart is a very cool trainer in the fact that it generates it’s own power and then provides resistance through that generator. You can take a look at the build of this trainer in my part 1 review TACX Bushido Smart Review, The Build. In there, we take the Bushido Smart apart and look at the insides. In this part of our review we will be looking at the calibration of this trainer and how well it reports power compared to a power meter. From there, we will see if we can mess with the adjustments to get the trainer reporting closer to real power.
Factors Influencing Power Output
Before we begin, I want to talk real quick about the factors that influence the power reporting for wheel on smart trainers. The first influencing factor is tire type. You can gain or lose 10 watts if you swap tires. Those tires specifically built for trainers (which I hate) provide large amounts of resistance. Race tires that you would use outside provide less resistance. Switch your tires out, you change the reporting power for your trainer.
The next influence is tire tension on the roller. This is the number one influencer and something we will use to “Dope” the watts a bit on our trainers. You can see an example of this in my article TACX Vortex Smart Review Part 2: Spin Down . The TACX Vortex Smart can be doped up to 100 watts over a power meter just by calibrating under high tire tension and then taking all that tension off after the spin down calibration.
The last influencing factor is tire pressure. It isn’t a major factor and we are only talking about 5 watts max, but it is important to keep tire pressure consistent with every workout. You really only worry about this with the tube type you are using. Use a thick butyl tube, and you will rarely have to pump up your tires. Use a latex tube, you will be pumping them up every other day.
Initial Calibration And Findings
The first step in calibrating this trainer is to get everything setup and your tire contact dialed in. Pump up your tire from 90 to 120psi. It doesn’t really matter what pressure your choose, as long as you stay consistent. I chose 100psi myself and then stick with that every time I get on the bike. This gives me consistency
TACX Utility App
Next, we head into the TACX Utility App. We will connect the Bushido Smart to the TACX utility App and then select calibration. Conduct your spin down and then center your tire contact in between the lines on the graph. Look at the image to the right and you will see what I am talking about. This is how TACX wants you to calibrate your trainer. They use the amount of time it takes the trainer to spin down to calculate the resistance and then flash your trainer.
Establishing The Base Line Power
Every smart trainer has what I call a “Base Line Power Curve”. That is the minimum resistance it can hold at a certain speed. This means you cannot go below the baseline and can only add resistance above that curve. Some people think their trainer is broken or the Training App they are using is not working right, when in reality, their wheel speed is too high. For example, you are doing an interval set on The Sufferfest Training Centre. On the off part of the intervals you are supposed to be resting at 130 watts but the trainer is holding 150 watts. This happens because your wheel speed is too fast and you need to shift up a few gears.
Looking at the image above, we can see at 36kph the trainer’s base power is above 200 watts. All this means, is you need to lower your wheel speed to hit the lower wattage numbers. I wanted to double check this baseline curve though. I do these tests with the trainer not connected to any app. This trainer generates it’s own power and I just wanted to make sure that nothing crazy was going on. The two images below are the Bushido Smart not connected to any App and then connected to the Sufferfest Training Centre on Standard Level 0. Standard Level 0 means no resistance is being applied to the trainer.
As you can see in the image above, we only get a slight variation on our base map when the trainer exceeds 40kph. Otherwise, the raw data says both curves follow along pretty close. I’m satisfied that the generator has no influence on the base map wether connected, or not connected to a training App. (disregard the 46kph typo on the first image)
Testing The Spin Down Calibration
We have spun down our trainer and have that line nice and center on the TACX Utility App. Now is the time we validate how reliable this spin down is for the Bushido Smart. I tested this out by using my stages power meter (Calibrated) and the Bushido Smart. I ran the Bushido Smart on the Sufferfest Training Centre and then captured the power meter on my Garmin 520. The results were not surprising.
The orange line is the Stages Power Meter and the blue line is the TACX Bushido Smart in ERG mode. As you can see, we are losing 30 to 40 watts when training. Now, before you throw your arms up in the air and say “Its Broke!”, you need to understand that most trainers act like this in some way. Some are worse than others. Again, take a look at my calibration on the TACX Vortex Smart. That trainer gives you massive bonus watts where the KICKR Snap is actually pretty darn close.
This is a big deal for Zwift users; especially users who want to race in Zwift. You are losing 40 watts from this spin down calibration. The TACX Bushido Smart is severely handicapping you. This is not only me, I have worked with other users on the Bushido Smart and they all notice the same thing. So, what do you do? I have the answers you are looking for. We can fix this.
Manipulating The Numbers
It is very easy to manipulate any wheel on trainer. If we understand that tire tension is one of the most important aspects of the spin down calculation, then we can manipulate that. The way you do it is really simple. The quick answer; we add lots of tire tension, calibrate and then flash our trainer, then take all that tension off at the end.
How To Do It Right
The first step is to get down on your knees and pray to the Wattage Gods for more watts. Just Kidding! Well, not about the getting on your knees part. You need to get down to the adjustment knob and add a bunch of tension on your tire. Then head back to the TACX Utility App and do a spin down. You want the line to be on or just above the “Too Tight” line like the image to the right.
At this point the TACX Utility App is going to send a calibration number to the TACX Bushido Smart. The App knows that the tire tension is too tight and will give you credit for extra watts. We will then head back to the tension adjuster and take all of that tension back off our tire. This will reduce friction and lift up your wattage numbers reported by the Bushido Smart. It is as simple as that. No need to go back in to the TACX Utility App, we need to keep the trainer thinking we have too much tension on the tire. (This is also why I like to use setting 2 when putting together TACX Trainers. It allows more tire contact.)
I went extreme to show you how things can be manipulated. You don’t want to go all the way to the right with the resistance. You want to be just on or just past the line to your right. Then, you only need to take about two turns of resistance off your resistance knob to get you close. Looking at the image below, we can see how much you can actually manipulate the power numbers by adjusting tire resistance.
By going extreme with the resistance and then taking all of that resistance off, we have gained roughly 80 to 90 watts on our FTP. It only starts coming back when the wheel speed is increased. You can see at the end of the graph, I started shifting down and raising power into the 300 watt range. This is when things started coming back within alignment. Again, you don’t need to go this extreme unless you want to prank your friends on Zwift.
How Do You Do It Correctly?
You want your 40 watts back you say? Okay, to do it correctly, we just need to calibrate the spin down to the right of the line. Look at the image to your right and that box is your target. Then, when you get down on your knees to pray to the Wattage Gods, you take two to even three turns of resistance off. That will get you closer to your real power numbers. No more getting killed by people in Zwift racing. The only true way to calibrate it correctly is with a power meter so you know how close your are, but take it from me, this will get you close.
I have my examples below. After doing my spin down fix, I rode the Sufferfest Training Center with the Bushido Smart connected as the Smart Trainer. The image below that is riding Zwift simultaneously while connected to my stages power meter. As you can see, we are now very close to reporting the same as a power meter. I’m actually surprised on how close I got it.
The Sufferfest With The TACX Bushido Smart
Zwift with Stages Power Meter Running at The Same Time
Okay, before we all get up in arms about accuracy and things like that. Let me tell you about the other trainers out there. The Elite Trainers are mapped from the Elite My E-Training App. You can go in there and change the numbers to whatever you want and get any result you want. CycleOps and Wahoo work much like the TACX trainers where they use a spin down calibration. In my testing, the Wahoo trainers are always the closest. They are within 10 to 15 watts of my power meter.
There is no possibility of finite accuracy without a strain gauge on these trainers. Most companies are not going to be putting strain gauges on their trainers either. The strain gauges break to easily (look at the 1stGen KICKR) and then the trainer is toast. I wouldn’t be surprised if some company in the future starts packaging Power Meters with smart trainers. Apps like Zwift and Trainer Road are already sort of doing this with power match. They link a user’s power meter to a smart trainer and drive the resistance from power meter numbers.
Stay tuned as I put the TACX Bushido Smart through my testing. There are going to be some limitations with that generator. I already know cranking out a low cadence isn’t going to work well with the 39×27 gear ratio. It won’t produce enough power to produce resistance. Also, don’t forget to subscribe to my Youtube Channel and take a look at the Comparisons Page when I am complete. Also, I have some links in the Basics Page if you need any indoor training accessories. In April, we are going to take the Bushido Smart head-to-head with the Wahoo KICKR Snap. This is the only trainer I believe that has a chance of taking down the KICKR Snap for “Best Mid-Range Trainer.” We will see. Thanks for reading everyone!