Tacx FLOW review

This review is for the Tacx FLOW Ergo trainer



Nutshell Review:
Pros:
-Great value for an ergo trainer
-Built in roll down calibration for repeatability
-Scaling ability to change calibration
-Repeatable setup ( cam actuated mount, cam setup at wheel)
-Two modes of operation, Ergo, and slope
-Lots of options on the display
-Includes cadence sensor
-Includes front wheel mount
-built in HRM that works with a Polar chest sensor
-Includes special skewer for mating to stand
-Upgradeable to the Tacx I-Magic for computer control of resitance unit, graphics, and programing, data download, etc...
-Available from Nashbar making returns easy

Cons:
-Suspect accuracy at high speeds, and high/low cadences
-Noise/vibration/harshness at high outputs
-response time to changes in wattage not immediate
-some creaking when out of the saddle
-Some quality control issues.
-Terrible manual.


Perspective of this review:
This trainer is used almost exclusively for intervals at set Power outputs. Most of the time this is done in the ERGO mode, where a wattage setting is entered, and the trainer holds that wattage regardless of cadence. I have no need for graphics or "spin-scan" features.

Other trainers I have used include the Cyclops Fluid, and Kreitler Rollers.

Setup:

I usually leave the bike in the stand for long periods of time, so don't really have a feel for how easy it is to put in and take out. But I do know that it is much easier than the Cyclops we have.


If you can see, the quick release is a special one that comes with the trainer. The end of it is shaped to fit into the stand perfectly. The orange handle is part of a cam system, so once the initial tension is set, it is repeatable. This is NOT a weight weenie quick release. I used to change it out, but now I just leave it on there.

The tension between the load unit and the tire is also a cam setup controlled by a dial. It is counter intuitive but you dial it out to make the tension harder, and in to make it easier. But the cam lever makes it repeatable which is nice

Open position:


Closed position:


There is also a cadence sensor that mounts to the chain stay via a rubber band/hook sort of thing with a very small wire that runs back to the load generator. Be careful of snagging it as it looks pretty delicate. There is a long cable that connects the load generator to the head unit. This is a telephone type connector at the end.

Calibration:
The Flow has a built in roll-down calibration in it. I recommend that you ride for at least 5-10 minutes to warm it up before calibrating. And try to pump up the rear tire to the same amount every time. I use 8 Bar, and air is lost on a daily basis so you have to remember to pump it up.

You press two buttons for 10 seconds and it takes you to the setup menu. Your weight and display options are entered, and then you are in the calibration mode. Press the start button and the display says "Speed Up" start pedaling faster and faster until the display says "Stop". The computer calculates how long it takes to roll to a stop and it displays a number between -4 and +4. I usually then adjust the rear tension until I can get it to calibrate to 0. The dial on the tension is really sensitive and small increments are suggested when changing the tension.

Sometimes if you pedal too fast you get an error, but for the most part is is pretty straightforward.

I read about, but have not done the Scaling feature. This allows you to scale your power readout. If you use another power device, such as a power tap or SRM to make comparisons, I guess you can use this scale factor to make corrections to the Flow output. I will discuss more later the results of some other's comparisons of power output on the Flow to SRM /Power tap and some of the potential inaccuracies of the FLOW.

The Display unit:


The display unit is pretty nice and allows you some customization. there are two lines of readout. You can choose which piece of info is put on top and on bottom. I think your choices are:
-Watts
-HR
-Speed
-Cadence

The one that is on top will correspond to the top most clock. The top clock also shows an arrow if you are below the average for that metric.

I almost always have cadence on top and Watts on the bottom. And rarely do I use the top clock's readout for any info.

Modes of Operation:
There are two modes of operation:
Slope and Ergo.

In Slope mode, you set the trainer between a # -4 and +9. There is no correlation between this setting and an actual % grade. It is just a resistance level. And then your wattage is a straight calculation from your speed. The faster you go the higher wattage you are doing.

You can use this mode to calculate your average wattage over time. I don't like to use this setting too much when doing intervals at a set power level because it requires constant monitoring to stay at a certain power level. Though I do like this mode for the rest portion of the interval.

Here is a graph that I found of someone using an SRM on the FLOW in slope mode:


from the looks of it the FLOW tracked the SRM fairly well.

In ERGO mode, you set the power and the load unit supposedly maintains that power level regardless of your cadence. I really like this mode for doing intervals, because you just set it and put your head down and go.

The unit allows you 10W increments. I've found that there is a delay when you start ramping up the wattage, before the load unit responds.

There is some issues with the accuracy in ERGO mode. Just from observation I found that at high cadences it seems easier at a given power setting. Here is a graph where the same guys tracked the error of the Flow vs the SRM at a variety of cadences/speeds in the ERGO mode:


Here is a direct cut/paste explaining the data:

The chart may be a bit hard to interpret so I should probably explain. The idea of an ergo is that you set the wattage you want (say, 250W) and off you go (Ron Popeil would say, "set it and forget it"); the ergo will match the load so that whatever speed you ride, you'll be generating 250 watts. So in an ideal world you'd want the percent error to be independent of your speed. The chart plots the error against kph (or, in this case, the ratio of the wattage setting to the speed), and if the ergo worked well
the pattern would have zero slope.

The observed pattern doesn't have zero slope.
Instead, it says that in ergo mode the Flow's electronic braking system fails to increase the load by the appropriate amount to keep power constant as wheel speed increases. If you look only at the black dots (where the scale factor is set at 100), it says that if you set the ergo for a constant 250W, the Flow will only have zero error if you're riding at 23kph. At 28kph, the Flow is only able to produce enough braking force to generate an actual load of about 200W (about a 20% error). At 36kph, the Flow was actually producing about 40% less load than it should have. The scaling factor moves the curve up and down, but doesn't fix the basic underlying problem.

The good news is that the error is stable and predictable. The bad news is that the slope of the error is huge, which sort of defeats the entire intent of the ergo feature.

I have also read of some people who found that when you upgrade the FLOW to the I-magic with a PC computer control of the load generator that these errors go away, and that the control of the unit seems more stable.

The I-magic provides a bunch of video-game style graphics, and you can even get a steering addon that is supposed to be pretty fun. But what intrigues me about it, is the Cadence software that comes with it that allows you to program in your own rides. This would be great for me to program in these interval workouts because I am always losing count of what rep and what set I'm on. It would make things really easy.

Also the computer interface would allow compatability with Peaks Coaching sofware for analysis of the ride.

When cadence falls below a certain level, it feels like the brake force gets excessive as if it is compensating for the lower cadence. The actual cadence will vary depending on what gear I am in, so if I'm in my highest gear I can get down to the mid 60s before it bogs down, but two gears up the cog set and that cadence is in the mid 70s.

Noise/vibration
Like any trainer, when you are hitting it pretty hard you get some noise. This one makes a high pitched whine. When using headphones/MP3 player I can drown it out no problem. There is some vibration that comes through the bars that can sometimes cause some tingling, but I think any trainer would do that.

When standing up, like any fixed trainer you can't rock the bike beneath you. The stand does creak on me. But I haven't tried to tighten the setting.

And like any trainer, it will eat your tires.

Conclusions:
I bought this unit from Nashbar with a 20% off coupon and from their returned goods bin. So I got it for like under $250. You cannot even get a Computrainer Stand (just the stand) for under $200. Given that the most basic computrainer goes for $800 new and holds it's value pretty well used, the Tacx Flow is an incredible value IMHO. Power taps and SRMS are also more expensive, but allow you to take it outside, though do not have ERGO capability. It puts power training into the reach of more people.

I think normal price is $379 and if you are patient you can find a 20% off coupon sometimes.

For someone using the trainer for simple intervals I think it fits the bill very well. Yes there is some suspect accuracy in the ergo mode. But I think the repeatability of the unit is very high, which means that when you are using the numbers only in comparison to yourself than it doesn't really matter.

When I do these intervals, I've found myself at the ragged edge, which regardless of the accuracy means that I am working as hard as possible which is always the final intent.

And when just riding on it, I like the feel of the tension when compared to a Cycleops. Not sure how to describe it, but if I just want to soft pedal and go easy it just feels more natural on the FLOW (in slope mode ) then the Cycleops.

Hope this is of use to those looking for a trainer.
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*** Long term updates.

I've had one problem with my trainer. I unhooked everything to take it on vacation and when I hooked the cadence sensor back up it was dead. I was able to order a new cadence sensor cable for under $10 and was back in business. Other than that it's been fine.

A friend got a new Flow 1/2007 and it was working fine at first but then the head unit died. It was registering power but not registering any data flow. He had bought it from a reputable dealer (Lick Bike) and they are in the process of getting him a new head unit.

They said head unit before he told them that we troubleshot it using my unit/cable and had isolated the problem at the head unit. So I suspect that this problem is no surprise to them.

Also he had a difficult time with the instructions and w/o info from here would not have understood the slope/ergo modes and how to use them. So the manual that comes with it needs some work.

*NOTE **2-20-2007

It seems that calibration does not hold throughout the workout. I set the calibration to zero after a warmup. Later in the workout, sometimes I'll check the calibration again and it will be at -1 or -2. It seems to be a constant as my friends FLOW does the same thing. I either increase power if I'm feeling good at the end or just keep it like it is.