Strange watt issue, what is "wrong"?

[borchgrevink]

Today I finished an FTP test on a CycleOps "pro" indoor bike which gave me an FTP of 289 watts (304 watts for 20 minutes). This "roller" is calibrated and gives very accurate watt readings (even calibrated with expensive watt pedals, so should be correct).

Last week I tried a standard FTP test on my Bkool Pro (firmware 3.06 I think, not the latest one). I had NO chance of managing 300 watts for 20 minutes on this test with the standard 2% incline.

What makes this even stranger is that another Bkooler managed 303 watts for 20 minutes on a Bkool but "only" 261 watts on the same CycleOps.

The confuse EVEN more: When there is a high incline on Bkool, eg. 10% I can manage over 330 watts for over 30 minutes (but again not even 300 watts for 20 minutes on 2% incline).

This all makes no sense to me. Anybody got any suggestions?

My thoughts: The CycleOps is probably correct, wattwise. The Bkool is probably a bit too kind on watts with high incline, at least with the old firmware. BUT WHAT CAN EXPLAIN THE OTHER DISCREPANCIES??? How can I sustain 304 watts for 20 minutes on CycleOps and not on Bkool, while @fredagstrimmen can sustain 303 watts on the Bkool and not on the CycleOps, and how can I then sustain 330 watts for 30 minutes on the Bkool????

A mystery of biblical porportions... :-)

 

[T.M.H.N.E.T]

They're not comparable

 

[borchgrevink]

But that doesn't explain the difference in sustainable watts between me and the other Bkooler.

 

[T.M.H.N.E.T]

It does, the Cycleops bike and a bkool trainer are not comparable, neither are you and another rider.

FTP is individual and in terms of a bkool trainer. The weight of the rider pressing the tyre to the roller, tyre wear, tyre type and pressure are all factors, as is temperature.

 

[borchgrevink]

Hmm, not totally into that solution. Of course it explains a lot, but does it really explain why I get higher FTP on the CycleOps and he on Bkool, but then again that I have higher watt on Bkool when incline is steeper? Shouldn't a rider who has higher watt on one dedicated Bkool roller compared to another, ALSO have higher watt or better times on Bkool when incline ia steeper?

Could difference in gears explain something?

 

[T.M.H.N.E.T]

You're assuming that both of you are riding the test indentically paced.

The ftps still aren't comparable, sorry that's the reality of it

 

[borchgrevink]

Thanks. Identically paced? Isn't watt watt?

 

[T.M.H.N.E.T]

Going easier at the start of the test or going too hard at the start and not sustaining the effort makes for different tests. There's no real way to suggest that either test was ridden exactly the same way,

It's just another variable in a big bowl of variables

 

[borchgrevink]

I get that. But why do people then use FTP to compare?

 

[borchgrevink]

Also, it can explain some of this, but that big a discrepancy, even between just Bkool rides?

 

[T.M.H.N.E.T]

I get that. But why do people then use FTP to compare?

FTP rider to rider is meaningless. Bkool software does adjust to W/KG if you're honest about it in your profile, to help combat unsportsmanlike conduct

Also, it can explain some of this, but that big a discrepancy, even between just Bkool rides?

Any of the factors above can be augmenting the power there too. From tyre pressure to ambient temperature on a ride to ride basis

 

[borchgrevink]

What if this is a consistent discrepancy, meaning one rider has high wattage when incline is low but low when incline is higher and vice versa every time?

Is it only me that thinks watt in Bkool sometimes is wonky? I haven't checked if the tendency for Bkool to give high watt readings in steep inclines have been changed in the latest firmware. Any thoughts?

 

[RickB]

Been off the scene for the Summer but I know the latest Firmware update did affect watt readings and the behaviour of the trainer, so an older Pro trainer may give very different readings than one with the latest firmware.

 

[borchgrevink]

Thanks for all the input. If anyone feel they have something more to contribute, feel free.

 

[bridgy]

"Watts" on Bkool are just a calculation the software makes based on the speed of the roller combined with the slope you're on and the rider's weight, so should always be taken with a pinch of salt, and I wouldn't be too surprised there's a difference between the FTP tests you've done on different trainers.

On very steep inclines, the resistance the trainer itself can apply can be maxed out - particularly for heavier riders. In these circumstances you can get exaggerated watts because the rider has overcome the max resistance to achieve a certain speed and the software thinks that resistance is higher than it is in reality - so calculates a higher watt figure than is the reality. This may be why you are getting higher watts on 10%+ inclines - it's the same for most riders on Bkool.

As to the differences between you and your friend, are you both on the same Bkool software and firmware? There's no point comparing unless you are.

Apart from that, the factors mentioned before like tyres, tyre pressure etc can all make a difference to speed which in turn will affect the watts Bkool says you are producing.