Power readings in Bkool

theboxers

TheBoxers on Cycle Sim sw
Some odd results on the power front for the last couple of rides. Bkool will be telling me I am doing 200W, but the vectors would be saying 210-225W.Doesn't matter whether slope or flat the vectors are reading 10-25W over Bkool. My averages are at least 10W higher on the Vectors. My PE is now higher for the same wattage on Bkool.

I have made one change. I have gone from a 28 to a 23 tyre. I have adjusted the diametre in Bkool to reflect the change.

I have a 25 tyre I can try to see if I can get closer to same reading from bkool and my vectiors.
 

borchgrevink

Well-Known Member
Adjusted diameter in Bkool? May I ask what you mean by that?
 

theboxers

TheBoxers on Cycle Sim sw
Adjusted diameter in Bkool? May I ask what you mean by that?
If you set up a training plan, there is a set of data it uses to set your work areas along with an FTP figure. Chainring teeth, cassette teeth and tyre diametre. I am not sure if it works on out of plan rides though.

I am going to put on another different tyre size as a test, a 25.
 

g00se

Über Member
Location
Norwich
What's the tyre pressure you're using? You may be loosing something in rolling resistance. Like with a power hub, I guess the bkool is calibrated for the power going down on the road, while the pedals are the power coming out of your legs. As the bkool has no calibration tool, tyres and tyre pressure can have an effect. If you can, add 20 PSI and see if that helps. Or try a different tyre?
 

theboxers

TheBoxers on Cycle Sim sw
125psi in the 28 maxxis refuse and 145 in the 23 decathlon trainer tyre. The printed max on each tyre. But I am one of the very largest mooses @130 something kilo. I've got a 25 refuse tyre that I will try as well.

I am not looking for 100% agreement. Just as close as possible to each other.
 
OP
gbrown

gbrown

Geoff on Bkool
Location
South Somerset
g00se has a good point, pedal based power meters would be expected to read higher than ones further down the drive chain. I've seen estimates of around 3% loss between the pedals and the rear wheel, and I would expect more between the rear wheel and the trainer as it relies on friction to transmit from the tyre to the roller.

Geoff
 

theboxers

TheBoxers on Cycle Sim sw
g00se has a good point, pedal based power meters would be expected to read higher than ones further down the drive chain. I've seen estimates of around 3% loss between the pedals and the rear wheel, and I would expect more between the rear wheel and the trainer as it relies on friction to transmit from the tyre to the roller.

Geoff
Yes that is something to keep in mind. I do feel though that 200W on the vectors is now harder to generate compared with previously.

I just want to try and get a similarity of numbers. Looking from screen to edge to screen to edge gets cumbersome. Also, to be honest,, it gets a bit confusing when working in power zones. First bkool appeared to be over reading and easier to maintain power on. Now it appears to be under and harder. This is for the same power on the vectors.

IMO under on bkool is the prefered option, for me, as it will make me work harder. But when away from bkool can skew the efforts a bit :sad::huh::headshake:
 
Last edited:

borchgrevink

Well-Known Member
Finished this "FTP-test" today: http://www.bkool.com/bkoolSessionHistory/showSessionSummary/1882737

Up nearly 10% in watt compared to my last "record" (set on a course with 9,8% average incline). To me this seems like evidence something isn't right, if not this is some part of the answer: http://cyclingtips.com/2013/09/climbing-and-time-trialling-how-power-outputs-are-affected/
Any thoughts on this? Thanks
 
First time poster on here - I have a BKool Pro but rarely use it as I am fortunate enough to live on the Spanish Costa Blanca where weather is mostly favourable. When I do use it, the power readings on the simulator are very different from the readings that my Garmin 1000 is displaying (which it is connected to a Stages Powermeter). This is especially noticeable when the simulator resistance is low (slight decline or flat) when I can comfortably ride at 45+ kmph. My Garmin will be displaying 250-270 watts while the BKool reading could be up around 350 watts - a variance of around 30%.
As I have the Bkool connected to my Strava account, the BKool date skews my Strava power curve (by overestimating my FTP).
I tried today to reduce the Simulator power reading by reducing my weight by 10 kgs but it didn't seem to make any difference.
 

CXRAndy

Guru
Location
Lincs
First time poster on here - I have a BKool Pro but rarely use it as I am fortunate enough to live on the Spanish Costa Blanca where weather is mostly favourable. When I do use it, the power readings on the simulator are very different from the readings that my Garmin 1000 is displaying (which it is connected to a Stages Powermeter). This is especially noticeable when the simulator resistance is low (slight decline or flat) when I can comfortably ride at 45+ kmph. My Garmin will be displaying 250-270 watts while the BKool reading could be up around 350 watts - a variance of around 30%.
As I have the Bkool connected to my Strava account, the BKool date skews my Strava power curve (by overestimating my FTP).
I tried today to reduce the Simulator power reading by reducing my weight by 10 kgs but it didn't seem to make any difference.
That's Bkool for you. It is widely known that Bkool Pro units over estimate the power output massively. Altering tyre pressure can also have a huge impact on power output as well. Bkool is fine for racing or training alone on Bkool platform, but if you have a power meter to compare this is when the problems occur. Unfortunately you cant add you stages PM as the source on Bkool Sim. You can if you use Zwift or most other platforms, then the Bkool unit is a dumb resistance device and works fine. A lot of riders do this now on Zwift.

Options
Ignore the difference and just accept it
Use Garmin reading whilst racing/training, ignore Bkool wattage(place sticker over screen)
Jump platforms to Zwift, BigringVR, Trainer-Road and add you Stages as power source, Bkool dumb resistance unit- works fine.
 
Top Bottom