Power resistance maxing out?

[borchgrevink]

I hear that the roller max out for many of you when it comes to resistance from 8%-10% depending on your weight.

How is this possible when the roller says it can offer 1200W of resistance? Am I misunderstanding anything?

 

[RickB]

The basics is the heavier you are the more resistance the unit needs to produce to simulate gravity. Resistance will be much different for a 60kg whippet on a 10% climb than a 120kg guy.

Dont know the mathematical formula for calculating resistance - just know than for my 84kg carcass it maxes resistance at just over 10% I think. I remember someone else who weights much more saying Bkool wasnt able to make it any harder once they got to about 6%.

This isnt a direct comparision with the Watts Bkool is telling us we are producing which is a different thing altogether to how many watts it needs to generate hills (clear as mud I'm sure! )

 

[gbrown]

I hear that the roller max out for many of you when it comes to resistance from 8%-10% depending on your weight.

How is this possible when the roller says it can offer 1200W of resistance? Am I misunderstanding anything?

1200W is a maximum, and as I understand it is only going to be approached when the wheel/roller speed is very high.

Power is calculated as torque times rpm and therefore the the maximum power will be at maximum resistance (torque) AND maximum roller speed (rpm), i.e. only when sprinting.

When climbing the rpm is much lower and hence the power is lower. if you sprint around 60 km/h and climb at around 15 km/h (or less) then expect maximum power to be around a quarter, or 300W, which seems to be about correct.

Your weight will determine the resistance required to simulate any particular gradient, so the heavier you are the lower the gradient at which the unit will reach maximum resistance.

Geoff

 

[theboxers]

The basics is the heavier you are the more resistance the unit needs to produce to simulate gravity. Resistance will be much different for a 60kg whippet on a 10% climb than a 120kg guy.

Dont know the mathematical formula for calculating resistance - just know than for my 84kg carcass it maxes resistance at just over 10% I think. I remember someone else who weights much more saying Bkool wasnt able to make it any harder once they got to about 6%.

This isnt a direct comparision with the Watts Bkool is telling us we are producing which is a different thing altogether to how many watts it needs to generate hills (clear as mud I'm sure! )

Currently my perceived work rate/resistance peaks at about 6%. I can maintain 70rpm and 6mph for a while after reaching this point at any indicated gradient above this. I was improving on cadence and speed up until just before Christmas, but lack of riding and ill health has knocked me back a bit.

I am currently 131kg. My ftp figure based on rides not a test is 199 watts.

 

[borchgrevink]

I thought speed would go down if incline got steeper?

 

[theboxers]

I thought speed would go down if incline got steeper?

That used to happen on the previous firmware on my bkool classic. The bsim software would provide a calculated speed for the trainer derived info plus cadence plus my weight afaict and display this in blue. It would be within a couple of points of a true speed for that gradient, my weight and reported power. My actual wheel speed would be much higher.

I did an alpe d'huez session and maintained a 5-6mph true wheel speed in the steepest sections. This was calculated down to between 1.5 and 3 mph dependant on gradient. So I spent over 2 hours on that session, pretty close to the calculated values derived from other sites. I have not attempted an alpe d'huez session since the firmware update.

But I have done some of the T100 league rides twice with significant improvements since the firmware update. Cheddar Gorge for example. From 27 minutes pre update to 16 post update. My physical state did not improve enough to give me an 11 minute advance. This was soft/firmware derived improvement, I don't want to give it back

Just accept that there are limitations to what any trainer can do and hope that the software is good enough to get within small margin of the true figures.

The Max resistance is still very hard to power through. It is just that some of us reach it earlier than most

 

[gbrown]

Currently my perceived work rate/resistance peaks at about 6%. I can maintain 70rpm and 6mph for a while after reaching this point at any indicated gradient above this. I was improving on cadence and speed up until just before Christmas, but lack of riding and ill health has knocked me back a bit.

I am currently 131kg. My ftp figure based on rides not a test is 199 watts.

Sounds spot on, at 131 kg you are 1.75 times heavier than 75 kg, and 1.75 x 6-7% would give 10.5-12% limit for a 75 kg rider, which is about what riders of that weight report.

That used to happen on the previous firmware on my bkool classic. The bsim software would provide a calculated speed for the trainer derived info plus cadence plus my weight afaict and display this in blue. It would be within a couple of points of a true speed for that gradient, my weight and reported power. My actual wheel speed would be much higher.

I appears that bkool have at times added to the software to try and adjust for the resistance maxing out, then withdrawn it again! I'm sure it is very hard to allow for all the variations in terrain and weight and speed/power, etc. so I can understand why they have withdrawn it, as it would be just as likely to introduce more problems than it solved.

Geoff

 

[theboxers]

It appears that bkool have at times added to the software to try and adjust for the resistance maxing out, then withdrawn it again! I'm sure it is very hard to allow for all the variations in terrain and weight and speed/power, etc. so I can understand why they have withdrawn it, as it would be just as likely to introduce more problems than it solved.

Geoff

The biggest down side to the calculated speed, as far as I see it, is the extended duration of the sessions. The d'Huez session that took me over 2 hours would be just over an hour on the new firmware. I am tempted to have another go just to see how quickly I can do it. But the mind says Noooooooo!!!!!!! remembering how hard the first 2 attempts (one incomplete) were.

 

[gbrown]

The biggest down side to the calculated speed, as far as I see it, is the extended duration of the sessions.

I know exactly what you mean about > 2 hour climbs, as it took me over 2 hours to get up Mont Ventoux. I found it quite difficult to get off the trainer when it finally ended...

A more accurate reflection of reality though, as it would take even longer in real life. In fact, it is doubtful that many of us could do it in reality!

I would say that accuracy is important, and you could always use the "Slope Reduction" feature to put it back to where you could do it in a reasonable time. The end result would be much the same, if you are sitting on the trainers maximum resistance in both cases.

But I guess Bkool have to appeal to as wide a range of users as possible, a bit like Zwift when I hear they are defaulting to 50% difficulty settings.

The d'Huez session that took me over 2 hours would be just over an hour on the new firmware. I am tempted to have another go just to see how quickly I can do it.

Just over an hour is a pretty competitive time, only the very fittest (and lightest) can get below an hour. Even at my fittest and down to 73 kg I only managed 62 minutes, although I did have the excuse of the Wahoo KICKR's much higher resistance.

Geoff

 

[borchgrevink]

So, if the simulator no longer compensates speed when power is maxing out there is no need to pedal harder than what the max is? "Wasted effort" when it comes to time?

 

[theboxers]

So, if the simulator no longer compensates speed when power is maxing out there is no need to pedal harder than what the max is? "Wasted effort" when it comes to time?

It is not power that is maxing out. It is resistance. If you can generate more power it will be picked up by the trainer as increased speed at that resistance and display a higher power.

The old fw I had on my trainer combined with the bsim software, at that time, provided a more accurate simulation as far a speed was concerned and consequently how long a session would take. However the resistance was short of where a true climb would be, for my weight, above 6%. But I would spend more time at max resistance than a lighter rider for any gradient above 6%.

 

[borchgrevink]

It is not power that is maxing out. It is resistance. If you can generate more power it will be picked up by the trainer as increased speed at that resistance and display a higher power.

The old fw I had on my trainer combined with the bsim software, at that time, provided a more accurate simulation as far a speed was concerned and consequently how long a session would take. However the resistance was short of where a true climb would be, for my weight, above 6%. But I would spend more time at max resistance than a lighter rider for any gradient above 6%.

OK. But it looked like speed was pretty constant for me, even though incline changed from 12-18%, but I didn´t pay too much attention to power. Will do the next time. Thanks!

 

[theboxers]

OK. But it looked like speed was pretty constant for me, even though incline changed from 12-18%, but I didn´t pay too much attention to power. Will do the next time. Thanks!

That is what happens now with my setup. Once I reach 6% (the point of max resistance for me, with my setup and registered weight), if I maintain the same cadence and gear selection, the speed/power will remain the same whatever the gradient above 6%. I am now getting a true wheel speed reading, in bsim instead of a calculated one, after 6%.

http://www.bkool.com/bkoolSessionHistory/showSessionSummary/1373748

This is an Alpe d'Huez session I attempted before the fw update. I was on a 34/32 which should have given me a speed of about 5mph @ the 60rpm cadence I was pushing. As you can see the speed was down to under 3mph at times.

Now on similar slopes I get 5+mph pushing 60rpm

 

[Vertego]

My recent experience, following the latest BSIM 'upgrade' has returned results of over 1000W up Sa Colobra at 9%+, doing over 90kmh. I never had such ridiculous results before the 'upgrade'.

Alpe d'Huez - 1:12:35, at an average 210W, 70rpm - http://www.bkool.com/bkoolSessionHistory/showSessionSummary/1461399

Bkool's response was to uninstall/reinstall the BSIM software.

 

[RJKflyer]

I recall going through all this with my Tacx iFlow - which was hopeless for me as a light guy.

Essentially I established that for me it could only simulate as follows, with the 'red' numbers being 'blue' in Bkool terms. The essence being, as noted above, you need torque and rpm to 'use' the brake capacity.