Inaccuracy of Pro 300PT indoorbike with powertap due heating up flywheel

[PaulMD]

yeah I hear your frustration there. Decreasing HR indoors would certainly confirm the power drop as I believe most folks would increase or at least plateau but not drop at constant power. I have hundreds of ergo workout records and doubt if there's a single one showing HR decrease over time.

What about the suggestion by Attybiker? I use a CT and warmup at tempo power for ~ 15min before performing 2-3 rolling resistance checks and accepting the 'calibration' (more of an offset rather than calibration). Perhaps a similar routine would enable your 300PT to give you acceptable results.

Yes, it's a good suggestion but for an indoortrainer of 1850 dollars it shouldn't be necessary. And for me the problem is that I have bought the indoortrainer because I have less time to train. I have appr. 40-60min. A 20 minute warming up to get my trainer more accurate was not what I was thinking about when I bought it.

 

[cPritch67]

At the moment I still don't have a reply from Cycleops. I am going to send them a second email.

Paul, ditch the emails and try calling them - if you call during hours, you'll actually get to speak to a live person.

 

[PaulMD]

Paul, ditch the emails and try calling them - if you call during hours, you'll actually get to speak to a live person.

At weightweenies.starbike.com Jesse Bartholomew readed my post. After I private messaged him I got an reply from Jereme Noffke:

Hey Paul-​

The heat on the flywheel will not affect the PowerTap. The Electronics are nowhere close the the braking surface of the flywheel. How are you measuring the temperature of the flywheel? ​

How are you determining there are 10 inch pounds of torque on the bike? How are you clearing torque (in detail)?​

Please let me know and I can better trouble shoot the issue.​

Regards,​

Jereme Noffke | Saris Cycling Group | P. 800-783-7257
​

So Cycleops says that not the heat affects the powertap? Hmmm. What would it be else? And the complete flywheel becomes hot: so the powertap also becomes hot.

Today I did a test ride. An easy ride without touching the resistance knob. So the resistance stayed the same.
Before I started I first zero torqued the powertap. Zero torque = 0
After 10 minutes I jumped of the bike to read the zero torque = 2 inch*lbs
After 20 minutes I jumped of the bike to read the zero torque and now it was already 4 inch*lbs.
After 25 minutes I did the same and the zero torque was 5 inch*lbs. Then I cleared the torque. Zero torque was again 0.
Between minute 20-25 and 25-30 I rode with the same resistance, the same speed en cadance for a couple of minutes. Only between 20-25 my zero torque was off by 5 inch*lbs. The effect of average power was huge! Because between 20-25 minutes I cycled with 254 watts and between 25-30 minutes I cycled with 232 watts!!

Conclusion: A low pace the powertap is inaccurate after 25 minutes. The difference with 5inch*lbs is 9.5% at 232 watts!!!
​

 

[acoggan]

Hey Paul,

Here's another experiment you might wish to try (provided that you have the time): set the zero offset, then pedal against no resistance for 30 min or so while periodically rechecking the zero. If the problem is truly due to heat-induced drift, then you should find no change. OTOH, if the zero offset is drifting for some other reason - and there have been reports of some hubs showing this behavior - then you should (may) still see some increase.

Just a thought...

 

[cPritch67]

If I can get some time tonight, I can try and do both of these tests (Paul's and Andy's) and report back on what happens with my PT300.

 

[rmur17]

At weightweenies.starbike.com Jesse Bartholomew readed my post. After I private messaged him I got an reply from Jereme Noffke:
[/b]
So Cycleops says that not the heat affects the powertap? Hmmm. What would it be else? And the complete flywheel becomes hot: so the powertap also becomes hot.

Today I did a test ride. An easy ride without touching the resistance knob. So the resistance stayed the same.
Before I started I first zero torqued the powertap. Zero torque = 0
After 10 minutes I jumped of the bike to read the zero torque = 2 inch*lbs
After 20 minutes I jumped of the bike to read the zero torque and now it was already 4 inch*lbs.
After 25 minutes I did the same and the zero torque was 5 inch*lbs. Then I cleared the torque. Zero torque was again 0.
Between minute 20-25 and 25-30 I rode with the same resistance, the same speed en cadance for a couple of minutes. Only between 20-25 my zero torque was off by 5 inch*lbs. The effect of average power was huge! Because between 20-25 minutes I cycled with 254 watts and between 25-30 minutes I cycled with 232 watts!!

Conclusion: A low pace the powertap is inaccurate after 25 minutes. The difference with 5inch*lbs is 9.5% at 232 watts!!!
[/left]

that lines up with the previous estimates.

re the flywheel -- well steel or alu alloy conducts heat pretty darned well. Cooling will be lessened near the hub due to the lower radial velocity at that point. I can't see their point to be honest unless there's an insulating layer of sufficient thickness to retard heat conduction from the 'rim' inwards.

Andy's test sounds good as well to confirm it's a heat problem and not something else with the hub.

 

[J-V]

Paul,

FWIW, I have seen no such drift issues with my 300PT. Always reads "0" at the beginning, always reads "0" at the end.

However, what I have noticed (and I believe I wrote in the forums awhile back) is the decrease in resistance over the course of the ride (i.e. for a given cadence, the power drops off maybe 20 watts over the course of 1 or 2 20-min. L4's, necessitating continually tightening the resistance setting). Saris told me this was brake pad/caliper heating.

But, it sounds like you have a different issue, and I'm sure they'll take care of it, though at what inconvenience to you I can only guess. One thing you might consider is contacting the local shop you bought it from (if so), or a local shop that sells them. When my flywheel went out of true, my LBS handled everything (even though I didn't buy it there), including swapping the flywheel from stock (they ordered themselves a new one), and even picking up and delivering the unit back to my home.

Good luck!

 

[PaulMD]

@acoggan: Yes, this week I have enough time for this kind of experiments. I just cycled 30 minutes without any resistance. The zero torque stayed 0 the whole 30 minutes. But I discovered that PowerAgent and CyclingPeaks can't read the file on my cycleops CPU. According to the cycleops CPU I did 30 minutes with an average of 6 watts . But in poweragent and cyclingpeaks I only see 24 seconds.

@warnerjh: That's good to hear (you don't have this annoying problem and for me maybe there is a solution). But how is the temperature of your flywheel after one hour > 200 watt? After the post of attybiker I was thinking that it was a common problem with the Pro 300PT. Because due the design the powertap has to increase in temperature during a workout.

@cPritch67: I am very curious what your Pro 300PT does with the zero torque after a workout. If I was you I shouldn't ride 30 minutes without resistance, my torque was fine afterwards. But I am very very curious if your zero torque will change after 30 minutes with more than 200 watts. Especially because warnerjh says he has no problems.

 

[J-V]

@warnerjh: That's good to hear (you don't have this annoying problem and for me maybe there is a solution). But how is the temperature of your flywheel after one hour > 200 watt? After the post of attybiker I was thinking that it was a common problem with the Pro 300PT. Because due the design the powertap has to increase in temperature during a workout.

The flywheel is always roughly the same warmth after any given ride (warm to the touch but not downright hot), whether it's my wife's 1/2-hour workout or a 1x60 at 260+ watts. Try getting in touch with Robb Zbierski at Saris, he'll get you going down the right path.

 

[PaulMD]

The flywheel is always roughly the same warmth after any given ride (warm to the touch but not downright hot), whether it's my wife's 1/2-hour workout or a 1x60 at 260+ watts. Try getting in touch with Robb Zbierski at Saris, he'll get you going down the right path.

At the moment Jereme is trying to help me. But I think that his first thought is that I am doing something wrong. His first line was that it was not due heat because the powertap is nowhere close to the braking surface of the flywheel. His second line was how I determined the temperature increase of the flywheel. I hope he will soon take my problem a little bit more serious. He has probably never ridden a cycleops indoortrainer because due the friction of 300 joule / second during 3600 seconds a lot of energy goes as heat into the flywheel and with metal as a good conducter of heat the compleet flywheel becomes hot. You don't have to be an expert to find out that the temperature of the hub is increasing a lot.

He also asked about hub calibration. But what those number say, I don't know:
Cooked 0000
Offset 0509
Raw 0509

 

[cPritch67]

@cPritch67: I am very curious what your Pro 300PT does with the zero torque after a workout. If I was you I shouldn't ride 30 minutes without resistance, my torque was fine afterwards. But I am very very curious if your zero torque will change after 30 minutes with more than 200 watts. Especially because warnerjh says he has no problems.

Paul
I was time constrained from doing the specific tests but here were my observations from my ride.

Indoor temp - upper 60's to 70ish, no fans
0 Min - 0'd torque
5 Min - avg 95W, 95Cadence - Check Torque = 1W - No Reset
10 Min - avg 105 W, 95 Cadence - Check Torque = 1W - No Reset
15 Min - avg 120 W, 95 Cadence - Check Torque = 2W - No Reset
20 Min - avg 250 W, 90 Cadence - Check Torque = 3W - No Reset
25 Min - avg 130 W, 95 Cadence - Check Torque = 3W - No Reset - Noticed flywheel warm to touch - not hot, def warmer near perimeter (where pads touch)
30 Min - avg 260 W, 95 Cadence - Check Torque = 3W - No Reset
35 Min - avg 260 W, 95 Cadence - Check Torque = 5W - Reset to 0
60 Min - avg 130 W, 105 Cadence - Check Torque = -0

So, yes, the torque drift is real and that was at relatively little power or long durations of power.

 

[rmur17]

Paul,

FWIW, I have seen no such drift issues with my 300PT. Always reads "0" at the beginning, always reads "0" at the end.

However, what I have noticed (and I believe I wrote in the forums awhile back) is the decrease in resistance over the course of the ride (i.e. for a given cadence, the power drops off maybe 20 watts over the course of 1 or 2 20-min. L4's, necessitating continually tightening the resistance setting). Saris told me this was brake pad/caliper heating.

But, it sounds like you have a different issue, and I'm sure they'll take care of it, though at what inconvenience to you I can only guess. One thing you might consider is contacting the local shop you bought it from (if so), or a local shop that sells them. When my flywheel went out of true, my LBS handled everything (even though I didn't buy it there), including swapping the flywheel from stock (they ordered themselves a new one), and even picking up and delivering the unit back to my home.

Good luck!

just to be sure: you are checking Torque correct and not Watts?

 

[cPritch67]

Paul
I was time constrained from doing the specific tests but here were my observations from my ride.

Indoor temp - upper 60's to 70ish, no fans
0 Min - 0'd torque
5 Min - avg 95W, 95Cadence - Check Torque = 1W - No Reset
10 Min - avg 105 W, 95 Cadence - Check Torque = 1in lbs - No Reset
15 Min - avg 120 W, 95 Cadence - Check Torque = 2in lbs - No Reset
20 Min - avg 250 W, 90 Cadence - Check Torque = 3in lbs - No Reset
25 Min - avg 130 W, 95 Cadence - Check Torque = 3in lbs - No Reset - Noticed flywheel warm to touch - not hot, def warmer near perimeter (where pads touch)
30 Min - avg 260 W, 95 Cadence - Check Torque = 3in lbs - No Reset
35 Min - avg 260 W, 95 Cadence - Check Torque = 5in lbs - Reset to 0
60 Min - avg 130 W, 105 Cadence - Check Torque = -0in lbs

So, yes, the torque drift is real and that was at relatively little power or long durations of power.

These are def torque readings above.....not Watts...and should read inch pounds, not W - I have corrected.

 

[PaulMD]

These are def torque readings above.....not Watts...and should read inch pounds, not W - I have corrected.

But I think we have to be sure warnerjh is reading torque (as he seems the only person with a pro 300PT that doesn't drift).

cPritch67 thanks for your test, out of 4 pro 300PT users three have confirmed the drift in the cycleops flywheel. I am becoming more and more concerned about a solution.

At the moment I only know one solution. Don't measure the power in the hub but in the crank itself. I hope cycleops is soon emailing me a serious mail about this problem.

I have my powertap sl 2.4 already on hold. First I want a solution for this problem.

 

[rmur17]

These are def torque readings above.....not Watts...and should read inch pounds, not W - I have corrected.

uhm I directed that to warnerjh .. sorry for the confusion! I realize if the flywheel has stopped you're going to see zero watts regardless of torque.

 

[cPritch67]

I have my powertap sl 2.4 already on hold. First I want a solution for this problem.

The reason I had to cut my test ride short was that UPS showed up with my just ordered 2.4 on Zipp 303 wheelset. I had to open the boxes and oogle for a bit. I will probably not have the 2.4 installed on the bike for a few weeks - hopefully I'll be one of the problem free (no drops) 2.4's.

I agree, we need to confirm that ??? is looking at torque, not watts.

 

[J-V]

But I think we have to be sure warnerjh is reading torque (as he seems the only person with a pro 300PT that doesn't drift).

Yes, torque.

I haven't been riding the 300PT for the last two weeks because the weather is good (been on the bike!), however my wife has. She's probably put 5 hours on it since I last rode and re-zeroed, and when I checked last night, the torque did indeed read "2" after spinning the crank and coming to rest (it was 'cold', hadn't been ridden that day). This is the first time I've seen this, and may simply be related to the (relatively long) length of time that has gone by since I last re-zeroed, since she doesn't ever do it.

 

[J-V]

FWIW, I did all these checks during the first few weeks of use, and I have to admit that since getting the flywheel changed, I doubt I've checked torque post-ride to confirm. That being said, I've noticed no difference between the perceived effort nor the downward drift of resistance that occurs over the duration of a ride. I have never had a decreasing HR over the course of an L4 interval, but I guess it's possible if I had not been re-setting the resistance along the way (due to the gradual decreases in wattage).

Couple of things of note: As above, it seems to me if the unit gradually starts to 'over-report' wattage, we would either increase wattage readings over an interval (at a static level of effort), or decrease heart rate (if we 'slow' to keep the wattage consistent). I haven't personally experienced either of these occurrences, at least as relates to my 'perceived efforts'. Secondly, if the resistance is indeed decreasing due to brakepad heating (as I believe, based upon both my perception of effort and the wattage reading), maybe it's doing so in an inversely proportional relationship to the wattage over-reporting, in which case the 'problem' may be canceling itself out, or accommodating itself, in other words.

This is getting complicated to keep straight in my head, so please point out any errors in my thinking described above...

 

[jeffh]

Paul,

When you set/checked the torque, did you unwind the tension first? I noticed that mine will read differently depending upon the chain tension - which seems to exist if I have the tension knob turned up and allow the cranks to stop spinning on their own. The torque also moves around if I place any weight on the pedals during the reading.

-jeff

I always thought that my Cycleops Pro 300PT with a powertap hub in the flywheel was pretty accurate. I have done two 60 minute timetrials and the last 30 minutes always felt a lot easier. That made me think because maybe the powertap was inaccurate during the hour due the fact that the flywheel because pretty hot after 30 minutes of riding > 250 watts.

Two days ago I zero torqued before a training. After the training the flywheel was hot and my torque was 10 inch-lbs. After a couple of hours when the flywheel was at room tempature the torque was 0 inch-lbs. Yesterday before my training the torque was still 0 inch-lbs but after the training it was again 9 inch-lbs.

- My question how much does this change in torque affect my average power? Is it off by more than 10 watts?
- And is this a known problem?

 

[PaulMD]

I have had a good conversation with Robb Zbierski from Cycleops. The problem I have with my powertap in the flywheel is quite unique and Cycleops is investigating the problem. They are very helpfull and they send me a new flywheel. When they receive my faulty flywheel they will test it why the torque is off after an workout because a normal flywheel won't have this problem.