Inaccuracy of Pro 300PT indoorbike with powertap due heating up flywheel - Page 3

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.

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

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rmur

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.

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.

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rmur

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.

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.

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'07 S-Works Tarmac SL, Polar CS600+Power
2008 Cervelo P3C, Zipp 900c+808

'07 Specialized Epic Marathon w/Crossmax SLRs
CycleOps Pro 300PT Indoor Cycle Trainer (my winter ride)

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...

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'07 S-Works Tarmac SL, Polar CS600+Power
2008 Cervelo P3C, Zipp 900c+808

'07 Specialized Epic Marathon w/Crossmax SLRs
CycleOps Pro 300PT Indoor Cycle Trainer (my winter ride)

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 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.

I knew Robb would take care of you...

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'07 S-Works Tarmac SL, Polar CS600+Power
2008 Cervelo P3C, Zipp 900c+808

'07 Specialized Epic Marathon w/Crossmax SLRs
CycleOps Pro 300PT Indoor Cycle Trainer (my winter ride)

So does this suggest that my flywheel/PT is "defective" and I should call Robb as well?

Here is what I posted to a couple other forums:


I had root canal on Wednesday an I was not quite able to perform my test has planned -- I could not maintain FTP for the workout so I stopped. However, I backed off a bit and at least did 20 minutes at L3 to wake my legs up a bit. Thankfully, I saw zero drift during this brief workout:

Start:
Torque: 0
Flywheel: Room Temperature
Hub: Room Temperature

After 10 minute Warm-up:
Torque: 0
Flywheel: Slightly warm
Hub: Room Temperature




After 20 minutes at 260 watts:
Torque: 0
Flywheel: Warm
Hub: Maybe a bit above room Temperature

After 20 minutes at 260 watts, there was no really temperature increase at the hub and all my torque zero readings were rock solid.

I received my new flywheel pretty fast (on tuesday morning). But I had no time to post here or to install the flywheel. Yesterday I installed the flywheel and did a 20 minute ride and I had no torque drift! Before and after the ride the torque was 0 inch pounds.

So my defective powertap hub is replaced with a good one

The downside of a accurate powertap is that my power is lower. I will post my new FTP when I have done a 60 minute timetrial on the Pro 300PT with the new flywheel.

@cPritch67: Torque drift is not normal for the 300PT. I think you should contact Saris.

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sweet. Did THEY pay for shipping? !

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rmur