PT Problems in the Rain

Aztec

I'm bitter. I did my 2nd (pouring) rain ride today. On the first one a few days ago, I splashed thru some standing water and POOF my PT quit transmitting from the hub (cadence, coming from a magnet only, kept working). It recovered later on.

Today, though, it conked out for a little while, came back, but the display itself faded right after that. When I got home and downloaded the data, I discovered that one of two things happened... either 1) I have become monstrously more powerful as shown by my 30 mins at over 1200w, or 2) the water has somehow zapped the hub. We'll see what happens when it dries out. The display an hour later is still all screwy and faded. I changed the batt, and it's still faded.

Is this normal PT rain stuff? If so, what a piece of junk. Is the SRM any better? I spend too much time in the rain to not have that utility. Plus, I use CyclingPeaks software, which now will have messed up cumulative stats. USELESS!

ric_stern/RST

sounds like the torque needs resetting on your hub. other than that i've ridden with my PT in some really crappy wet weather (ahh the joys of Wales!), and the hub has been fine. the only issues i occasionally have is that the reciever can get waterlogged and stops transmitting. i then leave it to dry out over night. you could also try taking the hub cap off in case any water has gotten in. allow it dry overnight. be careful when replacing the allen key bolts (some units you mustn't do more than 7 turns).

i think there's some special grease you can get from car shops to cover the entry points of the reciever.

if it is a hub fault (i've only heard of one Pro go faulty) then you'll need to send it back. you don't need to strip the rim/spokes off.

hope all is okay after it dries out
ric

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Woofer

Which version of the PowerTap hub? There is an older version that is notoriously water sensitive.

I've ridden my PowerTap for the past eight days in rain without problems. You have to remember to zero it at the start of every ride ( as one has to do the equivalent with the SRM) and check this periodically.

You can correct the data from a ride with a nonzero zero, so to speak. Don't have the link off the top of my head, though.

ric_stern/RST

woofer, aztec is talking about the shiny waterproof version, not the old Tune one (wow, my preproduction one still works!)

ric

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Aztec

Thanks, Ric.

The hub had a couple of very tiny droplets of water under the cover (less than 0.5mm across kinda tiny).

By receiver, are you referring to the unit next to the hub (I have mine mounted on the chainstay, not the seatstay, BTW)? I hadn't thought of that... it could've been the problem rather than the hub.

I replaced the battery in the unit in the computer/display unit, and the LED readout was still a little faded. An hour later, when I check it again, it was just plain dead. I tapped it and can see there's some condensation inside. Super.

ric_stern/RST

i believe, but not heard anything official that there was a few faulty CPUs that aren't waterproofed properly. let power tap know and they usually replace straight away.

yes the unit next to the hub. i mount mine on the seat stay

if you do upgrade to the SRM make sure it's a Pro system. The Amateur requires frequent calibration (monthly or so) with known certified masses, and the system drifts regularly. it's a hassle doing 3 x 4 calibrations on both cranks on a regular basis (even the pro may require these calibrations). and don't trust that the factory calibration is correct (as frequently it isn't).

and yes, you need to check the torque is zero, rather than just seeing if the power is zero when coasting. takes all of 2secs to check!

happy new year
ric

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Aztec

Today, after more drying time the display unit/CPU appears to be working again. I've sent Graber/Saris an email -- hopefully they replace it.

Bummer about the torque issue -- I hope this doesn't mean I've actually been riding at lower wattages than I thought!!

ric_stern/RST

if you open the CSV file in (e.g.) Excel and look for the lowest power in the file(s). Hopefully, these are zero along with torque being zero at the same time (and preferably speed is > 0). if this isn't the case the torque hasn't been zeroed and your power is inflated. you can, however, recalculate things to get the correct power values...

ric

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Woofer

One thing I have had happen that one has to be careful of is that sometimes the torque offset goes bad in the middle of a ride. I have had to rezero in the middle of a race - noticed I had nonzero watts during a long descent. Also, this past weekend I stopped to help others with a flat and the torque zero went wrong cause I noticed after the restart I set a new personal record for wattage.

Also, I've seen people make the same complaints about water and the SRM and the Polar so perhaps you've had a spot of bad luck. It's always a bad feeling to have a unit go bad. One thing to do is make sure you know which of your friends has the same brand of unit. That way you can always give them a call and interchange units with them to diagnose problems. This is the one hidden cost of any power measuring device - diagnosing problems is quite similar to diagnosing home computer problems.

ric_stern/RST

if your torque is going off on a regular basis, then barring large temp changes, or you stripping the hub and cassette on a regular basis there's most likely something wrong with your hub.

on any of my PT's it would be unusual for torque to drift off mid ride more than say twice a year (barring large temp changes).

ric

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Woofer

Absolutely. That's my experience as well. I have three powertaps but didn't want to seem to biased.

Generally this happens when indoors it is 70 and I start a ride and outside it's 45 or something, but that actually possible during some rides here as well. 95% of the time when I check the torque zero at the start, the zero looks OK.

gregkeller

when you say check the torque value, or zero the torque, and whatever, does that mean you just hold down the mode and select button until watts starts flashing and then make sure that number is 0, or is it going through the test mode for torque, or what? I had a power tap hub that was messed up, not sure what was wrong with it, but i sent it back to saris to be recalibrated. When i put it in the torque test mode, the number that was supposed to be 512 was down around 490. Don't know if the wide temp change of going inside (75) to outside (25) made a difference, i guess it could have, but i tried zeroing the torque when i did go outside, but that didn't do anything.

ric_stern/RST

hold down the mode or select button till "watts" flashes or disappears (depending on model) and make sure that number is zero while coasting and no pressure on the pedals.

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