Yet another PowerTap troubleshoot thread...

kmavm

When it's working well, I absolutely love my new powertap SL. However, I'm having a heck of a time keeping it working.

My failure mode doesn't seem similar to other problems I've seen posted about. My powertap works great, and then goes into a "coma" suddenly, and refuses to emerge.

On two rides so far, after about 2 hours of mostly flawless functioning, the CPU briefly drops a few times. Then, within a few minutes, the CPU goes into "---" mode, and just CANNOT be coaxed out. I've gotten off the bike, fiddled with the receiver, taken the CPU out of its cradle to try to clear any dirt or water that may have pooled around the electrical contacts, wiped dirt off the wireless receiver and carbon fiber windows on the hub. Nothing helps. My powertap has become a $1000 heart rate monitor .

The failure mode just doesn't make sense to me. The things that should cause a total failure of signal (low batteries in either the CPU or the hub, a bad electrical connection from the CPU to the receiver, or a poorly mounted receiver) shouldn't fail suddenly, and catastrophically, two hours into a ride. What am I overlooking?

These last few days have been somewhat moist. Not necessarily drenching wet, though I've ridden through at least one gully-washer. One ride, which I'm not counting among these "coma" rides, I was able to fix the symptom by taking the CPU off its cradle and drying the contacts. My impression was that the wet weather problem had mostly been solved with the SL hub.

Which square in the powertap troubleshooting board game should I jump to next? Replace the CPU batteries? The hub batteries? Wrap tin foil around my chainstays while I hold down the "mode" button for 15 minutes and do the hokey pokey? What? Someone give me hope that I'll be able to use this equipment; I fully believe in its promise, but thus far the flakiness level is so high that I'm frankly amazed a business would dare sell these things.

RapDaddyo

A few questions. When you get "---" for watts and speed, what are you getting for cadence? Do you have the CPU set up to get cadence from the crank only or from the hub, then crank (I think this is Setup3 IIRC)? How many hours/miles do you have on your PT? Have you ridden in the rain? Do you have something spongy between the stay and the receiver as recommended in another thread?

kmavm

Cadence reads "---" as well. I had not changed setup 4, which was in the factory default "hub only" setting. No wonder cadence was so weird. I've switched it to pedal, and will see if the cadence continues to register the next time this happens. Heart rate continues to register, by the way, so it's not as though the CPU is dead to the world.

Something like eight hours, 120 miles. (Lots of climbing.) I'm still definitely in the "break-in" phase.

I've done little but ride it in the rain. Yesterday, for three hours in an absolute downpour. No coma during the ride.

Is this still against conventional wisdom? A training buddy rides his SL through the rain without problems; I got the impression the weather sensitivity was a thing of the past...

Yes, I quickly found I needed this to prevent the "coasting over rough pavement" drops. Should I experiment with the spongy material? I initially tried a 2-3mm thick piece of foam rubber (thinking "the spongier the better!"), and then had more success with the adhesive backed rubber strip packaged with the unit.

RapDaddyo

That means you are losing the signal from the hub. No doubt you'll still have cadence once you change the setup. I don't like to get my cadence from the hub anyway for several reasons. Anyway, this is the classic symptom of losing the signal from the hub to the receiver, usually when freewheeling.

The seat stay mount has to accomplish two objectives: (1) dampen vibration to the receiver; and (2) keep the receiver parallel to the hub axis (i.e., prevent rotation on the stay). You can test this on a trainer or bike repair stand. You just get the hub spinning fast and then let it freewheel. You should get the dropouts if you still have a problem with the mount. There's a discussion of this somewhere, but the last time I checked the search function was off. Do a search on "PT display dropouts" or similar strings.

Never mind. Here's the thread http://www.cyclingforums.com/t274980-.html

kmavm

Thanks for your time, RD.

I'm afraid this diagnosis doesn't have the ring of truth to it. If the mounting is a problem, how come no amount of wiggling the receiver on the seat stay causes the coma to disappear? When not in "coma" mode, the connection doesn't seem very particular about how it's mounted; I can move up or down by a half-inch or so (all that's possible on my seatstay without exceeding 3 inches), in or out from the hub by much more than the 5 degrees recommended, without seeing any drops. But, once in "coma" mode, the connection is seemingly irrecoverable.

RapDaddyo

Well, it sounds as though you have one of two problems. Either the hub is not transmitting consistently or the hub is transmitting consistently but the problem lies in the receiver and wiring to the handlebar mount. What the computer is saying when you see the "---" is that it has lost the data stream from the hub. I think it's very unlikely that the computer is malfunctioning. One problem for some has been the vibration damping of the receiver's attachment to the stay. Maybe that's not your problem, but the pattern is similar -- inconsistent hub data stream. Maybe you have a pinched wire or a problem at the handlebar mount. I think I would have Saris send me a new receiver and would simply replace my receiver and handlebar mount entirely. If your hub batteries need to be replaced, you should get a blinking hub transmission icon in the upper left corner of the computer display. Or, you could just replace them. It takes only 5 minutes and costs ~$10.

wattsup?

I had similar problems to yours when I first got my PT SL. It would work for awhile, then just stop. I was having trouble with the HR as well. I ultimately had to have CycleOps send me out a new computer, cradle, and receiver. Through process of elimination, it turns out it was the computer itself that was faulty. I have had pretty good luck with mine since, although I haven't ridden in much rain.

I have had to replace the batteries in the hub since then, but the transmission icon was blinking indicating such. You might try to replace all the batteries in the interim to see if it solves the problem. It can't hurt, and you'll eventually need the batteries anyway. They are really common; I got mine at Target.

Hope this helps,

Ethan

kmavm

Umm. So that little circular icon in the upper left isn't supposed to be blinking? Because it's been blinking since the second I set the system up. Reading the manual carefully now ... yeah, I guess I was shipped a hub with old batteries! Neat! That sounds easy enough to fix. If only I had some 357 batteries lying around. I hope I can get some the morning of Christmas eve, before my long ride.

Thanks a ton, Ethan and RD!

kmavm

Famous last words. Walmart hooked me up with some 357 magnets at 1am on Christmas Eve. Gotta love capitalism.

However, I've finally discovered a reason for cyclists to lift weights: so they can remove the hub cover from their powertap SLs. The manual has some hilarious verbiage about how the O-rings "may cause the hub cover to resist the start of motion." It felt like I was trying to "unscrew" a stone. I tried everything I could think of to get that stinking cover off: elbow grease, a wrench, which, despite using a rag, really chewed up the soft plastic on the part of the hub cover I clamped it on, pliers. I don't own a bench vise.

Any other ideas? Google, and searching the topica wattage list, suggest that I am the only one having this problem. It's righty-tighty lefty-loosy, right? I.e., I'm trying to turn this thing counter-clockwise?

Sorry to be such a whiner. Look on the bright side: if things keep going poorly for me, there will be a very cheap PowerTap SL, with lightly marred hub cover, available shortly! Happy holidays...

RapDaddyo

When I have removed my hub cover, I have used one of those adjustable pliers like this http://www.sears.com/sr/javasr/prod...0&bidsite=CRAFT. I used a rag to protect the hub and secured the wheel by putting it flat on the floor with the tire wedged into the walls at a corner of the room and using my knee to keep it pressed against the walls. You need a pair of pliers with wide enough jaws to get reasonably parallel with the notched sections of the hub cover. You should be able to lay your hands on one of these adjustable pliers at just about any place that carries any tools at all (e.g., Walgreens or even a grocery store). If you can't, then here is an idea I haven't tried but should work. You could clamp two boards (e.g., 2x4s) to a table top with 4 "C" clamps, set wide enough apart for the notches in the hub cover. Again, use a rag to protect the hub. Insert the hub cover and turn the wheel. And, yes, turn counter-clockwise to loosen. When you replace it, use bicycle grease on the O-ring. But, if you don't have any, don't bother. Just remember to do it later. It helps with the seal and to keep the O-ring soft and pliable. If you've scratched up your hub cover, call Saris. I'll bet they will send you a replacement hub cover. Their customer service is pretty good. Good luck and enjoy your ride.

kmavm

While at WalMart, I bought the biggest monkey wrench (my translation of the manual's "spanner wrench" suggestion) available. It was about 3mm short of being able to span the big square in the middle. Maybe I'll just bring the stupid thing with me on my next trip.

Don't take this the wrong way, RD, but the fact that this bizaare, home-unimprovement daydream has occurred to you is not encouraging. It makes me think: "this should not be so hard." I was kind of led to believe I was buying a consumer product, here. I don't look forward to constructing novel tools to perform routine maintenance on the bloody thing. I already have a job. And a pet.

RapDaddyo

I don't take it the wrong way. But, I don't think that needing a special tool to replace the batteries renders a product worthless or even consumer unfriendly. Lots of things on a bike need a special tool. Try removing your cranks without the proper tools. Maybe you could argue that the hub cover should be able to be removed with something as common as a screwdriver, but I don't know how they would do that. The threaded hub cover and O-ring is key to keeping moisture out of the hub. I just view it as a product that requires a special tool. Actually, I'm surprised one can unscrew the hub cover with something as readily available as a pair of adjustable pliers -- I had one in my tool box and it isn't a very well equipped tool box. I'm actually more irritated with the flimsy receiver that needs to be attached with the right sort of buffer material to prevent drop-outs while coasting and the HR receiver on the computer -- I've gone through two computers so far. But, I've gone through the early stages of product development and I know the nature of unforseen problems such as the interference of the noisy SL hub with the receiver. I'm sure that caught them by surprise because it isn't a problem with the Pro -- different freewheel. As to the HR receiver, it would bug me more if I payed much attention to my HR, but after you ride with power for awhile you realize how irrelevant a HRM is. Anyway, I hope you got it working.

kmavm

Didn't mean to imply that it is. If I weren't completely convinced of the utility of training with power, I wouldn't be going to all this trouble.

And let me again say: THANKS! To both you and Ethan. The adjustable pliers worked for me, by the way, and yes, it was a dead/dying hub battery to blame, as I'm returning from a 3.5hr drop free ride with lots of descending over sketchy pavement.

I hear where you're coming from here, it's just a little bit amazing to me that powertap customers are so forgiving of these foibles. It's reminiscent of users of Apple computers, for whom all wrongs are excusable, as long as it's Apple doing it. It's cool though; as with Apple, it probably just means that most users are very, very happy with their units. When mine is working, as it is today, I do too, so far .

palewin

You're not the only one to find that it takes a big wrench to get the battery cover off. My solution was a pipe wrench, since they have really wide jaws. But if replacing the hub batteries doesn't do it, go back to Saris (by phone) & have them send you a loaner wheel, harness and computer. It may well be a PT Pro instead of an SL, but you can separately test the computer and the hub. Saris service is excellent, they will work with you to get the problem resolved. Its a lousy way to start with an SL, but once you get the unit working correctly, its very reliable. I've had mine out in soaking rain, and it never faltered; the only time (since the original repairs) that I've had a problem, it was truly worn-out batteries, and the fix was simple (with the aforementioned pipe wrench!). My experience so far is that the computer battery lasts a lot longer than the manual says, and the hub batteries about 30% less than the manual says.