"The 33"-Road Bike Racing - Powertap Help Needed

On my ride today, I was having trouple keeping my powertap's torque zeroed out. It was good for the first hour, but then in the second hour it was giving me some crazy high readings. Like what I felt should have been 235 (SST wattage) was showing up as 290. So I stopped and zeroed the torque and started going again. It would be normal for a bit and then bam, there it is again... crazy wattage. I go over to torque mode and it's not zero again. I zero again. After a while I think that it started to be normal and was reading normal wattage. Still, I was confused as to why it kept doing this. Anybody know what's up? Any suggestions?

was it really cold outside?

Probably about 55 degrees and foggy. Not cold. I have read about the cold thing with the strain gauges and everything. I usually set my bike outside twenty or so minutes before I roll out so the gauges can get acclimated.

But like I said, I was having more trouble with the torque not staying zeroed. Can the weather have anything to do with this?

My training partner is just now sending his wheel back to Saris for bouts of high readings. He's getting the $200 refurb done. They ran through some diagnostics with him and couldn't fix it. I swapped computers with him and he still saw the problem. I put his wheel on my bike, and I saw the problem (in case it was harness related).

Did you turn off auto-zero by mistake?

I had a simular issue but in the other direction.

I called there support and they took me through a few things and I ended up sending the wheel back and they recalabrated it for me. No cost...there support line is very helpful and no crazy hold times.

I would give them a call...

So this auto zero function. Where would I find it? Or is this in the manual?

So this auto zero function. Where would I find it? Or is this in the manual?

It's in the manual, on one of the setup pages. It should be on by default but its easy to turn stuff on/off by accident.

I checked the auto zero, it is still set to yes. Since it worked perfect for the last 30 minutes or so, I'm going to ride it tomorrow and see how it does before I call Saris or something like that.

I have an old Powertap. The old standard model, maybe from 2000. I was getting some super-high readings that I know I wasn't putting out (like 1500 watts while pedaling easy, mostly right after starting) so I tried to zero the torque. I held select while in watts mode until "watts" disappeared. I held it again for a few seconds, like the manual says.

And now all I get are zeros for wattage. Transmission is fine - I can get speed like I always could. Batteries are new. I don't know why that went wrong, but can I undo what I did? Just going back to the inaccurate jumps would be better than nothing.

You can probably reset it completely by reinstalling the firmware. It sounds like a conversation with Saris is in order. Phone them, not email though. They don't have parts for your PT any more, but they have a very generous upgrade program for owners of previous models. God love 'em.

Well, the problem is on the computer display too. And I'm too poor to afford a new one anytime soon. But I think I'll call them.