Powertap: What the...
 

OK, so I bought a PowerTap Pro+ a couple months ago, and it has been great, really educational and humbling. So, recently the hub started dropping signal randomly for 10-15 minutes at a time. Drat. I called Saris and they asked me to send the wheel in for service. No big deal, I guess. But, when I went to pull the cassette, the entire freehub body came with it! I pressed it back on, along with the little retaining cap that usually screws onto the axle. Is the whole assembly really just a pressure fit? Why?? thanks for any info.

Nothing weird there. For example, DTs hubs is just like that, you can remove the freewheel with your hands.

Like this

Wow, that's new to me. thanks.

I was surprised, too, when I prepared to send my PT back to Saris for service a few months ago.

It is unnerving the first time but it's normal. If it's the Shimano freehub used with Shimano/non-Red Sram cassettes it will start to have grooves where the cogs cut into the edges. That part sucks. GL

It is definitely the grooves caused by the cassette rings. Twist each ring counter-clockwise to get them out of the groove before trying to pull off each ring.

Did you replace the batteries in the hub and computer before calling Saris? When the hub batteries are getting low, the round hub connection icon on the computer starts to blink. Even though the hub is fairly new, it may be a good idea to change the batteries and see if that makes a difference.

There is a retaining cap for the freehub body that's threaded onto the axle. It definitely does not come off with just a tug. You definitely do have to unscrew something to get the freehub body to come off. You evidentially unscrewed something. The manual for the powertap has a good cut-away illustration of how the hub is put together.

Yeah, the splines are pretty heavily notched already; nothing new there. Brian, I looked at the documentation, and it appears there are two designs, one threaded (12mm axle) , the other a pressure fit (15mm axle). They say you can just remove the freehub body with a sharp tug. I'm still mystified why you would do it this way, but whatever.

Re the powertap problem: I did replace the batteries, to no effect. The hub just seems to stop transmitting randomly during a ride (or rather, transmits zero power, since the computer reads 0, not dashes). I can very often get it to start up again by hopping the wheel. So, I am pretty sure it is a problem with the hub internals.

I'd bet a dollar that the internal spacer tube the the magnet on it is rotating with the wheel causing the PT to think it's stopped moving. The trick to the PT bearings is seating them tightly enough to that the tube is held in place by the inner bearing races and not spinning with the hub itself. The magnet on that tube it what trips the electronics to come to life and is the index for the wheel revolution calcs. Either that tube is rotating freely or the taped on magnet is loose. At least those are the simplest options.

That sounds like a definite possibility. Is that something I could deal with on my own, without voiding the warranty?

I've gotten more than one email from customers who go to pull the plastic end cap for shipping off of their new powertap and all of a sudden think they broke it.

I actually like the feature as it has allowed me to do repairs on the side of the road during a ride once when

I've removed the bearings in mine, but I have a bearing puller and I had a stock of replacement bearings. Once you pull a cartridge bearing you should not reuse it. So, if your comfortable with r&r bearings then yes you could check it out. The non drive side bearing is what you want to pull if you decide to potentially kill your PT by doing so. There's a tube in there with a magnet taped to the drive side. The tube should be held in place by the inner races of the drive / non drive hub bearings. Even giving the NDS bearing a love tap on the outer races with a proper size socket and hammer may be enough to secure the tube if that's the problem. I doubt the magnet would un tape itself.

Thanks, that's good information. But since it's still under warranty, I think I will play it safe and send it in.

Probably your best bet.