Q about PT SL cadence.

joule

Just got the above and most things seem to work but the cadence has me stimied. When "C" is displayed on the PT computer and the cadence sensor is installed, am I supposed to see the cadence? Except for a few seconds the first time I spun the cranks it's always zero. Going into test mode #5, I get the 88s and see the top line show what appears to be the cadence. Bottom line (same one in normal mode) is always zero and according to the test mode docs, indicates the cadence from the hub. An obvious left over from previous models and again always zero in test mode.

Normal mode docs talk about holding down select button for 2 seconds which "appears" to disable the top and bottom line and display numbers in the middle display. What those numbers are I have no idea because they do not correspond to crank arm revolutions.

Running version 2.21 if that helps.

Spunout

Check Setup 4: Make sure you are default (pedal then hub) or pedal only and not hub only.

Your normal mode question, isn't this going into Torque mode? I've just tried that in mine, and it changes the T number (time) to something else...time to read the manual...

frenchyge

Agree, check the setup 4 menu, and a slight correction that the default setting is "hub, then pedal."

palewin

Why would you want the default to be hub, then pedal? The hub is going to "calculate" your cadence, I suspect that going downhill you will get some very high cadence stats. Anyway, I have mine set to "pedal only" and it works correctly. Having an actual, measured cadence was one of Saris's improvements on the earlier PTs which could only do the hub calculation.

frenchyge

Personally, I wouldn't, but that is the default mode. Unfortunately, there is no "Pedal, then Hub" mode at all, which would be my preference since I have a cadence magnet on my road bike, but not on my trainer bike.

The hub sorta calculates the cadence, but it does so by determining the time from one peak torque reading to the next, so there are no wacky readings when coasting downhill. Cadence will read zero when you're not pedalling.

bike boy

For the best readings are you saying its best to have pedal only?

frenchyge

Yes, if you have the magnet and cadence sensor hooked up, then you should choose "Pedal only." If you leave the computer in default (Hub, then Pedal) then it will almost always take the cadence from the hub and there'd be no reason to have the cadence sensor hooked up.

joule

According to the manual it says "Default = petal then hub" though I admit the way it is presented would make you think it's the other way around. With so many other errors in the manual however not sure what to believe. I set it on petal only for now.

bike boy

I have the cadence kit but if the hub only option gives good readings i might not bother with the extra cables etc.

What do you think, does it make much difference?

joule

Well on the bike stand it makes a big difference. Hub's virtual calculation makes testing the functionality pretty difficult. But once I put the bike on the trainer and road it seems to give good results. I've recently switched to petal only for now. Figured I'd run it that way for awhile and make sure everything works fine. Later, disconnect the cadence cable and see if I can spy any new issues or questionable data. If not, remove it.

frenchyge

You're right, it does say that. Sorry. I have a PT Pro, but have looked through the SL instruction manual on a couple occasions for different things. That page which lists the cadence options is identical to the PT Pro instruction manual, with the only difference being that "Default = hub then pedal" in the Pro manual. I thought they used the same computer, so I wonder what's up.

I may have to test mine during tomorrow's ride by putting it back to default and pedalling slowly while freewheeling down a hill (no torque on the hub, but pedals moving) to see if it reports the pedal cadence.

frenchyge

IMO, the hub does give pretty good readings in the range of normal ride cadences. I've found that the hub cadence gets a little flaky during high cadence drills, or during high power intervals at cadences higher than ~100 rpm. I've seen it reported somewhere that it won't compute cadences <40rpm, and my cadence data seems to be clipped at 140rpm on the high side, but that's not really a big issue for typical rides.

I've only recently hooked up my cadence sensor because I was doing some sprint testing at different higher cadences. Before that, I thought the hub cadence was sufficient.