SRM PCV Problems with Cadence under 80

mc83 said:

Hello, i have a SRM wired MTB Professional with PCV.
The Problem is:
[LEFT]If the cadence is below 80rpm, then gives the Powerkontrol no more value for the power and Cadence. Only when I step back quickly (over 80rpm), the values come back.

I hope you understand me.
Thanks[/LEFT]

1. Historically, the SRM hasn't calculated power when cadence is less than 40 rpm.

2. At least some recent SRMs have been fitted with not one, but two, reed switches in the crank, so as to be able to count half-revolutions for those interested in power over very short durations (e.g., track cyclists).

3. Putting 1 and 2 together, I think the explanation might be that your PCV thinks that the cadence is dropping below 40 rpm when it drops below 80 rpm. If so, you should be able to correct this via a check-box in the PowerControl configuration pop-up window that is accessible via the SRM software.

[LEFT]Thank you, I will look at the SRM software because if i look at what may change. I have the SRM German support demand, as do I, but unfortunately no answer.[/LEFT]

acoggan said:

1. Historically, the SRM hasn't calculated power when cadence is less than 40 rpm.

2. At least some recent SRMs have been fitted with not one, but two, reed switches in the crank, so as to be able to count half-revolutions for those interested in power over very short durations (e.g., track cyclists).

Interesting. My SRM Track is recording cadence down to 29 rpm but I think 30 is the effective limit on my unit. Below that and zippo.

Hello, i have news:
When i drive with two chainrings, than it works also under 40rpm!
The problem is with three chainrings.
But the SRM Crank must be work with three chainrings --> it is a MTB Version

Alex Simmons said:

Interesting. My SRM Track is recording cadence down to 29 rpm but I think 30 is the effective limit on my unit. Below that and zippo.

After my original post I did some field testing that happened to include pedaling at a very low cadence, and I now agree: the limit is definitely less than 40. Not sure precisely where I came up with that number...

mc83 said:

Hello, i have news:
When i drive with two chainrings, than it works also under 40rpm!
The problem is with three chainrings.
But the SRM Crank must be work with three chainrings --> it is a MTB Version

Do you mean that it works below 40 (80?) rpm when you take off the smallest chainring? Did you happen to move the sensor when you did so? (Getting the sensor close enough to the powermeter's plastic cover can be a problem with the MTB version...see the SRM manuals for more info.)

[FONT=Courier New][FONT=Courier New]I think that the sensor is not close enough to the plastic cover. But I can not get closer to it, because the sensor touches almost at the chainring screws from the small chainring (when i drive with 3 chainrings).[/FONT][/FONT]