calibration of wireless SRM in combination with 705

[BergHugi]

hallo,

I got a wireless SRM powermeter together with a Garmin 705 two weeks ago. Basically the combo works very fine however during several cross checks with a PT 2.4 mounted on the same bike I got consistently between 5 to 10W lower power values from the SRM. Repeated tests on on a steep hill showed that the PT 2.4 gives correct power values. I sat the zero offsets of both, the SRM / 705 combo and the PT 2.4 before every ride and every hill test. I suppose the slope, which the SRM transmit to the 705, is not accurate.

Do anybody know, whether there is a, maybe hidden, function in the 705 to manually enter the slope or a function to see the transmitted slope at least? Or do I need a PCVI form SRM to set the slope by my own via a callibration with known wights?

best wishes

 

[Biker Joe]

I currently use my Garmin 705 with the SRM wireless. I zero the unit before each ride however, I do not believe that is is necessary to enter the slope with the 705.

I also own a ZIPP PT 2.4 wheel and I have run them both simultaneously. My SRM/705 combo reads slightly differing power then the PT 2.4 wheel but is relative and negligible.

Personally, I prefer the SRM as I can change wheels anytime I like.
Wish I could be of more help.

 

[BergHugi]

hallo,

meanwhile I checked the slope with a known weight at the cranks. Indeed the factory preset slope was 1 Hz/Nm higher than the value I measured. This makes about 15 W lower power at 250W and a cadence of 100. Using a PCVI with the slope entered manually it shows the same power than my PT 2.4 wheel. However I would like to use a Garmin 705 with the SRM, thus I am waiting for a firmware update to be able to enter the slope manually. Alternatively I will send the cranks to SRM for a recalibration.

 

[Biker Joe]

I was researching this last night and found a discussion where someone stated that the SRM slope is sent to the Garmin 705 wirelessly so you don't have to measure it.


I don't have any idea if this is fact or fiction because the documentation I received with the SRM is less than stellar. SRM really needs to provide a complete manual for the wireless SRM.

Thanks