I run on my road bike a 4iii left side power meter and because of a significant left/right leg discrepancy I use a scale factor of 1.10 (meaning my left leg is 10% weaker than my left). I just bought a Sram Force left side power meter for my gravel bike and I’m trying to figure out how to adjust the Slope Adjustment from the AXS app to match my 4iii power meter. I doubt it’s as simple as simply setting the slope adjustment at 10% but maybe. Is there any calculation I could do to get close to 4iii scale factor setting?
If you know you have such an imbalance why have you purchased two left side meters? Either way it seems like your current scaling over-estimates your total power.
Being on a budget is why I went with left side. I used this information from 4iii to set my scale factor:
Example Calculation
Say you have a left/right power imbalance of 48/52 (48% L/52% R)
Left power = 48%
Right Power = 52%
Percentage error = 52 - 48 = 4%
The calculation will be: 1/(1+0.04) = 0.962
Then since your left leg is lower and the power is measured from the left leg, you need 1/0.962 = 1.042 to scale the power up to match what is being missed from your right leg.
One thing to be careful with as far as left/right imbalances, is that the imbalance isn’t always the same along the power curve or in different positions.
I had a nasty shattered femoral neck that required hip surgery and still have metal hardware that sticks out into my left glutes.
As a result, I have a huge left/right imbalance as well ( like 46/54 on easy rides )
I actually thought I had a broken power meter for a while since the difference using left only was SOO huge.
Once I tried a dual sided that shows left/right balance it showed pretty clearly what my issue was though lol.
I’ve found the harder the ride is, the lower the difference gets ( for me ) but also, if I get out of the saddle, I go basically to 50/50 cause I’m so much more quad dominant in that position, and that’s not affected by the surgery.
Were I to use a scaling factor on my left only, it would inflate my standing power by about 10%, and I don’t need that happening to me lolol
Because of how inconsistent the left/right imbalance is, I found I was better off saving my pennies for a 2 sided power meter, and won’t even consider single sided anymore.
I’m most likely in a similar situation as I’m pretty sure that at higher threshold, especially when climbing, I’ll tend to see higher power output which probably means I engage my weaker left leg more in those circumstances. I would say it probably balances out during a long ride.