Coast-Downs

[JulianBoulter]

Hi guys,

I tried my first set of Coast-Downs the other day, I think the workings of it all make sense but one thing I don't really get in the Coast-Downs dialog box is the relationship between the Riding Tilt % , the selected calibration rides, and the Coast-Downs Results.

That is, I know the calibration ride calculates wind scaling and riding tilt and sure enough, if I choose various calibration rides, I see the wind scaling factors associated with those profiles, in other words they change, and yet, no matter what calibration ride I choose, the Riding Tilt % is always coming out as -0.1% which I know is not set in those profiles as they are set to -0.7%.

I can see that playing with the Coast-Downs Results data modifies crr, cda, Aero, and Friction values, that I would expect, and also changing from crr fixed to crr adjusted modifies these values too and the Riding Tilt % and wind scaling stay constant, again, that makes sense as the calibration ride calculates the Riding Tilt % and wind scaling but I would have expected the Riding Tilt % to be what the calibration ride already calculated (-0.7%) and it is not.

So now am wondering if the Coast-Downs data is modifying the Riding Tilt % ???

Screen shots attached

Thanks

[Velocomp]

The default value of riding tilt is -0.7.

After your cal ride the value of riding tilt is dynamically adjusted during riding. It almost is never -0.7.

For coast-downs, we need to measure the actual value of riding tilt during the coast down, in order to calculate the value of fric.

You are in the land of ibike esoterica...

[JulianBoulter]

Thanks John

So what you are saying then is that the Coast-Down routine actually does measure and potentially modify riding tilt.

So to clarify, if I just perform calibration rides alone (no Coast-Downs) would I always expect to see -0.7 as the riding tilt % in the profile or is it just coincidence that both of my calibration rides have resulted in riding tilt of -0.7% in the profile? I thought one of the points of the calibration ride was to set riding tilt so I would expect to see that to be different from what you say is the default of -0.7

Also why would there be such a difference between my calibration ride riding tilts of -0.7 and the coast down riding tilts of -0.1? it seems to make quite a difference to the watts.

[lorduintah]

Riding tilt - are you in the same position during a normal ride and when you are doing the coast down? Yes, tire pressure can change the tilt.

If you are changing position, then the sensors may very well pick up the differences. The weight changes on the front wheel from sitting up and hunched over or in the drops can have an impact.

Regards,

Tom

[JulianBoulter]

Yes I always try to keep the same position which is hoods elbows bent, I guess tire pressure could affect it? the unit has always been very firmly locked to the stem.

Seems like I may have misunderstood riding tilt though, I always felt it was more about establishing the offset of the tilt of the unit on a given bike in order to calculate hill slope but it seems it is more about how it affects rider aerodynamics? I'm actually wondering how much the tilt would likley change during a ride to warrant calculating this dynamically? if it's calculated dynamically this means the aero value is always changing throughout the course of the ride then I guess?

So back to my original question, if I view the riding tilt % in the profile itself, should I expect to see something different from -0.7% ? i.e. calculated for my riding position? it's just that both my calibration rides resulted in a riding tilt of -0.7% and John was saying that should rarely be the case.

Come to think of it, if the riding tilt is being calculated dynamically anyway, what is the purpose of displaying a fixed value for riding tilt in the profile?