Hill simulations and imaginary gearing

(John Graham-Brown) #1

I sent this point to zwift’s info e-mail address, but this seems a more appropriate place to put it…

I am using the basic package with a garmin edge speed/cadence sensor, riding a felt-f85 with compact crankset on an elite mag speed trainer. It is clear from the gradient readouts that there are hill simulations, and for this I was consciously trying to slow my cadence. Even so however, looking at the gradients and the cadence I was maintaining I think I may have been riding in what would be in reality an imaginary gear. I would therefore suggest that as a feature it might be useful on initial set up to input gear configurations (crankset and rear cassette) and then use the speed and cadence data to inform the rider whether or not the gear they are riding in is actually realistic (rather than say gently spinning at 100+rpm up a 10%+ gradient without breaking a sweat). I would imagine that by knowing the highest and lowest gear ratios on a bike and referring these to the real time gradient speed/cadence and gradient data it would not be to difficult to calculate a simple yes/no function, so that if the “theoretical gear” was too low a message could be displayed telling the user to change to a higher sprocket to better simulate climbing?


I obviously haven’t done any of the maths, but logically I don’t see any reason why this couldn’t be possible (perhaps I am missing something obvious). Anyway I would be interested to know your thoughts on this, and besides that this is truly a terrific programme you have developed, so well done.

(Rob Toeppner) #2

I think they’d also have to factor in rider weight, and to a lesser extent rider size (for Cd calculations).

In fairness to Zwift though, it really shines when a smart trainer such as a KICKR is used.    The grade (and other factors) combine to deliver appropriate resistance, and you are free to counter that in whichever gear and cadence you desire.

(John Graham-Brown) #3

Good point about the weight, although do they already take that into account for hills, or is it just used for power calculations at the moment?

Yes, I think what I’m suggesting is that zwift has a feature to encourage the user to do what the kickr would do automatically, ie. higher resistance with lower cadence on steeper terrain, as at present on a bog standard turbo it is very easy to spin up steeper sections, when in reality that would be impossible. It obviously wouldn’t be quite the same experience as using a kickr, but a fair amount cheaper.

(Rob Fleischmann ZHCC) #4

John - I think you might be missing something here.  When I started on Zwift, my first question was, do I want to spin on the hills (using low gear on my “dumb” trainer) or do I want to generate power by, in fact pedaling in a higher gear.  The answer is quickly evident that, to ride at a similar pace to what you would normally climb at a particular grade, you need to generate power in a higher gear ratio.  Thus, if you were to ride a 10% grade and pedal in a gear ratio that would allow you to “gently” spin at 100 rpm, you won’t generate any speed (probably about 2 mph).  So, in other words, while you might climb in the real world in your 34:25 on a 10% grade at 80 rpm, on Zwift in order to generate the power necessary to match you real world speed, you will likely need to pedal in your 50:21 at 80 rpm.  At least, that’s my experience.  And yes, Zwift uses your profile weight to calculate your speed based on the power curve it is generating.  That’s why being honest about weight is so important.

(Eric C. (Zwift HQ)) #5

Moved to ‘Feature Requests.’

(Craig Orrell) #6

I wonder if Zwift would show a power profile to aim for based on your stats so that when you hit the grade you need to up your power output. I’m hoping to get to the island this week once my Ant+  dongle arrives. Looks like fun