I've submitted a Golden Cheetah feature request, after a difficulty I found recently doing some off-road CRR testing. I'm not sure how many people use the Aerolab chart for off-road testing. I'm sure the vast majority of users are doing CdA analyses for TT/Tri bikes.
The problem I encountered is that the CRR slider only goes to a maximum of 0.01, whereas my analysis needed to set a CRR greater than 0.01 (see chart below). Even on rough chipseal, the CRR for knobbly cyclocross tyres was around 0.01. This limitation in GC meant that I had to do the VE calculation outside of GC, in Excel. That gave the same result, but takes quite a bit more time.
If this is a very niche application, it's obviously not worth modifying GC. Perhaps a good option would be to create an alternative "off-road" version of the Aerolab Chung Analysis Chart, allowing CRRs up to at least 0.03. That would allow the fine scale of the current chart to be retained for the majority of road applications. By the way, "0.03" isn't a mistake, it's not missing a zero! My testing suggested it really could be that high. It's incredible to think rolling resistance losses off-road are an order of magnitude more than on the road, with about 150W (~half the losses) going into overcoming rolling resistance on a flat grass course.
I wanted to do this test to see if there is an optimum tyre pressure off road, in terms of CRR, for the purposes of my local summer cyclocross race series (which probably won't happen this year!). The conventional wisdom amongst CX racers is to set pressures as low as possible, but I couldn't find data to support this. It was also unclear to me how much this low pressure recommendation is coming from traction considerations. I found the results of this test quite interesting and surprising. There seems to be no minima for best usable pressure. The traditional practice of setting pressure as low as possible seems like a good one, even when only considering CRR. The differences seen in the session 3 repeats I think could be due to the grass becoming somewhat flattened from the multiple laps during the session 2 runs.
All this suggests suspension losses dominate over tyre deformation hysteresis losses for this kind of off-road situation.
The problem I encountered is that the CRR slider only goes to a maximum of 0.01, whereas my analysis needed to set a CRR greater than 0.01 (see chart below). Even on rough chipseal, the CRR for knobbly cyclocross tyres was around 0.01. This limitation in GC meant that I had to do the VE calculation outside of GC, in Excel. That gave the same result, but takes quite a bit more time.
If this is a very niche application, it's obviously not worth modifying GC. Perhaps a good option would be to create an alternative "off-road" version of the Aerolab Chung Analysis Chart, allowing CRRs up to at least 0.03. That would allow the fine scale of the current chart to be retained for the majority of road applications. By the way, "0.03" isn't a mistake, it's not missing a zero! My testing suggested it really could be that high. It's incredible to think rolling resistance losses off-road are an order of magnitude more than on the road, with about 150W (~half the losses) going into overcoming rolling resistance on a flat grass course.
I wanted to do this test to see if there is an optimum tyre pressure off road, in terms of CRR, for the purposes of my local summer cyclocross race series (which probably won't happen this year!). The conventional wisdom amongst CX racers is to set pressures as low as possible, but I couldn't find data to support this. It was also unclear to me how much this low pressure recommendation is coming from traction considerations. I found the results of this test quite interesting and surprising. There seems to be no minima for best usable pressure. The traditional practice of setting pressure as low as possible seems like a good one, even when only considering CRR. The differences seen in the session 3 repeats I think could be due to the grass becoming somewhat flattened from the multiple laps during the session 2 runs.
All this suggests suspension losses dominate over tyre deformation hysteresis losses for this kind of off-road situation.