Originally Posted by
PeteHski
There are not 20-30W differences between premium branded tyres of equivalent type. I haven't even seen that sort of difference between training and race tyres of the same brand. I use BBS for estimating times and that sort of difference would be a good 20 mins on a 5 hour ride. It would stand out like a sore thumb if it were actually true. If I put my actual average power over a course back into BBS, it's usually accurate to within a minute or two, so that sort of difference would be pretty dramatic. When I change from training to race tyres I alter the CRR by the same percentage as the drum tests for those tyres and that gives me accurate results. So they must be pretty accurate in relative terms.
Put a 28 mm tire onto a 23 mm wide rim instead of a 23 mm tire. You will see over 20 watts at 30 mph just for the aero effects. If the 28 mm tire is a GP4000 with butyl vs a 23 mm Supersonic with latex, I assure you.....it is way over 20 watts at 30 mph.
BBS does not measure anything. They estimate based upon your input. Do you ride at 30 mph?
You either did not read what I wrote or you do not understand. Crr is not a static parameter.