Quote:
Originally Posted by IamIan
Because rolling resistance is the force needed to deform the tire ... the faster you go the more tire rotations per second ... the more tire rotations per second the more deformations per second ... even if each deformation requires the same force.
If takes 100 joules of energy to lift 1 rock a distance of 2 meters ... it will take 10x as much to lift 10x as many equal rocks an equal distance.
As far as vehicle energy per mile goes it cancels out ... because rolling resistance for a given Vehicle weight and tire Crr increases linearly at the same rate the speed does ... which means you cover a given distance as much faster as the rolling resistance increases.
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Although technically the Crr of the tire does not remain fixed ... and the vehicle weight also changes ... But if you want to get into that level of technicality then aerodynamics isn't as simple as CdA anymore either... and that is probably more than most people will ever care about.
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Oh yes, that is indeed true, rolling resistance force is per meter from my memory in SI standard, so one would think it as a distance for given time, which gives you of course resistance force for given time, if that makes any sense for anyone else than me.
There is indeed lot happening with tires at speed, contact patch shape along changes a bit and so does pressure over contact patch, some part of rolling resistance comes from thread of contact patch and that also then changes quite a bit, sidewall deformation changes also as with speed tires 'grow' a bit, so there is bit helping force with deformation I believe.
From my memory sidewall deflection was larger cause of rolling resistance from those two.
Well, you could even start to think about heating of tire too and those effects if wanted to go further, but I think there is speed limit in human brain and certainly processing all that while driving will be rather taxing.
While attempting to create car to vehicle simulator of decent quality there is quite lot of physics stuff involved and some are bit related to this fuel saving hobby, I wonder if I could use simulator to do some testing of forces etc. Might try that at some point.