# Calculate rolling resistance for foam filled tire

Let us consider a bike wheel. Does anybody know a way to calculate how much does rolling resistance changes if the inner tire volume is filled with foam instead of air? Let's assume a foam hardness which equals a 2 bar inflation.

• This will depend on the surface in a different way to an air-filled tyre; you also can't really define a foam as being equivalent to a 2 bar inflation in practice because a normal tyre uses the whole volume to adjust for load and absorb impacts, i.e. a foam that matches that pressure in some ways won't match in others. May 16, 2018 at 16:39
• Rolling resistance depends on much more than just the inflation pressure so I don't really see how your assumption helps. May 16, 2018 at 16:39
• I don't quite understand your question. Any of the methods currently used to measure rolling resistance with a pneumatic tire would work with a non-pneumatic tire. Perhaps a better question could be "how can one calculate rolling resistance for a tire?" May 16, 2018 at 16:41
• @albus_c Calculating it probably requires approximation and finite-element analysis. People do whole PhDs in that kind of thing. Building one and measuring the rolling resistance would probably be much easier. May 16, 2018 at 17:31
• I can summarize some of the ways that rolling resistance is measured, but I'm pretty busy right now so I may not be able to provide a full answer for a couple of days. I'll upvote good answers. Basically, the methods involve controlling input power (whether zero or non-zero) and then calculating the drag that dissipates that power. Meanwhile, this bicycles.SE question talks about estimating drag. May 16, 2018 at 19:34