Originally Posted by
cubewheels
Yes, the difference in inflated width is very minimal.
That’s called a distinction without a difference.
Originally Posted by
cubewheels
But according to experience, you should increase pressure by as much as 20% with narrower rim …
20% is very specific, and I’m really struggling to wrap my head around the advice that a wider rim, which means a possibly larger inflated size, means 20% more pressure. But, again, as I said above, based both on actual experience and obsessive reading on the subject, a tire won’t see a dramatic increase in its inflated size (as measured on the outer sidewall dimension using a calipers), maybe 1-2 mm, on a larger rim (unless I guess we are talking about going from a 19 to a 35, but then you wouldn't be mounting the same tires either. Larger volume takes more air to inflate. But we don’t measure the volume of air we put in the tire, only the pressure, and last I checked larger volume tires can be run at lower pressures for both better feel and handling. If there is any required increase in pressure, it’s likely because you are using cheap tires with a low TPI and stiff sidewall, maybe a few psi at most, more likely 1-2 which is a distinction without a difference.