What exactly does 2.2" wheel mean? (Tires and wheels)

[toybaron]

Sorry for what may be a question with an obvious answer. I'm just wading back in RC and determined to finish some restorations started years ago, and also to run some older cars I have.

I'm trying to understand the measurement standards for wheels and tires.

I'm not following the differences between 1.9", 2" 2.2" wheels and the tires that are meant to match. Meaning; what measurement does 2.2" represent on a wheel? I assume something related to diameter, but for example I have a set of old Duratrax aluminum rims where the header card indicates 1.9" (part n# DTXC4023) but the measured diameter of the outer lip on the rim is 2.3".

There's no measurement I have found that reads 1.9..

Thanks in advance.

[RC10resto]

Should be 1.9" where the bead of the tire seats into the wheel

[jwscab]

exactly. the flange or side of the wheel may be significantly wider than the tire bead ID. that is the guiding dimension.