VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 Measuring size of rim

I know I have a 21 inch rim, but how do I measure another rim where I do not know the size? Even the 21" does not measure like I am use to measuring rims.

There are generally two relatively accurate ways to measure rims. If it is a split rim that fits over a wheel just measure the inside and add 1/2"-3/4". That is the thickness of the metal on the rim. The second is measure outer rim to rim and subtract twice the distance from outer part of rim to bottom of the seating surface.

You don't say the method of measuring a rim that you are used to. Chips method will work great. Another way of describing his method is that if you measure between the SHOULDERS of the rim in both directions ie width and diameter taking into consideration the thicKness of the rims metal that will give you the more modern size. If you are used to the older type of dimensions a 3" X 21" 1928 rim would be sized 33 X 6. You double the second number and subtract that from the first. A 1927 and earlier 2-1/2" X 21" rim would be 31 X 5, a 1929 3" X 20" rim would be 32 X 6. I still find it rather confusing and awkward to do the math, but it is a must if you are going to be working with brass era cars.