How do you measure a wheel's width?

[TomGolden]

Hi all,



I had the factory spare Michelin tire re-mounted on a spare alloy wheel I bought from another TDR member. So now I have the steel spare wheel sitting in the garage, and I tried to measure it to see what width it is. Do you measure the width from the very outside of the bead, or from the inner side of bead to bead?



Either way, it seems an odd size. I get 8 1/2" if I measure outside to outside, and 7 1/2" if I measure inside to inside. Just wondering, in case I decide to buy some more steel wheels from a wrecking yard so I can have maybe a second set of tires for my rare off roading activities.



Thanks,

Tom

 

[Beast2B]

Hey Tom, how ya been?

The measurement for the width of the wheel is kinda in between those two places. At the very outer edge of the diameter of the rim is a bit of a flare. Just inside the flare is the vertical (referenced to the ground in mounted/driving position) edge of the rim where the bead sits. The measurement is taken from the outside of that vertical surface with the calipers we used at a tire shop... HTH

 

[nickleinonen]

iirc from the dodge ram product literatures, the alloys are 8" wide and the steel wheels are 7. 5" wide. so if you were measuring the steel wheel, yeah then you got the numbers right. 7. 5" is the width of the wheel, but the overall width on almost every wheel is 1" over the actual size. the 1" extra is for the weight lip / safety ridge that most wheels have inside and out. [some don't have them on the outside, so they tend to be 1/8" - 1/4" under the 1" rule [first read of the 1" thing in an issue of sport truck magazine]

 

[Un-Hemi]

There is a normal way to specify and measure wheel widths... . then there are the tire shops.



I've seen tire shops use those calipers to measure wheel widths, and in more than a couple of instances the numbers weren't what the wheels were supposed to be. (calling a 6. 5" wheel a 7", etc. ) It's close enough for balancing, I guess; it's just a convenient way to measure a wheel with a mounted tire.



Wheels are spec'd by measuring from inside to inside. On CTDs there are 8" alloys and 7. 5" steels... . Be aware that older steel wheels are 6. 5", like on my '99.



Tom

 

[Beast2B]

I realized that I never have measured a wheel any other way after responding, but the calipers we used ALWAYS showed the proper width when compared to the manufacturers spec (within 1/8" or less). Maybe the calipers were calibrated to take the extra width into account... Never measured anything besides wheels with the calipers either!

Not very adventurous with the calipers, EH?!