GAWR and larger tire size question

[MrShadetree]

I’ve upgraded my tires from 225/60R18 to 255/55R18 and went from a 7 inch rim to an 8 inch rim. Will this change my GAWR or will it remain unchanged? If it does change how can it be recalculated?

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[heady]

GAWRs are fixed, they don't change and are just informational, they aren't used beyond a manufacturer complying with federal motor vehicle safety standards to be allowed to sell a new road legal vehicle, and are only present on manufacturer internal documents and the sticker on the body, which is not required to be present for an owner. GVWRs are legal limits when printed on your vehicle registration, and tire sidewall max load @ pressure ratings are legal limits for DOT weight scales, never ever exceed those ratings. Some states you can specify the GVWR on some registration types, and some you can't, they just use the manufacturer database value.

Practically speaking, you can modify axles and tires and amend the registration GVWR to suit the new characteristics in states where that is an option. The other practical consideration is those tires and wheels simply weigh more, so if you go off factory specs and registration, you've reduced your payload based on GVWR if you drive over a scale, even though it's unsprung weight, the scale doesn't know any better.

 

[Random]

Here I am thinking of

 

[Escapologist]

I came across something about a decade ago, I was researching an econobox, I cannot recall what model it was. Anyway, payload was something super low like 700lb or something, enough to be a "holy shit that's low." and ppl were also complaining that their first tire change cost them like 3-5mpg. So it transpired that for CAFE or impressive EPA numbers, the manufacturer had put lightweight LRR eco tires on the car for North American market that had really low load rating, so they had also stated GAWR and GVWR lower. Taking it a deep dive, it transpired that the Euro and Aus market models had 1100 payload and higher GAWR and GVWR, and were supplied with "normal" tires. Further investigation showed no differences in part numbers for any brake, suspension, axle components.... pretty much the GAWR was determined by the tires in that case.

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