billiebob
Well-known member
Only 3 countries still officially use Imperial measure.
The USA, Liberia and Myanmar.
In every other country, Metric is the official unit of measure.
In America before we used Light Truck sizing of say 33x10.50.. we used F70, G70 etc.
Metric, which was once called Euro became the standard in the 1970s.
Tire height was rarely a selling point until ******** Cepek started selling the Super Swamper floatation tires.
235 is the section width. 85 is the profile, ie 85% of the width. Probably more accurate than 33", which is rarely 33".
Back Space vs Offset... Back space is definitely easier to understand but offset is better from an engineering point.
Offset is measured from the wheel centerline. Technically, all else equal, having the hub on the centerline will support more weight. Negative offset, in the 1960s termed reverse, moves the wheel out, positive offset, used in all front wheel drives, move the tire in. Negative offset, less backspace means the front wheel will need a bigger wheelwell to steer. Hence 4x4s running big tires on rims with less backspace need lots of lift to clear the front wheel wells. Positive offset, ie FWD, allows a smaller wheel well for the front steering tires, allowing a more compact and aerodynamic design.
Using either or both terms just takes a while to understand what/why the two measures measure.
The USA, Liberia and Myanmar.
In every other country, Metric is the official unit of measure.
In America before we used Light Truck sizing of say 33x10.50.. we used F70, G70 etc.
Metric, which was once called Euro became the standard in the 1970s.
Tire height was rarely a selling point until ******** Cepek started selling the Super Swamper floatation tires.
235 is the section width. 85 is the profile, ie 85% of the width. Probably more accurate than 33", which is rarely 33".
Back Space vs Offset... Back space is definitely easier to understand but offset is better from an engineering point.
Offset is measured from the wheel centerline. Technically, all else equal, having the hub on the centerline will support more weight. Negative offset, in the 1960s termed reverse, moves the wheel out, positive offset, used in all front wheel drives, move the tire in. Negative offset, less backspace means the front wheel will need a bigger wheelwell to steer. Hence 4x4s running big tires on rims with less backspace need lots of lift to clear the front wheel wells. Positive offset, ie FWD, allows a smaller wheel well for the front steering tires, allowing a more compact and aerodynamic design.
Using either or both terms just takes a while to understand what/why the two measures measure.
Last edited:
