"Oz Cuda" had a question about 215/70 14 BFG and Firestone RWL tire specs. Here is the answer I just PM'd him and I'm posting here because maybe it will be helpful...
"We updated the specs on the BFG, removing the tread width number. BFG doesn't publish tread widths normally, so this was a mistake. We feel the FS tread width is accurate at 7.0".
As I mention the spec itself is a little iffy. That is why many maufacturers no longer publish it. There is no industry standard for how to measure tread width. Just laying a ruler across the tread area doesn't work because many tires have a slight crown to the tread profile. The radius of the shoulder varies from one tire to the next, making it hard to define where the tread stops and shoulder begins.
The ideal way would be to establish a load parameter for each size and measure the widest spot of the contact patch. But this is not something anyone can easily do out in the field, or for us to accomplish."
Thanks for your question.
