why are not all 295s the same?

[PolishDude]

today i noticed a huge difference with how my stock z06 goodyear 295 looks compared to my friends toyo t1r 295s...the specs are exactly the same but when you look at the two tires from the back mine looks like it has a much bigger footprint then his, and we are both on z06 wheels so wheels have no play in it, his look like 265s compared to my tires, how is this possible?

[Luke@tirerack]

not all tires are constructed the same even if they are the same size the foot print can vary dramatically

[anmracing]

Also keep in mind that the measurements are taken at the widest part of the tire on an "Ideal" rim. Meaning if a mfg says a tire is a 295, it is 295mm at its widest point on a rim that they think it will fit best on (10-12 inch for an example). So any mfg can have a tire measured on their "Ideal" rim but the tread is not measured that way so if you look at a data sheet for tire brands they will have an "Ideal" rim measurement and a tread measurement. Soooo, say mfg "A" states that they have a tire that is a 295, aproximately 12 inches (give or take..) then they will make the tread (Again, as an example) 11.5 inches. Then mfg "B" may have the same 295 width but they want a more squared off look so they would make their tread 12 inches. Basically the tread is not measured the same as the actual width of the tire.
Andrew

[Luke@tirerack]

section width = widest part of tire
tread width = well, tread width

[Wah]

If the specs are still up, try the section widths of 305/35/18 Hoosier A/R3S03/4 with 315/30/18 Pirelli PZero Corsa. You'll be surprised

[skeet]

My BFG Comp T/A's in 275x40x17 on 9.5 rim measure 10.4 inches wide at the tread and my Bridgestone RE750's same size and same wheel measure 9.5 wide. The T/A's actually look like 315's.