Re: THe NAC Lots-O-Post Thread
Mine isn't the most built in the world....running into money and time issues with wife and house, but still compared to a lot of people who've got not clue, it's worlds ahead. And it needs lots more for me to be happy!! haha, never will be done!
The sidewall on the Q78s say "Q78." It's an old-school tire size scheme that the military used to use, alpha numeric....I don't think any other tire manufacturers still make sizes using that tire size scheme?? Here's the best explanation I've found:
Alpha-numeric System:
* This load-based system was introduced worldwide in 1968. The designation takes into account the load carrying capability and aspect ratio in the alpha character with aspect ratio and wheel diameter also included, for example: Q78-16
o Q designates the load and size relationship (with some typical section widths listed below):
+ Letters for passenger cars range from A - N:
# A =
# B =
# C =
# D =
# E =
# F =
# G =
# H =
# I =
# J =
# K =
# L78/15 = 30x 9.5
# N78/15 = 31x 9.5
+ Above N indicates truck and severe use duty:
# O =
# P78/15 = 33x10.0
# Q78/15 = 36x11.5
# Q78/16 = 36x10.5
# R78/15 = 37x12.5
# R85/16 = 37x12.0
# S =
+ If this were a radial, an R would precede the Q
o 78 indicates the series, better described as the size relationship between the sidewall height (section height) and the sidewall-to-sidewall width (section width)
+ A 78-series tire has a sidewall height whose measurement is 78% of that of the section width
o 16 indicates wheel diameter
o There is no real "formula" to calculate the missing tire dimensions independently
+ One might be tempted to use a formula similar to the P-metric size designation:
# OD = (2 * (SecWidth) * Aspect) + ID
+ This works somewhat for a given series, but tends to fall apart between series, since the letter designation ties in a load and size rating.