actually you are incorrect on this one! I worked in a running shop for 2.5 years, probably saw about 10,000 pairs of old shoes. Most pronators (ie. most of the population), will wear out the outside rear corner of their shoe first. This is where the initial impact takes places; their foot will then roll towards the middle (and inside) as the foot begins to flatten out. Most people are heel strikers (which is not as bad as everyone on slowtwitch will tell you), and if your foot pronates the outside of your foot would have to hit first? Where else would wear out? Shoe companies know this, that is why on most shoes, there will be breaks (lines in the outsole) on the ouside of the heel, and many will a more beveled “catch” area on that rear corner". These features allow for the first and hardest impact. (they may also reduce some of the wear, although most people will still wear this area out first).
I have seen some rare excepts, but we are talking 1 in 1,000 people here (and I think I can count on one hand the amount of supinators I saw while working).
The case could be made that a neutral person might wear out the outside heel first, if they are in too stable a shoe, and are simply not able to pronate into a neutral position.
I am a perfect example of this, I always wear out the rear corner of my shoe, and I definitely pronate (wear the 21s and a pretty decent orthotic).
The important thing is to have someone who knows take a look and make the call. TREAD PATTERN IS NOT THE SOLUTION FOR DIAGNOSING SHOE TYPE! I am only telling you what I have seen with majorities and generalities.
I’ll absolutely accept that the majority of running shoes wear out “diagonally” from outer heal to big toe, but that wear pattern actually describes neutral to mild pronators, which, you’re correct, do make up the vast majority of the population. That outer rear corner of the heal will wear a lot more quickly the more a person walks in a shoe, too. That’s how the foot is supposed to fall in the averge walking gait of an average person. You’re “supposed to” pronate as a means of natural shock absorption. A severe pronator will wear the inside edge of the shoe from heal to toe and are about as rare as a true supinator. Severe pronators need focused PT and probably an orthotic in the mean time. If the shoe is wearing along the outer edge from strike zone to toe, the runner’s a supinator.
And, I also agree, heal striking is more common than not in runners and, no, it’s not a bad thing. It is pretty inefficient all things considered, particularly depending on how far in front of your center of gravity that strike occurs (same applies to mid-/forefoot striking, actually). As much or more than being technique driven, most heal-/mid-/forefoot striking is a function of the flexibility and strength of the foot, ankle, and lower leg and of the weight of the runner. Pace is very correlated to striking, too, but it’s chicken and egg scenario for which causes the other. You see many more of the mid-/forefoot strikers in the neutral to supinator categories because they tend to be stronger and/or have stiffer arches/feet and have less access to pronation as shock absorption. Ankle movement and foot/leg joint cartilage are used instead.
People should absolutely buy the shoes that fit their running, but, if it were entirely based on gait, I’d hazard about as many people should be in one pound structure shoes as end up in Newtons. That middle chunk of the bell curve should be working on their running form and building their foot and calf strength, rather than relying on shoes and insoles to fix it for them. They won’t “fix” anything for them and may actually hinder improvement.
Aaaaand done with this soapbox. 