Scale question; why 1/24 and 1/25

as odd as it sounds, that one unit can make a difference when it comes to things like decals.  a few of the stock car kits I've put together, I would swear it was a 1:25 kit with 1:24 decals, cuz they would be just slightly too big.. enough to be noticable too.  On one of those I had to majorly improvise the hood decals too..

but other than that really it doesn't seem to make much of a difference.  I finished building a Peterbilt truck, in 1:25 scale its 11 7/8th inches, but if it was 1:24 scale it would bump it up to 12 4/11th inches.. so its like 1/4th of an inch difference.  Really, unless you happen to line up two of the same car in the diff scales next to each other, or try to use parts across the scales, I don't think the diff matters.  

I've often wondered that myself, but here's what I've noticed mostly.
Ususally:
AMT/ERTL, MPC, Lindberg = 1:25
Revell of Germany, Tamiya, Revell, Monogram, Revell Monogram = 1:24

Of course thats not a rule, I have some of all of those that are more "unique" in their scales.  

And also you have cars in random scales, I saw an old 32 Ford (I think) in 1:8 scale, and I've seen several in 1:16 scale.   

It is curious though... because one time I had two old Cadillac Eldorados, one being a 1:25, and the other a 1:32, and even that much of a diff was only like 1 1/2 inches diff..

Also, according to wikipedia, 1:24 is a "common dollhouse scale", and 1:25 is "common for model villages in europe" so that may have somthing to do with it.

Good question! I've always wondered this myself. I built car models as a kid in the early 70's and it was the same thing back then. Some kits were 1/24 and some were 1/25.

 I really can't tell the difference unless I try to swap parts as Wingform said. Even then some parts will work just fine. You have to consider the tolerance of manufacturing errors is probably within the difference between scales on some kits. (Even within the same scale, some kits do not have perfect dimensions)

I read something about this recently, I don't remember the specifics but it had to do with the source of data. As I recall AMT along with some others (Johan, maybe Revell?) built promos so they received actual engineering drawings from the auto manufacturers. These used an engineering scale one of which happened to be 1:25. Other manufacturers made their calculations off of measurements from the 1-1 and scaled them down so 1:24 (1 inch = 2 feet) was an easy scale to use.

It seems like with the exception of Monogram 1:25 has been the preferred scale in the US. Most Japanese and European companies went with the english measurement based 1:24 which seems odd since they have used the metric system for decades.  

Great discussion, thanks.

Aaronw, my nephew is a firefighter.  I sometimes think of making a fire truck for him some day.  I bookmarked the links you gave.

Brian