Tire buying and load question

I, unfortunately, am not a trusting sole, so I take my car to Toyota only. This, however, costs a bundle.... $500 later I had an oil change and 4 new tires. Not sure what the rating actually is, but they showed me several models compatable with my '01. Good Luck, T

 

Classic Prius comes with 84 load rated tires. Based on max. gross front axle weight, 81 load tires ought to be sufficient, and this describes most 175-width tires. I believe this is the crux of the debate, and in earlier years it was a hot one.

I drove a lot of miles on 81 load rated tire with never a problem. But I still decline to recommend them, because the driver takes on a serious responsibility to keep the inflation pressure very near the sidewall limits.

Have since changed to 185 width tires. This solves the load issue, improves handling, and costs a few tenths of a cent per mile in extra fuel costs. It's an individual decision.

 

Probably no more common than driving on 81-load rated 175 width tires. Like I say, not everyone thinks that's such a bad idea. It's just that I can't recommend it because below Toyota's spec, no control over your driving conditions, etc.

One rule of thumb is that you can tell if tires are running overloaded under particular conditions of inflation pressure, vehicle weight and speed. The "hot" tire pressure is supposed to be within 10% of the (previously measured) "cold" pressure. If >10%, tires need more air. If adding more air would put you over the cold max inflation pressure on the tire sidewall, then the tires are not up to the task you are giving them.

With the 81 rated Goodyear Allegras, I was only able to exceed 10% once, with extended, aggressive downhill mountain driving. As I did not have them at max inflation pressure already, I had not run out of options.