Tire Pressure for the 215/45 17s -- Here We Go Again!

*shrug*

I ran my 215/45/17s at 60 psi and they were showing a tiny bit more wear in the center so I backed them down to the sidewall pressure (50psi or 55psi I cannot remember) but I have not driven on them enough to know if that helped the center wear. I switched back to my 15s due to loss of MPG.

Even at 60psi the wear was pretty minimal so going close to sidewall likely wouldn't produce much middle-wear. Now we can get into arguing about burst pressures..... LOL

 

33 psi is to low for any road tire, especially low profile. I would just do what you did with Gen II, maybe a bit more. Low profile soaks up alot more road vibration though, anything over 46 psi is probably to much. Go by the sidewall. The last Toyo's I had that where low profile..anything over 46-48 was to much.

 

I like the 51 PSI max the sidewall says. But then I like higher pressures and my bottom is immune from NVH. Besides the higher you go, the easier to shoot for a 70 MPG tank.

Wayne

 

Factory recommended tire pressures are a compromise between ride, handling and wear (as observed in the extensive testing Toyota does on the Prius). The max pressure number is the tire manufacturer's safe number based on testing, probably with a margin of safety thrown in. For autocrossing we usually ran considerably higher than the manufacturer's suggested numbers, but below the max rating on the sidewall to get maximum handling performance (too high and the tire tends to bulge to the point it is only riding on the center, reducing contact area). For maximum mileage I assume the smallest contact patch would be best, but this comes at the expense of ride and wear, and possibly safety (less contact patch = worse handling and braking). Everyone has to make their own decisions. I run the recommended numbers on my 2006 for best all around performance (but I'm certainly not a hypermiler).

 

Not quite true. Modern steel belted radials don't bulge in the middle like the old bias-ply tires. The only thing that will change will be the shoulder tread lifting off the pavement, the wear of which happened to be a common complaint amongst Prius owners. Having seen many tires "overinflated" for there natural life, tread wear turns out to be very even across the tread unless there is an alignment problem.

Wayne

 

Wayne, have you seen this generalization applied to wider tires? I'm curious because I noticed a tiny bit more wear in the center of my 215s (on the Prius) when I kept them overinflated as well as on the 275s and 315s I used to run on my Trans Am and my GMC truck. What else would cause the center to wear like that?

 

I have not heard of abnormal center wear except for very wide tires. Did you measure the tread depth, center and sides?

Wayne

 

I did not measure them when I noticed this problem because I was taking them off and storing them away. Next time I'm at my friends house, where they are stored, I will measure them.

 

Had my V 3 weeks now. Tires were 33/32 from the dealer at delivery. I asked the same air pressure question here weeks ago, and after advice (very good stuff from the great folks here) brought them up to 43/41. After a bit of driving I did notice a slightly harsher ride and perhaps a bit more tire noise. Subjective....
I decided to bring them to 38/37. Seems to feel and sound fine. With such a low profile tire, I'm surprised the ride is not punishing. The car handles extremely well, and the steering ratio is great.
Honestly, I'm not one to be super-concerned about squeezing an extra MPG or two for the sake of very high tire pressure or really babying the accelerator. I find myself driving much more conservatively with my Prius, but not super-duper hyper. 1st 850 miles of very mixed driving 48.3. A/C on all the time. I'm VERY OK with that number.
Off topic, but IMO the Prius should have 3 tire/wheel combos - 15s for the I&II, 16s for the III&IV, and 17s for the V.