David is correct, but he politely didn't mention that he personally runs his tires at 37/36. I run at 38/37. Lots of people who don't mind a harsh ride run even higher (42/41, or even at the max tire ratings, e.g., 52/51). The recommended pressures are very low, which makes the ride soft and muted, but gives too much flex or rollover in the tires when going around curves, IMHO.
I run my 17s (Toyos) at 37/36 as well. I found myself not too sensitive to pressure differences - tried from factory 33/32 up to 42/41, and several notches in between. Although not dramatically different IMO I found 37/36 just right. And confirmation of that general pressure range by folks here is OK by me. There's lots of posts on threads here about this topic.
But what is the impact on braking? It seems to me that overinflating tires (by over 50% in some cases) would increase braking distance for the same reason that it improves FE. Is there real data that says otherwise?
I came across a paper at the NHTSA (if I remember correctly) that indicated higher pressure in the tires improve braking in wet conditions. It was dated in the 1990s but I remember it saying something about getting the water pushed around instead of riding on a layer of water. All I know from personal experience is I can take turns at higher velocities than the tail-gating jerk that follows me several miles down the six lane highway. It is of course a question of experience so I know what I'm dealing with and it doesn't hurt that the top-heavy, soft tired SUV driver has as much skill taking a turn as they do maintaining a safe following distance or passing. Bob Wilson
I'm not a gearhead, so I can't give you an authoritative answer, but if you review the other threads on this topic you'll find lots of gearheads and performance drivers saying that "breakaway" or the tendency for harder tires to lose grip is really only going to happen at extremely high pressures. There is no way adding 5 lbs of PSI on tires rates for 52 PSI is going to negatively affect my stopping distance. There are also other threads that say you get .5 to 1 improved mpg for each extra 10 lbs of PSI. Some people also claim it extends tire life, as long as you don't overdo it.
I believe what you are referring to discussed hydroplaning, not braking. But I could be wrong. I'm sure you are a superior driver but that has nothing to do with the physics of an emergency stop. BTW, hypermilers have also been known to tailgate/draft. Doesn't "breakaway" refer to handling in a turn? I agree that 5 lbs over probably is not a big deal, but there are many that go 10-20 over. Besides I don't think the maximum pressure rating takes into consideration the vehicle on which the tire is actually mounted. A heavier vehicle may have a higher recommended pressure, but a high pressure on light car like the Prius might not be a safe idea. Again, I'm wondering if there are real test data. Even a foot or two could kill a child. But maybe saving ~$20/year is worth that risk that to some.
Thanks for proving yet again that I'm not a gearhead and have no business commenting here! On the issue of safety, doesn't the handling issue count for something? I think everyone agrees that softer tires mean higher rolling resistance, which, if not taken to extremes, probably means shorter stopping distance. There's obviously a balancing going on between ride comfort, braking, rolling resistance (mpg) and handling. Based on what I've read at PriusChat, it is hard for me to believe that running 5 to 10 over would create much difference in the stopping distance, but I'm certainly open to objective evidence, as you suggest. Do try searching for other threads on the same topic, since it annoys some people to rehash the same thing over and over.
I have looked on both my front and rear door jams and can find now where to pressure them up. I'm currently back to 40/39 after experimenting with 36/35. Noticably rougher, but (maybe it's in my head) it seems easier to hit 50 mpg now in my V when I want to work at it. 40 is pretty much my limit. I know many go a lot higher, but I don't think trading off safety for FE is such a great idea.
I don't mean to be simply a contrarian, but where is the evidence you are trading off safety for fuel economy by running at 40psi?
I decided to try a higher tire pressure, as recommended in many of these threads. This afternoon, I set the tire pressure, then got out the Owner's Manual to see how to reset the TPMS system. It took me over 5 minutes to find the TPMS reset button. Could Toyota have made it any harder to find this button? I realize this isn't used much, but the Owners Manual should at least give a decent clue as to how to find it.
Care to share where you found it? I am thinking of adjusting my Tire Pressure as well and assume if I raise the tire Pressure 6-8 PSI I should also set the TPMS??? Isn't that accurate? Please let us know where the button is since I know it has to flash 3 times or something to acknowledge that the TPMS has been reset but I never looked for it yet. Thanks!
Trace an imaginary line down the center of the steering column cover. Keep looking and about 2 or 3 inches in back of where the dashboard ends you will see two buttons. One is marked OFF and it turns the PCS off, the other is marked SET and that's the one. (Only the V version has the PCS button of course) I have to get down on my knees outside the car and look in to find them.
Thanks TUMBLEWEED. Guess I have to limber up some before getting stuck under the dash! LOL Will take a look and let you know if I can find it but the instructions sound pretty clear and we both have V's so I won't touch the PCS button.... Trick is to find the button so you can reset it or have the partner check to see if the light flashed 3 times which confirmed reset. That's the other key here right?? Thanks Tumbleweed....for getting back on this...BTW, How do you like your V? I love mine!
Hi Bob, Page 443 of the Owner's Manual on PDF shows where the reset button is. BTW, took only a minute to find searching "reset" in the PDF.
Don't worry about the PCS button, it's the one on the right, if you turn it off by mistake like I did you will get a PCS light on the dash board. Just push it again and the PCS will come back on (light off). I think you should be able to do it by feel, you just have to reach way under, they are little round black push buttons.
Thanks Boo, Also Thank You for the PDF today. I was able to download it this morning, and got it fine. Appreciate that. Bob
What the door sticker gives you is a way low pressure. On my 2010 package V with the 17" tires, the tires are max rated at 51 PSI, so if you follow the door sticker, you will be almost 20 lbs under the max. This might be OK ... IF you are running empty and in town a slow speed ... and you aren't concerned about your MPG. Having been a Goodyear dealer in my younger days, I know that car maker PSI suggestions give you a nice, soft ride BUT ... your mileage will suffer a lot your handling will suffer and your tires are likely to squeal a lot on turns your tires will likely wear out much faster Having just completed a 3500 mile tour of several western states ... with my tires at 46/44, I observed a few things ... 80+ MPH for hours at a time on a decent highway is smooth and quiet handling, steering, and braking is great by actual measure of tread wear, I should get at least 40,000 miles on the Brigestones ... which for this particular tire is good This car is NOT as light as some posters seem to think ... and you need the pressures up.
