The improvement in fuel mileage, in their opinion, might not be worth the added harshness and noise of the ride, which could be seen as a negative selling point. Of course, if they really wanted to get tricky, I could imagine that they would set a higher pressure as the "standard" reccomended pressure, with an alternate, lower pressure for a softer ride. I run about 40psi in my HCH as opposed to the recommended 30. However, the manual actually reccomends increasing this to 35 or 36 in the event of higher-speed driving, stating that the 30psi recocmended would run too hot. If 6psi "overinflation" is actually considered safer at high speeds, I'd wager 30psi isn't selected for safety/performance reasons but for comfort.

This suggests there's a fairly broad ranges of tire inflation, even give then same load (more weight requires more pressure), where things like braking performance all fall within acceptable ranges, but the automakers reccomend the lower-end of that range for the sake of a smoother/quieter ride.

I found handling and steering-feel (seriosuly lacking at stock pressure) is dramatically improved, and my coast-down distances on certain hills (how far the car will roll on its own) is much longer, proof that rolling resistance is lower. The ride is a bit bumpier and noisier though on rough surfaces, but if you live in an area with fairly smooth well-maintained roads, it's not a big deal.

As for overinflation causing greater wear in the center, while that may have been true in the past, I don't see how that could possibly be an issue on a steel-belted radial tire as the steel belts prevent outward bulging in the center. If anything, an overinflated tire should wear less overall due to less flexing.

 

Well I certainly learned something today and my pressures will be going up to 42/40 and the first opportunity. Thanks!!

 

Isn't this forum terrific? I'm addicted. (Like that wasn't patently obvious. If it weren't for a dual monitor setup -- GreenHybrid and GMail on one, work on the other, I'd probably never get any work done! )

 

Thanks to those who provided the supportive links! Now, let's start hearing some comparisons to see how the higher pressures might help boost gas mileage!

 

Thought I'd drop a quick note for folks that have a new TCH direct from the dealer and haven't checked the tire pressure yet. [Editor's note: This started out as a quick note and wound up being a long senseless babble. Apologies to the reader.]

I bought my TCH about 2.5 weeks ago.

I have a digital tire pressure meter at home. The car has the stock P215/60R16 Michelin's on it.

When I first bought the car, I checked the pressure when I was parked outside the front of my house. The meter read 39.5 and 39.0 depending on the tire. I didn't adjust the pressure because they weren't definitely "cold".

I just had the chance to check them "cold" for the first time (two weeks later). Each tire was either 39.0 or 38.5. (Which basically means the dealer filled them to 39.)

I'm inclined to err on the side of going w/the manufacturer's recommended tire pressure.

Warning: I admit that zero scientific/logic evidence goes into the following approach--it is just gut reaction.

I read this thread, thought about it a bit, and lowered each tire to 36.0 pressure. As noted here, the manufacturer's is 32PSI (or 35PSI at sustained high-speed). I'm going to run with them at 36 for a week or two....and think about whether I want to drop it down to 35, 34, 33 or 32.

In general, I'd rather have the pressure be a bit too high rather than a bit too low, which is why I'm up at 36. Frankly, my guess is I'll wind up lowering them to 33 or 34 after my next tank or two. It just bugs me not to be within the manufacturer's recommended range.

I know it is "safe" to keep them a bit over-inflated, which is why I'm trying 36. We'll see if that lasts (the back of my brain is already bugging me about it as I'm typing this).

One last point/question: No one here has talked about how the tire pressure might affect the performance of the VDIM system. Presumably, the system can adjust some for varied tire pressure, but my assumption would be that it would perform better (or at least be designed to perform) at the manufacturer's recommended pressure.

Any thoughts on this last point? (Or on my illogical 36 PSI strategy? )

 

I'd be inclined to go along with your logic about VDIM. It was undoubtedly programmed to work optimally at the pressure that Toyota recommends. Not that it won't still work at other pressures, just that the programming would be optimized for the recommended pressure.

 

IMPORTANT TIP: Each time you change your tire pressure settings, you must reset your TIRE PRESSURE WARNING RESET SWITCH. This should be done, for example, if you change from running 32 PSI to 34 PSI, or from 38 PSI to 37 PSI, etc. Your sensor must accurately recognize your starting pressures to properly detect if a change in your tire pressures might occur. So, for all of you who are experimenting with tire pressures, don't forget to do a reset EACH time. The simple instructions are on Page 174 of the Owner's Manual. Basically, you Power ON, then press the Reset switch in the glovebox for a few seconds until your tire pressure icon on the main gauge display slowly flashes three times.

 

*THANK YOU* (You'd think they'd put this on the same page as the Recommended Tire Pressure. There's no mention of it on that page. Very very stupid manual writing.)

 

On my HCH I noticed little difference in FE after changing the tire pressure from recommended to MAX psi. What I did notice was better handling and stopping in both the rain and dry. I noticed a huge handling improvement in the rain with tires at or near MAX psi.

FE didn't change at all.

 

OK, I'll bite. I've gone to 38psi. So far by MFD Tank Ave I've been doing about 37mpg. I'm still only 2/3rds thru my 1st tank though, so I won't have too much past history to compare with but what the hell, I'll try and see. When I went to change pressures, I noted the dealer already had them all at 35psi instead of 32psi.