Handling on the IV

tire air pressure? pretty common for dealers to under inflate tires for the test drive, gives a smoother ride, but the car wallows around like a drunk.

 

If I were disappointed with the handling on the 2010 Prius, the first thing I would try is the CUSCO Strut Tower Brace.

It's $235 at Sigma Automotive: Toyota Prius 2010 ZVW30 Performance, Handling & Electronic Accessories :: Sigma Automotive

In the 4 photos below, the Strut Tower Brace is shown in the top photo (the bottom 3 photos are chassis braces also made by CUSCO):

[imglink]http://www.sigmaautomotive.com/jdm/prius_zvw30/per_cusco_strengthening.jpg[/imglink]

 

Push the tires up to 50, and take 'er out and bend it around those
curves. Probably feel a radical difference.
.
_H*

 

Let us know how it worked out

 

I come from an SCCA racing background, so I'm used to some truly tight handling cars like my '71 Datsun 510. On racing slicks, you could throw the steering wheel as hard as you could muster at 90mph and the thing would whip into right into the turn without even flinching. And yeah, the Prius will never handle like one of those. But with tires at 52 psi front and 50psi rear, I find the handling to be more than adequate for a mid-size sedan and cornering to be confident and responsive.

 

Great insight, thanks...

I'm planning to do this at the dealer (I HATE paying for things like air at a gas station--what has this world come to?) when I go to pickup my new 2010... would there be any warranty issues with this or would they have no say in going higher than recommended pressure?

What is the factory tire Max PSI number anyway? 36F/34R?

TIA

 

I would imagine that a dealer would balk at setting tire pressure higher than the maximum pressure stated on the tire sidewall for liability reasons.

 

The factory recommended psi is 35F/33R. There is a plate on the inside driver's door that shows these numbers.

 

Off topic but I LOVE the avatar!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Yup, you can bet your life that the dealer will not set the tire pressure to anything other than oem specs.
When I take my car in for service, I tell them to not check/change the tire pressure and they always note "set by customer " on the service work order.

 

I am not disagreeing with your experience, but isn't this unusual? I thought lower pressure (within reason) helped handling by virtue of more contact area? And I would assume consistent tire pressures of 50psi plus would help mpg at the cost of shorter life of the tires due to center wear. Asking to learn...

 

Lower pressure would help traction (such as needed for drag racing) but not necessarily handling. Lower pressure would allow more flex when going around curves. Thus raising pressure would help up to a point. That point would be when you put so much pressure so that while taking a curve you have decreased grip to the point that the car breaks loose in a curve as you have exceeded the cars ability to stick to the road while cornering.

There are a lot of discussions about high pressures. I'll stay away from those as I'm not an advocate of that due to the safety reasons I've mentioned above. A lot of people do it though.

 

It might improve dry traction, but lower pressures reduce handling quality by making the tires more flexible. Think of it this way: you increase pressure, the tires become stiffer, and there is a more direct link between the steering input and the tread contact on the road. Lower pressures make handling more "mushy" because the tire will flex more when you turn the wheel, delaying the car's response to your input. It's a very noticeable effect.

 

As correctly noted by previous posters, lower pressure would probably have higher ultimate grip on dry roads. However, in real world conditions, pre-breakaway handling is typically more important than the absolute maximum lateral G number. For instance, does the car feel confident when entering a turn? Does it get 'squirrely' when you jerk the wheel suddenly to avoid an unexpected obstacle? Does it hydroplane on wet days? Those types of concerns are usually much more important on a daily driver than the absolute cornering force. And those concerns generally improve with higher tire pressure due to the increased sidewall stiffness, also as correctly noted by previous posters. As for the center wear issue, all I can say is that I have never actually seen a set of tires worn more in the middle than on the edges. Never. I suppose it could happen, maybe... but I've never seen it. Even if it would happen, one would have to run the numbers to see if the shortening of tire life outweighed the fuel saved by reduced rolling resistance. A whole 'nuther conversation, to be sure.

 

I've tried various tire pressures from 40/40 at delivery to 42/40, 35/33, 44/42 and now 38/36, and I like the ride and road feel at 38/36 the best so far. 35/33 felt sluggish, and 44/42 felt floaty, but so far 38/36 is just right.

 

+1 to 'floaty' at higher pressures. At 52/50 I do get a bit of a floaty feeling in some situations, but not enough to bother me or cause concern... and not more than I've noticed in any of my mid-sized sedans. And the rolling resistance is just SO low at that pressure... it seems to keep going forever!

 

The guy who raced SCCA, what did you run for tire pressure while racing? I know that you can't really make comparisons with real racing tires, but when I raced SSC (show room stock) many years ago and we were required to run DOT tires, we ran tire pressure around 40ish, but running a different class and running slicks, we ran around 30, if I remember correctly.
Point being that low air pressure will help in deep sand or something, but certainly not on the highway.
I can remember at least one fiasco about Firestones and SUV's and blowouts and if I remember correctly the most likely cause was a lower than normal spec for air pressure by the manufacturer who was seeking a smooth ride for the SUV.
Never heard of blowouts from overinflated tires, unless way overinflated.
Reason is underinflated leads to overheating from excessive flexing, just like bending a coat hanger back and forth

 

Girl, actually

But that aside, the pressure varied a lot with tires and track condition. As best I recall, it was always rather high - 40+, I think. We would use a tire pyrometer to measure temps across the surface and then adjust pressure and suspension geometry to even them out. So if both edges were hot and the center was cold, we added more pressure. If the center ran hot and both edges were equally cold, we dropped the pressure. If outside edges were hot, we'd dial in more camber or less toe-in, etc. I remember a pretty significant change when we went from the old bias ply slicks to radial slicks, but I can't remember exactly what pressures we ran on either - it was 15 years ago. Regardless, that situation was quite different - much more about maximum lateral acceleration with the expectation that the driver (me) would learn to deal with quirks, twitchiness, or discomfort. All that mattered was carrying an extra few MPH through the turn... totally different considerations than a street vehicle.