Tire pressure/short trips and mileage

If you can't walk such short distance then try to advantage the initial downhill portion of your trip. Press the gas paddle gently to gain some momentum and then supplement it with the gravity to gain some additional speed. You should have the ICE on (arrows coming out of it) to warm up, but still should be able to achieve some decent MPG. Coast to the stop signs. By the time you complete this downhill portion of your trip you will have a partially warmed up engine for the second leg. Try to make your stop as short as possible so you don't lose too much of that gained heat.

Good luck,

 

Does tire pressure really make a big difference. If it does, why doesn't the manufacturer recommend a higher tire pressure.

 

Toyota is worried about complaints that the ride is harsh so they spec 35/22 PSI in tires that are rated safe at 44 PSI cold.

Running 42/40 as I do has benefits. First, it does noticeably, but not dramatically, improve MPG. If you have the OE Goodyear Integrity tires which have very soft sidewalls, higher psi will reduce the scrubbing of tread edges in turns thereby extending tire life. It also reduces the high speed instability of these tires (a noticeable side-to-side wobble).

Better tires are a significant improvement for a Prius. I now have 130,500 miles on mine and am well into my third set of tires. Both the Michelin "Energy Saving" and my present Nokian WRs were/are significantly better than the OE Integrity tires in all aspects with the WRs also greatly improving traction in wet/cold weather. See the attached zipped Excel spreadsheet for detailed data on my experience.

Enjoy your new Prius.

JeffD

 

wantaprius,

Air your tires up to 40/38 and don't worry about your tires. With your short trips, you will probably experience mileage around 40 to 42 MPG. You will not void your warranty or cause a warning light to come on by increasing your tire pressure. That's just lack of knowledge talk and plain bunk. You will actually increase your tire life instead of decreasing it as efusco states. Short trips and low tire pressure are big MPG killers. Pay attention to your MFD Energy display and it will teach you how to drive with varying throttle pressure to improve your gas mileage. Good luck and enjoy driving your new prii.!!!

 

There are a couple of things to consider:
Negative
1. The ride will be firmer and rough seams in pavement will give a thump.
2. Traction in the wet is likely to be slightly reduced--and the low rolling resistance Integrities are already less grippy than many tires.
3. Need to re-initialize your tire pressure warning system.
4. Dealer/tire shops are more likely to fiddle with your tire pressures.

Positive
1. The car should handle better in cornering.
2. The tires should last longer. The claims of "tires wearing out sooner" are the opposite of what owners are reporting and are non-sensical when you consider that rolling friction is reduced, not increased.
3. There is more safety margin if tire is losing air, the warning system (if reinitialized) will activate at 75% of your set point (40 psig normal would warn at 30 psig if I understand correctly.)
4. Increased fuel economy.
5. Stiffer sidewalls should make the car squirm less.

Considerations:
1. When you increase your tire pressure, don't forget to reinitialize the TPWS. The instructions are in the manual and shouldn't be too difficult to follow.
2. The claim that the tires will wear unevenly at increased pressure has not been observed by users of the Integrities. The assumption for the higher wear claim is that the center of the tread will bow out and result in uneven wear. In reality this doesn't happen at pressures below maximum sidewall and instead less edgewear is observed with higher inflation.
3. The tires are still set below the max rating on the sidewall and should therefore still be within warranty. If you have a problem with your tires and are concerned they might hassle you about this, reduce the pressure in the tires before you take it into the shop.

 

In heavy rains I doubt there will be any issue with higher pressure and in fact it might be helpful in maintaining contact with the pavement. My concern is more with wet conditions in general rather than water covered roads. I do expect some reduced traction in the wet with higher pressure. (I would very much like to see this quantified.) Less body roll means more precise handling in my experience so there are tradeoffs.

When considering rolling resistance my understanding is that there are two primary components: rolling friction of the tread contact patch and flexure of the sidewall. I do not know the relative distribution but recognize that higher inflation pressures will reduce sidewall flexure--this can actually be felt by the driver in the form of a firmer ride. Sidewall flexure is the major component of heat buildup in tires as I understand it and is what tends to result in tread/sidewall separation in underinflated tires.

 

TPWS = tire pressure warning system. Some Prius options will tell you when a tire's pressure changes a lot.