Newbie Tire Questions

No worries

 

Well, my approach was to increase tire pressure to improve gas mileage, but not optimize it, because the additional (small?) gas savings from absolutely maximizing (safe) tire pressure was not worth the research time and risk (in case I went too high!).

My method was this:

Max tire pressure is 44 (oem Goodyear Integrity's on the front).

Knowing that daytime temperature can rise 10-15 degrees, which can increase tire pressure by 1 or maybe 2 pounds.

And driving raises tire pressure by 3-5 pounds.

All this from the Edmunds article, if I recall. Or maybe it was from KBB.

Being conservative on this issue:

44 - 2 - 5 = 37

So I've got 37 psi (cold measurement) on the front, 35 on the rear.

That's working well and gas mileage has increased noticeably. I'll save $60-130 in gas this year as a result.

Fwiw, the top-selling TireTech gauge is great , does all I need, and is cheap. Especially for the savings it creates.

 

Toyota seems to use the same 15" tires on all non-Touting Gen 4 Prius. I set my 2017 Prius Two tires to 39 front, 36 rear. This is what is recommended for the Two Eco. For the Two, they recommend 36 front & 35 rear.

When I received my car, the dealer had set 32 on all tires. I still got 59 MPG in the 150 mile drive home.

 

Makes sense.

Fwiw, I'm on a Prius gen 3.

Your mpg it's already so high, you'll save less than the gen 3's, but still will save something. !

 

The "MAX COLD" is just that, COLD pressure. You are accounting for things that the tire engineers have already considered. There is not and never has been a suggestion by a tire OEM to REDUCE inflation pressure because the day will warm, tires will warm when you drive, etc.

If you had applied that logic and math to "MAX HOT", which does not exist, you would have been correct in your calculations.

Typical burst pressures for automotive tires are twice the "COLD MAX" pressure indicated on the sidewall.

You are spot-on ("safe tire pressure") with regard to the potential of over inflation to cause degradation of handling, braking and comfort.

 

Jimbo (and 05),

What tire pressure might I want to have for winter driving?

I've still got the (lame, imo) OEM Goodyear Integrity's on the front, and the ok Goodyear LS2's on the rear.
I'm starting to notice some rear tire slip on the rears on fairly angled road curves (there's one near my house that I have to drive through all the time.) It's a bit of a down hill..I don't think it's banked. More tire slip than I want, and it feels like if I really gave it gas, I could spin out that rear end. I've been gentling it into the one curve to control things.

FWIW, my tires were like 38/33 when this happened. (I set them at 38/36, I'm sure of it...but I must have made some mistake, I guess, since on re-check they were 38/33.)

(I will re-check tire pressure regularly to see if there's any ongoing leak in the rears).

Any way, back on topic:
With winter coming, I'm thinking of possibly lowering all tire pressures to like 35/33? Shouldn't that help increase traction, with these LRR (i think they're both LRR) tires? or is the difference not that much? or should I / can I go a bit lower, even?

I'm especially interested in figuring this out before actual ice, etc come on. I also live on fairly steep hill (both the street and driveway. Not the steepest, but a notable grade ! )

My thought is to lower tire pressure on the bad days, then maybe put them back up on dry weeks if I'm feeling it. I definitely don't want to spin out.

To recap...I wouldn't mind going even lower than 35/33 if safe and advised for traction, even if gas mileage suffered 25%, to be safer until the tires wear down in a few years.

Thanks for any advice,
pnb

 

Might be a TPMS sensor that has been corroded or damaged. I'd check the tire pressure and the tires themselves. Could be a low tire or it could be one tire is needing to be replaced.