Tires and pressure Options

[lsintampa]

Here goes, maybe I'm not understanding something and there is opportunity for me to learn.

Firstly, what happened to the "tire calculator"?

Now onto the discussion. Porsche 914's for the most part call for tire pressures to be about 23PSI front and 26PSI rear. I may be off some, but for "most" 914's I think those numbers to be "horseshoe" close enough.

BUT, wouldn't one think that the PSI for the car is based on the tire size that came on the car?

IDK, but I would put some big bucks on the fact that most of us are NOT running on stock wheels / tire combination.

So I wonder for my setup - I'm running Yoko Avid envigor's 195/65/15's on 15X6 cookie cutters - what tire pressure should I be using?

It's just hard for me to understand the relationship between the car / tire size / and tire pressure. IE, if I put that same tire on a different car - would that car's recommended pressure be different?

Enlighten me please.

Thanks,

Len

PS - I wish you all a joyous holiday season and may we all enjoy a healthy new year!


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[Tom_T]

Hi Len,

There was some Java script issue with the tire size calculator on here the stopped it from working, but you can google for them. Here's a link to one of several which I'd found doing that.....

https://www.tacomaworld.com/tirecalc

As others have said above, the tire pressure is a function of the size & weight they're carrying, etc. - so it'll vary on non-stock tire sizes &/or resto-mod cars at different weights.

IIRC the 3 OEM stock 155(/80)SR15 or 165(/80)SR15 or ...HR15 size tires ran more like at 26 psi or more, & the spare on the 914/4 models were to be kept at about 40 psi IIRC while in the trunk because it supplied the air pressure to the windshield washer system, but you're supposed to drop it to the proper tire pressure when used on the car.

As for other sizes of tires &/or on -6 or -8 or Subie/WBX conversions carrying more weight - you'll have to do what any auto mfgr. does to get the recommended tire pressures.

That is, you'll need to weigh on a CAT scale/etc., calculate or look up the per axle weight to be carried with 2 passengers & full fuel/fluids & luggage capacity, then divide that by 2 per wheel - then go to the tire makers' websites for their psi per weight chart (or email them to request one to be sent to you). Then use that chart to get the proper pressure for the load each tire at the 4 positions require.

The tire pressure on the side walls is the maximum for the maximum rated load, so you typically don't run them at the max.

Happy Holidays! (IMG:style_emoticons/default/beerchug.gif) (IMG:style_emoticons/default/santa_smiley.gif)
Tom
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