Tire size question - 1996 Saturn SL2

[rearviewmirror]

My Saturn ('96 SL2 1.9l DOHC) calls for a 185/65-15, my car has 195/60-15 on it currently. Could this wider although stiffer tire cause the fuel economy to drop by 1-2 MPG? I'm just curious, if this is the case I might consider switching to some thinner LRR tires sooner than later.. Of course being hasty would incur a cost that would take a long time to recoup in saving a few MPG's.

My original thread w/ fuel economy is here: http://www.gassavers.org/showthread.php?t=4095

[Bill in Houston]

Originally Posted by rearviewmirror

Could this wider although stiffer tire cause the fuel economy to drop by 1-2 MPG?

yep.

[lovemysan]

185/65/15 is a hard size to shop for. I'd wait for your current tires to wear out. Someone probly upsized the tires because the correct size was not available. Its not hurting much.

[rearviewmirror]

Originally Posted by lovemysan

185/65/15 is a hard size to shop for. I'd wait for your current tires to wear out. Someone probly upsized the tires because the correct size was not available. Its not hurting much.

That's exactly what happened, my friend owns a shop, they had those in stock, I get them for next to nothing so I said go for it. That was ~20k miles ago so another 20k and I can replace them. It wouldn't be a wise investment to ditch them now as it would take forever to make up the cost. I wonder it changes the tire inflation though. The 185's called for 32 front, 26 rear, I am running 35 in all 4, the max inflation is 44PSI. I wonder if I can still step it up a bit.

[cfg83]

rearviewmirror -

Originally Posted by rearviewmirror

That's exactly what happened, my friend owns a shop, they had those in stock, I get them for next to nothing so I said go for it. That was ~20k miles ago so another 20k and I can replace them. It wouldn't be a wise investment to ditch them now as it would take forever to make up the cost. I wonder it changes the tire inflation though. The 185's called for 32 front, 26 rear, I am running 35 in all 4, the max inflation is 44PSI. I wonder if I can still step it up a bit.

Yeah, definitely keep your tires until you've worn them out. There is a really good tire-tech website that I can't find right now that says something like "if all else fails, apply the 10% rule". Take the max rated PSI and subtract 10%. In this case, 44 PSI - 4.4 lbs = 39.6 => about 40 PSI. If you do that, you should get MPG benefit without having to worry about over-inflation.

CarloSW2