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4249 Views 7 Replies 4 Participants Last post by  BurnsSide42
I need new tires this month, so I've been perusing the local used tire selection with the intent of saving some money. I found a pretty good deal on some Michelins, but they're 225/55/16. Would they fit on the stock Deltas (stock tire: 215/55/16)? I checked the speed difference, and it's less than a 2% difference from stock. Would there be any advantages/disadvantages to using this size? Would they wear funky or anything? Would they be fat enough to rub anywhere?
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Well, they'll be wider and taller:

225 mm wide vs. 215 mm wide. Both 55% profile, but 55% of 215 = 118.25 mm from tread surface to rim while 55% of 225 is 123.75 mm.

So total diameter of the 215 tire is 25.132 inches
The total diameter of the 225 tire is 25.744 inches.

That's an increase in diamater of 2%.

The 215 tire's total circumference is 496 inches
The 225 tire's total circumference is 520 inches.

That's in increase of over 5%.

It may fit on the rim, but your speedometer will be wrong, not to mention the potential for tire rub.

My suggestion, check out this site, you can find the proper profile size relative to your width:

BTW, you're fairly close to me -- about an hour and a half.
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496 and 520 inch circumferences? Those are both over 40 feet. The diameters sound right, but a 40 foot circumference sounds way off.
talladega, what are you talking about lol. circumference on a 225 is 80.9 inches, vs 79.5 inches
DOH! I think my conversion tables from metric to inches F'd me while doing the math. Point I was trying to make was that there will be a change, and the tires will be taller affecting speedometer.

:rolleyes: I'll just go back into my cave now...

Edit: Double DOH. I think I know what I did: I figured area, not circumference. Did Pi r squared, not 2 Pi R.

I R an ijit.
^ Ok, that makes sense, easy mistake. The link you posted, Talladega, suggested 225/50. I put the 50 and the 55 into another size comparison calculator, which said the 55 would be a little bigger than stock (obviously), and the 50 would be smaller by the same amount. They were both a hair under 2% different, and the speedometer would be 1 mph off (at 60 mph) in either direction, depending on the tire. So going purely by the numbers, the 225/55 or 50 should work. I wouldn't think they'd be too fat in real life, since people run 235s on 8 inch wide wheels. Any thoughts on fitment/handling/wear, numbers aside? Has anyone ever tried anything besides a 215/55/16 on the stock wheel?
If you're okay with the variance on the speedometer, I'd say go for it: I'm running 205/45-16's on both c900's, when for a while I was running 205/50-16 and originally 195-55-15's stock. I was rubbing with the 50's, but now it's running fine. Speedometer slightly off, even though the Powerdog site indicates less than a 1% variance.
Just go visit a local Saab dealer's dumpster/tire pile after hours - you'll find the size you need there :) Price is good too.... lol

I'd stick with the 215/55/16 IMHO or get some 225/50/16 I always thought the 215/55/16 was a good size for Saab's - cheap tire, plenty of options and the ride is a nice cross of handling well and just smooth enough.
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