tire size explanation XXX/YY R ZZ

XXX is the tire width at widest point in millimeters (i.e. 195, 205).

YY is the "aspect ratio". If 60, then the height of the tire is 60% of the width.

The number after R (ZZ) denotes the rim size in inches.

The tire size may be proceeded by a P (passenger) or and LT (light truck). Or it may just be the tire size.

The stock size for most C900s (excluding certain models like the SPG) is (P)195/60R15. This is a good tire size (that's why Saab picked it) for the C900 with 5.5X15 inch rims (5.5 inches wide).

Let's see:
For 195/60R15:(outside diameter is proportional to) 195*.6=117
For 205/55R15: 205*.55=112.75
For 185/65R15: 185*.65=120.25

Since the outside diameter is very close for these sizes, they are commonly used. The 185 would be the best in the snow (narrower tire with equal loading has higher contact pressure). The 205 would have the best dry traction and handling (due to width). However the 205 is regard by some as being too wide for the C900. Slightly too wide for the wheel well may mean (bad for stone chips, mud, etc). Also since our rim is relatively narrow (5.5 inches) it may not be the best choice. According to the tire and rim association, a 205/55R15 is an acceptable size for 5.5 inches but it seems to be pushing the envelope.

Other sizes people run:
205/50R15, 195/55R15, 195/50R15 and 195/65R15.

The higher aspect ratio tires (195/65) give better ride in exchange for handling (more sidewall).

The lower aspect ratio tires would be stiffer but due to the decrease in outside diameter there an increased chance for rim damage should you hit a pothole in March after the snow plows are done destroying the expressways.

All of these "other sizes" introduce significant speedo error due to the larger changes in outside diameter.

But to each his own. Someone on this BB runs 215/65R15.

• I am SOOO confused on performance tire size! Please HELP, Ktang, Mon, 27 Nov 2000 15:49:31
  • Re: 205/55, TJ, Wed, 31 Jan 2001 01:05:19
  • tire help..., Bogie, Tue, 28 Nov 2000 10:35:52
  • 195/60/15's ....quit whining!!!, Karel, Mon, 27 Nov 2000 23:07:18
    • Hiss...bowl of milk table two...the Karel party of one, Ktang, Tue, 28 Nov 2000 02:36:48
  • MY 2 Kronor, saw, Mon, 27 Nov 2000 20:20:58
  • has anybody tried Michelin Pilot XGT H4's? Any good?, moby, Mon, 27 Nov 2000 19:51:08
    • ? buy tires worth more than car? Now, THAT's catty...., JohnB, Tue, 28 Nov 2000 07:35:51
      • i'm talking about my SPG now and they're $77 at tirerack jeez, moby, Tue, 28 Nov 2000 19:44:06
    • Consider BFGoodrich Touring T/A VR4 all seasons, 205/55 for $62?, Ktang, Mon, 27 Nov 2000 22:31:08
      • I give ...... Super choice at a great price!, Kevin K , Tue, 28 Nov 2000 00:15:21
  • what is important?, Kevin K , Mon, 27 Nov 2000 17:01:41
  • Scott - can we consider an FAQ for tire SIZE?, Mike H, Mon, 27 Nov 2000 16:39:30 <-- Viewing This Message

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• Prev by Date: good info - thanks for correction (nm), bryan m, Mon, 27 Nov 2000 16:32:44
• Next by Date: Re: HELP! A-arm swap nightmare..., RS, Mon, 27 Nov 2000 16:44:31
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