Poobah Posted July 16, 2004 Report Share Posted July 16, 2004 The standard size tire for late model Eldorados is P 225/60 R 16. I know 16 is the diameter of the wheel but what about the 225 and the 60? Also, what do the P and the R stand for? Happiness is owning a Cadillac with no codes. Link to comment Share on other sites More sharing options...
Ben Posted July 16, 2004 Report Share Posted July 16, 2004 225mm tire width, 60% of that is sidewall length. P I think is passenger, not sure about the R Link to comment Share on other sites More sharing options...
KHE Posted July 16, 2004 Report Share Posted July 16, 2004 I believe "R" stands for "radial". Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
JasonA Posted July 16, 2004 Report Share Posted July 16, 2004 R stands for Radial. And you can tell the speed rating of the tire by looking at the two or three digit load rating, and the letter behind it. Like 102H for example. 102 is the load rating (I think that might mean 1020 pounds per tire, but I'm not sure) and the H is the speed rating (130 mph). Jason(2001 STS, White Diamond) "When you turn your car on...does it return the favor?" Link to comment Share on other sites More sharing options...
Willie Hank Posted July 16, 2004 Report Share Posted July 16, 2004 The standard size tire for late model Eldorados is P 225/60 R 16. I know 16 is the diameter of the wheel but what about the 225 and the 60? Also, what do the P and the R stand for? 225 is tread width in millimeters. Nominally speaking, the tread width is 225mm /25.4mm = 8.85". This will vary slightly from tire mfr'r. to mfr.'r. 60 is the tire "series" or aspect ratio, expressed as a percentage, that is, the ratio of the tire sidewall height to the treadth width. Th lower the number, the the lower the tire profile. For this tire, the sidewall height is 60% of the tread width, or 225mm x .60 = 135mm. Now you can calculate the overall nominal tire diameter as follows: ((225mm x .60) x 2))/25.4mm + 16" = 26.63" diameter. An equivalent tire diameter in a 50 series (or aspect ratio) would be a P245/50R17 (that what I have on my "93 STS, as shown: ((245mm x .50) x 2))/25.4mm + 17" = 26.65" diameter. Bear in mind the tread width is 20mm/25.4mm = .79" wider. It is odd the tire designation mixes metric units with english units, but that is the way it. is. Looks like others answered the letter designations. Link to comment Share on other sites More sharing options...
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