40th Anniversary Opt tire sizes

[Beachbumm61]

am looking to put a w speed rated tire on my ruby but cant fine a tire in both 255-45-17 and 285-40-17....... will any other tires fit the rims and still have wheel well clearance

 

[wrenchmantee]

When I had 17" rims , I used 245/45zr17 on front...275/40zr17. To me them looked a little better. The speed-o-meter at 60mph will actually be going 59.3 mph.

 

[stang-etr96]

A (W) rated of (ZR) rated tire for all practicile purpose's is the same. Depending on vehicle weight and loading. So unless you do alot of AutoBaun driving in Germany at a constant 160 mph I think you'll be just fine on the roads of PA.
OBTW the width of the tire, 245, 255, 275, or 285 has no effect on the "speedo" its the second set of numbers or "aspect ratio" 45, 40, 35, that changes your diameter that will have an effect on your "speedo"

 

[wrenchmantee]

Begg to differ! The wideth of the tire DOES effect the aspect ratio....and does effect the speed-o-meter. But the ZR is a factor in the handeling and cornering of the tire, It is not just a speed rating. But check out this tool I found on this site at the bottom of the page...takes a few seconds to load, then plug in the numbers.http://www.joby.se/corvette/div/corvette_wheels/

 

[stang-etr96]

Thats a pretty kool tool. Thanks for the education! BUT, a little info is left out. The two digit number either before or sometimes after is the load carrying rating! Could be anywere from 70 to 110. The higher the tire's load index number, the greater its load carrying capacity.

89 = 1,279 pounds
88 = 1,235 pounds
87 = 1,201 pounds
86 = 1,168 pounds
85 = 1,135 pounds etc.

A tire with a higher load index than that of the Original Equipment tire indicates an increase in load capacity. A tire with a load index equal to that of the Original Equipment tire indicates an equivalent load capacity. A tire with a lower load index than the Original Equipment tire indicates the tire does not equal the load capacity of the original.

Typically, the load indexes of the tires used on passenger cars and light trucks range from 70 to 110.

Load Index/Pounds Load Index/Pounds

71 761 91 1356
72 783 92 1389
73 805 93 1433
74 827 94 1477
75 853 95 1521
76 882 96 1565
77 908 97 1609
78 937 98 1653
79 963 99 1709
80 992 100 1764
81 1019 101 1819
82 1047 102 1874
83 1074 103 1929
84 1102 104 1984
85 1135 105 2039
86 1168 106 2094
87 1201 107 2149
88 1235 108 2205
89 1279 109 2271
90 1323 110 2337

A plus or minus of one or two mph isn't enough to worry about on American roads when the speed limits don't exceed 70 MPH. Oh, I'm not saying a short blast at WOT dosn't happen, but unless your running a 12hr. road course and pulling 1.5 G turns you'll never reach the limits of the tire on your C4. IMHO your splitting hairs (are you an engineer?), I still think a (W) or a (ZR) rated tire are so close in specs. that the average Joe that dosen't professionally race should buy which everone your local tire store has on hand and enjoy the drive.

Check out the info off this site:
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35

When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities.

W 168 mph 270 km/h Exotic Sports Cars
Y 186 mph 300 km/h Exotic Sports Cars


While a Z-speed rating still often appears in the tire size designation of these tires, such as 225/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph, 240 km/h; the W in the service description indicates the tire's 168 mph, 270 km/h maximum speed.

225/50ZR16 in excess of 149 mph, 240 km/h
205/45ZR17 88W 168 mph, 270 km/h
285/35ZR19 99Y 186 mph, 300 km/h


Most recently, when the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h indicated by the service description as shown below:

285/35ZR19 99Y 186 mph, 300 km/h
285/35ZR19 (99Y) in excess of 186 mph, 300 km/h


As vehicles have increased their top speeds into Autobahn-only ranges, the tire speed ratings have evolved to better identify the tires capability, allowing drivers to match the speed of their tires with the top speed of their vehicle.

 

[wrenchmantee]

Yea, that little chart helped me find the best size when I went to 18's. I did know about the load indexing and all that stuff. BTW I was a Tire Kingdom Store Manager for 10 years ...TIRES & Repairs are what I do, A.S.E. Tech also. That's a sweet yellow ride you got!

 

[Z07coupe]

I just looked at TireRack.com and found 3 tires with W rating in both 255/45/17 and 285/40/17. Kuhmos and Firestones. Is this what you want, or am I missing something?