RE: [Chevelle-List] Rear Tire Size

[396guy]

P275/40R17 is 25.7" tall with a 4.3" sidewall, the P275/70R17 is 32.2" tall with a 7.6" sidewall.  In this case, it's the sidewall difference (aspect ratio) that gives it the added height.

 

I suggest you visit http://www.miata.net/garage/tirecalc.html and compare different tire/wheel sizes.

 

The 275/40 tire calculates to 275mm x .40 = 109mm (4.3" - about); the 275/70 using the same formula of 275mm x .70 = 192.5mm and that should be 7.6".  Now, add the sidewall height (x2 since you're taking two measurements into account for the overall height) to the rim size of 17" and you get 17 + (4.3" x 2 = 8.6") for 25.6" (a tenth off).  The 70 series would be 17 + (7.6" x 2 = 15.2") or 32.2".  Voila!

 

Now, which tire will fit is determined not only by the height of the tire but the width and backspacing of the rim.

 

Dale

-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Kelly C. Hanna
Sent: Friday, February 22, 2002 12:18 AM
To: [EMAIL PROTECTED]
Subject: Re: [Chevelle-List] Rear Tire Size

At 12:01 AM 02/22/2002, you wrote:

So a P275/40R17 is a lower profile tire than the P275/60R17?

Yes

 But they have the same tread width and diameter?

No, the tread width will be similar, but the diameter will be smaller as the number gets smaller.

Kelly C. Hanna
El Camino Country
www.hannawoodworks.com