 Stock tire diameter? |
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| Elliot Cannon |
 Feb 14 2013, 08:41 PM
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#1
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914 Guru  Group: Retired Members Posts: 8,487 Joined: 29-December 06 From: Paso Robles Ca. (Central coast) Member No.: 7,407 Region Association: None 
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I re-measured my old wheels and tires. I thought they were 25 inches in diameter. Turns out they are actually 26.5 inches. Does anyone know what the diameter of a stock, mounted and inflated tire is? With my old tires, my speedometer was spot on at 70 mph and I'd like to keep it as close to that as I can when I buy new tires.
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Replies(1 - 6)
| walterolin |
Feb 14 2013, 09:07 PM
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Senior Member Group: Members Posts: 685 Joined: 30-November 11 From: Louisville, Ky Member No.: 13,838 Region Association: South East States |
Steel wheels, 1970, Michelin 165SR15 measured 25 inches, one on the car, spare on the ground same.
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| Krieger |
Feb 14 2013, 09:22 PM
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Advanced Member Group: Members Posts: 4,721 Joined: 24-May 04 From: Santa Rosa CA Member No.: 2,104 Region Association: None
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Dang pilots! Next thing you know you will be putting a timer on the dash and making "standard" rate turns when its foggy. I have an older Panorama article out and it list the "Theoreticle Unloaded Diameter" of a the original 165R 15 tire as 25.7" Yes I am splitting hairs too. 205/55/16 vs 205/50/16...
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| Krieger |
Feb 14 2013, 09:32 PM
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#4
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Advanced Member Group: Members Posts: 4,721 Joined: 24-May 04 From: Santa Rosa CA Member No.: 2,104 Region Association: None
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Love the new cell. March '95
Attached thumbnail(s) 
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| Spoke |
Feb 14 2013, 10:37 PM
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#5
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Jerry Group: Members Posts: 6,986 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None
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You can calculate the diameter with this formula:
Dia = [Rim size in inches] + 2 x [(Width in mm)/25.4] x [profile]/100 Ex: 165/80/15 Dia = 15 + 2 x 165/25.4 x 80/100 = 25.4 inches Or go to this site: Tire Size Calculator |
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| falconfp2001 |
Feb 15 2013, 12:08 AM
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Pancho Pantera Group: Members Posts: 451 Joined: 5-December 10 From: Downey, CA Member No.: 12,456 Region Association: Southwest Region |
This is the tire calculator that I prefer.
http://www.miata.net/garage/tirecalc.html I found that a 205/65 15 will barely fit width wise but is almost perfect for diameter. Kept my cruising speed the same and looks nice under the fenders. I have pedrini's and the fit is perfect but tight. |
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| 76-914 |
Feb 15 2013, 06:50 PM
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#7
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Repeat Offender & Resident Subaru Antagonist Group: Members Posts: 13,505 Joined: 23-January 09 From: Temecula, CA Member No.: 9,964 Region Association: Southern California
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(IMG:style_emoticons/default/poke.gif) or this and look where I found it http://www.914world.com/specs/tirecalc.php
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