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356 Tires, Types, Sizes

September 23, 2010 | Research & Identification

Based on contributions from John Audette, Stan Hanks, Linus Pauling Jr., Carl Swirsding, and many others

 

A frequently discussed topic is tires for our cars: what fits, similarity to original equipment, rim size, etc. Below is a list of tires that are used on the 356, and information on calculating tire size. If you have comments or additions, please email Barry Lee Brisco, Website Technical Editor, at barry.brisco@356registry.com .

The 356 Registry is making this information available for your use and does not make any specific recommendations on any information contained here. Please read the Full Disclaimer at the bottom of this page.

Comparative Tire Sizes

 

Size Sidewall Height (mm/inches) Circumference (mm/inches) % of Stock Fits Rim Brands
165/78 128.7/5.1 2029/79.9 100% 4.5" or 5.5" Michelin XZX (hard to find!), Michelin X Stop, BF Goodrich (3/4" whitewall), Dunlop D20, BF Goodrich Silvertown (2 1/4" whitewall), Nankang (Sears), Goodyear Centred (185R15)
165/80 131.8/5.19 2024/79.7 99.7% 4.5" or 5.5" Kumho Powerstar 758 (discontinued in 2010), Vredestein Sprint Plus and Sprint Classic, Nexen SB802, Nankang CX668
175/70 122.5/4.8 1966/77.4 96.9% 4.5" or 5.5" Michelin Rainforce MX4, Pirelli Cinturato
185/65 120.3/4.7 1950/76.8 93.4% 4.5" or 5.5" Bridgestone Potenza, Conti CH95, Dunlop SP Sport A2 Plus, Falken ZIEX ZE512, Kumho Powerstar 758, Michelin Artic Alpine, Michelin MXV4 Plus, Michelin Rainforce MX4, Michelin Symetry GNX, Pirelli P250, Pirelli P2500, Yoko Avid T4, Yoko Guardex 600
185/70 129.5/5.1 2010/79.1 99.0% 4.5" or 5.5" Michelin XWX, Vredestein Sprint Classic, Vredestein Sprint +
195/55 107.3/4.2 1870/73.6 92.2% 5.5" Kumho Ecsta Supra 712, Nitto NT250
195/60 117.0/4.6 1931/76.1 95.2% 5.5" Conti CH95, Dunlap Qualifier TR, Michelin Artic Alpin, Michelin MXV4 Plus, Michelin MXV4 Plus XSE, Michelin Pilot XGT H4, Michelin Rainforce MX4, Michelin X-One Durablack, Nitto NT 460, Pirelli P6000 Sport Veloce, Semperit Direct Grip M828, Yoko Avid H4, Yoko Avid T4, Yoko Avid Touring, Yoko Guardex 600, Yoko Guardex F720
195/65 126.8 1993/78.5 98.2% 5.5" Conti CH95, Dunlap SP Sport 5000V, Goodyear Eagle LS (H), Kumho Powerstar 758, Michelin MXV4 Plus, Michelin MXV4 Plus XSE, Michelin MXV4 XSE, Michelin Pilot Alpin, Michelin Pilot Primacy, Michelin Pilot XGT H4, Michelin Rainforce MX4, Michelin Symetry GNX, Pirelli P6000 Sport Veloce, Yoko Avid H4, Yoko Avid T4, Yoko AVS dB, Yoko Guardex 600


Calculating Tire Dimensions

Tire diameter is calculated using the following formula:
(Width of Tire X Aspect Ratio X 2) + Wheel Diameter = Tire diameter

Here's how to use that formula using the 165/78 size as an example.


Drawing Courtesty of TireRack
Tire Width
The first number - 165 - is the width of the tire in millimeters, measured from sidewall to sidewall. To convert to inches, divide by 25.4 In this example, the width is 165mm or 6.50".

Aspect Ratio - Sidewall Height
The second number - 78 - is the aspect ratio. This is a ratio of sidewall height to width. We have calculated the width of the tire to be 6.50". If we multiply 6.50" by the aspect ratio of .78, we find that the height of one sidewall is 5.07" (or .78 x 165mm = 128.7mm, the number used in the chart below).

Outside Diameter
To determine the outside diameter of a tire, take the sidewall height and multiply by 2,(remember that the diameter is made up of 2 sidewalls, the one above the wheel, and the one below the wheel) and add the diameter of the wheel to get your answer. In our example: (165mm x .78 x 2 = 257.4mm) + (381.0mm (15")) = 638.4mm or 25.1"

Circumference
This can be a helpful measurement in determining the accuracy of your speedometer. The stock circumference is 79.9". By computing the circumference of your tires, and comparing it to the stock circumference, you can calculate a percentage deviation that you can then apply to your speedometer readings. For example:

  • Stock circumference: 79.9"
  • Your tires: 185/65
  • Your outside diameter: 24.5"
  • Your Circumference: 76.8" [formula is (outside diameter) x (3.14)]
  • % of Stock circumference: 96.2%
  • Speedometer adjustment: substract 3.8%

So in this example, your actual speed is at 96% of what your speedometer indicates. If it indicates you're going 70mph, your actual speed is 67mph.


Other 356 Registry Articles on Tires
Tire Inflation Pressures
Tire Safety and Date Codes
Tires With Tubes – Original Yes, Needed? No
Wheel Weights and Types

Tire Resources Online
www.tireindustry.org
http://www.apa.ca

3 Comments

Profile missing thumb
Edwin Ek
April 08, 2012 at 9:35 PM
Wonder if there is a mistake in this very useful tire chart. 165 80 tires are shown as having a smaller circumference than 165 78 tires. Greater overall height, the d in the formula for circumference pi*d, gives greater circumference. 80 sidewalls are taller than 78's.
Profile missing thumb
Edwin Ek
April 08, 2012 at 9:35 PM
Wonder if there is a mistake in this very useful tire chart. 165 80 tires are shown as having a smaller circumference than 165 78 tires. Greater overall height, the d in the formula for circumference pi*d, gives greater circumference. 80 sidewalls are taller than 78's.
Profile missing thumb
Paul Allen
July 30, 2016 at 6:39 PM
Corrected chart and excel file here: http://forum.porsche356registry.org/viewtopic.php?f=1&t=27101&start=255#p270160