Converting old tyre size with table: This must be observed

Classic tyre sizes are no longer produced mainly for technical reasons. If you are looking for a suitable equivalent for your classic, you are therefore not only faced with a visual challenge. You also need to know that and to what extent the specifications for the dimensions of tyres of that time have changed. Good thing you're here, because we've provided a table here to help you convert old tyre sizes.

The dimensions of cross-ply tyres are given in inches and the overall height is always 80% of the tyre width. For radial tyres, the tyre width is given in millimetres. The tyre cross-section is given as a percentage directly behind the width of the tread.

Autor: Max Berger
Posição: Venda
Atualizado: 20.10.2023


Vintage tyre table: Conversion at a glance


 Inch measurement Metric measurement
1965-1977  Height
60
 
Height
70
 
Height
80 
5.50-12 165/60 R12 165/70 R12 155/80 R12
5.60-12
6.00-12      
5.20-13 165/60 R13 145/70 R13 135/80 R13
5.60-13 175/60 R13 155/70 R13 145/80 R13
6.15-13 185/60 R13 165/70 R13 155/80 R13
6.40-13 195/60 R13 175/70 R13 165/80 R13
6.70-13 205/60 R13 185/70 R13 175/80 R13
6.90-13      
7.00-13 215/60 R13 195/70 R13 185/80 R13
7.25-13      
7.75-13     195/80 R13
5.20-14 165/60 R14 145/70 R14 135/80 R14
5.60-14 175/60 R14 155/70 R14 145/80 R14
5.90-14      
6.15-14 185/60 R14 165/70 R14 155/80 R14
6.45-14 195/60 R14 175/70 R14 165/80 R14
6.95-14 205/60 R14 185/70 R14 175/80 R14
 Inch measurement Metric measurement
1965-1977  Height
60  
Height
70
 
Height
80
 
7.35-14 215/60 R13 195/70 R14 185/80 R14
7.75-14 225/60 R14 200/70 R14 195/80 R14
8.25-14 235/60 R14 205/70 R14 205/80 R14
8.55-14 245/60 R14 215/70 R14 215/80 R14
8.85-14 255/60 R14 225/70 R14 225/80 R14
9.15-14 265/60 R14 235/70 R14  
5.60-15 185/60 R15 165/70 R15 155/80 R15
6.35-15 195/60 R15 175/70 R15 165/80 R15
6.85-15 205/60 R15 185/70 R15 175/80 R15
       
7.35-15 215/60 R15 195/70 R15 185/80 R15
7.75-15 225/60 R15 205/70 R15 195/80 R15
8.15-15 235/60 R15 215/70 R15 205/80 R15
8.25-15
8.45-15 245/60 R15 225/70 R15 215/80 R15
8.55-15
8.85-15 255/60 R15 235/70 R15 225/80 R15
8.90-15
9.00-15 265/60 R15 245/70 R15 230/80 R15
9.15-15     235/80 R15
      255/80 R15
1949-1964 1965-1970 1970-1980 Since 1960 Since 1980

Height

80-90

Height

50-78

Height

82

Height

75-80

Height

70

Height

65

Height

60

Height

50

 5.20-10      145R10   165/70 R10      
5.20-12      145R12 145/80 R12 165/70 R12      
5.60-12 6.00-12   155R12 155/80 R12        
            165/65 R13    
      145R13          
      155R13 155/80 R13 175/70 R13   195/60 R13 215/50 R13
5.60-13 6.00-13 A 165R13 165/80 R13 185/70 R13   205/60 R13  
  6.50-13 B 165R14 175/80 R13        
    C 175R13 185/80 R13        
  7.00-12 D            
      185R13          
5.60-14 6.00-14   195R13     175/65 R14    
6.00-14 6.45-14   145R14   175/70 R14 185/65 R14    
    B 155R14 175/75 R14 185/70 R14 195/65 R14 205/60 R14  
6.50-14 6.95-14 C 175R14 185/75 R14 195/70 R14   215/60 R14  
    D            
7.00-14 7.35-14 E 185R14 195/75 R14 205/70 R14   225/60 R14 245/50 R14
7.50-14 7.75-14 F 195R14 205/75 R14 215/70 R14   235/60 R14  
8.00-14 8.25-14 G 205R14 215/75 R14 225/70 R14   245/60 R14 265/50 R14
8.50-14 8.55-14 H 215R14 225/75 R14        
9.00-14   J 225R14          
9.50-14   L            
  5.60-15 A 155R15 155/80 R15     195/60 R15  
6.00-15   B 165R15 165/80 R15 185/70 R15 185/65 R15 205/60 R15 225/50 R15
6.50-15 6.85-15 C 175R15   195/70 R15 195/65 R15 215/60 R15  
    D       205/65 R15    
  7.35-15 E 185R15 195/75 R15 205/70 R15   225/60 R15  
6.70-15 7.75-15 F 195R15 205/75 R15 215/70 R15 215/65 R15 235/60 R15  
  8.15-15              
7.10-15   G 205R15 215/75 R15 225/70 R15 235/65 R15 245/60 R15 265/50 R15
  5.25-15              
  8.45-15              
7.60-15   H 215R15 225/75 R15  235/70 R15   255/60 R15 275/50 R15
  8.55-15              
8.00-15 8.85-15 J 225R15 225/75 R15  235/70 R15   265/60 R15  
8.20-15 9.00-15 K            
  9.15-15 L 235R15 235/75 R15  225/70 R15   275/60 R15 295/50 R15
    N            

 

Convert old tyre size: Basic questions

Various key figures and abbreviations provide information about the different properties of tyres, such as ...

  • ... the tyre width (in inches or mm),
  • ... the height ratio (height to width ratio),
  • ... the rim diameter & the load index (maximum permissible load per wheel)
  • ... or the speed index (maximum permissible speed). 
Over the years, the way these dimensions are indicated has evolved. Where classic tyres made do with 2 indices to tell their owners everything they needed to know, modern tyres have up to 5 relevant indices that can be found on the tyre. We will break down what these mean in the next section.


What do the key figures on modern tyres actually mean?

Let's look at the 185 65 H R 13 tyre data and break down the records using the example:
  • 185: Indicates the width of the tread in mm measured from side wall to side wall.
  • 65 : Indicates the height of the tyre wall relative to the tread - here, for example, 65 % of 185 mm, i.e. 120.5 mm.
  • H: Stands for the speed index. H corresponds to a top speed of 210 km/h.
  • R: Indicates that the tyre is a radial tyre.
  • 13: Indicates in inches the diameter of the rim on which the tyre is to be mounted.
However, if you drive a classic, you will notice that some tyre size measurements are given in inches. So our example tyre would show 6.15 x 13 (bias-ply) instead of 185 65 H R 1 (radial). How to arrive at this is shown in the table above.
But before that, a very important question needs to be clarified: When do the tyres of a classic car need to be changed at all?

When does a vintage tyre need to be replaced?

Unlike tyres on everyday vehicles, classic car tyres are rarely changed due to wear. This is because classic vehicles are rarely moved so frequently that the tread wears out even after years. The main reason for replacement is age-related hardening. It brings with it cracks and brittleness, and so a significant safety risk arises with tyres that are too old.

Some sources recommend a change every 10 years, others after 8 years. Depending on the mileage, however, it can make sense to change the tyres of a classic car after 5 to 6 years. A change is also beneficial in the case of longer standing times and flat tyres, and minimises the risk of accidents. 

Info: The age of the tyres can be read off the tyre sidewall: The first two digits of the four-digit DOT number stand for the calendar week, the other two for the year in which the tyre was produced.

Which tyres are better: Radial or bias-ply tyres?

This question is quickly answered. In any case, radial tyres offer greater driving safety than cross-ply tyres. They have been established since the 1980s and have virtually replaced diagonal tyres. You can therefore confidently convert your classic to this type of tyre and thus eliminate a safety risk.

Should the tubes also be replaced when changing the tyres?

Yes, because an inner tube also wears out, even in high-quality designs, and can cause massive pressure marks on the tyre over the years. This has a negative effect on the life expectancy of the tyres. It is therefore advisable to replace the inner tubes when changing the tyres.

Learn more about wheel, tyres and rims

How is a wheel constructed, what is important to consider? For all terms around wheel, tyre and rim, please visit our Youtube channel!

Convert old tyre size and buy the right tyre online

Now you hopefully know which tyre fits your classic and can convert your old tyre size thanks to our table. Replacing old tyres these days unfortunately involves conversion and some compromises. But it doesn't have to be! At Limora, you are guaranteed to find the tyre that visually matches your enthusiast vehicle. From manufacturers like Michelin to Blockley to Dunlop, we offer high-quality tyres, inner tubes and rim tapes.