I think I want to get new tyres for my '64 MGB.
The car came with the original '64 steel rims (14" x 4.5"). I currently
have my spare set of 'B tyres (175/70-14) on the car; they're mounted on
the later Rostyle steel rims, 14" x 5.5"
I seem to remember that putting 175/70-14 tyres on 4.5" rims is not
supposed to be a good idea. I've tried to figure out the differences
between the original 4.5" tyres, 165/80-14, and my preferred choice,
175/70-14. Using Neville D. Newman's tires.c program, I found:
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
165/80-14 5.2in 12.2in 24.4in 76.6in 827 0.0%
175/70-14 4.8in 11.8in 23.6in 74.3in 853 -3.1%
185/70-14 5.1in 12.1in 24.2in 76.0in 834 -0.8%
It seems to me that the real issue in wether the rims can carry the tyre
is the ratio between the tread with and the rim width:
Specification TreadWidth Ratio 4.5" Ratio 5.5"
165/80-14 6.5in 1.44 1.18
175/70-14 6.9in 1.53 1.25
185/70-14 7.3in 1.62 1.33
But, I'm sure what to make of this information.
Any words of advice on which tyres to mount on early MGB steel rims?
...robert
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