|Steel rims to alloy
940GL, which has original tyre size 195/65/R15, be fitted with tyre size
205/70/R15 or 205/75/R15?
The original rims are made of steel. I would like to change to 15" alloy
rims, which are normally fitted to a
Volvo 760GLE. How do I get a rough
measurement? A dealer told me that tyre size 205/70/R15 or 205/75/R15 is
not suitable for the Volvo 940GL while other dealers said it can be done.
The original tyres for the 940 (195/65R15) have an overall diameter of
635mm and your suggested replacement is 205/70R15 which has a OD of 669mm.
The difference is 34mm or 5.3% which is way above the 3% that is normally
accepted by the industry. You could use 205/60R15 with an OD of 627mm with
the same rims. I do not have the specs for the 760 wheels, but if you are
thinking of using them you should make sure that the wheel offsets are the
same or else you could have queer handling and heavy steering. Actually,
working out the OD of the tyre is quite simple: 195/65 is worked out as 195x
0.65 = 126.75 As the tyre is round, you will have to multiply this figure by
2 to give 253.50mm.
15" is converted as 15 x 25.4= 381.99mm.
Therefore the overall diameter of the tyre is approximately = 381.99 +
253.50 = 635.49mm.