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I got my 1987 sedan with a set of Firestone 175/80/14. The car documents say 175SR14. When I found a set of Virgos last year, I had a set of 195/60/15 (Continental) put on them, as I read that this is a compatible 15" alternative. But with the new wheels on the car, I thought they looked a tad bit smaller – subjectively, they don’t seem to fill out the wheel openings like the old wheels did.
Also, the speedometer was a bit more off the mark now. When passing these digital signs along the road telling the drivers the correct speed, I used to see 78 kmh with the 175/80/14 tires when my speedo read 80. Fair enough. But now with the 195/60/15 tires, the speedo reads 80 kmh when my actual speed is 76. Of course, it is just another 2 extra kmh off, but as it all adds up, now the speedo suddenly feels all wrong.
To get a factual grip on things, I finally measured three sets of wheels (all of them with ca 5-8,000 km mileage), and there is a 2-2.5% difference:
Firestone 175/80/14: 1975 mm circumference
Continental 195/60/15: 1926 mm circ.
Dunlop 185/70/14: 1935 mm circ.
I know that the tire calculators aren’t absolutely accurate, there are differences between makes etc. But it still seems that 195/65/15 will be closer to the original 175/80/14 than my current 195/60/15. In the chase for a tire that will fill the wheel openings better and give more precise speedo readings, I will seriously consider going up one size next time I need new tires. I will certainly measure the circumference before I buy.
Comments?
Erling.
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My 240 Page
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