Pagoda SL Group
W113 Pagoda SL Group => Drive train, fuel, suspension, steering & brakes => Topic started by: prefervintage on May 22, 2020, 04:26:27
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Hi all...for years, my '69 280SL has had an almost 2:1 relationship between RPM and speed...i.e., ~2 grand, 40 MPH.... ~4,000 RPM, 80 MPH....it's actually a tad bit more on RPM....more like 2200 for 40 MPH...I don't have trans slippage...I've never replaced or tried to lube the speedo cable...what is the norm for these cars? As the tachs / speedos age, has anyone seen much of a reading change? I could see how extra friction in a dry cable could result in a lower reading, but don't believe there would be much effect in the instruments as they age...Should the relationship between the two be exactly 2:1? I had a hard time finding tires for my car...I'm running Uniroyal Tiger Paw AWP II 195/75R14S...one of the few I could still find with a whitewall and as close to the same aspect ratio as I could find to original...thanks in advance for any input...Joe
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The relation between rpm and mph depends on the gear ratio of the differential in your car. See:
https://www.sl113.org/wiki/DriveShaft/Differential
Also search for Hankook Optimo or Maxxis and you'll find lots of opinions:
https://www.sl113.org/forums/index.php?topic=28832.msg209041#msg209041
https://www.sl113.org/forums/index.php?topic=15847.msg184433#msg184433
Tire sizes: https://www.sl113.org/wiki/WheelsTires/TireSize