I bought my W124 from a non M-B dealer who put new 205/60R15's on the 300TE 4M. According to a web site this tire is smaller in circumference by 12% than the 195/65R15's they replaced
Does this mean my speedo will read 12% lower than I'm actually traveling? That seems like a lot. I've paced traffic in known areas and seem to be pretty close to actual speed. Any tips?
Thanks - don't want to attract the constables.
Best,
Hazen

__________________
Hazen Arnold
Happiness is a well stocked
garage.

Actually, i think you misplaced a decimal point somewhere. THe error should be somewhere in the range of 1.2%, which is practically negligable. I run 205/60R15 with no ill effects..

anthony

Going from a 195/65/15 to a 205/60/15 is actually what I recommend. If you want to calculate the error, there is a nice website that someone posted earlier.

http://www.paspeedo.com/calculator.htm

You if you type a speed of 100 mph, its basically taking the percentage difference, and you can see there is less then a 1.2% difference.

SAfe to say if you are doing 100mph, your speedo will be peg under 100mph. That means you ar doing 49.4 mph when it says 50mph. Not much of a difference at all. Enjoy.

__________________
Chirag (Charlie) Patel
--------------------------------------------
- 03 Mercedes S600 Sport TTV12
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- 04 Lexus RX330
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4 Sale:
- 99 BMW M3 E36 Coup with Dinan SC, Upgraded to an RMS Stage 3 with Aftercooler, 12psi, and 500+hp @ flywheel.

Thanks for the response, guys. Decimal points are IMPORTANT! My old algebra teacher would be ticked.
Best,
Hazen

__________________
Hazen Arnold
Happiness is a well stocked
garage.

You don't need to use paspeedo.com, all you need is a calculator, or a piece of paper with old time basic math skills.

One of the nice things about the tire sizes of the last twenty years or so is that you can easily calculate the diameter from the size.

First Number/25.4 X second number as a decimal X 2 + dia.

example: 195/65 - 15

195/25.4 x .65 X 2 + 15 = 24.98" diameter

This is the calculated tire diameter, if you need the circumference, you can simply multiply times pi to get the calculated circumference. The calculated circumference will not be the same as the rolling circumference but close enough for most purposes.

If you wish to compare one tire size to another to determine the speedometer error percentage, simply calculate the two sizes and divide one by the other to determine the percentage difference. The diameter is directly proportional to the circumference, so there's no need to calculate the circumference to derive the percentage difference.

Have a great day,