Anyone who has been on the board for a while is probably familiar with the discussion thread about moving one’s 240 from a 14 inch wheel to a 15 inch wheel. I too have been mulling this over for more years than I care to admit. Recently, I was reviewing all the members’ input again and had an interesting realization – the speedometer gearing for all the subject cars.

The speedometer on my ’79 240 sedan (14 inch and 175 x 80?) was a 0.980 factor. The speedometer on my ’89 240 wagon (14 inch and 185 / 80) is 9800 (due to the electronic sender it is in pulses per unit). The speedometer on my mechanic’s 85 240 turbo wagon (195 / 60 x 15) is a 0.980 factor.

A consideration implied in some of the discussion thread was the assumption that the speedometer for a wagon was matched to its wheel / tire size. Yet the above data suggests that Volvo may have chosen the “98” factor to be in the middle of the error band for all 240 versions. It would also be interesting to see what the 740s used. I suspect is was a “98” version also.

If I’m missing something, maybe someone on the board can point that out. If Chris Herbst still visits the board, he may have some good insight, as I believe he was a Volvo mechanic for a while?

Thanks in advance for your consideration of this question.

Nick . . .