Thanks for your responses guys -- on both boards.
I know better to expect any speedometer to be 100% accurate. And I know the tires I have affect the reading on the speedo -- which happens to be a mechanical (like everything else on the car
) Jaeger that reads up to 140 MPH on the dial as per a question on the BB.
The only reason I posted the question is because it seems to be reading different speeds this year than it did last year. Last year the difference to the true speed was very direct and linear. This year it seems that the faster I go, the bigger the difference between the true speed and the speed that is registered. Nothing has changed on the car -- the tires, suspension, etc. are identical and untouched.
Normally I wouldn't expect a mechanical speedo to be adjustable, but I thought I had read something a while back that indicated that they might be, and I was just looking for confirmation on that particular point. I'm certainly not buying a new speedo, but I thought if it was designed to be adjustable, I'd save myself a few mental calculations as I'm rolling down the road.
--Toronto