Hey guys, I'm going to be driving to DCS and one of the only concerns I have is that my speedometer reads about 10mph faster than it should read. What should I do? Located in Pittsburgh, PA.
Location: Pittsburgh, PA
Posts: 133
My VIN: 3610
Hey guys, I'm going to be driving to DCS and one of the only concerns I have is that my speedometer reads about 10mph faster than it should read. What should I do? Located in Pittsburgh, PA.
Location: North Bay, Ontario, Canada
Posts: 481
My VIN: 4692
Are your front tires the original size (195/60R 14)? The speedo runs off the left front wheel, so it you've increased or decreased circumference at all, you'll affect the speedo readout. I'm predicting you have narrower or lower profile tires up front than spec (so the wheel has to turn faster to keep up speed). This will artificially inflate your odometer reading as you drive, though.
Not the end of the world for sake of driving your car, so long as you keep your bearings as to how fast you're actually going. A dash mounted GPS will help keep you on track.
Location: Maple Grove, MN (Minneapolis)
Posts: 1,423
My VIN: 05457
Another thought: Do you have the original 85 mph speedometer gauge or a different one (I think 130 mph is the most common replacement)? If the graphic was updated but the gearing on your angle drive was not that would result in your reported speed being off quite a bit.
David Proehl
Location: Pittsburgh, PA
Posts: 133
My VIN: 3610
I have the correct size tires in the front, and I have the 170 mph speedometer.
Location: Maple Grove, MN (Minneapolis)
Posts: 1,423
My VIN: 05457
There it is! That is it. Your gearing is wrong. Either in the binnacle or at the angle drive. Not sure which, but that is what is going on.Originally Posted by Delorean3610
David Proehl
Location: Northern Michigan
Posts: 1,147
My VIN: 1880
Club(s): (DCO) (DCUK)
Or the speedo needle needs to be removed and reseated, pointing a bit lower on the left.
Patrick C.
VIN 1880
Posts: 4,808
My VIN: 3937
Does it read 10 mph faster at all speeds? Or just in the centre of the gauge, for example? I'd assume it doesn't sit at 10 mph when you're parked, but have you compared it to a known speedometer (GPS as suggested) and documented what you find? You might benefit from a co-pilot doing your data recording though and leaving the driving up to you.
Sept. 81, auto, black interior
Posts: 942
1:1 angle drive. OEM ratio is 8:9.
Bill Robertson
#5939
Location: Northern NJ
Posts: 8,581
My VIN: 10757 1st place Concourse 1998
The speedometer head needs to be removed and calibrated. At 60 MPH the cable should be turning 1,000 RPM's. Typically speedometers are calibrated at 60 MPH and checked across the band. The tolerance is + - 5%. If odometer is also reading fast the gearing is wrong. You can check it over a measured mile.
David Teitelbaum
Posts: 942
Wouldn't it be a lot easier just to put a proper ratio angle drive on the car?
Bill Robertson
#5939
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