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>> For years, many people have been reporting to me as much as a 10 MPH error on the 9000 when traveling at freeway speeds (reading high).
I've had five Saabs (3 9K's) and only my '95 Aero has shown any significant speedo error (~6% fast). It aggravates the hell out of me, as I'm constantly figuring in my head, "Now if I want to really go 65...94% of 65 is...." I sometimes feel I need to carry a calculator in the car.
>> ...mileage markers on the freeway and a stopwatch), and was shocked to see that I was going about 60 mph when my speedo indicated 66 mph.
Mileage markers are usually close, but I wouldn't trust them on a short-run test, as you may run into one or a series that are incorrectly spaced. IOW, check it every mile for 20 miles with a stopwatch.
>> Oh, and when I measured the 3% error at 60 mph, my car had the automatic transmission.
So it now has a 5-speed? If so, that is likely your problem. Speedo gears are calculated for car models, specifically for wheel/tire sizes. If you installed a 5-speed in your car it likely has the wrong speedo gear for it. After much general yet diluted discussion here, I have yet to figure out what is involved in changing the speedo gear on a transaxle.
Even then you'd be guessing, unless you found the specific gear for your car.
>> I believe the wider wheel stretches the tire slightly, and decreases the overall rolling diameter slightly, but to the tune of 7% ???
No.
>> Does anyone else think that a 10% speedo error is a bit much?
Yes. That would aggravate the hell out of me, but at least it's easier to figure the correct speed with a 10% error than 6% like I have.
You could try going to a larger tire and wheel size to compensate somewhat. An Aero or Super Aero wheel would allow placing 205-55-16 tires on your car, which by my calculation would lower your error by 4%, only a partial success.
If it turns out that changing the speedo gear is easy and a number of different gears are available from, trial and error might be the way to go here. Your '87 may be a cable-driven speedometer, yet I think my '95 is electronic, so I don't know how both are driven in the transaxle.
, Tue, 6 Mar 2001 19:17:08, Mon, 5 Mar 2001 19:01:18
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