My speedometer was broken and I had the entire dash unit replaced. Now the new (used) speedometer is not calibrated correctly. I am comparing it to my Garmin. It is progressively under stating my speed so that by the time I am going 65 mph per the speedometer, Garmin reports I am actually only going 60 mph. Is it possible to recalibrate the speedometer?
It’s seldom worth the cost or the effort…The GPS unit is not the best judge of speedometer accuracy…Instead, find one of those radar speed warning signs that tell you your exact speed as you approach the sign…
Or, in lieu of that, find a cop and blow by him doing what you think may be 85.
When he stops you, ask “How fast was I going, officer??”.
I’m with Caddy. From the looks of it, it requires some special tool. Just correlate your GPS to certain speeds and put a sticker around the regular speeds you’re supposed to go and call it a day.
If we knew the year, make, and model of the vehicle we could better answer.
In my car, for example, resetting the speedo needle requires removing one screw, unplugging the gage cluster, sitting over a cup of coffee in the kitchen, unclipping the plastic “lens”, pulling the needle up and replacing it at a slightly different zero point, and reversing the process. The hardest part of the whole operation is making the coffee.
In my old Toyota pickup, it would have been pretty much major surgery.
On a previous thread, most people said the GPS was very accurate.
Generally a modern GPS is very accurate. Normally they are more accurate than the standard Speedometer. Of course that is not saying much as most OEM speedometers intentionally display more mph than you are going.
The manufacturers don’t want to be taken to court if someone gets a ticket or has an accident due to a readout error.
I notice a few people indicating that their speedometer is not accurate and it is reading too fast. That is to assure that they will be safe, if their measurement is reading too slow and you get caught on injured in an accident related to speed. GPS can be extremely accurate, but the units designed for highway use are usually adjusted to keep you safe and legal in the event of an error in the speed reported by the speedometer.
The best way to calibrate the speedo is with a timed mile test. At 60 mph, you should cover a mile in exactly 60 seconds. Find a straight flat stretch of road marked with calibration markers at one mile intervals, and check the calibration that way.
I expect if you find your speedo to be off, the cheapest way to get it fixed is simply to replace it with an original OEM speedo made for your make/model/year. You’ll probably need to get this from a dealer.
Almost all speedos, even new OEMs, read 2 to 7 mph faster than actual speed. I just figure out how optimistic mine is and adjust my driving accordingly. Slightly bigger tires would also help compensate if your vehicle can take them safely.
If you have an electronically controlled speedometer (it can still have analog style gauges) you can often adjust the speedometer with a hand held tuner. I have one that I used to recalibrate my speedometer/odometer on my Mustang when I had 4.10 gears installed. I also was able to recalibrate the speedometer on my Bronco years ago when I put 33 inch tires and 4.56 gears on it. In that instance changing a value for the speedometer constant whilst the cluster was in a diagnostic mode allowed for speedometer recalibration (I still had to do the math to come up with the proper value to enter though).
A speedo can be recalibrated, but due to legal issues not all shops are allowed to mess with it. Check with local dealers, shops, and/or perhaps DMV office for info on a shop that can do this work.