Speedometer Calibration

dllubin

dllubin

Don
I checked my speedometer calibration yesterday against a GPS and found that it reads about 5 mph low at 50 mph. I've never checked it against a GPS before as the last time it ran, a GPS cost thousands of dollars. Don't know if it has always read this high or not. One contributor is running 185-60/13 tires but that would only contribute a 2.8% decrease compare to the 145-82/13 tires the car came with from the factory. I'm seeing being about 10% off.

Are there any options on speedo cable gears, or calibration of the speedometer itself?
 
I got one of these, because I too am lazy to actually solve the problem. :)

I have tested it is a few cars and it is very accurate and updates quickly. All of my Fiat speedos are off because of age and the 185/60/13 tire issue. I kept trying to memorize the offset for each car, but finally gave up. This device is pretty small, so the more "features" you try to display, the less useful it is. If you click thru and look at the sample screens, I use the screen with the speed in large font on top, then the time and voltage shown in small font down below. It is probably over priced, but it is nice to know how fast I am going with a high degree of precision rather than guessing.
 
To me that seems rather affordable for a standalone GPS unit. But I've never shopped for them so don't really know. Kind of cool; could completely replace the speedo on a custom dash.

Don, I don't believe they are user calibratable. But a speedo repair shop should be able do it.
 
That looks like a nice unit, especially for the price. Right now, I've got a Garmin GPS mounted on the ash tray. I used to use it before I had a car with one built in. When I bought it in 2007, I'm sure I had no thought of ever using it in the X1/9, which was a dozen years in retirement at that point. It was their top of the line trail GPS and has some unusual features like a skydiving app, a fishing app, and the ability to handle multiple mapsets. Back then, I was using it for my bike and geocaching with as USGS topo map, and a Garmin mapset for car navigation.
 
Dr.Jeff said:
That sounds like a whole lot more than just a GPS speedo.

These speedos don't have navigation, etc...primarily speed for the most part.
Here is a bare bones version for $20:
https://www.walmart.com/ip/Car-Digi...MIu9L88Imi5AIVBarsCh0nawWpEAQYASABEgIaefD_BwE
Click to expand...
Yes, that is true. Although these days I would not be surprised if you could find a navigation GPS for about the same price. Seems like those went sub $100 many years ago. If I did not already have this unit, I might look for one like JimD noted. The display on it is very customizable so I might set it to one data field with a big font to show speed. That would be much easier to read than the stock speedo. It has a trans reflective LCD display so bright sunlight does not affect it, and it has a backlight for night.
 
dllubin said:
Although these days I would not be surprised if you could find a navigation GPS for about the same price.
Click to expand...
You're probably right. With the advent of all these features available on smartphones, the demand for standalone devices must be small. But for what we are talking about (to use as a car speedometer) these are great. When I was looking at them online, I noticed most are featured for use on bicycles, or other sporting activities (must be battery powered). But the ones I referenced can be hardwired for power.
 
Easy to solve. Remove the glass from the speedometer. Pull the dial. Use gps to drive 50 km/h and put the dial back at 50 km/h. Have someone help you to prevent getting of the road.
 
Mxgrds said:
Easy to solve. Remove the glass from the speedometer. Pull the dial. Use gps to drive 50 km/h and put the dial back at 50 km/h. Have someone help you to prevent getting of the road.
Click to expand...
Probably safer and easier to get the rear wheels up off the ground. The hard part will be moving the dial!
 
This is why you should read all posts even if not interested in the topic, I had no idea there were simple stand-alone GPS speedos. I have been using an app on my phone but tend to walk away from the car leaving my pone on it's magnetic holder on the dash. This seems so much better.
And, like the rest of you, I find that almost all Fiat speedos are off. The one in my 124 coupe was off so bad I got my label maker out and made little speed stickies to put on the speedo.

And how did we calibrate our speedos back in the day....by using mileage markers on the interstates and a stopwatch!
 
Here are a couple pictures I took this AM. The screen is pretty small, but the unit seems bigger than it needs to be. I have it perched on top of the gauge cluster, but it would sit nicely above the vent to the left of the cluster. I haven't tried that yet, I just opted for straight on viewing for now. It has to be plugged in to the lighter as there is no battery in it. The plug goes into the back of the unit and I really wish it had gone onto the side so that it could sit in front of the actual speedo. The angle it sits at on top of the gauge pod is not ideal depending on where the sun is shining from. The large speed is still visible despite the glare, but the smaller voltage and clock data is washed out. I only noticed this issue because I was late to where I was heading and my car has no clock.
20190827_081837.jpg 20190827_081710.jpg
 
carl said:
This is why you should read all posts even if not interested in the topic, I had no idea there were simple stand-alone GPS speedometers
Click to expand...
Indeed. The subject is about callibrating the speedometer not about installing a second one.
 
JimD said:
It has to be plugged in to the lighter as there is no battery in it. The plug goes into the back of the unit and I really wish it had gone onto the side so that it could sit in front of the actual speedo. The angle it sits at on top of the gauge pod is not ideal depending on where the sun is shining from.
Click to expand...
Jim, looking at your pics I see what you mean. One of the units I saw online is flat so it can be mounted right against the stock gauge if desired, or onto the dash face somewhere. And the power input is on the side (edge). It would not be difficult to bring a switched (and fused) hot lead from somewhere behind the dash up to any of these rather than using the cigarette lighter. The screens are described as a bit larger than some of the others.

The listing has a couple different models with various features. But they are fairly basic, and really affordable. Look at the last image in the listing (to the right) to better see how they are configured. The description tells the differences between the models:
https://www.aliexpress.com/item/400...chweb0_0,searchweb201602_5,searchweb201603_53

They are also available on eBay, just look for the model number.
 
Dr.Jeff said:
One of the units I saw online is flat so it can be mounted right against the stock gauge if desired, or onto the dash face somewhere. And the power input is on the side (edge).
Click to expand...

The flat ones were interesting for sure. If I had not already bought this one, I might try those instead. However, I don't need 2 .... yet.
 
JimD said:
However, I don't need 2 .... yet.
Click to expand...
Understood. Funny, I really don't even need one (I don't drive the car enough to worry about it). But now that I've seen these I will get it just because they are neat and so inexpensive.

One question about them. How quickly do they keep up with speed changes? Depending on the frequency of satellite signal retrieval, and speed of processing, they might lag considerably when you are driving and constantly changing speed? I know the navigation on my old smartphone isn't very accurate at times, when the signal lags. But that might be a cell signal reception issue, don't know.
 
The first use it seemed slow to engage. Apparently it stores the satellites it finds after that initial start up. On the road the speed changes were pretty I identical to what I saw on my Garmin GPS and the Google maps app on my phone. Yes, I had all 3 set up on the dash. Gotta test stuff you know.
 
I think the takeaway from this thread so far is that recalibrating the stock speedo is not easy...to the point that if you need accuracy then the GPS system is the way to go. I know it's not what you asked but 10 years ago all you would have gotten from the original question is....crickets.
 
JimD said:
The first use it seemed slow to engage. Apparently it stores the satellites it finds after that initial start up.
Click to expand...
Thanks Jim. I read some mixed reviews about the response time, but I never put too much validity in online reviews....you have no idea what sort of person wrote it (and there are a LOT of idiots out there, like me :oops:).

I did a little more reading about the "flat" models offered. Basically every seller seems to carry the same units. The C60 is speed only with a little smaller display/digits. The C60S is the same but with a different mounting type. The C80 has speed, time, distance and is a bit bigger. The C90 is the largest and has more display items...frankly too much for my interest. I ordered a C80 for $17 on eBay. It includes a 'post' mount that can be added to the rear, much like some of the common cell phone mounts. Not sure how I would mount it, but decided this might be good for the "outlaw" project that will be a tribute to track cars - but for the street (basically a rusty POS parts car being revived). This, a tachometer, and a couple idiot lights are about all I will need. But I may throw a couple of leftover VDO gauges in if I get motivated (e.g. temp, oil press).

Thanks for bringing these to our attention. ;)
 
You must log in or register to reply here.
Back
Top