Speedometer self calibrating?

[Gvsukids]

Both of my JTs showed about 2 mph over reality.

Next class action lawsuit for Jeep.

Maybe a long thing needle nose?

Yes.

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[ShadowsPapa]

The analog always 1-2 mi higher is due to the needle spacing being too far from the dial face. Lean your head over a little.

Tires circumstances expand at higher speed and once heated up. Therefore, you can only calibrated the accuracy at either lower or higher speed, not both. If calibrated between 0-50 mph, it will show a couple mph higher when doing 80 mph.

That's called parallax error - and that's not it with these. Even looking straight-on at it, it's off. The needle's end is what I look at, and it's off.
Besides, there's really hardly any gap between the needle and the face of the gauge so the difference in the two planes is minimal.
Been using analog gauges since I was 14, back in the 1970s and this one is just plain off.
Until these JTs, I've never had a speedometer pointer that was literally off as far as these. Even when the odometer is calibrated and the digital speedo is accurate, the needle is wrong.
It's not the parallax error thing where the needle or pointer are on a different plane.
Use the end of the needle or pointer - it's wrong.

 

[ShadowsPapa]

Next class action lawsuit for Jeep.


Yes.

I don't think I'll be suing and end up with $1.54 for my troubles.
Besides, their attorneys would simply blame it on my not using the digital speedometer they supply.

When you own and drive cars with the gear ratios changed, tire changed, other mods, you get used to knowing how to compensate.

Oddly, I found the speedometer and odometer of my wife's 4xe to be as exact as anything I've ever worked on or driven. Yes, it's digital only, no analog gauge to it (because there's so many other gauges and displays crowded into the cluster, I assume) but it's extremely accurate.
Took me a while to get used to having digital only, no analog needle to look at. But the other gauges and indicators were cool to monitor over the more than 3,000 miles we put on it last week.

Oh, back on another topic from earlier - the change in tire circumference due to speed isn't going to change it THAT much..... I've proven that with mine, and done comparing using various tire sizes when choosing the tires I put on mine. Some change, but it's fractional. You can be pretty accurate. On the odometer, it averages out extremely well and the speedometer isn't off enough to throw you into the next mph.
If these were wide racing slicks, yeah, those babies grow a lot and you can see the back of the car jump up when they spin up in the water before the tree. Those tires flex a heck of a lot, these - not so much. I had a car with tires that barely cleared the rear wheel opening lips when I was younger - they all but rubbed when sitting. (L 50s, I think) and they didn't touch much at speed.

Speedometer accuracy is a percentage - when someone says "it's off 3 mph" - at what speed?
It will only be off 3 mph at a given speed- faster and it will be off more mph, slower and it will be off fewer mph. OTOH, the analog gauge speedometer in both of mine always seem to read about 2 mph higher. It's as if the thing is assembled with the needle not at true 0 so it seems to always be that much off - not a percentage but actually always off that much. That tells me it's a gauge issue, not a calibration or gear ratio thing. Those are percentages.

 

[sharpsicle]

Next class action lawsuit for Jeep.

You'd have to show that a speedometer reading 1mph or 2mph above actual speed is a safety hazard.


....good luck....

 

[Gvsukids]

Took me a while to get used to having digital only, no analog needle to look at.

First thing my wife wanted was the digital speedometer at the top of the display because the analog one was too far off center.

 

[ShadowsPapa]

First thing my wife wanted was the digital speedometer at the top of the display because the analog one was too far off center.

Really?
While it's true that most have historically been centered above the steering column and thus the driver's face, there's been speedometers in the past that were so wide, the left and right ends were clear off about where this one is now and talk about parallax....... the needle was often well off the gauge face not to mention the distance clear over to the left or right of the speedometer.
Seems to me the early 60s Ford - like a Galaxy, had a speedometer that took the whole width of the cluster area and the divisions were a guess at best. The numbers in the middle of the speedometer range were often very close together in those old wide speedometers.
Even being off like these are, they are better than what we had when I learned driving.
Not a fan of digital - it's just not how I work when judging things like speed. Digital is too black and white with no "this is how close you are to the next level" visually. Just don't like 'em.
No choice in a Wrangler 4xe, though - oddly, the tach and the Kw meter for usage or charging are analog type gauges with a needle! Weird.

 

[ShadowsPapa]

You'd have to show that a speedometer reading 1mph or 2mph above actual speed is a safety hazard.


....good luck....

I can prove it beyond a shadow of a doubt. Any doubters can drive with my wife in the passenger seat and have her think you are speeding. Trust me, it's a health and safety hazard LOL
I've told her over and over - the speedometer is reading high! Then I pass a radar sign and show her, see - I'm going exactly 35 and look at how the speedometer is reading about 37 (small town - they'll nail your butt)

 

[Lunentucker]

My digital, analog, and GPS always seem to match perfectly. It's probably just another advantage of having a Mojave. It just gets better and better! 🟠

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