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[jonsheritahe04]

I made the same mistake with Waze and thought the same as you, must be auto correcting. Since getting the right tire size calibration there is a noticeable difference in the shift points and how hard the machine seems to be working. On the interstate I was seeing mostly 6th gear running close to 2800 RPMs @ 65/70 MPH. Now with the right calibration it’s slightly less than 2k in 8th. Just my un-scientific observation since going to 35s

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[jonsheritahe04]

Get the ZAutomotive extension cable set so that you only have to do it one time.

Thanks for the tip. Just ordered mine

 

[Hootbro]

Your analog gauge is actually displaying about +2 in both pics.

His pictures are not dead center on the speedo but to the left. I would expect there to be some parallax effect of the needle showing more right of center.

 

[Kevin_D]

Also, an easy way to dial in your calibration... without having to measure anything:

1. Go out on a straight road and set cruise at a given speed (ie indicated on jeep 60mph).

2. Use a GPS speed program (Waze will work) with phone not connected to vehicle to get true speed.

3. Use the two speeds to calculate your % offset.

4. Increase your tire size setting by that %. Done!

This is useful since there is a lot of variation in actual tire sizes and it's not really that easy to measure a true tire size.

Take home message, set the tire size properly. It gets the speedo and shift points back in check.

You’ll get more accurate results if you use distance traveled with mile markers over 10 miles vs. the odometer. Then figure the percentage.

Kevin

 

[Gvsukids]

My analog gauge has actually been off a mile or two from the factory so it looks the same.

Why not get that fixed?

 

[John in the Woods]

This thread broke my heart.

I thought my speedo was reset by the dealer when I upped to 37s. But I realized I’d only ever checked it on the speedometer app with my phone plugged in. Sure enough after reading this, I turned off bluetooth and left my phone unplugged. Cruise set at 40 mph on the dash read 45 mph on the phone. A few seconds after I plugged it in, the phone jumped down to 40. As soon as I unplugged it, right back up to 45. Heartbreaker.

The good news: Even with a rack, RTT and an awning, the truck has been doing stunningly well at 80 mph (which I thought was me cruising on I-95 at 72 mph), and I’m getting 10 percent better fuel mileage than I thought. Gotta look on the bright side.

 

[briscoelab]

Well, good news is that you know now! Plus, it will drive even better once you set to correct tire size, since it will get teh shift points back in line.

I’m really glad more people are realizing this. It is very unintuitive how things work when plugged into the USB.

 

[Maximus Gladius]

Doesn’t warranty last longer to if the gauges all look slower than it should be?

(stupid question…. What’s waze?)

 

[Gvsukids]

(stupid question…. What’s waze?)

Similar to Google maps.

 

[John in the Woods]

Doesn’t warranty last longer to if the gauges all look slower than it should be?

(stupid question…. What’s waze?)

Great point!

 

[Lunentucker]

Similar to Google maps.

But tells you where the cops are.

 

[Gvsukids]

But tells you where the cops are.

There's an option on Google maps to add a speed trap.

 

[WILDHOBO]

This thread broke my heart.

I thought my speedo was reset by the dealer when I upped to 37s. But I realized I’d only ever checked it on the speedometer app with my phone plugged in. Sure enough after reading this, I turned off bluetooth and left my phone unplugged. Cruise set at 40 mph on the dash read 45 mph on the phone. A few seconds after I plugged it in, the phone jumped down to 40. As soon as I unplugged it, right back up to 45. Heartbreaker.

The good news: Even with a rack, RTT and an awning, the truck has been doing stunningly well at 80 mph (which I thought was me cruising on I-95 at 72 mph), and I’m getting 10 percent better fuel mileage than I thought. Gotta look on the bright side.

The bad news being that your odometer has gone up too much.

 

[briscoelab]

The bad news being that your odometer has gone up too much.

Running a larger tire, with the computer thinking it is smaller means your odometer reads lower than it should. That's why the jeep is reading a slower than actual speed.

 

[WILDHOBO]

Running a larger tire, with the computer thinking it is smaller means your odometer reads lower than it should. That's why the jeep is reading a slower than actual speed.

If his speedometer is reading 45 instead of 40, it thinks he’s going faster and further than he is.

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