Speedometer Calibration After Bigger Tires and Lower Gears

[Connor B]

Hello all,

Not sure if this is the right thread to post in so if it is wrong, sorry.

I've been thinking and researching about what I need to do to fix the speedometer so that it reads right after a tire and/or gear change. I've seen that you don't need to change anything to correct the speedo if you only do a gear change. That doesn't seem right though in my mind. I read about a transmission speedo gear that can be changed out and also just an electronic fix as well. I'm not sure which one applies to my truck though.

I also am not sure what needs to be done with my 2011 Ford Ranger XLT 4x4 5-speed manual to fix the speedo after I do the tire upgrade and gear change. I believe I have 3.73 gears now and I will be going to 4.56. I have approx. 29" tires and will be going up to 33" tires after I have the gears changed.

Can anyone tell me what I need to do and confirm what the right thing to do is to correctly calibrate the speedo for the new tire size and gears?

Thanks in advance.

 

[Dirtman]

2011 speedo is digital so must be done via the computer, there are no mechanical cables or gears like older models. Cheapest way to do it yourself is to use Forscan. You'll need a Windows laptop, a OBD2 to USB adapter, and Forscan software. The software is free, an adapter will set you back between $30-$100 bucks. If you don't go that route you'll have to find a local tuner shop and pay them to do it for you. You need to correct the speedo for both a gear change and tire change, both effect the speedometer reading.

 

[Connor B]

2011 speedo is digital so must be done via the computer, there are no mechanical cables or gears like older models. Cheapest way to do it yourself is to use Forscan. You'll need a Windows laptop, a OBD2 to USB adapter, and Forscan software. The software is free, an adapter will set you back between $30-$100 bucks. If you don't go that route you'll have to find a local tuner shop and pay them to do it for you. You need to correct the speedo for both a gear change and tire change, both effect the speedometer reading.

Thanks for the reply. Nice and simple it seems even with a digital speedo. I'll definitely look into that. I was expecting it to be more expensive and harder to do on my own.

 

[RonD]

If you used 35" tires and 4.56 ratio speedometer would still be correct
Actual ratio would be 3.78, so the same, assuming you have 3.73 now

33" and 4.56 would give actual ratio of 4.01, so wouldn't be to far off, if you were showing 60MPH you would actually be going 56MPH
At 40MPH actual would be 37MPH
At 70MPH actual would be 65MPH

 

[gw33gp]

Dakota Digital also makes a calibrator that can be used to correct the speedometer. It is a little more complicated because you must tie into the wires going to the speedometer. I like it because I switch back and forth from 31" to 33" tires with 4.56 gears about four times a year. Once installed it is very easy to recalibrate.

If you are going to need the recalibration just one time, going into the computer yourself or having someone do it is the way to go. Even if you eventually need another change, if you have the equipment and software to do it, it should not be difficult to recalibrate.

 

[Dirtman]

If you used 35" tires and 4.56 ratio speedometer would still be correct
Actual ratio would be 3.78, so the same, assuming you have 3.73 now

33" and 4.56 would give actual ratio of 4.01, so wouldn't be to far off, if you were showing 60MPH you would actually be going 56MPH
At 40MPH actual would be 37MPH
At 70MPH actual would be 65MPH

This is why I like Forscan... You don't need to do "math". It will bring up the factory spec, you just input the new tire size and gear ratio and bleep bloop done.

 

[RonD]

Dakota Digital's new speed converter has Bluetooth and an APP, says you can now do all adjustment from your phone
SGI-1000BT : https://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=1192/mode=prod/prd1192.htm

I didn't think they were that hard to adjust directly, lol

 

[Dirtman]

There just an app for everything these days.

 

[Connor B]

If you used 35" tires and 4.56 ratio speedometer would still be correct
Actual ratio would be 3.78, so the same, assuming you have 3.73 now

33" and 4.56 would give actual ratio of 4.01, so wouldn't be to far off, if you were showing 60MPH you would actually be going 56MPH
At 40MPH actual would be 37MPH
At 70MPH actual would be 65MPH

Thanks for the info.

I am wanting to have a little bit of increased power as well as having stock performance returned. I will be using this to tow my jet ski to the lake every weekend through a canyon so a little more power is what I'm after. I also want a little more power for when I go off-roading too. That's why I chose 33" tires and to go with 4.56 gears.

 

[Connor B]

There just an app for everything these days.

Ain't that the truth lol

 

[RonD]

Thanks for the info.

I am wanting to have a little bit of increased power as well as having stock performance returned. I will be using this to tow my jet ski to the lake every weekend through a canyon so a little more power is what I'm after. I also want a little more power for when I go off-roading too. That's why I chose 33" tires and to go with 4.56 gears.

Then use 32" tires with the 4.56, that would be 4.12, so 4.10, best for off the line and towing power
But would need speed calibration

One of the problems with larger tires is their added weight and the taller stance, so you lose power and MPG