Speedometer recalibration with IID Tool

Jimmy Brooks · Oct 14, 2020

Hey guys,I’ve been trying to re-calibrate my speedometer with my IID tool and I’m having a bit of trouble. I am running 265/65/18s with a total diameter of 31.5 inches. I told the IID tool that I had 32 inch tires and I was on the freeway and the speedometer says I’m going “72” MPH but Waze says I’m going 79. I could also tell that I was going much faster then 72 MPH so I’m just a bit confused on what I am doing wrong. I am doing this under Tire Size MSB - IPC. Anyone else had this issue? And for the guys who run the same tire sizes me, what did you put to make it accurate?

Thanks!

avslash · Oct 14, 2020

It is not intuitive. There is another parameter that can be changed that effects the speedometer calculation besides the Tire Size in the CCF.

I apologize, as my IID Tool is currently in Massachusetts and I'm in Texas, so I can't plug it in and look. I seem to remember it being somewhere below tire size in the menu structure, but what it was called is escaping me.

I had the same issue of maxed out tire size adjustment but speedo was still way off. Adjusted this other parameter it is now spot on when compared against GPS.

Maybe someone else can recall the parameter name in the ccf.

DaytonaRS7 · Oct 14, 2020

try...menu>car config> instrument pack>tire radius

Jimmy Brooks · Oct 14, 2020

I had my radius set at 18 thinking that it had to do with wheel radius. I can recall that before it said the radius was 19 because I ran factory oem 19” wheels but I could be thinking of something else. I’ll try that tonight and get back to you.

DaytonaRS7 said:
try...menu>car config> instrument pack>tire radius

Jimmy Brooks · Oct 14, 2020

If I send you a screenshot of the menu would that help you remember what you could’ve changed?

avslash said:
It is not intuitive. There is another parameter that can be changed that effects the speedometer calculation besides the Tire Size in the CCF.

I apologize, as my IID Tool is currently in Massachusetts and I'm in Texas, so I can't plug it in and look. I seem to remember it being somewhere below tire size in the menu structure, but what it was called is escaping me.

I had the same issue of maxed out tire size adjustment but speedo was still way off. Adjusted this other parameter it is now spot on when compared against GPS.

Maybe someone else can recall the parameter name in the ccf.

DaytonaRS7 · Oct 14, 2020

Jimmy Brooks said:
I had my radius set at 18 thinking that it had to do with wheel radius. I can recall that before it said the radius was 19 because I ran factory oem 19” wheels but I could be thinking of something else. I’ll try that tonight and get back to you.

id consider "tire radius" to be the actual [rubber] tire.

not to mention, even if you thought you should plug in info for the wheel, 18 would be the diameter.

Jimmy Brooks · Oct 14, 2020

Here are my settings as of now

DaytonaRS7 · Oct 14, 2020

change...
tire rolling circumfrence to 2517
tyre rolling diameter to 402

Michael Gain · Oct 14, 2020

Thank you for this! It's on my to-do list as well. I'm sure I messed up the settings the first time. I am so grateful for the wealth of knowledge contained on this forum and its members

Jimmy Brooks · Oct 14, 2020

the highest I can set it to is 2385mm for the rolling circumference

DaytonaRS7 said:
change...
tire rolling circumfrence to 2517
tyre rolling diameter to 402

Speedometer recalibration with IID Tool

Jimmy Brooks

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avslash

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DaytonaRS7

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Jimmy Brooks

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Jimmy Brooks

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DaytonaRS7

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Jimmy Brooks

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Jimmy Brooks

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