Flashing computer for larger tire size question

[Tim99GT]

This might be a dumb question, but i wanted to ask here to see what the general forum population does.

 

Back story:

I have 295-55-20 trail grapplers on my 2014 sierra and have flashed my computer to 33" tires.

 

Questions:

When you guys and gals flash your computers for larger tires, do you flash for the actual tire spec size? Or do you go off of the size of the tire as it sits on the truck?

 

The reason i ask is because my tire's actual spec size is 32.91" tall, however, when on the truck they measure ~ 32". I know this may be splitting hairs but I'm just curious as to if i should reprogram to 32" or say 32.5", or leave it be at 33".

 

What are yalls thoughts on this and how would you flash your computer given this situation?

 

Thanks in advance!

Tim

[RyanbabZ71]

How are you measuring?

 

 

Ryan

[Tim99GT]

I'm not sure i understand your question Ryan.

If you're talking about measuring the tire while on the truck, i use a tape measure and measure from the ground to the top of the tire lug.

[RyanbabZ71]

Yea that's what I was wondering. To get an more accurate measurement mark the ground with chalk and the tire, drive the truck (2 people work best) and mark when it does a full revolution. Should be close to the tire mfg specification. With my 2000 I went with the tire mfg. for example I had tires that were 32.8 per spec, programmer only did .25 increments so I went with 32.75

 

 

Ryan

[crafferty]

In my experience what both of you guys are saying doesn't really matter. For example on my 2012 I don't remember the details but it was lifted with 33's. In my DiabloTrinity the tires were set at like 33.5x12.2r20 (in metric) just a real hairball size. But that's what it took to get my speedo correct. Now in my 2014 silverado with a 6" lift and 35's my tires in metric are 343x56r20 (35x13.5r20). In my intune they are set at 343x51r20 and speedo is once again spot on at all mph. My recommendation would be to convert your tire to metric, plug that in and then move in incrediments of 10 +/- with the aspect ration (middle number).

[NitroDatsik]

How do you flash the computer?

[rockyridge26]

You have to buy one of these

[crafferty]

You have to buy one of these

Don't recommend a product like that for anyone. Those things are worthless when you factor in for a couple more bucks you can get an intune.

[rockyridge26]

Don't recommend a product like that for anyone. Those things are worthless when you factor in for a couple more bucks you can get an intune.

I bought my truck used with a lift already installed and I found that in the box in the center console when I got the truck home lol

[crafferty]

I bought my truck used with a lift already installed and I found that in the box in the center console when I got the truck home lol

Jeez whoever bought that was an idiot, glad it wasn't you.

[Big Whiskey]

To the OP, I've always heard it's best to use the number that your tires actually measure on the truck. Your wheel speed sensors don't care what the manufacturer specs are...only what they really measure.