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Larger tires. To tune or not?


Crooks

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I put 275/65R20 34.1" tires on my truck. I havent tuned it and dont know if I will. How far off is my speedo and the mileage on the DIC? The AFM doesnt come on as much either. I wont do anything that might void my warranty.

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Check it with a Garmin or something. They're right on and then you can see the difference on your speedo. If you fear voiding your warranty don't tune. The AFM will rarely engage now since the larger rotating force of the heavier tire. I have 35's on my Cummins and at 60mph on the dash the Garmin reads 67-68. You may be able to get a hand held just to correct the speedo with out any issues with warranty.

 

 

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Use this site http://tire-size-conversion.com/tire-size-calculator/ and enter in the before and after tire size. Looks like low speed only varies about 1-2 mph, but at 70 mph it says it will be off by almost 5mph. Also dont have a link but read on another post that GM can now see how many times the ecu has been flashed, so if you want to keep your warranty I would check to see if a dealership can adjust it. I would love to flash my 14 since it made such a huge difference on my 08 but think I'll wait a few years.

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I put 275/65R20 34.1" tires on my truck. I havent tuned it and dont know if I will. How far off is my speedo and the mileage on the DIC? The AFM doesnt come on as much either. I wont do anything that might void my warranty.

 

62 on speedo is 65 mph actually

71 on speedo is 75 mph actually

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I put 275/65R20 34.1" tires on my truck. I havent tuned it and dont know if I will. How far off is my speedo and the mileage on the DIC? The AFM doesnt come on as much either. I wont do anything that might void my warranty.

 

I talked to my dealer last week about getting mine adjusted from them; right now they said they can only do 35/36" tires but they will have more in the future. I also said something about getting the programmer and doing it myself and they said I'm better off dealing with it the way it is now because GM will try to blame anything involving warranty on whatever I connect.

 

These guys told me that someone did a leveling kit and got in a wreck which people got hurt, airbags did not deploy and they tried to blame the customer for putting on the leveling kit. Basically they are going to point the finger at you for anything but they have to actually prove that you did something to make it happen.

 

Your size is not drastic enough, I would just deal with it the way it is and know that your mileage is off and getting better mpg than it says

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Means you will have more miles on the truck than the odo will actually be showing if you don't correct.

 

Exactly hes going further than what the truck can calculate.

 

OP, I think getting a tune is a must when changing the tire size. Even if all you do is have it calibrated for tire size. But if you are gonna tune it, might as well get it running better too and get some extra HP out of the motor.

 

Blackbear Performance has great tuning options.

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Exactly hes going further than what the truck can calculate.

 

OP, I think getting a tune is a must when changing the tire size. Even if all you do is have it calibrated for tire size. But if you are gonna tune it, might as well get it running better too and get some extra HP out of the motor.

 

Blackbear Performance has great tuning options.

 

Doing a tune to get HP will completely void warranty which he doesn't want to do

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Doing a tune to get HP will completely void warranty which he doesn't want to do

 

Even just reprogramming is going to leave a log file on the PCM which technically is a warranty voidable offense according to GM. So either way he's gonna have to deal with it. Gotta pay to play.

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Even just reprogramming is going to leave a log file on the PCM which technically is a warranty voidable offense according to GM. So either way he's gonna have to deal with it. Gotta pay to play.

 

I agree that's why I said to just leave it and deal with it the way it is. If it was a larger lift and larger tires I would look into it.

 

Technically GM cant void your warranty just like that but if something goes wrong you will have to fight them for it in court and by that time you will be fed up with GM all together.

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I am pretty sure the dealer can reprogram your tire sizes. Did it on my 04< cost half an hour of labor and the speedo/odometer will read true. Give them a call, worst they can say is no.

 

On another note, how good it the Blackbear tune? What kind of numbers does it truly get/gain?

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I am pretty sure the dealer can reprogram your tire sizes. Did it on my 04< cost half an hour of labor and the speedo/odometer will read true. Give them a call, worst they can say is no.

 

On another note, how good it the Blackbear tune? What kind of numbers does it truly get/gain?

 

 

 

I talked to my dealer last week about getting mine adjusted from them; right now they said they can only do 35/36" tires but they will have more in the future. I also said something about getting the programmer and doing it myself and they said I'm better off dealing with it the way it is now because GM will try to blame anything involving warranty on whatever I connect.

 

 

According to mine they cant do anything for these trucks yet

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