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If you get bigger tires, you're going to need to adjust the speedo. There's no way around it. Unless you change the rear diff to compensate for the larger tires.
It would just be easier to have the speedo re-calibrated.

Were you asking how big you could go on the '00 Sierra without a lift?
 

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speedo

Newer cars and truck no longer have a cable, (Good & Bad). They are electric.

Someplace on one of my other forum they had a site that will actually help you to calculate what gear you need to change to make the speedo right.

I will have to look around to find it, unless of course some one here knows it.

I forget the math, but when you change tires there is a formula to tell you how far off the speedo will be.
 

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Thats right , I don't have a lift, and I don't want my speedo off at all, but I was wondering if there was any way to have the computer reprogramed for the larger tires at a shop or something like that
You should be able to have that done at a shop, but I wouldn't know what the approx charge would be for it.
Maybe someone else would know.
 

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Here's the deal, I know someone who has 285/75/R17 on the same truck that you drive and has no problems (clearance wise). I have since put 285/70R17 on my '99 Yukon with very little bump on full suspension travel. My speedo is off exactly 6.2%. I simply rely on the math to tell me how fast I am going. I have noticed however that I only calculate it when I see a cop. :biggrin: Now I have read and am pretty sure that the Hypertech Power Programmer will adjust the Speedo if you have changed tire size. You simply plug in your tire size and it automatically adjusts. The PP is about $350-$400 but in addition to an accurate speedo you get improved performance!
 

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Discussion Starter · #7 ·
I would do something like that, but since it is technically a company truck, I would be worried about doing something like a preformance tuner, but I just hate the way the tires look on the truck now, you can see so much weel well above the tire plus who wouldn't want a little more meat
 

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It may not be as big as you want but you could probably do one size bigger. I think you have the 265's on there now, you could go to a 275 with little effect and it may look a little better.
 

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Here's the deal, I know someone who has 285/75/R17 on the same truck that you drive and has no problems (clearance wise). I have since put 285/70R17 on my '99 Yukon with very little bump on full suspension travel. My speedo is off exactly 6.2%. I simply rely on the math to tell me how fast I am going. I have noticed however that I only calculate it when I see a cop. :biggrin: Now I have read and am pretty sure that the Hypertech Power Programmer will adjust the Speedo if you have changed tire size. You simply plug in your tire size and it automatically adjusts. The PP is about $350-$400 but in addition to an accurate speedo you get improved performance!
Jay is right. I've heard Computer will compensate up to 3% after that size its game over. New rolling radius will have to be modified in comp.
 

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Well if you have a 2000 Sierra, you'll have 245/75/R16 stock. If you bump up to 265, your speedo wont change. If you bump up to 285s it will change. I have a Wait4Me custom PCM tune. They did some performance stuff and calibrated for the bigger tires. It was 158 shipped...75 if you mail them your PCM core. ;) I'm happy with it!
 

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I have 275/65/R20s (35/10.5/20) on my truck 03 thay put the speedo off 5 mph but I went and bought a hypertech programmer in gave the power back that the larger tires took away and set the speedo back right
 
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