Computer Reprogramming???

I have a friend that has a 2000 GMC Sierra Z71 1/2 ton,5.3 4x4. He wants to put new tires and wheels on. 275/55/20 I told him he has to reprogram the computer,But doesn`t
believe me. Am I right or wrong? If I`m right,what would it effect,or what problems might occur? Mechanical or electronic,not clearance.
Thanks, Bill
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Bill wrote:

He can get a programmer from Summit Racing...

I have no problems with my 01 Blazer
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Bill wrote:

I think he does have to reprogram. I think the shift points in the tranny and the speed o will be off. But I'm not 100% sure.
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He is going to need a Hyhpertech Power Programmer III. This will allo
him to set tire size so his speedo is right on. It also adds power an for the money works out very well. He will need part number (30023 from them. Look around average price I think is around 350
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He does not "have" to reprogram. Size is not that dif (less than 2" dia) Speedo will be off 4.7% it will read 60 and he will be going about 63. No other problems will result from this small a change.

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