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I was at the dealer today getting my windshield washer fixed, they were slow, only 8 cars scheduled so I took the opportuntiy to discuss bigger tires.......I asked the service writer "what is the biggest tire I could put on my truck without voiding the warranty" Actually got an honest reply I think...."GM has a policy to void warranty on anything bigger than next size up" (meaning 265's I suppose). He went on to volunteer that "they can re-program the speedo for any size tire, but they can not re-program the ABS system or the tranny shift points." GM is most concerned about Tranny shift points with bigger tires making the tranny shift too soon? or is it too late? ABS I had not heard before, but bigger tires seems to confuse the ABS system which is calculated on tire size, weight, traction slippage when braking etc.


Interesting explanation, anyway, after 36K you can put whatever you want on the truck and takes your chances and they can program for it at a cost of course and I don't know what they charge to do it.


I have 35K now on the original Firepops and looks like I can safely get 5K-10K more then they have to go!


Have a great Christmas Holiday to Everyone!
 

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Very interesting info. from your service writer. I guess it would make sense that 265's might be o.k. since half tons with the Z 71 package come with 265's. I upgraded to 265's....only notice the speedo and odo are off.....until Mr. Quadzilla makes things right tomorrow.


Thanks Again for the info.


Wayne
 

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I know that with a programmer you can run any tire that you want and you can change the shift patterns and change the speedo to make it read correctly. Just and FYI, if you are running anything else on your truck you can still install the program and just change the tire size so that the speedo will read correctly..
 

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From what I'm told, the only things you actually CAN change with the stock programming is for the ABS. The Stealer told me he fixed for the speedo, but the GPS still reports the same error with my 265's.


--Rob
 

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Same here only with 285's.Service writer said they could calibrate ABS to 265's only,charged 20 something.Speed-o was still off until corrected by Predator,the only thing its good for.
 

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How far off was your speedo off? I know that changing tire size will effect your speed but only going up one size....to the naked eye this change really should go unnoticed. I also think speedo shows a faster speed than you are actually driving from the factory..even with stock tires.
 

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My 285's on my previous 2002 and now my 2004 have mad the speed-o be off by 3mph.


My dealer said there wasn't a problem with warr. but I think I'll get a second opinion. Haven't had any trouble with shift points either. A tad when towing at 65mph but I can live with how it's working now that I have the 5th gear lock out. Why didn't they have that when the Allison first came out beats me.





cmc
 

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Went to the dealer yesturday and they tried to change my ABS...they said they could not...I have read that you can!


Bullseye, can you get info from your dealer about how they would go about doing this...the local GM could not figure it out!
 

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Bigger tires do not void warranty. That would brake a federal law.


Now, if they caused a problem (a warranty issue) that was caused by the tires (and the dealer has to prove this beyond a reasonable doubt), then that could void your warranty. Not the mere fact that you put bigger tires, 4" exhaust, K&N filter, mod boxes, programmers, seat covers, etc.!


Federal law prohibits dealerships from voiding warranty with any aftermarket truck item, whether it be performance or cosmetic.
 

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MacGordon said:
Bigger tires do not void warranty.

This sounds good in theory, but the truth of the matter is, my last Chevy had its ENTIRE warranty voided due to aftermarket modifications, even though no modifications ever caused any issues. Luckily I made it through the 3/36 without any issues short of an air bag sensor, but it really turned me away from Chevy for several years.


I'm sure I might have been able to win a legal case, but who can afford to go against GM in a legal matter.
 

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We used to call that 'Fighting CityHall'. Maybe win but at what cost? The legal fees could buy one a new D*dge.
 
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