35" Tires, Speedo Calibration and factory warranty...

m3n00b · April 4, 2019

So I'll be lifting and putting on 35inchers.

My warranty states any variance of more than 4% of the speedo will void the warranty. 35s will be a 10% variance. My shop wants to use a superchips flashcal to correct the speedo. Will a simple calibration with no other tuning cause issues if I have an engine rlissue?

Jacoby · April 4, 2019

Technically it could. Any time you jack with the computer the dealer can tell you to go pound sand. Its a risk we all take. 35's are only gonna put you off by about 5mph. I drove my truck for almost a year with the speedo out of whack. If youre worried about it Id just leave it alone and remember youre actually going 5mph faster than what the speedo reads

m3n00b · April 4, 2019

Technically it could. Any time you jack with the computer the dealer can tell you to go pound sand. Its a risk we all take. 35's are only gonna put you off by about 5mph. I drove my truck for almost a year with the speedo out of whack. If youre worried about it Id just leave it alone and remember youre actually going 5mph faster than what the speedo reads

I'm not worried about me driving too fast, I'm worried about the warranty being voided due to mileage discrepancies

Jacoby · April 4, 2019

Ok I answered your 1st question. If the dealer goes in and sees you made a change to the computer they can void your warranty.

Im not sure what you mean by mileage discrepancies? If you bought the truck new then there is no prior mileage to gauge a discrepancy as all the miles are yours. If you bought the truck used then the only way they could determine a discrepancy is if the mileage you have at the time is somehow less than the mileage was when you bought it 2nd hand. You cant roll back the odometers on these things so I don't see that happening.

If a service guy goes out for a drive and says the speedo is off by 5mph I don't think they'll void your warranty. If they do then theyre just being assholes

wforrest08 · April 4, 2019

Must be a aftermarket/3rd party warranty? A lift and tires will be cause enough to deny a claim if the dealer/GM want. Somebody will pipe in and quote Moss Ferguson Act and “they” have to prove that your mods did the damage, ect. Yep that’s all true but there are cases of guys waiting weeks, months, years to get work done/claims paid OR denied and flagged for all future warranty repairs, so your making payments on a truck you can’t use. Then again some dealers are glad to have the warranty work and don’t go looking for things to deny you. Every dealership is different in that regard apparently some have to much work they don’t want GMs warranty money...

Hypertech makes a “tuner” that only corrects the speedo for tire and/gear changes. It won’t do anything else. This is what the “big” Chevy dealer around here uses on the new trucks they lift and sell off the lot. I had them do the level and wheels/tires and this after I bought mine from another dealer. If I would have had to have or do have to have since I still have factory power train left I’ll take it to that dealer since they did it I’m sure they will let it slide unless corporate gets involved.

The problem is no matter which one you use to do it, it will show up on the flash hit counter in the ecm. It counts every time the ecm is flashed then that number is counted against how many reflashes have or haven’t been done by a dealer. So if your truck had a recall and the dealer had to reflash the ecm it would show one extra hit on counter. If somebody else reflashes the ecm then there’s another so two hits. Your motor throws a rod out the side of the block before GM pays the dealer warranty pay on major repairs GM can request pics of damage and/or of aftermarket parts, warrantied parts to be sent to them and for a tech to check if there are any extra hits on the counter so in this example there would be one extra and supposedly it only shows that a reflash was done but “they” can’t see what if any parameters where changed so “they” can assume whatever that tune changed was the problem. If you reflash your current tune back to factory before you take it in then it just shows up as yet another unaccounted for hit on the counter...

If it’s a 3rd party warranty for the power train I have no idea how they would handle this?

2017Darkness · April 5, 2019

19 hours ago, Jacoby said:

35's are only gonna put you off by about 5mph

Not exactly...I have 35's and I'm good until about 45mph. At 50-65mph it's 5mph off, the difference creeps up after that. 73 is about 8 off, 75 is about 10 and it keeps going up from there.

Jacoby · April 5, 2019

Yes exactly I verified it with GPS. There is no way your speedo is accurate till 45mph then all of the sudden its off. Your wheel speed will be different from the get go. It doesn't all the sudden change once you reach a certain mph

2017Darkness · April 5, 2019

43 minutes ago, Jacoby said:

Yes exactly I verified it with GPS. There is no way your speedo is accurate till 45mph then all of the sudden its off. Your wheel speed will be different from the get go. It doesn't all the sudden change once you reach a certain mph

I appreciate your OPINION, but:

https://tiresize.com/comparison/

and I verified mine with 2 types of GPS, one being a GPS radar detector

Vehicle speed is not read at the wheel, VSS is in the transfer case

Edited April 5, 2019 by 2017Darkness

Jacoby · April 5, 2019

Despite what my signature says, I didn’t state an opinion. I was off by “about” 5mph at any speed in my truck. The consensus is on any forum that 35’s put you off by “about” 5mph. While maybe not exact it’s pretty much in that ball park.