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Larger Tires & Speedo / Transmission Shift Point question

sh00ter

By sh00ter
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sh00ter Enthusiast

sh00ter

Posted
Posted (edited)

I searched in the Wheels, Tires, & TPMS section but didn't find the info I need.

 

My truck will come with 275/55R/20 on Crew Cab GMC. I selected the All Terrain option but I suspect they'll really be street tires. My dealer will give me credit for the tires that come on it & I need to select what I got get for the exchange . I'd like to put a great looking tire that's maybe slightly larger & better looking. The questions is: can the dealer reflash the computer to reflect correct speedometer readings & change the transmission shift point accordingly?

 

A related question is that I only need something that will occasionally be in mud here in the Southeast. But, I still want a tire that will be quiet & a good rain tire. Any suggestions will be appreciated.

Edited by sh00ter
RyanbabZ71 Senior Enthusiast

RyanbabZ71

Posted
Posted

Have you asked the dealer? For the GMT800/900 models Gm would not do any programming outside of the stock tire sizes so you either leave as is or get a custom tune/handheld programmer

  • Like 1
sh00ter Enthusiast

sh00ter

Posted
  • Author
Posted

No I haven't asked because I don't have the truck yet. I recall having it done on a Duramax 2500 several years ago but they only had a limited choice of sizes built into the programmer. I don't want to go really large but maybe up a notch or two.

TJay74 Senior Enthusiast

TJay74

Posted
Posted

Dealer can not reprogram for any other size than stock, heck they don't even program for stock. All of the stock tires have the same rolling circumference.

 

Your only option will be aftermarket. Either invest in the hypertech tire calibrator and a custom tune (which could put your warranty at risk).

  • Like 1
1kwik72 Enthusiast

1kwik72

Posted
Posted

Shooter I am in the same situation as mine will come with the all season tire (no other options with 6.2 and max tow). I have all the equipment to program the truck myself but it doesn't do me any good because all the stock size tires are all within a quarter inch of each other. I dont want to mess with an aftermarket tuner so my options are limited.

 

I am pretty sure I am going to go with Cooper Zeon LTZ in the stock size. They were recommended by my buddy at Discount Tire, and they have decent reviews. I also have a customer with them on his Dodge and he really likes them and said they are quiet. I briefly entertained running 305/50/20s which are about an inch wider and the same height but thinking about it I don't want to deal with them rubbing without a level kit.

 

Craig

sh00ter Enthusiast

sh00ter

Posted
  • Author
Posted (edited)

Shooter I am in the same situation as mine will come with the all season tire (no other options with 6.2 and max tow). I have all the equipment to program the truck myself but it doesn't do me any good because all the stock size tires are all within a quarter inch of each other. I dont want to mess with an aftermarket tuner so my options are limited.

 

 

I don't really want to go the aftermarket programmer way either. I

choose the AT tires when the order was placed & think it will come

with Goodyears which I'm not crazy about. My dealer has already said

he'll swap them or give me credit toward a new set. If he has a truck on

the lot with Bridgestone Dueler AT tires in the stock size, I'll

probably just ask him to swap those out. I've had great results with

them before.

Edited by sh00ter
DanielAcosta Enthusiast

DanielAcosta

Posted
Posted

My dealer did a free reprogram, but was limited to sizes that are "stock" so it only made a slight difference. I invested in a Hypertech and it was worth it. My tires are 2.5 inches taller than stock, so if yours are only 1/2 inch or less taller than stock it might not be worthwhile. Coopers are highly rated, but according to my Discount Tire dealer not as quiet or long-lasting as the Toyos, which actually have a tread life warranty. I had two sets of Toyos on my Tundra; the first set still had life left after 60K miles. 15K with the Toyos on my Sierra, and still totally impressed. Quiet on the highway and great off-road, rain, mud, snow. Just did some rough rock crawling this weekend and I was the only vehicle that didn't air down, still did great.

  • 10 months later...
skwr1 Enthusiast

skwr1

Posted
Posted

My dealer did a free reprogram, but was limited to sizes that are "stock" so it only made a slight difference. I invested in a Hypertech and it was worth it. My tires are 2.5 inches taller than stock, so if yours are only 1/2 inch or less taller than stock it might not be worthwhile. Coopers are highly rated, but according to my Discount Tire dealer not as quiet or long-lasting as the Toyos, which actually have a tread life warranty. I had two sets of Toyos on my Tundra; the first set still had life left after 60K miles. 15K with the Toyos on my Sierra, and still totally impressed. Quiet on the highway and great off-road, rain, mud, snow. Just did some rough rock crawling this weekend and I was the only vehicle that didn't air down, still did great.

What benefit did you notice from your Hypertech speedometer calibrator, beside an accurate speedo? I'm considering buying one instread of an actual programmer. Thanks!

DanielAcosta Enthusiast

DanielAcosta

Posted
Posted

What benefit did you notice from your Hypertech speedometer calibrator, beside an accurate speedo? I'm considering buying one instread of an actual programmer. Thanks!

It will correct the shift points and V4 operation, which in turn improves your fuel economy. After 34K miles I'm still averaging 20mpg overall, which seems pretty good to me for a 4wd lifted truck with a stock epa rating of 16/22/18. Take time to calibrate yours with a gps for best results. Even though my tires are 34 inches tall, the Hypertech entry that worked best for me was 33 inches, which is the height of the tires when compressed by the weight of the truck. Good luck.

skwr1 Enthusiast

skwr1

Posted
Posted

It will correct the shift points and V4 operation, which in turn improves your fuel economy. After 34K miles I'm still averaging 20mpg overall, which seems pretty good to me for a 4wd lifted truck with a stock epa rating of 16/22/18. Take time to calibrate yours with a gps for best results. Even though my tires are 34 inches tall, the Hypertech entry that worked best for me was 33 inches, which is the height of the tires when compressed by the weight of the truck. Good luck.

Thanks a lot...mine is on order!

skwr1 Enthusiast

skwr1

Posted
Posted

It will correct the shift points and V4 operation, which in turn improves your fuel economy. After 34K miles I'm still averaging 20mpg overall, which seems pretty good to me for a 4wd lifted truck with a stock epa rating of 16/22/18. Take time to calibrate yours with a gps for best results. Even though my tires are 34 inches tall, the Hypertech entry that worked best for me was 33 inches, which is the height of the tires when compressed by the weight of the truck. Good luck.

With a "Tuner" one should return it to "stock" when going in for service...with the "Speedometer calibrator" is this necessary? Can the Hypertech unit get messed up if the shop flashes your truck?

Thanks again!

DanielAcosta Enthusiast

DanielAcosta

Posted
Posted

With a "Tuner" one should return it to "stock" when going in for service...with the "Speedometer calibrator" is this necessary? Can the Hypertech unit get messed up if the shop flashes your truck?

Thanks again!

Yes, it will get messed up if you don't return to stock before having any ECM/BCM etc work done by the dealer. If they are just doing routine service, no big deal you can leave the Hypertech tune installed. But if they are plugging into the port under your dash to make any changes, return your truck to stock, let them do their thing, then program the Hypertech again. Takes about 10 minutes to return to stock, then another 10 minutes later to put the tune in again.

DanielAcosta Enthusiast

DanielAcosta

Posted
Posted

Yes, it will get messed up if you don't return to stock before having any ECM/BCM etc work done by the dealer. If they are just doing routine service, no big deal you can leave the Hypertech tune installed. But if they are plugging into the port under your dash to make any changes, return your truck to stock, let them do their thing, then program the Hypertech again. Takes about 10 minutes to return to stock, then another 10 minutes later to put the tune in again.

Just to clarify, the speedometer calibrator is the same as a tune because it reprograms the truck's ecm, so treat it just like a tuner even thought all you're changing is the tire size to correct the speedometer/odometer. For mine, the most accurate results were obtained by putting in a 33 inch tire size (even though they are 34's) because 33 is the height with the weight of the truck on the tires. I did a lot of experimenting in 1/4 inch increments, then checking with two gps's, before finally coming up with that result. Take the time to experiment with yours before settling on a final number.

Vanished Enthusiast

Vanished

Posted
Posted

I'm sure it leaves a 'fingerprint' even after being returned to 'stock' that the dealership can find.. If needed...

 

 

Sent from my iPhone using Tapatalk

DanielAcosta Enthusiast

DanielAcosta

Posted
Posted

I'm sure it leaves a 'fingerprint' even after being returned to 'stock' that the dealership can find.. If needed...

 

 

Sent from my iPhone using Tapatalk

Don't know if it leaves a trace or not. Just did another software update at the dealer today, deprogrammed Hypertech before, let the dealer do their thing, then put Hypertech back in. No issues. BTW, if you're on the fence about any of the software upgrades, do it. Every update I've done in the last year has improved something. Today's update improved the a/c operation and phone syncing, along with improved radio and DIC performance. Best to get these done while you're still under warranty, because it's up to the dealer and GM to goodwill these updates after the basic 3/36 expires.

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