Work truck tire sizes. Why?!

[BrizzoDaIzzo]

Sorry for the long post.  This has been a headache to try and find “factual” information on instead of “opinions”.  
 

I have a 2019 Silverado work truck V-6 , 6 speed, with 3:42 gearing.  I have a stock suspension. The 2019 work truck comes with three tire options From factory. 

1. 17" 255/­70R17 all-season, blackwall tires (my current tire)

2.  17" 265/­65R17 all-terrain, blackwall tires

3. 17" LT265/­70R17C all-terrain, blackwall tires

 

However, ...

the Silverado Custom  (with the same 3:42 gearing) comes with the following tire opens. 
1.20” 275/­60R20 all-season, blackwall tires

2. 20”275/­60R20SL all-terrain, blackwall tires

3. 22” 275/­50R22SL all-season, blackwall tires

 

 

My current truck has the 17” 255/70R17 all seasons. I love my truck, but I absolutely hate these tires/wheels. They look like baby wheels on a big truck. Way too much fender well free space. Looks like the truck missed “leg day“. 

 

My question is if I purchase the OEM wheels and tires for the custom, is there any issue with them fitting my work truck? As far as I know both trucks have the exact same suspension, body clearance, control arms, wheel well clearance, etc.

 

I was looking at going with the 20”275/­60R20SL all-terrain, blackwall tires. 

 

The only changes that I could forsee that would happen are the following...

 

1. An increase in wheel diameter of current 31.1” increasing to 33”. 
2.a width increase from 10” to 10.8”

3.  A sidewall decrease from 7” to 6.5”

4. A revs/mile decrease from 650 to 612 (affecting speedometer speed by .058%)

5. A new effective gear ratio of 3.22:1

6. A change in tire run pressure from 35psi to 32psi. (Annoyingly setting of my TPMS “low pressure” alarm )

 

several questions....

 

1.will these custom tires fit my work truck? I can’t  Find any reason that they won’t

2. Will the dealer reprogram my speedometer for the percentage difference, and replacard/reprogram my ECM with the new psi setting to 32psi. (Not sure if they will since the Vin number of my truck does not include these tire size as  “options“.) I really don’t want my low pressure alarm going off 24/7. 
3. Will I noticed the change in new affective gear ratio from 3.42, to 3.22? (I’m assuming I won’t since it is the exact same gearing/tire size as the custom. 
 

Man, there sure is a lot to changing a tire size. Almost doesn’t even seem worth the trouble. Am I going down a bad rabbit hole?
 

Just an FYI, I am not interested in lift kits, aftermarket speedometer programmers, etc. . Would like to stick OEM as much as possible. 

 

 

 

 

 

[topgear1224]

Yes if you buy GM accessory wheels the dealer is authorized to change your speedometer. However there is a chart of what is authorized. Don't know if they'll do it with just OEM wheels

Work truck come with tiny tires because they are cheaper for companies, and "unlock" additional performance.



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[BrizzoDaIzzo]

8 minutes ago, topgear1224 said:

Yes if you buy GM accessory wheels the dealer is authorized to change your speedometer. However there is a chart of what is authorized. Don't know if they'll do it with just OEM wheels

Work truck come with tiny tires because they are cheaper for companies, and "unlock" additional performance.



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So I logged into the Chevy app and looked at wheel accessories with my vin number. All they offer are 18 inch and 22 inch wheels. I can’t understand why they don’t offer the 20 inch. I don’t think 18s are going to make enough of a visual difference, and 22s are just a bit too big and goddy for me. Oh well, back to square one

[hollywoodsle]

12 minutes ago, topgear1224 said:

Yes if you buy GM accessory wheels the dealer is authorized to change your speedometer. However there is a chart of what is authorized. Don't know if they'll do it with just OEM wheels

Work truck come with tiny tires because they are cheaper for companies, and "unlock" additional performance.



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This is not entirely correct.

 

Condition / Concern

A request may be made for a variety of reasons to change the tire size on a vehicle. 

Recommendations / Instructions

General Motors will ONLY support a tire calibration for tires that have been sized, tested and designed for the vehicle in question and its applications.  The only way to confirm that a calibration is available would be to visit YOUR sales department. Using the sales order guide, if you can build a vehicle, using the same make, model year, trim, and meet any restrictions listed in the tire section, GM will have a corresponding calibration available. 

Note: When changing tire size for new vehicles prior to the first sale and/or a tire/wheel size that may require a different pressure or alter the cargo carrying capacity of the vehicle, refer to #12-00-89-007B: Dealer Responsibility for Cargo Carrying Capacity Labeling.  

Once the tire application has been confirmed per the sales guide, contact Techline Customer Support Center to determine calibration availability. 

Please do not call Technical Assistance Center for these concerns. 

Note: There may be a cost to the customer for this service. This is NOT a feature that is covered under the manufacturer's warranty. 

Examples: 

First example -  A customer with a 2019 Chevrolet Silverado 1WT Regular Cab built with 255/70/R17 tires would like to install a set of wheels and tires from a 2019 Silverado 1CX Double Cab, which came with 275/60/R20 size tires. Based on the order guide, the 1WT trim is only available with either 255/70R17 or 265/70R17 size tires. For this reason, a calibration will not be offered for this application

Edited September 2, 2020 by hollywoodsle

[aseibel]

Seems like you've already done your research and know what you're getting into.

 

Only suggestion I have is, go ahead and match an OEM wheel option and tire SIZE, but select the tires you like best from any local tire distributor. OEM tires are bottom of the barrel garbage. You can find many better options for your type of use and visual appeal.

 

Unless you want to do this as cheap as possible, then you can find ready to use take-offs from someone else who ditched their OEM setup for aftermarket.

[BrizzoDaIzzo]

44 minutes ago, hollywoodsle said:

 

Examples: 

First example -  A customer with a 2019 Chevrolet Silverado 1WT Regular Cab built with 255/70/R17 tires would like to install a set of wheels and tires from a 2019 Silverado 1CX Double Cab, which came with 275/60/R20 size tires. Based on the order guide, the 1WT trim is only available with either 255/70R17 or 265/70R17 size tires. For this reason, a calibration will not be offered for this application

Ouch!   This sucks.  I figured that since the work truck and the custom truck have theEXACT SAME  body, suspension, engine, tranny, clearances, gear ratios that it would not be an issue.   The whole reason I was going OEM was to get everything re-calibrated and reprogrammed as planned.
 

Oh well, looks like I’m going to buy somebody else’s OEM takeoffs and have the constant annoying low tire pressure alarm.  Speedometer will be off by about 1%, probably not enough to really care.  
 

I tried to do with the “right way“, however I learned the lesson very quickly on here that that isn't the “right way“.  
 

this is kind of ridiculous figuring that GM specifically offers a 22 inch rim for my truck on their accessories website according to my Vin number. I even called GM and asked why they don’t offer a 20 and the guy in the parts department, laughed and said yeah this doesn’t make sense. He said all he showed according to my vin was an 18 inch and a 22 inch accessory wheel that could be ordered.
 

So aside from the dealer not being able to reprogram and re-calibrate things, does anyone else see any possible issues with doing this? i’d rather not make a $2000 mistake. Or worse, destroy something. 
 

just to reconfirm, I am using an OEM rim off of a custom Silverado of the same year, same tire specs offered on the custom, however will be aftermarket tires. The tires will be the same size specs that GM offers on the custom new

Edited September 2, 2020 by BrizzoDaIzzo

[aseibel]

1 hour ago, BrizzoDaIzzo said:

Oh well, looks like I’m going to buy somebody else’s OEM takeoffs and have the constant annoying low tire pressure alarm.  

I don't think you will have any problems with that. If you actually inflate the new tires to exactly 32 psi, I'm pretty sure that won't even set off the pressure alarm if your truck is set for 35 psi. I can't find documentation, but I thought they have to lose significant pressure (like >25%?) before the light goes on.

I know I've had my tires 1-2 psi low before with no lights.

 

If you mount them yourself and they clear the brakes, you should be good to go. 

[walshie]

I don't think your tire pressure alarm will be going off. That's only a couple psi, plus you could pump new ones up a few psi with no issues.

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[Salsa De Piña]

All three of my GMs set off the TPMS when they're at about 75% of the recommended pressure, so I doubt that's anything to worry about.

 

I'm sure if you're willing to drop a few grand on wheels and tires, the dealership will play ball and take two minutes to recalibrate your speedo/odo.  Otherwise I'd be calling up a different dealer.  Many aftermarket tuners can make this adjustment as well.

 

You need to move the decimal point over in your revs/mile calculation.  If you don't get anything recalibrated, your speedo and odo will be under by 5.8%.

[BrizzoDaIzzo]

32 minutes ago, Salsa De Piña said:

All three of my GMs set off the TPMS when they're at about 75% of the recommended pressure, so I doubt that's anything to worry about.

 

I'm sure if you're willing to drop a few grand on wheels and tires, the dealership will play ball and take two minutes to recalibrate your speedo/odo.  Otherwise I'd be calling up a different dealer.  Many aftermarket tuners can make this adjustment as well.

 

You need to move the decimal point over in your revs/mile calculation.  If you don't get anything recalibrated, your speedo and odo will be under by 5.8%.

Hey thanks for the info. After talking with the dealer, in order to replacard the TPMS/load pressure (door sticker of recommended psi)...they have to have a authorization code from big GM. (This is apparently the process that reprogrammed the “brains“ of the trucks electronic control module to see the new tire pressure as normal.) Apparently, they said that big GM won’t give them this code unless it’s a “stock“ tire that is “included in “on the work truck model. It is not.

 

I find this humorous because they sell a 22 inch wheel for the work truck in the “Chevrolet accessories“ department. That’s  not stock either.   Ugh!  

 

as far as aftermarket speedometer programmers for the 2019 Silverado speedometer, they only have a kind of crappy solution.  You have to plug-in a “interface“ box that kind of makes up the speed difference. But it must stay in place and is not an actual reprogramming of the ECM. It might be able to be reprogrammed with the high end aftermarket scan tool, but I really don’t wanna spend $1000 on such a device. Maybe I’ll see if the local tire shop can wing it. However, I still think they will probably need the GM code and it probably can’t be hacked like earlier models could. Either way, so much for doing it the “right“ way.  

 

as far as the speed calculation(yes my original math might have been wrong), I thought I took the The old revolutions per mile of 650 and divided by the new revolutions of 612 and got 1.06% speedometer difference.  I could be wrong.  
 

does anyone know if the new gear ratio of 3.22:1 vs the 3.42:1 will bog me down? I’m just guessing that it won’t, because the Silverado custom has this exact same set up and I don’t hear any complaints about it being slower than a work truck. 

Edited September 2, 2020 by BrizzoDaIzzo
Spelling mistakes

[BrizzoDaIzzo]

New gear ratio information

[newdude]

3 hours ago, BrizzoDaIzzo said:

Sorry for the long post.  This has been a headache to try and find “factual” information on instead of “opinions”.  
 

My current truck has the 17” 255/70R17 all seasons. I love my truck, but I absolutely hate these tires/wheels. They look like baby wheels on a big truck. Way too much fender well free space. Looks like the truck missed “leg day“. 

 

My question is if I purchase the OEM wheels and tires for the custom, is there any issue with them fitting my work truck? As far as I know both trucks have the exact same suspension, body clearance, control arms, wheel well clearance, etc.

 

1.will these custom tires fit my work truck? I can’t  Find any reason that they won’t

2. Will the dealer reprogram my speedometer for the percentage difference, and replacard/reprogram my ECM with the new psi setting to 32psi. (Not sure if they will since the Vin number of my truck does not include these tire size as  “options“.) I really don’t want my low pressure alarm going off 24/7. 
3. Will I noticed the change in new affective gear ratio from 3.42, to 3.22? (I’m assuming I won’t since it is the exact same gearing/tire size as the custom. 
 

Man, there sure is a lot to changing a tire size. Almost doesn’t even seem worth the trouble. Am I going down a bad rabbit hole?
 

Just an FYI, I am not interested in lift kits, aftermarket speedometer programmers, etc. . Would like to stick OEM as much as possible. 

 

 

 

2 options that I see here that would work.  Avoid the Hypertech inline calibrator at all costs.    

 

Option #1.  Change the tire size on the 20" wheel.  You can do a P275/55R20 which is a 31.9" tire.  This would only throw off your speedometer 1.5mph (2.5% faster) than stock.  So you'd go from a 31 to a 32 inch tire more or less.  This would be the least hassle route to get a touch larger tire in there on a 20" wheel.    

 

Option #2.  Have your dealer pull up GM Service Information Document ID: 5254629.  This is a calibrations chart for going from 17" or 18" wheels up to 22" wheels and shows what needs to be programmed.  I use the 22" one as the 20" and 22" have the same tire diameter, and GM has accessory 22" wheels but no 20" wheels.  Your dealer would have to try and get an authorization for programming the truck by calling GM Tech Line, which would grant, if they approve, the recalibration of the ECM (for the speedo), Power steering control module, EBCM and Body Control Module.  A big heads up however.  If your truck is a regular cab, or has VYU snow plow prep, GM DOES NOT have a calibration file for those.  

 

All of the 2019+up new body wheels will fit 2019+up new body trucks, no issues.  

 

Edited September 2, 2020 by newdude

[BrizzoDaIzzo]

1 hour ago, newdude said:

... if they approve, the recalibration of the ECM (for the speedo), Power steering control module, EBCM and Body Control Module.  A big heads up however.  

 

This statement alone has convinced me to probably never increase my tire size. I did not realize that the power steering and body control module also had to be reprogrammed. What a nightmare. oh well, time to look for some new “aggressive as I can get” tires on 17 inch wheels.  

 

 

[topgear1224]

This statement alone has convinced me to probably never increase my tire size. I did not realize that the power steering and body control module also had to be reprogrammed. What a nightmare. [emoji24] oh well, time to look for some new “aggressive as I can get” tires on 17 inch wheels.  [emoji2357]
 
 

The wheel size (rim) actually has nothing to do with it it's changing the overall diameter that could couse issues. (Likely incorrect speed, if you got REAL crazy could have some badly behaving shift schedules)


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[topgear1224]

This is not entirely correct.
 

Condition / Concern

A request may be made for a variety of reasons to change the tire size on a vehicle. 

Recommendations / Instructions

General Motors will ONLY support a tire calibration for tires that have been sized, tested and designed for the vehicle in question and its applications.  The only way to confirm that a calibration is available would be to visit YOUR sales department. Using the sales order guide, if you can build a vehicle, using the same make, model year, trim, and meet any restrictions listed in the tire section, GM will have a corresponding calibration available. 
Note: When changing tire size for new vehicles prior to the first sale and/or a tire/wheel size that may require a different pressure or alter the cargo carrying capacity of the vehicle, refer to #12-00-89-007B: Dealer Responsibility for Cargo Carrying Capacity Labeling.  
Once the tire application has been confirmed per the sales guide, contact Techline Customer Support Center to determine calibration availability. 
Please do not call Technical Assistance Center for these concerns. 
Note: There may be a cost to the customer for this service. This is NOT a feature that is covered under the manufacturer's warranty. 
Examples:  First example -  A customer with a 2019 Chevrolet Silverado 1WT Regular Cab built with 255/70/R17 tires would like to install a set of wheels and tires from a 2019 Silverado 1CX Double Cab, which came with 275/60/R20 size tires. Based on the order guide, the 1WT trim is only available with either 255/70R17 or 265/70R17 size tires. For this reason, a calibration will not be offered for this application

Yep. You have to stay in an overall diameter offered by GM.

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