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A real before/after analysis of heavier AT tires w/ level vs. stock

crushNchowda

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Rkaroll953 Enthusiast

Rkaroll953

Posted
Posted

i have a 5.3 3.42 ratio truck. i stuffed the biggest tire under it. 295/70/18 trail grapplers (70 lbs). lost a little power. haven't driven it enough to notice gas mileage yet. Could be snake oil but i do think it shifts better with them, as i am a huge critic of the a-holes who programmed these transmissions. im sure i will be getting 17-18 highway tho. i have a company car so i probably wouldn't have gone so big if i had to drive the truck every day, but i only drive it 6-8000 miles a year so im not to hurt over the mileage.

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royalkangaroo Enthusiast

royalkangaroo

Posted
Posted

Not to veer off topic, but are your 5100s set at max height? That setup looks perfect!

 

I have the exact setup. Installed the bilstein 5100s at 4000 miles. added 275/60/20 Duratrac all terrains with 20 x 9 fuel coupler wheels to replace my factory 20 x 9 wheels. I still have the air dam installed

I now have 18000 miles and I average 14-15 mpg

Thornton Enthusiast

Thornton

Posted
Posted

Not to veer off topic, but are your 5100s set at max height? That setup looks perfect!

 

 

Yep. 5100's set at max. I actually got 2" of lift from them regardless of the 1.8 claim

crushNchowda Senior Enthusiast

crushNchowda

Posted
  • Author
Posted

Yep. 5100's set at max. I actually got 2" of lift from them regardless of the 1.8 claim

 

Reminds me - all this yapping & I never posted any pics of the result lol! I also found that the bilsteins raised more than the 1.8" - I got 2" on the nose w/ my stock tires still on (and I'm 100% certain that's correct because anything under 2" & my passenger door would scrape on the retaining wall adjacent to my driveway) - w/ the new Nittos @ 38 psi front 36 psi rear I'm showing 2.75" total lift.....which is a little higher than I expected only going to a 33" tire but I guess combo of brand new tread on the nittos & more air in the tire? Either way I'll take it & also go on record as saying THIS is how a truck should sit right from the factory to begin with.

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AskMeAboutMySilverado Enthusiast

AskMeAboutMySilverado

Posted
Posted

For everyone that is complaining about the padding, just test it for yourself. It is very easy to download countless free MPH Speed apps in your phone's app store. Before you leave or get moving, open the app. Jump on the highway and let the app do the work. GPS on your phone is very very accurate. Way more accurate than your speedometer. Take a mental note. Done. Questions answered.

TxTruckMan Senior Enthusiast

TxTruckMan

Posted
Posted

But I'll also go on record now and stick w/ my original tune - you guys out there running these tires & especially the much heavier ones are NUTS if you don't think its gonna kill your performance, mpg's, & wreak havoc on pretty much everything else that goes along w/ it like bushings/bearings etc. as I said. Running the heavy AT's on those 5.3 trucks ESPECIALLY ones w/ the 3.08's must be damn near depressing how gutless the trucks become, don't kid yourselves.

 

I'll chime in with my recent experiment/experience on different tires.

 

My 2015 Denali (4x4 6.2L) came with 285/45R22s HL Duelers, not the AT ones. Over about a year I averaged 17-17.5 mpg. Last summer I bought a set of 18" GM factor take offs and mounted 275/65R18 Duratracs - P series, not LT. They are exactly the same height, but the Duratracs are 0.5" narrower with 2" more sidewall.

 

I have basically no modifications to my truck - all stock. The original 22s weighed in at 89 pounds. The 18's with Duratracs weighed in at 74 pounds - 15 pounds less. So I was expecting a wash or maybe better MPGs. I had them on my truck until 3 weeks ago. Over the ~9 months, I averaged 16-16.5 mpg with the 18" Duratracs.

 

I was shocked that the lighter tire resulted in worse mileage. I never thought this would be the case. It's obvious that rolling resistance has a greater impact to MPGs than weight. I run the 22's at 32 psi, and the 18's at 35 psi.

TxTruckMan Senior Enthusiast

TxTruckMan

Posted
Posted

For everyone that is complaining about the padding, just test it for yourself. It is very easy to download countless free MPH Speed apps in your phone's app store. Before you leave or get moving, open the app. Jump on the highway and let the app do the work. GPS on your phone is very very accurate. Way more accurate than your speedometer. Take a mental note. Done. Questions answered.

I think the problem is that GM assumes that everybody is running exactly the same size tires. But if you look at the different tire sizes available from factory, they actually vary in diameter by nearly a half inch. So, I don't think it's that GM puts padding in the speedo, it's that they are lazy and just assume one tires size for everybody.

 

My truck runs right on with 285/45R22s = 32.1".

275/55R20 = 31.9"

265/65R18 = 31.6"

265/70R17 = 31.6"

Annhl8rX Enthusiast

Annhl8rX

Posted
Posted

I think the problem is that GM assumes that everybody is running exactly the same size tires. But if you look at the different tire sizes available from factory, they actually vary in diameter by nearly a half inch. So, I don't think it's that GM puts padding in the speedo, it's that they are lazy and just assume one tires size for everybody.

 

My truck runs right on with 285/45R22s = 32.1".

275/55R20 = 31.9"

265/65R18 = 31.6"

265/70R17 = 31.6"

I imagine they way they'd justify using the same settings for the different sizes is due to tread wear. The smallest size is likely most accurate when new (while the tire diameter is its biggest), the middle sizes when half worn, and the largest when most worn. Speedometer readings will never be completely accurate at all stages in the life of a tire.

batman53201 Enthusiast

batman53201

Posted
Posted

The speedo isn't "padded" fast from the factory and when you add bigger tires your speedo shows even slower, so all you're doing is increasing the "padding". Whereas stock maybe it showed 70 but you're really doing 68, when you add bigger tires you'll show 70 but really be doing 65

I think you got that backwards

mfbearded Enthusiast

mfbearded

Posted
Posted

i didnt buy a pickup cause i was looking for fuel efficiency. im not attacking post, i get the point is for research, my stance is more for guys that are looking for a truck or get one and mod it up and complain the mpgs suck. i leveled mine out, threw toyo rt tires on, exhaust...watched my mpgs dive...but the look and sound, and feeling i get more than makes up the difference. but again...hat off to your cause

country_09 Enthusiast

country_09

Posted
Posted

I have a 14 6.2 with headers/intake/tune...It didn't stay stock long but I averaged 19-20 hwy and 15-16 city Iirc. Did intake/headers/tune and 2.5" leveled with 295/55 trail grapplers and 20x10s. Still averaged 18-19 hwy and around 14-15 city. Added 1.25" body and 275/60 toyo at2s (which weigh 43lbs according to toyo) that I put on thinkin mpg would go up and def rides better...mpg stayed the same. But I'm happy with how it looks and drives, plus a 6.2 gettin 18-20 hwy is awesome. I'd have been happy with 14-15 hwy

tanner709 Enthusiast

tanner709

Posted
Posted

I think the problem is that GM assumes that everybody is running exactly the same size tires. But if you look at the different tire sizes available from factory, they actually vary in diameter by nearly a half inch. So, I don't think it's that GM puts padding in the speedo, it's that they are lazy and just assume one tires size for everybody.

 

My truck runs right on with 285/45R22s = 32.1".

275/55R20 = 31.9"

265/65R18 = 31.6"

265/70R17 = 31.6"

GM doesn't assume they are the same size, it is most definitely factored into tire diameter calculations per vehicle.

 

I imagine they way they'd justify using the same settings for the different sizes is due to tread wear. The smallest size is likely most accurate when new (while the tire diameter is its biggest), the middle sizes when half worn, and the largest when most worn. Speedometer readings will never be completely accurate at all stages in the life of a tire.

Exactly!

 

I think you got that backwards

A lot of people struggle with the concept that you'll be doing higher speeds, they tend to think engine RPM is directly correlated...

 

This is purely hypothetical:

So say with a 31.5" tire @ 2000RPM you do 70mph.

with the 35" tire @ 2000RPM the speedo reads 65-68mph. When in actually the diameter difference has you @ 72-75mph.

 

Like mentioned a million times, use a GPS to verify.

TxTruckMan Senior Enthusiast

TxTruckMan

Posted
Posted

GM doesn't assume they are the same size, it is most definitely factored into tire diameter calculations per vehicle.

So you think that GM has a different speedo calibration for each tire size? I highly doubt that. If so, then it would be necessary to update the speedo when going to GM 22" wheels from the stock tire. That never happens.

Sierra706 Senior Enthusiast

Sierra706

Posted
Posted

So you think that GM has a different speedo calibration for each tire size? I highly doubt that. If so, then it would be necessary to update the speedo when going to GM 22" wheels from the stock tire. That never happens.

They do, my dealer showed me the sizes they can program for. The difference is pretty small, and some dealers are lazy so it's not always done.

 

 

Sent from my iPhone using Tapatalk

TxTruckMan Senior Enthusiast

TxTruckMan

Posted
Posted

They do, my dealer showed me the sizes they can program for. The difference is pretty small, and some dealers are lazy so it's not always done.

 

 

Sent from my iPhone using Tapatalk

Huh. Never knew that.

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