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Wheel Tire help on '18 silverado, 285/70/17

brian2382

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tanner709 Enthusiast

tanner709

Posted
Posted
12 hours ago, brian2382 said:

do you have another picture to that? The second picture is broken and I am very curious to see what it looks like

[IMG]

 

Does that work? Notice how the tire is almost stretched to fit.  The sidewall is no longer as concave as it should be.

 

I would expect to lose 2-3mpg at the most. You can lower this number by selecting the correct tire and wheel combo.

 

Look for a lighter tire (T believe cooper ST maxx tires are one of the lightest LTs) and look for a light wheel. This will also help with the "unsprung weight" issue mentioned above.

 If you choose wisely, you can end up with a better tire/wheel combo, for right around the same weight as stock.

 

Do you really need a LT rated tire or is a P-rated duratrac or something similar, a better fit for your use?

carsonj493 Enthusiast

carsonj493

Posted
Posted

I’m running 17x9 wheels with a 0 offset and 295/70R17’s on my 2014 Silverado with a 2.5” level. The 295’s rub some at full lock so you should be good with 285’s. 

 

As far as MPG, stock I was averaging around 18 mpg and now I am getting around 15 mpg according to the lie meter in the gauges. However I am in Texas and spend a lot of drive time going 75-80 mph on the highway, which isn’t exactly a good speed for fuel economy. I can get 16-17 mpg going around 60 mph. So ?‍♂️

 

But I am not sure on the accuracy due to the tire size change.. I hand calculated once after getting the wheels/tires, but don’t remember exactly how close it was. 

155A364C-C6F7-447F-8A40-486F8C19FDA8.jpeg

04B5996A-169A-4BCB-A694-AB759BA0FBD3.jpeg

tanner709 Enthusiast

tanner709

Posted
Posted
44 minutes ago, carsonj493 said:

I’m running 17x9 wheels with a 0 offset and 295/70R17’s on my 2014 Silverado with a 2.5” level. The 295’s rub some at full lock so you should be good with 285’s. 

 

As far as MPG, stock I was averaging around 18 mpg and now I am getting around 15 mpg according to the lie meter in the gauges. However I am in Texas and spend a lot of drive time going 75-80 mph on the highway, which isn’t exactly a good speed for fuel economy. I can get 16-17 mpg going around 60 mph. So ?‍♂️

 

But I am not sure on the accuracy due to the tire size change.. I hand calculated once after getting the wheels/tires, but don’t remember exactly how close it was. 

155A364C-C6F7-447F-8A40-486F8C19FDA8.jpeg

04B5996A-169A-4BCB-A694-AB759BA0FBD3.jpeg

your speedo measures revolutions

 

radius/diameter/circumference difference can calculate the MPG error.

 

Divide your new tire diamater (33.3") by the stock (31.6") = 1.05.

 

Therefore your speedo is reading about 5% under, and so is the trip.

 

16mpg x 1.05 = 16.8mpg actual. so you only really lost 1-1.5mpg at 60mph speeds.

 

 

carsonj493 Enthusiast

carsonj493

Posted
Posted
23 hours ago, tanner709 said:

your speedo measures revolutions

 

radius/diameter/circumference difference can calculate the MPG error.

 

Divide your new tire diamater (33.3") by the stock (31.6") = 1.05.

 

Therefore your speedo is reading about 5% under, and so is the trip.

 

16mpg x 1.05 = 16.8mpg actual. so you only really lost 1-1.5mpg at 60mph speeds.

 

 

I hear what you saying, but in reality I am pretty confident that I lost more than just 1mpg.. My AFM doesn’t kick in near as often, the added weight and rolling resistance has made me have to be heavier on the throttle, and I definitely have to stop at the gas station more often. 

 

I didn't mention above, but when I was stock I could get about 20-21 mpg going 60mph, But overall I averaged about 18 stock and about 14-15 mpg  average after the wheels and tires.

 

So considering I got about 20 -21mpg stock at 60mph and now get about 17mpg at 60mph as you pointed out after adjusting for the tires, that would really be around a 3-4mpg loss. 

 

I will try and remember to hand calculate my fuel economy with my next fill up to get a real world number. 

Kubs Enthusiast

Kubs

Posted
Posted

I have 285/70R17 on 17x9 wheels but I already had a 2.5" level when I put them on.  My wheels have a -12 offset so I still had to pull the fender liner back and cut a small amount off the plastic trim on the lower rear section of the front wheel well.  I think a 285/70R17 would be a tight fit with no lift/level.

tanner709 Enthusiast

tanner709

Posted
Posted
1 hour ago, carsonj493 said:

I hear what you saying, but in reality I am pretty confident that I lost more than just 1mpg.. My AFM doesn’t kick in near as often, the added weight and rolling resistance has made me have to be heavier on the throttle, and I definitely have to stop at the gas station more often. 

 

I didn't mention above, but when I was stock I could get about 20-21 mpg going 60mph, But overall I averaged about 18 stock and about 14-15 mpg  average after the wheels and tires.

 

So considering I got about 20 -21mpg stock at 60mph and now get about 17mpg at 60mph as you pointed out after adjusting for the tires, that would really be around a 3-4mpg loss. 

 

I will try and remember to hand calculate my fuel economy with my next fill up to get a real world number. 

No doubt, 3.42 gearing doesn't play well with those larger, heavier tires. My truck was gutless after tire size increases.

carsonj493 Enthusiast

carsonj493

Posted
Posted
46 minutes ago, tanner709 said:

No doubt, 3.42 gearing doesn't play well with those larger, heavier tires. My truck was gutless after tire size increases.

Yup. Are you running a tune? I have been thinking about getting a tune to fix the speedo, disable AFM, make the tranny act better, and of course to add some power. 

tanner709 Enthusiast

tanner709

Posted
Posted
2 minutes ago, carsonj493 said:

Yup. Are you running a tune? I have been thinking about getting a tune to fix the speedo, disable AFM, make the tranny act better, and of course to add some power. 

No, I traded in my '16. I'm in a Trailboss Custom now. still a 5.3 with 6speed and 3.42 but man it would eat my old truck alive.

  • 2 weeks later...
carsonj493 Enthusiast

carsonj493

Posted
Posted

Fuel economy update as promised. @tanner709

 

Odometer reading 

1st fill up: 70,153 miles

2nd fill up: 70,474 miles

(321 miles)

 

Miles driven: *337 miles

*5% factored in due to tire size

(321 x 1.05 = 337.05)

 

2nd fill up= 21.921 gallons

 

337 / 21.921= 15.373

 

MPG (computer reading): 15.3 mpg

MPG (hand calculated): 15.4 mpg

 

Is that right? The computer is nearly spot on despite having larger tires?

 

That is mostly highway driving. 50% going 65mph and 50% going 80 mph roughly. 

brian2382 Enthusiast

brian2382

Posted
  • Author
Posted
On 7/30/2019 at 7:36 PM, carsonj493 said:

Fuel economy update as promised. @tanner709

 

Odometer reading 

1st fill up: 70,153 miles

2nd fill up: 70,474 miles

(321 miles)

 

Miles driven: *337 miles

*5% factored in due to tire size

(321 x 1.05 = 337.05)

 

2nd fill up= 21.921 gallons

 

337 / 21.921= 15.373

 

MPG (computer reading): 15.3 mpg

MPG (hand calculated): 15.4 mpg

 

Is that right? The computer is nearly spot on despite having larger tires?

 

That is mostly highway driving. 50% going 65mph and 50% going 80 mph roughly. 

God damn, thats interesting. I am doing the same thing right now before the tires. On flat land, cruise control set to 64mph (55mph zone), I have a best 50 mile average of 27.5mpg.... okay okay... my WIFE has a best 50 mile average of 27.5 on my truck. But I have achieved a 26mpg 50 mile average.  My normal average with daily driving in cities and hwy is typically around 21-22mpg though.

 

I really hope changing tires doesn't bring me down to 15mpg lmao. I will throw those bad boys back on. 

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