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Effect of larger tires on mpg

lipets

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lipets Enthusiast

lipets

Posted
Posted

according an online calculator @ 4lo.com

 

Based on 4.10 rear

 

245 dia = 30.5" w=9.6

265 dia = 31.6" w=10.4" effective rear axle drops to 3.96

285 dia = 32.8" w=11.2" effective rear axle drops to 3.8

 

Am I understanding this correctly,

if I increase the tire size which will reduce the axle ratio my mpg will increase?

 

Or will the increase in tire weight and width negate it?

 

I tow monthly ( long like 1200 miles) 6,000 trailer with 2,000 in the cargo bed

my 2500 8.1 gets about 9.5 mpg at 68mpg.

 

I'm trying to increase that mpg a little, I only have 9,000 miles on it so far with Mobil 1, otherwise stock.

GeoHawk Enthusiast

GeoHawk

Posted
Posted

I think it kinda depends on how big you go. I went from 245/75-16s to 265/75-16s on my '03 and didn't really notice any difference. A larger increase in tire size would add considerable rolling resistance and would negate the effective axle ratio decrease.

jonaddis84 Enthusiast

jonaddis84

Posted
Posted

Your MPG should increase, the engine has enough torque that it wont be struggling whatsoever to turn the added weight/diameter. Therefore the adjusted final drive ratio decrease would mean less RPMs at speed. The actual results would vary depending on the tire, if you got something really knobby there will be considerable more rolling friction which will hurt mpg.

 

Plus, if you dont correct the speedo with a tune, your truck will gain value every mile you drive (at least over the stock tires it will), your odometer will be quite a bit less than actual after awhile.

GMSea97 Enthusiast

GMSea97

Posted
Posted

What you want for mpg increase...talking tires. Is a tall, thin tire. The height changes your ratio but if you don't increase your width you don't add friction. Look how thin the tires are on the little economy cars.

Shaners Senior Enthusiast

Shaners

Posted
Posted

On my '01 6.0L I put 265/75/16 Michelin LTX M/S and I saw no difference in MPG's over stock size.

 

On my '05 Dmax I put the more aggressive Bridgestone REVO's 265/75/16 and lost a little MPG's over stock size tires.

HDdave Enthusiast

HDdave

Posted
Posted

I went from michelin 245's to BFG AT 285's. I actually lost close to 1 MPG on my 6.0 with 4:10's. I don't really care though, it looks wayyy better.

srlbotanical Enthusiast

srlbotanical

Posted
Posted
I went from michelin 245's to BFG AT 285's. I actually lost close to 1 MPG on my 6.0 with 4:10's. I don't really care though, it looks wayyy better.

 

Exactly

silveradoHO Enthusiast

silveradoHO

Posted
Posted

When calculating mileage, you also have to take into acount that with a larger tire your speedo will be off. I switched from 265's to 285's and according to discount tire's website, when my speedo says 65 I'm actually going 67.26. Difference would be even more (about 4.5mph) switching from 245 to 285. I just got my new tires yeterday so I'll post back later my mpg, but I'm not expecting much either way.

way_out_there Enthusiast

way_out_there

Posted
Posted
I went from a 245 to a 265 and mine went down 1mpg or so. I notice the engine revs a little higher than before.

 

Huh??? How could your engine RPM increase when you increased your tire size? It would have to decrease.

 

The mileage decrease I understand, and is normal.

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