Effect of new wheels/tires on fuel economy? - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

ajcarson11 · 10-25-2015, 08:27 PM

Evening All,

Have been looking into new wheels/tires recently, and spoke with a fellow owner at a meet who recently changed from stock wheels/tires to 18x8.75 wheels and new performance tires. He mentioned that his fuel economy suffered around 5mpg overall (from 34mpg to 29mpg). This seems excessive to me -- but is this the price that one pays for adding additional weight/contact patch?

Any thoughts? Is the main culprit weight, or contact patch (rolling resistance)? Can I really expect something as substantial as 5mpg?

Thanks

stevesnj · 10-25-2015, 09:17 PM

Weight, contact patch and more rotating mass.

superleggera · 10-25-2015, 09:17 PM

I averaged approximately 27.0 mpg combined with my stock wheels/tires (including a 16" winter tire setup) and approx 25.6 mpg with 18x9.5 wheels and 245 michelin pilot super sports, so I wouldn't say it is a noticeable difference. Also I find myself driving more aggressively with the new wheel/tire setup so that can't help either.

edit: for more comparability, I checked just stock wheels/tires (excluding winter tires) and my avg mpg is 27.3

mav1178 · 10-25-2015, 09:33 PM

Quote:

Originally Posted by stevesnj

Weight, contact patch and more rotating mass.

And rolling resistance too.

86Hiro · 10-25-2015, 09:58 PM

Rolling diameter....Guess that can be considered 'rotating mass' as well

churchx · 10-25-2015, 11:06 PM

Rolling resistance imho might be biggest culprit (apart from how heavy he was on go-pedal. We can only guess if he drove somewhat same and if it was during same seasons and with somewhat similar A/C usage). And imho rolling resistance changes not just from area of contact patch so i wouldn't draw equal sign, but also from rubber compound. Wheel+tire weight .. it mostly matters in frequent accelerating/decelerating, but posted mpg numbers imho somewhat assume that he cruised steady large portion of total distance driven?

frumplejoon · 10-26-2015, 01:18 AM

My fuel economy dropped from 29 combined with stock tires to 25.5 highway on 245/40R17 Rival. It's a pretty big drop, mostly due to rolling resistance from the compound and extra width.

ajcarson11 · 10-26-2015, 11:46 AM

Right -- So it looks like rolling resistance from compound and contact patch matters. So extra grippy treads might worsen fuel economy then?

It would be interesting to see a study done here. I can take 1-2mpg, but 5mpg highway would be noticable.

c4lvinnn · 10-26-2015, 11:50 AM

my dash reads 27.1MPG right now. 255/35/18 on 18x9.5s.

80% city, 20% highway and I still tend to drive more "aggressively" compared to stock wheel/tires

jc0522 · 10-26-2015, 01:32 PM

I went from stocks to staggered 18x8.5 F and 18x9.5 R. I went from 26.7MPG to about ~25.0 MPG.

wparsons · 10-26-2015, 02:19 PM

Wider tires don't mean a bigger contact patch, just a different shaped one.

My money would be on the compound being mostly at fault, significantly stickier tires can hurt straightaway speeds, so it's not surprise they would also effect fuel mileage.

mav1178 · 10-26-2015, 02:35 PM

Quote:

Originally Posted by ajcarson11

It would be interesting to see a study done here. I can take 1-2mpg, but 5mpg highway would be noticable.

If you want to document it, throw away all comments that say "my dash gauge says..."

-alex

lamawithonel · 10-26-2015, 10:09 PM

EcoModder.com has a lot of info on this.

http://ecomodder.com/forum/fuel-econ...cations.php#c7

10-25-2015, 08:27 PM	#1
ajcarson11 Senior Member Join Date: Jun 2015 Drives: 2013 Subaru BRZ Limited (Black) Location: Indianapolis Posts: 511 Thanks: 253 Thanked 206 Times in 149 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	Effect of new wheels/tires on fuel economy? Evening All, Have been looking into new wheels/tires recently, and spoke with a fellow owner at a meet who recently changed from stock wheels/tires to 18x8.75 wheels and new performance tires. He mentioned that his fuel economy suffered around 5mpg overall (from 34mpg to 29mpg). This seems excessive to me -- but is this the price that one pays for adding additional weight/contact patch? Any thoughts? Is the main culprit weight, or contact patch (rolling resistance)? Can I really expect something as substantial as 5mpg? Thanks

10-25-2015, 09:17 PM	#2
stevesnj Senior Member Join Date: May 2013 Drives: 2016 FR-S Oceanic Blue Location: Southern NJ Posts: 2,958 Thanks: 2,158 Thanked 1,601 Times in 923 Posts Mentioned: 30 Post(s) Tagged: 2 Thread(s)	Weight, contact patch and more rotating mass. __________________ My 2016 Build thread TRD Exhaust with custom quad tips, TRD Lowering Springs,TRD Quick shifter,LED;DRL, Projectors, and turn signals. Re-badge, 86 Nanny, WinmaxW2 Pads, K&N Drop In, Antenna delete

10-26-2015, 10:09 PM	#13
lamawithonel Member Join Date: Mar 2014 Drives: 2014 Subaru BRZ Ltd. Location: Mid-Atlantic Posts: 53 Thanks: 131 Thanked 36 Times in 20 Posts Mentioned: 0 Post(s) Tagged: 1 Thread(s)	EcoModder.com has a lot of info on this. http://ecomodder.com/forum/fuel-econ...cations.php#c7 __________________ question everythinglearn somethinganswer nothing

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10-25-2015, 09:17 PM	#3
superleggera Senior Member Join Date: May 2014 Drives: BRZ / MX5 / S4 Location: MA Posts: 232 Thanks: 31 Thanked 64 Times in 51 Posts Mentioned: 4 Post(s) Tagged: 0 Thread(s)	I averaged approximately 27.0 mpg combined with my stock wheels/tires (including a 16" winter tire setup) and approx 25.6 mpg with 18x9.5 wheels and 245 michelin pilot super sports, so I wouldn't say it is a noticeable difference. Also I find myself driving more aggressively with the new wheel/tire setup so that can't help either. edit: for more comparability, I checked just stock wheels/tires (excluding winter tires) and my avg mpg is 27.3

10-25-2015, 09:58 PM	#5
86Hiro Senior Member Join Date: Jul 2015 Drives: 2013 FR-S Location: Wauchula,FL Posts: 213 Thanks: 4 Thanked 43 Times in 35 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	Rolling diameter....Guess that can be considered 'rotating mass' as well

10-25-2015, 11:06 PM	#6
churchx Senior Member Join Date: Mar 2015 Drives: 2014 GT86 Location: Latvia, Riga Posts: 4,335 Thanks: 698 Thanked 2,086 Times in 1,436 Posts Mentioned: 53 Post(s) Tagged: 1 Thread(s)	Rolling resistance imho might be biggest culprit (apart from how heavy he was on go-pedal. We can only guess if he drove somewhat same and if it was during same seasons and with somewhat similar A/C usage). And imho rolling resistance changes not just from area of contact patch so i wouldn't draw equal sign, but also from rubber compound. Wheel+tire weight .. it mostly matters in frequent accelerating/decelerating, but posted mpg numbers imho somewhat assume that he cruised steady large portion of total distance driven?

10-26-2015, 01:18 AM	#7
frumplejoon Member Join Date: Apr 2013 Drives: '99 Camry, E36 M3 (RIP), BRZ Location: US Posts: 16 Thanks: 1 Thanked 3 Times in 2 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	My fuel economy dropped from 29 combined with stock tires to 25.5 highway on 245/40R17 Rival. It's a pretty big drop, mostly due to rolling resistance from the compound and extra width.

10-26-2015, 11:46 AM	#8
ajcarson11 Senior Member Join Date: Jun 2015 Drives: 2013 Subaru BRZ Limited (Black) Location: Indianapolis Posts: 511 Thanks: 253 Thanked 206 Times in 149 Posts Mentioned: 3 Post(s) Tagged: 0 Thread(s)	Right -- So it looks like rolling resistance from compound and contact patch matters. So extra grippy treads might worsen fuel economy then? It would be interesting to see a study done here. I can take 1-2mpg, but 5mpg highway would be noticable.

10-26-2015, 11:50 AM	#9
c4lvinnn Senior Member Join Date: May 2015 Drives: Toyobaruion Location: Texas Posts: 307 Thanks: 26 Thanked 236 Times in 109 Posts Mentioned: 1 Post(s) Tagged: 1 Thread(s)	my dash reads 27.1MPG right now. 255/35/18 on 18x9.5s. 80% city, 20% highway and I still tend to drive more "aggressively" compared to stock wheel/tires

10-26-2015, 01:32 PM	#10
jc0522 Member Join Date: Apr 2015 Drives: 2014 BRZ Location: SoCal 949 Posts: 51 Thanks: 6 Thanked 15 Times in 10 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	I went from stocks to staggered 18x8.5 F and 18x9.5 R. I went from 26.7MPG to about ~25.0 MPG.

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