changed rims = worse gas mileage?!?! im pissed

[PHENOMenalVinyl]

ok i recently got the infiniti g35 sport rims on my coupe. They are 18 in and 8.5in wide on the front and 18 in by 8.0 in the rear.

Why am i getting worse gas mileage? Does it reeally change the gas mileage when you change your rims? I used to put cruise control on n it said 35.8 at 67mph, now it reads 30.1 at 67.1mph???? Thats a big diffrence.

And should i test the car to c if a mile is still a mile?/test the car to c if it says its going the right speed/saying its going the right speed? What i mean is i was tolld when you change your tires it can change the circumferance of the wheel which in turn screws up speed/odometer.

[Scandinavian Flick]

yeah the larger wheel increases the rotational weight, whcih requires more power to turn, which in turn uses more fuel....also your braking distance will increase too.... but hey the wheels look sweet, and your car will be able to coast further... so good times... also what size tires are on those wheels

[Scandinavian Flick]

also i just noticed.. you are running the wider rims on the front?

[spockrock]

also i just noticed.. you are running the wider rims on the front?

its fwd drive you might as well.

[spockrock]

ok i recently got the infiniti g35 sport rims on my coupe. They are 18 in and 8.5in wide on the front and 18 in by 8.0 in the rear.

Why am i getting worse gas mileage? Does it reeally change the gas mileage when you change your rims? I used to put cruise control on n it said 35.8 at 67mph, now it reads 30.1 at 67.1mph???? Thats a big diffrence.

And should i test the car to c if a mile is still a mile?/test the car to c if it says its going the right speed/saying its going the right speed? What i mean is i was tolld when you change your tires it can change the circumferance of the wheel which in turn screws up speed/odometer.

what are your tire sizes by chance the problem could be if your overall wheel diameter is off by a lot you maybe traveling faster then the speedometer thinks you are, and if you are going faster than usual then yes you will be using more gas.

but yes generally speaking Scandinavian flick is right larger wheels = increased gas mileage.
Modified by spockrock at 10:05 AM 7/13/2008

[beeristasty]

You current wheel diameter is probably not equal to your stock wheel diameter. On the other side, you now also have 5 inches more tire width vs stock, so your contact patch is larger.

As for the weight, heavier wheels carry more momentum, so its debatable that they negatively affect mileage at steady highway speeds. Going into the city is a totally different story though.

[audtatious]

Not sure if you have the 2.5 or 3.5 coupe so I will address both...

As mentioned before, you have gone up to a larger rim. The rim is probably heavier than the factory one thus it adds more weight/moving mass that can have a negative aspect on gas mileage. If you have the 3.5 then you have gone from a 17" rim with a 215/55 tire to a 18" rim with a 225/55 tire. The rims are larger and the tires have a wider contact patch on the road. From a speed calculation perspective, you current setup is 5.4% slower than the factory rims/tires. When your speedometer says you are going 60mph you are actually going 63.3mph.

For the 2.5 models, they come with 215/60/16's so you have gone up 2" in rim diameter and still have the larger contact patch. Your speedometor is now 6.1% too slow and at 60mph you are actually doing 63.6mph.

[rjdmmfl1]

Not sure if you have the 2.5 or 3.5 coupe so I will address both...

As mentioned before, you have gone up to a larger rim. The rim is probably heavier than the factory one thus it adds more weight/moving mass that can have a negative aspect on gas mileage. If you have the 3.5 then you have gone from a 17" rim with a 215/55 tire to a 18" rim with a 225/55 tire. The rims are larger and the tires have a wider contact patch on the road. From a speed calculation perspective, you current setup is 5.4% slower than the factory rims/tires. When your speedometer says you are going 60mph you are actually going 63.3mph.

For the 2.5 models, they come with 215/60/16's so you have gone up 2" in rim diameter and still have the larger contact patch. Your speedometor is now 6.1% too slow and at 60mph you are actually doing 63.6mph.

Matt, is there a sticky somewhere with this information? Its asked alot, and I don't think enough people realize how changing their wheels affects their vehicle in totality (acceleration due to extra weight, gas mileage due to weight plus increase tire contact with road , etc) Thanks for the informative post!

[fullvietFX]

The Infiniti G35 19" Forged Rays are lighter than every other wheel Nissan offers other. Also use this link to see if you are using the right sizes.

http://www.1010tires.com/TireSizeCalculator.asp

[PHENOMenalVinyl]

Not sure if you have the 2.5 or 3.5 coupe so I will address both...

As mentioned before, you have gone up to a larger rim. The rim is probably heavier than the factory one thus it adds more weight/moving mass that can have a negative aspect on gas mileage. If you have the 3.5 then you have gone from a 17" rim with a 215/55 tire to a 18" rim with a 225/55 tire. The rims are larger and the tires have a wider contact patch on the road. From a speed calculation perspective, you current setup is 5.4% slower than the factory rims/tires. When your speedometer says you are going 60mph you are actually going 63.3mph.

For the 2.5 models, they come with 215/60/16's so you have gone up 2" in rim diameter and still have the larger contact patch. Your speedometor is now 6.1% too slow and at 60mph you are actually doing 63.6mph.

ok i have the 2.5 but i also have these rim/tire specs from the kid wen i boughtt em....im not sure if this is wat everyone is askin but .....they are 18's 225/55R18 back and 245/55R18 front so i have bigger on the front.

So with this its normal to see a decrease in gas mileage. And i should shift like 3mph before i think i am actually going.

Can this just get fixed bc cant this screw up my odometer?

Oh and it actually coasts less so i forgot who said it will coast better, it doesnt

[Hussain]

did you photoshop the pic in your signature? your car looks REALLY LOW, like you have air bags or something. looks like its almost scraping the ground.

[audtatious]

Matt, is there a sticky somewhere with this information? Its asked alot, and I don't think enough people realize how changing their wheels affects their vehicle in totality (acceleration due to extra weight, gas mileage due to weight plus increase tire contact with road , etc) Thanks for the informative post!

It's not specifically posted anywhere. I can write a NICO article similar to the dyno-tech one.

[audtatious]

ok i have the 2.5 but i also have these rim/tire specs from the kid wen i boughtt em....im not sure if this is wat everyone is askin but .....they are 18's 225/55R18 back and 245/55R18 front so i have bigger on the front.

So with this its normal to see a decrease in gas mileage. And i should shift like 3mph before i think i am actually going.

Can this just get fixed bc cant this screw up my odometer?

Oh and it actually coasts less so i forgot who said it will coast better, it doesnt

OK, based on the 245's in the front then your speedometer is actually 9.4% slower. So, at 60mph you are actually doing 65.6mph

[spockrock]

ok i have the 2.5 but i also have these rim/tire specs from the kid wen i boughtt em....im not sure if this is wat everyone is askin but .....they are 18's 225/55R18 back and 245/55R18 front so i have bigger on the front.

So with this its normal to see a decrease in gas mileage. And i should shift like 3mph before i think i am actually going.

Can this just get fixed bc cant this screw up my odometer?

Oh and it actually coasts less so i forgot who said it will coast better, it doesnt

Dude that's way off spec, no wonder, easiest way to fix this is get new tires, how did you not figure this in before buying new rims?? As audatious pointed out you are 9.4% out of spec off spec.

You should either get the computer re-calibrated, or you need to get either 245/45/18 or 245/40/18 tires for the front and 225/45/18 for the rear tires.

http://www.miata.net/garage/tirecalc.html <<- use that tool to see how much your wheels and tires are off by, you spec tires are 215/60/16.

[jusjus]

Yra I've been noticing too. BEfore with the stock 16" rims, computer calculated that I could run nearly 650-700km per tank. Now I only get about 550-600 per tank with the 19" rims even though the tire diameter is the same. Probably cuz rims are heavier.

[LongBeachCoupe]

did you photoshop the pic in your signature? your car looks REALLY LOW, like you have air bags or something. looks like its almost scraping the ground.

I think he did... bc i dont think he even has the eibachs...

Why are all those "will it fit" threads stickyd.. hmmm..

[PHENOMenalVinyl]

ok ima check it out like go next to another car n c bc todasy i passed a speed thing n it said 43 n i was doin 43.

But if it is the way u say it is, is it going to screw up my odometer???? Like will it read more miles/less miles than im actually driving??

And is it bad to be riding on these tires for my car?? bc if its just speed i dont give a ****.....does it change in rpms like if it says 6000 rpm is it 6000 or is it actually higher like the speed????

[spockrock]

ok ima check it out like go next to another car n c bc todasy i passed a speed thing n it said 43 n i was doin 43.

But if it is the way u say it is, is it going to screw up my odometer???? Like will it read more miles/less miles than im actually driving??

And is it bad to be riding on these tires for my car?? bc if its just speed i dont give a ****.....does it change in rpms like if it says 6000 rpm is it 6000 or is it actually higher like the speed????

yes it should throw off the odometer, if I am not mistaken, the odometer reading is based on the overall circumference of the tire.

No it wont change your rpms, that is the speed of the engine that won't change. Your speedometer and odometer will be thrown off.

[PHENOMenalVinyl]

ok but which way is the odometer off will it read im going more or less miles

[spockrock]

ok but which way is the odometer off will it read im going more or less miles

If I told you it will tell you that odometer is reading less mileage will you get the problem fix or are you going to keep rolling on the same tires and then sell the car 5 years down the road and sell the car with 20 000 miles on it even though it should be at 22 000 miles??

[audtatious]

ok ima check it out like go next to another car n c bc todasy i passed a speed thing n it said 43 n i was doin 43.

But if it is the way u say it is, is it going to screw up my odometer???? Like will it read more miles/less miles than im actually driving??

Those speed check signs always show me going slower than I am....Yes, your odo will show less miles by 9.4% (94 miles less for every 1000 miles)

[LongBeachCoupe]

This may be the wheel setup of choice for leasers!

[PHENOMenalVinyl]

ok well just so u know im only going to have these tires on till prob sept so wen i switch to my stockers wen i go bk to school ill get new tires 4 em but i guess i should make a note of wen i got these so i can write down the real ammount of miles its going

[PHENOMenalVinyl]

n im gonna really have to watch my speed now bc of the incrrease in numbers bc i can get gunned thinkin im goin 65 wen ill b goin like 71 or watever he was sayin....i wonder if i will now top out at like 107 now????? guess ill have to try it but i dont think it does bc i topped it out the other day with it sayin 113 so maby it kinda changed my governor not knowing it

[spockrock]

n im gonna really have to watch my speed now bc of the incrrease in numbers bc i can get gunned thinkin im goin 65 wen ill b goin like 71 or watever he was sayin....i wonder if i will now top out at like 107 now????? guess ill have to try it but i dont think it does bc i topped it out the other day with it sayin 113 so maby it kinda changed my governor not knowing it

The governor reads your speedometer, so in reality you actually were going over 113, it doesn't magically know your speed, if your car thinks its going 86MPH then that's what the governor sees.

[spockrock]

This may be the wheel setup of choice for leasers!

If you don't mind changing tires between service checks.

[audtatious]

I have yet seen a dealership say anything to anyone going +2 tire/rim size.

[Rex]

The Infiniti G35 19" Forged Rays are lighter than every other wheel Nissan offers other. Also use this link to see if you are using the right sizes.

http://www.1010tires.com/TireSizeCalculator.asp

I don't think they're not lighter than the 18" Forged Rays, that were offered on the 350Z or the 18" Forged wheels that were offered on the Alimta SE-R Sedan.

ok i have the 2.5 but i also have these rim/tire specs from the kid wen i boughtt em....im not sure if this is wat everyone is askin but .....they are 18's 225/55R18 back and 245/55R18 front so i have bigger on the front.

I highly doubt they're 55 series tires?? I'm thinking you mean 225/45 & 245/45. Any way you slice that it's still a taller tire, thus you're going faster and farther than the speedometer indicates.

And, thew G35 Coupe 7 spoke wheels are 18x8.0 F & R, they came with staggered tire sizes though.

[Scandinavian Flick]

well thinking about it, on a 12000 mile per year lease you will be able to travel an additional 1128 miles, so good times to that

[spockrock]

I have yet seen a dealership say anything to anyone going +2 tire/rim size.

Oh I was referring to LBC's comment on getting free miles out of a leased car, by getting a wheel and tire package that puts you over spec by 10%, I don't think they would factor in the 10% differential or tell you to put tires that bring it to spec.