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View Full Version : Does a lift & Bigger tires decrease your gas mileage dramatically ??



Neno
08-13-2008, 09:21 PM
I have never had a lift on a vehicle, and I was wondering if putting a lift on, and bigger tires make a huge difference ??? I do a ton of driving for my job, so could you guys tell me roughly how many miles per gallon +/- that you think you lose ??

Henthorn
08-13-2008, 09:25 PM
Depends on the vehicle.

Lift by itself not really unless you figure in aerodynamic loss.

Tires/wheels.. yes it can. Bigger tire and your effectively altering your ratio even though you dont have a different gear ratio per se. Your turning a bigger mass of sprund weight as well.

Bigger tires will reduce your rpm at any given speed, but stop and go requires more power to initialy start off.

Lots of factors here.. what are you considering??

Neno
08-13-2008, 09:29 PM
Depends on the vehicle.

Lift by itself not really unless you figure in aerodynamic loss.

Tires/wheels.. yes it can. Bigger tire and your effectively altering your ratio even though you dont have a different gear ratio per se. Your turning a bigger mass of sprund weight as well.

Bigger tires will reduce your rpm at any given speed, but stop and go requires more power to initialy start off.

Lots of factors here.. what are you considering??

nothing too big. Maybee 32' or 33's

Henthorn
08-13-2008, 09:37 PM
depending on the size of tires you have right now, it may be a negligible difference.. or It could be a little more than that--

just to give a reference... I have a 2008 JK that came with 29's. Its a 6spd manual and has 3.73 gear ratio.

Stock I was getting about 22-23mpg on the hwy, now I get about 19-20.. not a huge difference, but still there.

Neno
08-13-2008, 09:42 PM
depending on the size of tires you have right now, it may be a negligible difference.. or It could be a little more than that--

just to give a reference... I have a 2008 JK that came with 29's. Its a 6spd manual and has 3.73 gear ratio.

Stock I was getting about 22-23mpg on the hwy, now I get about 19-20.. not a huge difference, but still there.

what size tires do you run now ??

OlneyJeeps
08-13-2008, 09:48 PM
Time to get a quick note in before this turns into 37 page thread (ratio thread)... effect of gas milage is most dramaticly effected by 2 factors: auto/manual trans and driving style
a manual will almost always (all other things being equal) give better milage (next to 0 parasitic loss), how much really is determined by how you drive... jackrabbit starts are tremendous gas wasters, use of brakes is largest waste ... getting the big meats up to speed sucks up a lot of fuel but builds inertia....easy to throw out the window (along with your gas $$) when you hit the brakes (the same could be said for larger vehicles)

AZJeeps
08-14-2008, 09:41 AM
Which Jeep are you thinking about changing the tire size? If it is the TJ then the move to 33s won't be much of an issue because it has 4.11s for gears. Which in my opinion that is near perfect for a ratio for those tires and daily driving. Just keep the starts slower and coast more to come to a stop.

Now if it is the XJ you are thinking about, then the 32s is the max I would go, because you most likely have 3.55 gears if still stock. If you put on 31s with those gears and do only highway driving, the Jeep loves it and you can get great mileage as long as there are no hills. My old 88' with 31s gets about 18mpg. My 90' with 32s gets about 16-17mpg.

Now both of these number DO NOT account for speedo error. So in reality they do a little bit better because if you keep stock gears and change the tire size it will move farther in one rotation on the larger tire then the smaller tire but it will still read the same for distance as far as the speedo cares.

mingoglia
08-14-2008, 10:09 AM
Tires/wheels can make a big difference. For example on the Prius just swapping out the super light factory aluminum wheels with heavier aluminum wheels (from a Toyota Xion for example...which some people do) or swapping to another tire can affect mileage as much as 5mpg. That's up to 10% on the Prius. Now on a Jeep if you're switching from the factory wheels (which are relatively light) and moving to a steelie with mud tires I'm sure you can potentially see much more than a 10% drop in fuel economy because of the drastic switch. Just switching to a steelie and keeping the same exact tire will probably account for a 10% drop by itself.

Mike

Howyadoin
08-14-2008, 10:38 AM
Yes. Do you wheel your Jeep, or just want looks? What type of wheeling do you do? What percentage of your mileage is wheeling?

Howyadoin
08-14-2008, 10:40 AM
Tires/wheels can make a big difference. For example on the Prius just swapping out the super light factory aluminum wheels with heavier aluminum wheels (from a Toyota Xion for example...which some people do) or swapping to another tire can affect mileage as much as 5mpg. That's up to 10% on the Prius. Now on a Jeep if you're switching from the factory wheels (which are relatively light) and moving to a steelie with mud tires I'm sure you can potentially see much more than a 10% drop in fuel economy because of the drastic switch. Just switching to a steelie and keeping the same exact tire will probably account for a 10% drop by itself.

Mike

You should definately run some steelies on the Prius!:eek::sifone:

RubiJk
08-14-2008, 10:46 AM
depending on the size of tires you have right now, it may be a negligible difference.. or It could be a little more than that--

just to give a reference... I have a 2008 JK that came with 29's. Its a 6spd manual and has 3.73 gear ratio.

Stock I was getting about 22-23mpg on the hwy, now I get about 19-20.. not a huge difference, but still there.

19-20?????? :eek:

You lucky bastage! I get 12-13 around town and MAYBE 16-17 hwy. Damn steelies... I might swap them out to the lighter Prius wheels!

TRLR8TDTJ
08-14-2008, 10:50 AM
You also have to factor cool points in. Cool points cancel out gas mileage most of the time. Say you get 17mpg now with Jeep stock. With say 33's you will get like 15mpg, but if you factor in at least 2 cool points it will be a wash. This works the same with lowering Jeep. That can drastically lower the cool points. If you drive a Prius of something like that it uses different type of point system. Those are measured in ghey points, and tinting your windows and anything that will protect your idenity will subtract some of the ghey points.

Kyle

RubiJk
08-14-2008, 11:03 AM
You also have to factor cool points in. Cool points cancel out gas mileage most of the time. Say you get 17mpg now with Jeep stock. With say 33's you will get like 15mpg, but if you factor in at least 2 cool points it will be a wash. This works the same with lowering Jeep. That can drastically lower the cool points. If you drive a Prius of something like that it uses different type of point system. Those are measured in ghey points, and tinting your windows and anything that will protect your idenity will subtract some of the ghey points.

Kyle

:laugh4: :smilielol5:

Howyadoin
08-14-2008, 11:06 AM
You also have to factor cool points in. Cool points cancel out gas mileage most of the time. Say you get 17mpg now with Jeep stock. With say 33's you will get like 15mpg, but if you factor in at least 2 cool points it will be a wash. This works the same with lowering Jeep. That can drastically lower the cool points. If you drive a Prius of something like that it uses different type of point system. Those are measured in ghey points, and tinting your windows and anything that will protect your idenity will subtract some of the ghey points.

Kyle

OUCH!:pinch:

Neno
08-14-2008, 12:16 PM
Yes. Do you wheel your Jeep, or just want looks? What type of wheeling do you do? What percentage of your mileage is wheeling?

I do quite a bit of offroading. Nothing extreme like alot of the guys on here. I do climb a little, alot of forest service, non forest service road. I'm not a rock crawler, so I don't need anything to extreme. I would say 5-10% of my wheeling is offroad. I basically just want more clearance, and a little more beefy of a look than the stock TJ

Henthorn
08-14-2008, 01:31 PM
what size tires do you run now ??

running 33's.

Henthorn
08-14-2008, 01:34 PM
19-20?????? :eek:

You lucky bastage! I get 12-13 around town and MAYBE 16-17 hwy. Damn steelies... I might swap them out to the lighter Prius wheels!

lol.. Im using cragar soft 8 steelies....

mingoglia
08-14-2008, 02:19 PM
You also have to factor cool points in. Cool points cancel out gas mileage most of the time. Say you get 17mpg now with Jeep stock. With say 33's you will get like 15mpg, but if you factor in at least 2 cool points it will be a wash. This works the same with lowering Jeep. That can drastically lower the cool points. If you drive a Prius of something like that it uses different type of point system. Those are measured in ghey points, and tinting your windows and anything that will protect your idenity will subtract some of the ghey points.

Kyle

I'm thinking of a suitable come back... but nothing is coming to mind. So yea, a Prius certainly racks up the ghey points. I try to counter the ghey points with the Jeep but I don't think I've driven it in about a month so I'm mighty ghey right about now. Good thing I have dark tinted windows, eh? :stooge_larry:

Howyadoin
08-14-2008, 04:09 PM
Good thing I have dark tinted windows, eh? :stooge_larry:


"Is that your Prius outside"?.............."what's a Prius"?:laugh2: