Save gas tip, install lightweight wheels

[A-Dingo-Ate-My-Baby]

I didn't think this would make much of a difference

but it really does.

I am averaging 1.5-2 mpg more on a whole tank just with the
use of lightweight aftermarket alloy wheels in stock 15 inch size

[this is interstate driving on rolling hills pinned at 68mph. this route is
where I do all my occasional mpg checks. out and back is 490 miles]

[daf62757]

Can you make the entire round trip on one tank or do you have to refuel?

[A-Dingo-Ate-My-Baby]

Originally Posted by daf62757

Can you make the entire round trip on one tank or do you have to refuel?

I do 225 miles steady interstate, and then about 20 miles surface traffic which includes a fillup,
then 20 more miles surface speeds, then drive back 225 miles on same highway back to origin



I get 41mpg to 39mpg on my route, depending on traffic
and if I have to pass someone, or get accidental drafts, weather/wind...normal variables

it'll go to 42+ if i go slower than 65mph but I can't do that, it is not reasonable for the other
users of the interstate to deal with a slowpoke

[CrankyOldMan]

[devilsadvocate] What is the expected fuel cost savings over the life of the investment? Do you break even before the rims are unusable?

[/devilsadvocate]

[nemelek]

It's always good to save gas. However depending on the cost of the rims it might take 80,000 miles to break even.

[A-Dingo-Ate-My-Baby]

Originally Posted by CrankyOldMan

[devilsadvocate] What is the expected fuel cost savings over the life of the investment? Do you break even before the rims are unusable?

[/devilsadvocate]

what ? rims unusable ? they have no lifetime. they will last forever if I don't damage them

I am not concerned with any of this, or hypermiling, or anything else along these lines.
I am just saying that MPG's will increase if you use lighter rims, which is a no-brainer anyway due to weight.

I am not going to factor anything else in, or compare the carbon footprint of manufacturing a steel
rim vs an alloy cast and all that tree-hugging crap.

cost benefit x time ?

the yaris handles better (steering is improved), accelerates quicker, stops faster, gets better MPG's, and these benefits are immediate

lessee...
I will throw out a wild guess...I reckon it will be somewhere near 47,000 miles
before I reap the cost of the rims if gas is 3.5 bucks a gallon. good enough if you are
going to keep the car for 100,000 or more miles

[CrankyOldMan]

Originally Posted by A-Dingo-Ate-My-Baby

what ? rims unusable ? they have no lifetime. they will last forever if I don't damage them

Well, I realized that as I was posting it, I just couldn't think of a better way to describe the length of time they will be in use, barring some catastrophic and premature end of your car. =) I'm very curious to see how this holds up long-term.

[Idahotom]

I am thinking of getting an extra set of wheels just for my dedicated winter tires, so this is good to know.... there is a reason the big rigs use a lot of alloy wheels, and it ain't because they look good, they save fuel.

[Ah Yum]

I have 11 lb wheels and NST underdrive pulley set. I hypermile, and last tank was 52.7 MPG US city. But that's through rigorous efforts. Lightweight wheel doesn't pay itself off through the marginal fuel savings. This coming from a city driver too. With constant load on the highway, any wheel-weight savings have even less impact on rotational inertia or fuel economy. It's mostly cosmetic and some acceleration improvement on first two gears. The length of your trip keeping your drivetrain in optimal operating temperature has more to do with your noticeable mileage improvement.

[A-Dingo-Ate-My-Baby]

Originally Posted by Ah Yum

I have 11 lb wheels and NST underdrive pulley set. I hypermile, and last tank was 52.7 MPG US city. But that's through rigorous efforts. Lightweight wheel doesn't pay itself off through the marginal fuel savings. This coming from a city driver too. With constant load on the highway, any wheel-weight savings have even less impact on rotational inertia or fuel economy. It's mostly cosmetic and some acceleration improvement on first two gears. The length of your trip keeping your drivetrain in optimal operating temperature has more to do with your noticeable mileage improvement.

my post stands.

[Kaotic Lazagna]

Gonna quickly chime in. I had two sets of rims, one lighter and one heavier. My heavier set gives me better gas mileage on the freeway, but poorer if it's city driving; and vice-versa.

[A-Dingo-Ate-My-Baby]

^ agreed
I am seeing even better mpg improvement on my short, daily work commute

avg usually 29 +-, now steady 32 +-

[djct_watt]

Originally Posted by Kaotic Lazagna

Gonna quickly chime in. I had two sets of rims, one lighter and one heavier. My heavier set gives me better gas mileage on the freeway, but poorer if it's city driving; and vice-versa.

Same diameter, width, and tires? The biggest factor in rotational inertia (by an exponential factor is wheel radius and not weight).

Rot.Inertia = Mass x (Radius^2)

But in terms of maintaining speed (e.g. highway driving), I imagine that rolling resistance (tire and width) would be a bigger factor than weight.

Reducing wheel weight and radius will increase acceleration and braking performance, which will have a positive effect on city/performance driving. It's the reason that any REAL sports car has the smallest wheels possible that will clear the brakes.

I suppose that increased rotational inertia will help keep the wheels from losing momentum. However, any reduction in losses will be 100% offset by the increase in energy needed to recover lost momentum. I'd do the math and equations for all to see, but I'm just too lazy.

I think the gains/losses people tend to associate with bigger (and sometimes heavier) wheels are attributable to the fact that they use a completely different set of tires, hence making any comparison invalid (e.g. grip, handling, traction, etc), or they completely ignore the relevance of wheel width, comparing stock 185mm wide 15's vs 215mm 17's.

PS I have no idea if that even applies to you, Kaotic, (and I think it doesn't, but I'm just rambling venting about a complete different subject matter).

[flg]

I do better in the summer months than the fall and winter and spring. What hemisphere do you live in. Is warmer temperatures responsible for your improvement?
As many have posted wheel weight alone is an unlikely reason for such a gain. If you want better milage, don't install a CAI!

[A-Dingo-Ate-My-Baby]

ok I am done testing with my new rims with the old goodyear L-crap OEM tires

just put on the new Michelin Harmony and they are .3 % smaller diameter, even though
the size on the sidewall is the same. odd. anyhow I will run new mpg sets with
the .3% offset programmed into scangauge for accurate results.

[flg]

Your new tires are .075" smaller? How are you measureing that?
It is not uncommon for the tire size, as specified, to vary in actuall dimensions between styles and brands.
The actuall diameter for calculations should be 2 x the axle to ground measurement (Radius). That will also vary with tire presure/temperature and speed.

[A-Dingo-Ate-My-Baby]

Originally Posted by flg

Your new tires are .075" smaller? How are you measureing that?
It is not uncommon for the tire size, as specified, to vary in actuall dimensions between styles and brands.
The actuall diameter for calculations should be 2 x the axle to ground measurement (Radius). That will also vary with tire presure/temperature and speed.

with a GPS, car odometer, highway mile markers,
and canbus tool taking readings of speed from transmission

I have a lot of free time on my 225 mile trips

with the new Michelins mounted my car says I am going 70.2-.5 mph when
I am actually going 70...roughly. figured that is close to .3 percent smaller tire

so since I think I am very accurate (or nearly accurate) when I calculate
MPG's, I want to program the appropriate offset into my scangauge

[ljming99]

Take low rolling resistance tyres and install light weight wheel lug nuts =D