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I have looked in the forum and am now slightly confused.
I have an '05 HCH MT and am looking at what modifications I can make to improve the MPG. I'm looking at mods because I'm not the only one driving it and I'd like to keep the avg. MPG up.

I've been looking at reducing weight and one of the first steps would be to get lighter wheels. I think the factory wheels are around 18 to 20lbs each. I have found Kosei K1 TS wheels that are 9.3lbs. That gives a total reduction of about 40lbs of unsprung rotating weight.

CleanMPG member Tim has these wheels on his HCH.
http://www.cleanmpg.com/photos/data/500/medium/Car_Aug_06_004.jpg

Looking at some of the posts about aftermarket wheels, the concern seems to be a loss of the aero properties of the factory wheels.
http://www.cleanmpg.com/forums/hardware/t-cool-looking-lrr-wheelstires--2552.html

I read the thread about the moon-like hubcaps that said that they gave at most a 2 MPG improvement if any.
http://www.cleanmpg.com/forums/hardware/t-aero-hub-caps-2735.html

So, my question is this: Is it worth the $500 to get the 40lb reduction, and if so how much of a MPG change would you think I'll get?

FYI: I drive 500 to 600 miles each week with 15%/85% city/hwy, and the highway miles are on fairly flat roads, so it doesn't take long for a small change to add up. I even changed my route to shave 3/10ths of a mile per day. ;)

- Altair

I would guess about a 2-3 MPG improvement. But that's a completely uneducated guess.

remember, the wheel weight is not only dead weight, its rotating weight, which takes more energy for each pound. Thus, 40lb on the wheels is like 80lb dead weight.

I second WartHog's comment and also want to mention that Larry (Diamond Larry) did just what you are looking at doing for his Saturn (not long before getting the Prius -- so back in the April/May timeframe?). As I recall he did see a fairly noticeable difference in glide distance.

Larry, do you want to chip in with your experiences?

As to whether or not it would be worth the $500 -- that depends on what your goal is. Are you looking for them to pay for themselves in gas savings? It would probably take a REALLY long time to do that. Are you instead looking to be as clean as possible by eking out as much mileage as possible? I could be worth it for that effort but that is highly subjective. Of course it probably won't hurt the looks of the car, either. ;)

The aero advantage vs. wheel mass debate goes on . Pretty much a draw to me . When I ordered the Focus, I optioned the 15" alloys as they were the lightest wheel (15.9#) offered in this line. I also felt they were the most attractive. Pick several wheels by which one *you* think looks the best , narrow it down by which ones are the lightest , choose the best looking lightest wheel (AND tire- tire weight is nearly always overlooked)then grab your credit card and be happy . The FE will be a side benefit to a hot looking ride .
Best of luck finding the right one and Do post pics ;)

Perhaps, we'd all say better if your roll is long enough and you rarely need to accel/decel.

That Civic looks beautiufl with those wheels. Way better than the stock hybrids! I'd be happy on looks alone!

Hi 99HXCivic:

___Have you see the light blue HCH-II like Altair’s with the EX wheels on it in the gallery?

___Good Luck

___Wayne

I'm just guessing, that weight matters a little more during acceleration and slow speed driving, and aero matters more for high speed driving. But that is just my opinion. I was thinking about doing the same thing, since 1 of my tires has a slow leak.

Weight matters regardless if its rotating. It takes more energy to keep a heavier object rotating that it does a lighter weight object. This is more pronounced the further the weight gets from the center of the rotation. Don't forget about tires, they have significant weight to them as well. Most tire manufactures list weights for their tires online, but rolling resistance should be the key factor when deciding on a tire for high FE driving.

so giving the weight, would it be better to have lower profile tires if wheel size stays the same and rolling resistance stays the same?

If it means stepping up in rim size no. An increase in rim diameter will net a larger increase in weight since metal weighs much more than rubber. Then again it all depends on your rim choice.

Remember there is the golden triangle rule about rim selection. There are three variables, Strength, Light weight, and cost. You pick two. You can have a strong and light rim but its going to cost $$$. On the counter side, you can have a light and cheap rim but your going to have to worry about it bending every time you hit a pothole.

If your willing to spend the money, you'll probably be able to find a set of really lightweight and strong rims that will weigh less stock rims, but in that case you'd also be able to find a rim that weighed even less if you just stayed the same size. On a note about tires, just because they are low profile doesn't automatically mean they will weigh less. The sidewall on those low profile tires are much thicker in order to be able to carry the same amount of weight.



The best option for FE driving would be to pick the smallest diameter rim that will fit over your brakes and fit a tire to that. Plus it will give more sidewall to soak up road harshness.

You'll have to consider rim width as well. You can get narrower rims that retain the same diameter, but then you run into load ratings on tires as tire width plays a role in the load rating as well as handling characteristics.

You'd probably be best to stay the same rim size as stock, just finding a lighter rim thats within your budget and picking a good LRR tire to mate to it. Just be VERY cautions with lightweight rims that are really cheap. I've seen cheap lightweight rims explode on the track... and thats not fun when your driving 100+ mph. Obviously those speeds are not something a hypermiler would experience, but the same holds true. Rim fatigue is a great concern...

I'm in a lowered del sol Harshness does not bother me :D As far as cheap light weight, what would you consider cheap?

Depends on the weight. Obviously the lighter the weight, the more $$$ it takes while staying strong.

vaguely speaking, anything under $150-200 in a light weight rim I would consider "cheap"

They might not explode, but hitting potholes and bending them to the point of being not repairable is a big concern. Keep in mind this is coming from an ex-racer so when it comes to safety, money should be the last concern.

Your tires and wheels are the only thing touching the road and allowing you to control the car. Don't skimp there as you will regret it one day.

On a different note, the next important thing is brakes. Rotor weight can be safely reduced with lightweight two piece rotors, but then your also looking at $$$ for a proper system and that is most likely out of the scope of hypermiling (unless your going extreme ;))

I picked up around 2 MPG when I put the drag wheels on my Camaro

I'll be buying a new set of wheels for the yaris when the spring gets here :)

PS, thoes wheels you have the picture of are sexy, and that price and weight are nice as well

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I don't know how much the HCH-1 wheels weigh, but the HCH-2 wheels look more similar to the Insight wheels, which are some of the lightest / most aero wheels around. I'd try to snag a set of factory HCH-2 wheels if you are just looking for MPG bump.

If you just want it too look better, pick something you like in an OE size, or +1 at most.

My opinion is truly seat of the pants. I cycle quite a bit, and frankly I can only tell the difference in wheel weight when I accelerate. Aerodynamics however I feel. Fewer spokes equal easier pedalling.

Louis B

I cycle too, and I know my Zipp 404's are way more aero than my Ksyrium SL's, Ritchey Protocol's, Campy Eurus, and Shimano 540's. My HED 3's give me fast workouts too. And it's very noticable in my workouts that my HED 3 equipped Cervelo Soloist has a higher avg speed per watt stats than my other road bikes.

I cycle too, and I know my Zipp 404's are way more aero than my Ksyrium SL's, Ritchey Protocol's, Campy Eurus, and Shimano 540's. My HED 3's give me fast workouts too. And it's very noticable in my workouts that my HED 3 equipped Cervelo Soloist has a higher avg speed per watt stats than my other road bikes.

Do you feel any diff in steady speed cruising due to weight?

That is a considerable savings in weight for the $. Are they forged by chance? I doubt it for the price. Rotating mass is a very big hit regarding acceleration and thus gas mileage. I would like to second guess what was mentioned earlier... That the weight of the rims out weighs the weight of the tire. It takes very little metal to increase the diameter of a rim an inch versus the amount of solid rubber sidewall that would be decreased. I think the rim size weight gain versus tire wall weight savings would be negligible. It does not take more energy to keep a larger diameter wheel rotating... I swear, Newton's law. An object in motion tends to stay in motion. It would, however, take more energy to accelerate a larger rim/wheel combo. Have you thought about a lighten flywheel? Shaving a few pounds in your flywheel is like removing 300 lbs from your vehicle in first gear (and it goes down from there). You will see many benefits from going with lighter wheels other than just fuel economy. You will have an improved ride (unsprung mass), better handling, better braking (that whole Newton's Law thing again), and they look good. I would go for it because it really isn't that much dough. Just my $.02 :Banane09:

It's true that a larger rim may not weigh much more than a smaller one of the same design. The problem is that the weight is farther from the center. That makes a BIG increase in rotating inertia.

According to this wikipedia article (http://en.wikipedia.org/wiki/List_of_moments_of_inertia), rotational inertia increases with the square of the radius. For example, ignoring the spokes and only looking at the rim part of the wheel, moving a single size, from 14" to 15" gives you:
14^2 = 196, 15^2 = 225
(225-196)/196 = ~15% greater rotational inertia.

Uh, it's actually worse. Just looking at the RIM (not the hub and spokes) is a good first approximation.

So, the just looking at the RIM (not the hub and spokes) and holding design/manufacturing process constant, the mass of the RIM is:

m = k*2*pi*r*w (where "k" is a constant related to the design/manufacturing process, r is the radius, and w is the width).

So:

eq 1a: m0 = k*2*pi*r0*w
eq 1b: m1 = k*2*pi*r1*w

eq 1c: m1/m0 = r1/r2

Then the thin shell inertia approximation for the rim:

eq 2a: I0 = m0*r0^2
eq 2b: I1 = m1*r1^2

eq 2c: I1/I0 = m1/m0*r1^2/r0^2

Substituting eq 1c from above for m1/m0:

eq 2d: I1/I0 = r1/r0 * r1^2/r0^2
eq 2e: I1/I0 = r1^3/r0^3


Finally, remembering that a 14" wheel is a 14" DIAMETER wheel, (7" radius), and the "+1" of the 15" wheel (7.5" radius):

I1/I0 = 7.5^3/7.0^3 = 1.23

So, the rim portion of the wheel costs a whopping 23% increase in rim inertia going from a 14" wheel to a 15" wheel. The inertia increase of the whole wheel of course will be lower, because we've ignored the inertia of the hub and spokes.


Finally, the difference in inertia of the tires might surprise you. The hard thing is generally available tire weights (example, at tire rack) are not always as accurate as we'd like. BUT, given two tires of the same outside diameter and compatible load indexes for a given application, the +1 tire is "about the same" weight as the OEM tires. So just like we ignored the change in inertia due to the spokes, to a first approximation we can also ignore the change in inertia due to the tire. But again, the change inertia of the wheel/tire combination of course will be WAY below the 23% increase from the rim alone.

-mr. bill

Thanks for going through all that. I was doing a quick and dirty version.

Whoa, reading those calculations makes my brain hurt :cconfused:. So I guess that the layman's version is: upsizing to a larger wheel will most likely hurt FE. :)

One final BOTE.

The stock wheel weight and the stock tire weight are about the same.
The dimensions of the stock wheel and the stock tire are such that about 1/4 of the rotational inertia is from the wheel, and 3/4 of the rotational inertia is from the tire. (Ballpark.)

So, in the end, a +1 wheel will cost you on the order of 2-5% in rotational inertia.


-mr. bill

What about the effects of rolling resisitance? A lot of lower profile tires have a max pressure in the neighborhood of 51 psi versus 44 psi. Does anyone know how much of an effect this would have when going from a stock rim size/higher profile tire to a larger diameter rim/low profile tire (maintaining the stock overall diameter)?

What about the effects of rolling resisitance? A lot of lower profile tires have a max pressure in the neighborhood of 51 psi versus 44 psi. Does anyone know how much of an effect this would have when going from a stock rim size/higher profile tire to a larger diameter rim/low profile tire (maintaining the stock overall diameter)?

Generally, the width of the tire has the greatest effect on rolling resistance, and usually the increased diameter wheel is matched up to a wider tire. Here's a great thread focusing on tire's dimension's effects on FE ... http://www.cleanmpg.com/forums/showthread.php?t=10648

There's a website on weight of wheels. Keep in mind, most of the weights are submitted by people using bathroom scales.

http://www.wheelweights.net

Near empty vehicles may get improved FE with up gear / higher final drive ratios...My 4 speed tranny is short legged at highway speeds so larger diameter tyres on standard rims have increased final drive. No instrumentation, but, I drive usually alone without load so I'm sure the lower engine rpm is saving gas.

Do you feel any diff in steady speed cruising due to weight?

I have the same ZIPP 404s as this guy. I also have the slower Ksyrium SLs. The ZIPPs do maintain a faster constant speed increase of about 2mph. I can go 20mph instead of 18mph.

smaller wheels are better generally...to a certain extent except when coasting.

It takes more energy to keep a heavier object rotating than it does a lighter weight object.

This is absolutely not true. See Newton's first law: I. Every object in a state of uniform motion remains in that state of motion unless an external force is applied to it. However it does take more energy to accelerate it to the same speed.

On the interstate at constant speed, the amount of force the engine is applying to the wheels (amount of gas used) is exactly the same as the amount of force against the direction of motion aka resistance. However in the case of lighter wheels the amount of resistance barely changes. There's still the same amount of rolling resistance from wheels, axels, etc. and the same amount of aero drag. Due to the lightening of the car there will be a very small reduction in rolling resistance, but for constant speed interstate driving, lightening of the wheels virtually makes no difference

However for driving in town, lightening the wheels makes a difference as clearly the motor needs to accelerate the wheels not only "longitudinal" but also rotationally. So reducing the wheel weight will increase FE more than just reducing the weight of the car for in town driving.

However thinking about this: let's say a 40lb wheel weight reduction is worth an effective 80lb reduction. 80lb is 2.8% of 2877lbs (stock weight). So assuming that resistance for in town driving was 0 and gas was only used to accelerate the car you would improve in town mpg by a maximum of 2.8%. However I would imagine that for in-town driving typical of a normal hypermiler resistance from the tires, axels, and aerodynamics would account for at least half the gas they use. So in that case you're looking at a 1.4% improvement in FE.

Taking that 1.4% increase times 15% of your driving = 0.21% increase in FE.

Physics Conclusion: Get low rolling resistance tires. They play a much larger role in the FE you will get then tire weight.

Note: I tried to vote 0 increase as 0.21% certainly doesn't equate to even 1 mpg. However the original post was in 2007??? Who's digging up 2 year old threads?

This is absolutely not true. See Newton's first law: I. Every object in a state of uniform motion remains in that state of motion unless an external force is applied to it. However it does take more energy to accelerate it to the same speed.



This is only true for a vacuum. There is air resistance and friction along with bending.

Does anybody know how much the Alloy wheels on the 2009 Honda Civic Sedan LX-S weigh? I believe those are the same ones used on the previous year Honda Civic EX and EX-L THey are 16 inch alloy wheels, sorry no pic yet!

What is more how do they compare weight wise to the CIVIC LX and DX-VP steel wheels with cover?

Thanks,

Mark

http://www.collegehillshonda.com/storeart/civic/sedan/2009/42700-sna-a81.jpg

Found the Pic of the WHeel. I believe i do have the TPMS...on the car... Don't really care for it, as i Check the tire presure regularly ..... I wonder if i can pull another fuse... =) to disable it. (Day time running lights went first)

-Mark

they look the same but I haven't seen them side-by-side