Relationship btw rim, tyre sizes and fuel consumption

orion · LvL 2 Joined: 02 Dec 2007 Posts: 82 Location: Kuala Lumpur

Wider tyres and bigger rims will cause the per kilometer fuel consumption to go up i.e. a set 16 inch 205 will have better mileage compared to a 17 inch 225, right?

FD2s with older 16 in rims will be more fuel efficient than the later version FD2s with 17 in rims. Can anyone confirm this?

blackberrybloke · Posted: Fri Dec 28, 2007 6:41 pm Post subject:

i reckon that making sure you have the right and adequate tires pressures are more vital in preserving a good FC.

no offenses to the females drivers out there, but most of them just don't care to inflate their wheels. just observe the next time when you do drive

mcwk · Committee Joined: 17 Apr 2007 Posts: 2168 Location: Melaka

orion wrote:

FD2s with older 16 in rims will be more fuel efficient than the later version FD2s with 17 in rims. Can anyone confirm this?

This I would like to know also, as I too am using stock 16" rims. However, I do understand that it would be quite difficult to see any change in fuel consumption unless it's very significant. My own monitoring of FC has an average of 11.4km/l and a standard deviation of 1.2 based on 28 consecutive readings....

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hotel kilo · ACE Joined: 29 Sep 2006 Posts: 2199 Location: Klang Valley

There are many variables especially when comparing to different set ups with different driving styles / conditions.

In general assuming car is similarly loaded and driving style & condiditons similar, you can say wider tyres will be worse off. Thread design and compound also has an effect so this has to be a constant. However for rim size, IMO weight plays more of a factor than size....lighter the better but they cost a lot.

orion · LvL 2 Joined: 02 Dec 2007 Posts: 82 Location: Kuala Lumpur

Interesting .... but let's narrow it down a bit shall we?

1. Weight of rims - I checked the rim weight list, the weight diff between 16 and 17 inch rim will be approx 2 lbs / 1kg or thereabouts. Making total weight diff between 8 to 10 lbs for the whole car, assuming all else are the same. But question is : will 8 to 10 lbs make any significant dent in the FC? After all, it is approx 2kg diff for a 1315kg car. That translates to 0.15% difference, rather small. Unless someone tells me that the weight diff between a really good rim and the stock rims can go as high as 50%.

2. Tyre widths - 205 vs 225mm, the 17 inch wheel will definately have more friction/resistance. But I'm not sure how to measure this one.

3. Total wheel sizes - for 17 in tyres, the circumference of the wheel is 53.38 in and for 16, it's 50.24 in. (C=2*pi*r) So for every revolution, 17 in wheel covers 6.7% more in terms of distance. This should work in favour of the 17 in wheel. So over 100kms, that's at least 6.7kms additional (correct me if I'm wrong).

So it seems that 17 in wheels should fare better on FC than 16 in, in theory at least!

But what are your real life experiences here? Any FD2 16 in and 17 in rims care to comment / input your FC numbers?

hotel kilo · ACE Joined: 29 Sep 2006 Posts: 2199 Location: Klang Valley

orion wrote:

Interesting .... but let's narrow it down a bit shall we?

1. Weight of rims - I checked the rim weight list, the weight diff between 16 and 17 inch rim will be approx 2 lbs / 1kg or thereabouts. Making total weight diff between 8 to 10 lbs for the whole car, assuming all else are the same. But question is : will 8 to 10 lbs make any significant dent in the FC? After all, it is approx 2kg diff for a 1315kg car. That translates to 0.15% difference, rather small. Unless someone tells me that the weight diff between a really good rim and the stock rims can go as high as 50%.

The saving primarilly should be looked not in terms of total weight but on unsprung weight i.e. weight not supported by the car. Not really sure how it measures effects on FC but a 2kg saving in unsprung weight can see up to 5ps saving on the dyno which should have better FC since engine mods and others are constant.

wrote:

2. Tyre widths - 205 vs 225mm, the 17 inch wheel will definately have more friction/resistance. But I'm not sure how to measure this one.

I've no idea how to measure this as well but it may be offset by going for low drag / high mileage thread design.

wrote:

3. Total wheel sizes - for 17 in tyres, the circumference of the wheel is 53.38 in and for 16, it's 50.24 in. (C=2*pi*r) So for every revolution, 17 in wheel covers 6.7% more in terms of distance. This should work in favour of the 17 in wheel. So over 100kms, that's at least 6.7kms additional (correct me if I'm wrong).

So it seems that 17 in wheels should fare better on FC than 16 in, in theory at least!

On this point I think you're over simplifying it as other factors mentioned would hinder the work to cover those distances. But assuming the both wheels & tyre package weighs the same and tyre width and model the same....your point would be correct

wrote:

But what are your real life experiences here? Any FD2 16 in and 17 in rims care to comment / input your FC numbers?

No real life experiences on FC or the FD as my main concern was primarilly with power saving related to unsprung weight.

Civic_DC · Posted: Sat Dec 29, 2007 2:49 am Post subject:

I have three question over here!

1. What kind of our stock 2.0S 16 inch rims made of? Normal Alloy?

2. Is it possible for a 17 inch "Light Weight Alloy" Rim to be lighter than our stock 2.0S 16 inch rim?

3. What kind of tyres each member have used to help boost FC in our FD's? Goodyear F1? or Michelin Energy or PP/PP2?

Thanks.

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Civic_DC aka Chris

hotel kilo · ACE Joined: 29 Sep 2006 Posts: 2199 Location: Klang Valley

Civic_DC wrote:

I have three question over here!

1. What kind of our stock 2.0S 16 inch rims made of? Normal Alloy?

2. Is it possible for a 17 inch "Light Weight Alloy" Rim to be lighter than our stock 2.0S 16 inch rim?

3. What kind of tyres each member have used to help boost FC in our FD's? Goodyear F1? or Michelin Energy or PP/PP2?

Thanks.

1) Not really sure but likely aluminium and/or mixture of both aluminium and magnesium

2) Yes definitely.

3) Not really a concern for me but from my siblings feedback and the general writeups low resistance/ high FC claim tyres suhc as Michelin Energy would boost FC

Civic_DC · Posted: Sun Dec 30, 2007 11:04 pm Post subject:

Thanks Bro hotel kilo. BTW does any sifus hereknows how much our stock 2.0S 16 inch rims weight? I mean kilograms? Thanks.

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Civic_DC aka Chris

hotel kilo · ACE Joined: 29 Sep 2006 Posts: 2199 Location: Klang Valley

Civic_DC wrote:

Thanks Bro hotel kilo. BTW does any sifus hereknows how much our stock 2.0S 16 inch rims weight? I mean kilograms? Thanks.

I haven't weight it but I reckon somehwere between 8-9kg thereabouts.

Civic_DC · Posted: Tue Jan 01, 2008 2:27 am Post subject:

Quite heavy...hmmm...considering upgrade from stock 16 to 17 enkei rims.

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Civic_DC aka Chris

hotel kilo · ACE Joined: 29 Sep 2006 Posts: 2199 Location: Klang Valley

Civic_DC wrote:

Quite heavy...hmmm...considering upgrade from stock 16 to 17 enkei rims.

The stock 17" is supposed to be off the previous gen CTR (EP3R) and this weighs out to about 9kg. If weight is your objective choose wisely.

hotel kilo · ACE Joined: 29 Sep 2006 Posts: 2199 Location: Klang Valley

hotel kilo wrote:

orion wrote:

Interesting .... but let's narrow it down a bit shall we?

1. Weight of rims - I checked the rim weight list, the weight diff between 16 and 17 inch rim will be approx 2 lbs / 1kg or thereabouts. Making total weight diff between 8 to 10 lbs for the whole car, assuming all else are the same. But question is : will 8 to 10 lbs make any significant dent in the FC? After all, it is approx 2kg diff for a 1315kg car. That translates to 0.15% difference, rather small. Unless someone tells me that the weight diff between a really good rim and the stock rims can go as high as 50%.

The saving primarilly should be looked not in terms of total weight but on unsprung weight i.e. weight not supported by the car. Not really sure how it measures effects on FC but a 2kg saving in unsprung weight can see up to 5ps saving on the dyno which should have better FC since engine mods and others are constant.

Just some info to add on the wight of wheels and its effect on FC. Refering to Wong KN's article on the new Jazz/Fit on Temple of VTEC Asia, it is mentioned that on the optional 16" wheel set up, FC is rated at 10km/l more than std. So to answer your question it would be yes but I don't know what the difference in weights are though.

mcwk · Committee Joined: 17 Apr 2007 Posts: 2168 Location: Melaka

orion wrote:

1. Weight of rims - I checked the rim weight list, the weight diff between 16 and 17 inch rim will be approx 2 lbs / 1kg or thereabouts. Making total weight diff between 8 to 10 lbs for the whole car, assuming all else are the same. But question is : will 8 to 10 lbs make any significant dent in the FC? After all, it is approx 2kg diff for a 1315kg car. That translates to 0.15% difference, rather small. Unless someone tells me that the weight diff between a really good rim and the stock rims can go as high as 50%.

Hi Bro Orion,

Generally, it takes more torque to accelerate a heavier wheel at the same rate as a lighter wheel. By wheel, I mean rim + tire. Also, the distribution of the mass relative to the rotational axis will play a role, since torque = force x distance and force = mass x acceleration, hence acceleration = torque / (distance x mass). Acceleration in this case, is rate of change in angular (rotational) velocity.

A real life example of this is an ice skater doing a spin. When he or she starts out with arms stretched out, the spin is slow, but as he or she draws his or her arms closer to the body, the speed of the spin increases. Try spinning round with your arms outstretched and close to your body - you'll be able to feel the difference yourself. Back to our wheel, we can speed up and slow down the spin of a lighter wheel faster than a heavier one, but ideally the distribution of weight should be as close to the center of the wheel as possible.

Do correct me if I've made a mistake here - it's been years since I was a student....

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