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View Full Version : Fuel Consumption Question - Rims - Please look



tradertt
03-17-2003, 01:39 AM
Hi, I have a question which I wonder any one with experience could help answer.

If .. IF I have 2 choices of Wheel Rims ..

1) A 15 inch rim that is heavy (8kg)
2) A 16 inch Rim that is light (6kg)

Which will have a higher fuel consumption? I know that it takes effort and of course more fuel to move a rim that is of bigger size ... but with its weight into effect ... will it be offset or even have better fuel consumption than the 15 inch one?

Thank you for this silly question.

Dave Russell
03-17-2003, 04:20 AM
I'll bite,

The rim diameter alone does not tell much without the tire size also. A larger overall tire diameter will give a taller effective gear ratio if it is on the driving wheels & should result in less fuel consumption due to less engine revolutions per mile traveled. On the non-driven wheels it doesn't make much difference one way or the other.

On the average vehicle the weight difference of the wheels is such a small part of the overall vehicle weight that it will make no measurable difference.

A narrower & harder tire of any size will give better mileage due to less rolling resistance. Most of these differences could only be measured in some sort of carefully supervised mileage competition.
D

tradertt
03-17-2003, 05:20 AM
Although 1 or 2 kg may not seem much as compared to the vehicle wt .. but do not forget the property of INertia ... it takes a whole lot of effort to get a tire moving from a stop ...

Sometimes it makes me wonder if its worth while getting a RIM that is ultra light - OZ - or getting a heavier rim which is much cheaper. Wonder how much fuel will I save in the end ...

Dave Russell
03-17-2003, 02:49 PM
Inertia applies to the entire vehicle weight (mass), not just the wheels. It is obvious that the entire vehicle must me accelerated along with the wheels. It is not just the rotating inertia but the "linear inertia" also which has to be considered. You can't just move the wheels without moving the rest of the vehicle.

If for some reason you wanted to just consider the rotating portion, the axles, Brake drums, drive shaft, transmission, clutch, & all engine rotating components must also be considered. All totalled, probably around 68 kg.

If the vehicle were a bicycle the wheel weight would be a much larger portion of the total & there could be a noticeable difference, but I assume that you are not discussing bicycles.
D

tradertt
03-17-2003, 03:02 PM
Lolz. ... I have been brainwashed into thinking that weight is an important factor in choosing a RIM .... What will then be your major consideration for a GOOD RIM?

Dave Russell
03-17-2003, 03:25 PM
Anyone out there---- Hellllp!!!
D

Dave Russell
03-17-2003, 06:42 PM
You are so vague about this rim question that it is hard to give any specific information. Is the rim on a car, bicycle, motorcycle, wheel barrow, tractor, or what.

By "rim" do you mean the wheel? The main consideration on wheel selection would be that it fits the tire which you desire to use, is sturdy enough, & has the look that you want. Wheel has to be coordinated with the tire.
D


<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by tradertt:
Lolz. ... I have been brainwashed into thinking that weight is an important factor in choosing a RIM .... What will then be your major consideration for a GOOD RIM?<hr></blockquote>

tradertt
03-18-2003, 01:07 AM
Take a look at this .. what I wanted to do is to ...

fill up this gap between my wheels and the body of my N16
Please advice. I forgot to check my tire specs but I believe its either

175/70R14
185/65R14

How can I fill up the gap ... what sort of rims can I change to ? Would it adversly affect my fuel consumption?

https://www.autopia.org/forums/attachment.php?s=&postid=188015

https://www.autopia.org/forums/attachment.php?s=&postid=188016

Dave Russell
03-18-2003, 01:56 AM
I have reached the limit of knowledge on this subject. I haven't the slightest idea what an N16 is or what to do with it. Someone else will have to take it from here.
D

MattP
03-18-2003, 02:26 AM
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by tradertt:
Lolz. ... I have been brainwashed into thinking that weight is an important factor in choosing a RIM .... What will then be your major consideration for a GOOD RIM?<hr></blockquote>

Round is definately better. The square ones just eat the gasoline. images/icons/tongue.gif Wheels are mostly a visual decision. I think that it would take pretty extreme conditions for the few kgs on the wheels to matter at all.

I don't know what a N16 is either. And which axis do you want to fill? Have you anyone with the size tires and wheels you are thinking of? Can you measure them for the fit? Plus I notice that you list a 15" wheel and a 16" wheel then two 14" tires, this will make a difference as well.

If it helps, for fuel economy the rule of thumb is 100 lbs = 1 MPG. So for each 100 lbs you can trim from your car you gain 1 mile per gallon. I also saw some gains by installing a K&N low restriction filter, and Bosch platinium +4 plugs to improve my ignition. This was on a 97 Ford Escort with Fuel injection, so I don't know how applicable this will be to a N16

MattP

[ 03-18-2003: Message edited by: MattP ]</p>

tradertt
03-18-2003, 04:12 AM
Lolz... sorry about that graemlins/crazy.gif

Dave Thielke
03-18-2003, 10:20 PM
I think the big advantage in the light rims not in fuel mileage, but thier effect on the unsprung weight ratio which in turn means better handling, hopefully.
Dave T

MattP
03-19-2003, 02:10 AM
I tried to get to your pictures, but I am not an autopia member, and they also don't allow links to the pictures so that they can show up here. Anywhere else you can post them? It might help clear up some of the confusion here.

MattP