Ok here are some results conserning wheel weigths which comes from my memory:
1. wheel weight affect fuel consumption
2. Effect depends do you do most of driving in city (bigger effect) or highway (smaller effect) What is your cars total weight. 10% lighter car gives 2 to 8% better fuel consumption depending on the source and test method city vs highway. Rotating weights affect 4 times their own weigth to overall weight. So if you save one pound you can calculate that you have saved 4 pounds... Also the car driving characteristics change to better response etc.
3. You will see much better effects in fuel consumtion if you go from your stock wheel size to one or even two size smaller rims. Your front brake calibers dictate how small rims you can put there. Note that there is big difference in the inner shape of the rims. Racing rims are can eat inside much bigger brakes. 3mm clearance is more than enough to brake calibers.
4. Usually this means that you have to add narrower and taller height profile tires to keep the revs at same level or even lower them which is good for FE. Both lower the fuel consumtion hugely. On my Seat Cordoba 1.9 TDI stock tire size was 185/65R14 and with 175/80R14 on from I saw immediately about 10% better fuel consumtion figures. Smaller rim and taller tire give always the best results. On my Lupo 3L I now moved from 145/80R14 to 175/70R14 and fuel consumtion get worse about 15% and the winter tires are best LRR tires out there. My winter wheels are also little bit heavier
5. Check that your weight limits on the tire narrower and taller is enough if you care about that kind of things.
Aerodynamic effect.
Smooth hubcaps lower the fuel consumtion about maximum of 5-6% so that might easily have bigger effect than the lighter wheels which you should always note.
Best setup is:
- about 30mm narrower tires than stock
- about 5-10% taller tires than stock.
- usually that setup means that you cannot get easily LRR tires but that is not the most important factor. Effect of LRR tire and worst tire is about 5% to fuel consumtion in tyre tests. You can get that 5% better RR by putting 50 PSI on the tires .
- Most lightweigth rims you can afford (weight saving will not give ROI never on rims) on most cars lighter rims cannot be seen at the pump.
- Try to buy aerodynamic rims or install smooth wheel covers:
http://tuneko.com/TuneCover---Alumin...el-hubcaps.php
Best setups in my cars:
at seat cordoba vario 1.9 tdi, stock size 185/65R14
front 175/80R14 toyo 350
rear 175/70R14 Michelin energy savers
This setup needs -60 front and -30 rear lowering kit or just -30mm in the front to get the stance correct
Lupo 3L stock size 155/65R14
145/80R14 Bridgestone B381 ecopia with Lupo magnesium wheels which are pretty light.
I also tried
135R15 2cv tires at the front but it did not give better FE on my Lupo
So for starters I would use the current wheels and put there narrower and taller tires. If you put there higher pressures you can use 1" wider wheels what is the recommedation. This gives also little bit better aero.
What comes to buses or other cars 1% difference is not measurable in normal driving on any vehicle.
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