Video: Can Skinnier Tires Increase Fuel Economy?

[naplm00]

Also, if you are goin to these lenghths why not just repack the wheel bearings?

[orange4boy]

The testing done in the previous examples showed changes in the CD of the vehicles so in these cases it had nothing to do with rolling resistance.

In these cases it mainly has to do with frontal area. In most road vehicles all four tires can be considered part of the frontal area. Generally, the front tires do not shield the rear ones. This kind of favouable shielding or flow control can be partly achieved with side skirts like on Basjoos civic. Without this kind of flow control, under car air flows slightly outward from the centre line of the car approaching the wheels at a yaw angle of about 15 degrees for the front wheels (sometimes much higher) and at a lesser angle at the rear.

There may be changes in the RR of the tires with changes in aspect ratio but in these cases it was not measured.

[euromodder]

Originally Posted by Piwoslaw

Going from wide to narrow usually means that the tire is not as tall. Could the Cd change have been from the vehicle's body being slightly lower, closer to the ground?

Dunno about Poland, but if we want to change our tyres, we have to keep to within a few % of the original diameter.
In order to get the same diameter, there will be more rubber around the rim.

[Ni87]

I'm just planning on keeping the original tire width. But as far as tires and rims go in goin to go from 185/65-r14 to a 185/55r16. In hopes that i still gain some economy from going to a lower profile tire and still keep safety, drivability, and comfort. I was thinking of doing a smaller rear tire but I can't get skinnier Yokohamas for the rim size. They're my favourite brand and is one heck of a long lasting tire. I'll let you guys know how the set up goes when spring comes around.

[Grant-53]

Consider that there is a range of ply materials, compounds, and tread designs available in a given size that is recommended for each specific vehicle. Unless I am driving at a closed course event I prefer a tire with a fairly high temp rating, a tread wear rating above 400, and a tread pattern with many narrow siping grooves. I have to consider the cost of fuel versus body damage. I did put some aluminum rims and Stage I tires on a '95 Prizm 5 spd with good results in terms of handling. Fuel economy stayed about the same. After 50+ years riding bikes I would advise that there is no simple answer to selecting the right tire for a given application. The trick is to find the right combination for the conditions.

[Ecky]

Larger rims have more of the rotating mass toward the outside, so even if they're not any heavier (which they almost certainly will be), they'll feel a lot heavier due to the extra inertia. Chances are you lose economy and gain some ride harshness.

[royanddoreen]

I wonder if the rpms were the same or were there diff o.d. Tires?

[litesong]

Originally Posted by Ni87

....... go from 185/65-r14 to a 185/55r16......

Three years ago, I experimented with used larger wheels/tires on two cars, both receiving tires, 30MM wider & 2 inches taller. On both cars steering & handling became wonderful. The small car (with low-geared transmission), now has lower rpms at the same speed & really feels like a larger car. Both cars feel good AND provide increased MPG. However, the large tires on both cars are close to the mudflaps & wheel wells, so have no room for snow chains. In regions of snowy, hard winters, snow wheel/tire changes would be necessary.