Top 5 most fuel efficient tires (Lowest Rolling resistance: LRR)

[oil pan 4]

How did this "narrow is better" and smaller is better myth start?

[CapriRacer]

Originally Posted by oil pan 4

How did this "narrow is better" and smaller is better myth start?

If you don't have the Smithers data to look at, it might be logical. But the thing the Smithers data points out is that there is a HUGE difference in RR within the same size - AND - that larger tires are more efficient.

If folks were to try to do A-B type testing - which is what would happen in the real world - then the small differences obtained by tire size would be lost in the mud.

But the one thing the Smithers data doesn't address is what happens when you adjust the inflation pressure to get the same load carrying capacity. That is still an unknown. We have some indication - and the indication is that this is the only scenario where "smaller is better" actually works. Needless to say, if the intent is to wring the last bit of RR out of a tire, then that is NOT where you want to go.

[bwilson4web]

You may want to look at the Sumitomo line. They are also rated low-RR and is the tire Toyota service centers use as replacements. Best of all, they seem to have reasonable prices. However, if you live in a area with a lot of snow and ice, the Sumitomo might not be the best all-weather tire.

Bob Wilson

[euromodder]

Originally Posted by CapriRacer

We have some indication - and the indication is that this is the only scenario where "smaller is better" actually works.

There's also the aero-component of drag.
Wider is not better for aero drag.

Rain on the road has less of an impact on narrow tyres.

[some_other_dave]

Originally Posted by CapriRacer

If you don't have the Smithers data to look at, it might be logical. But the thing the Smithers data points out is that there is a HUGE difference in RR within the same size - AND - that larger tires are more efficient.

"Larger" as in wider? Is this a coefficient thing, or a total drag thing? If the analogy with aero holds, and if the improved RR is the coefficient, it may be possible for narrower to be better than wider.

I haven't looked at the Smithers data, so I don't know what it says.

-soD

[Vekke]

I will try to do some kind of coastdown test with two suberb tires:
145/80R14 Bridgestone B381 Ecopias. Original Audi 3L tire size.
175/70R14 Nokian Hakkapeliitta R. One of the best LRR tire available at the moment.

So the test will be a coastdown test from 140 km/h to 0. I will measure the distance diffence but also the times which it will take to 140-65 (aero) and 65-0 (Rolling resistance). I will appreciate more aero but those are also 3% taller so I have to test them also while driving to see which is actually better... Rolling resistance wise Nokians should be best with clear margin . Pressures in both tire sets always 3.5 bar.

[Hubert Farnsworth]

Originally Posted by Vekke

I will try to do some kind of coastdown test with two suberb tires:
145/80R14 Bridgestone B381 Ecopias. Original Audi 3L tire size.
175/70R14 Nokian Hakkapeliitta R. One of the best LRR tire available at the moment.

So the test will be a coastdown test from 140 km/h to 0. I will measure the distance diffence but also the times which it will take to 140-65 (aero) and 65-0 (Rolling resistance). I will appreciate more aero but those are also 3% taller so I have to test them also while driving to see which is actually better... Rolling resistance wise Nokians should be best with clear margin . Pressures in both tire sets always 3.5 bar.

Rolling resistance always plays a role, however its effects are masked by the aerodynamic road load forces above a certain speed. Therefore the force that it requires to overcome the sum total of the wind resistance, grade resistance and road load force combine in their effects upon the coast down distance from any speed. As a rough calibration it may be possible to roughly estimate the forces required through the use of the road load calculations, however they will only be as accurate as the input data, which will require knowing the rolling resistance of the tire (a standard tire might have a crr of 0.010 and a lrr tire a 0.008), the aerodynamic coefficent of drag, the target speed or speed range, the frontal area and the mass of the vehicle.

[bandit86]

Slightly off topic but not, 1995 land river discovery needs tires. Stock size is 225 75 16. Would like to go up to a 245 size, something more aggressive. Any suggestions? I had 235 85 16 on my last one and my fe dropped to half but worked great off road

[CapriRacer]

Originally Posted by bandit86

Slightly off topic but not, 1995 land river discovery needs tires. Stock size is 225 75 16. Would like to go up to a 245 size, something more aggressive. Any suggestions? I had 235 85 16 on my last one and my fe dropped to half but worked great off road

First off, you need to be aware that your vehickle originally came with P type tires - and it appears you are using LT type tire on it.

The difference between these 2 tires is that LT are designed to carry much more load than P type tires - and that means the materials used have to be more robust. I call this higher "unit loading". What comes along with this is the materials generate more rolling resistance.

Plus, LT type tires do not like flexing as much, so you need to use 15 psi more pressure to get the same load carrying capacity (for the same dimensions)

This thread has discussed the "Larger is better for RR" principal, so going from an LT225/75R16 to an LT245/75R16 would be directionally better - but as has been said before, the effect is small.

If you are using the vehicle off road, then I think you need to ignore that fuel economy aspects and chose tires basded on their off road performance - and that means you're in the wrong place to be asking such a question.

[bandit86]

If A tire does not like to flex much would that not mean it should have lower rolling resistance? Like not compressing the side wall as it turns? Granted it has more more weight

Actually I was thinking of a mud+snow tire

What about siping, does that make a difference?