Discussion on tire efficiency

[tasdrouille]

Originally Posted by Ernie Rogers

Hello, Racer,

I think I will try logic, and you point out the errors--

1. Low rolling resistance tires never wear well.
2. Tires with hard tread material always wear well.
3. Therefore low rolling resistance tires never have hard tread material.

What do you think?

Ernie, what do you base your assumptions on? LRR tires usually wear well provided adequate inflation pressure is maintained. Said inflation being usually higher that placard recommended pressure.

[CapriRacer]

Originally Posted by Ernie Rogers

Hello, Racer,

I think I will try logic, and you point out the errors--

1. Low rolling resistance tires never wear well.

..........

Remember it's a triangle and traction is the third leg.

So it is possible to make a tire with good RR and good wear properties, but it will suffer somewhat in the traction department.

This might be a good example of the complexity.

Originally Posted by NeilBlanchard

Hi Ernie,

The upcoming Michelin HydroEdge "Green-X" tires are LRR and they are rated 800 on the treadwear estimate.

When Michelin says these are good for RR, are they comparing these tires to regular replacement tires? If so, then they may get good wear, but their RR would be only be better than regular replacement ires, but not as good for RR as some OEM tires - which would have either wear or traction complaints (or both).

Also, keep in mind that most tire wear occurs in the cornering mode. So if most of your travel is in a straight line, even potentially poor wearing tires will wear well.

Originally Posted by Ernie Rogers

......

2. Tires with hard tread material always wear well.

.............

Again, keeping in mind that it's a triangle, harder rubbers tend to wear well.

Originally Posted by Ernie Rogers

.........


3. Therefore low rolling resistance tires never have hard tread material.

What do you think?

I think that is a good rule of thumb. The problem would be comparing tires with different families of rubber chemistry.

For example, different manufacturers will have slightly different rubber formulations - and the rule would apply within that family, but will have some variation between families.

This also means that even within a given tire manufacturer, if different families of rubber compounds are compared, you'll get different hardnesses compared to the wear / traction / RR triangle - such as the difference between an all carbon black formulation vs a silica / carbon black mixture.

Another factor to consider is that there are tricks that can be employed to improve the wear. Tread elements using large blocks wear better than those with small blocks. But this hurts snow traction.

Another trick would be to use more non-skid depth. An increase in original tread depth from 11/32nds to 12/32nds appears to increase the usable tread aby 11%, but you will get something less than that (Wear rates are not linear relative to tread depth.)

[Ernie Rogers]

Originally Posted by NeilBlanchard

Hi Ernie,

The upcoming Michelin HydroEdge "Green-X" tires are LRR and they are rated 800 on the treadwear estimate.

Thanks, Neil, for the info.

I don't know how you feel, I find it maddening that they didn't have the guts to give us the rolling resistance coefficient. How am I to know how this tire compares with the Michelin Energy MXV4 S8 tires they are putting on the high-mileage VW diesels?

Ernie

[Ernie Rogers]

Originally Posted by tasdrouille

Ernie, what do you base your assumptions on? LRR tires usually wear well provided adequate inflation pressure is maintained. Said inflation being usually higher that placard recommended pressure.

Hello, Tas, and all you Prius II drivers,

A Prius-driving friend was complaining about getting only 25,000 miles on a set of tires. (He drives like a maniac in my opinion.) I told him he would be much happier if he raised his tire pressure. I just got an email from him saying he has been running at 45 psi the last year, and he has been amazed by the increased fuel economy (Duh!) and the last tire set lasted for 7,000 miles past the tire warranty.

I think I get 30,000 miles past the tire warranty, but then my wheels and tires are sized more appropriately to the size of my car (a Beetle TDI). I bet Toyota will have that problem fixed on the next design.

Oh, about my assumptions--well, I don't know about the tire "triangle". I think it is an eternal law that if it's good for you, then you won't like it. Here's the same rule for food--

If that food isn't good for you, you can be darn sure it's delicious.

Despite Racer's learned remarks, I still believe--

Soft rubber = poor wear = good efficiency.

Just seems biblical to me. ("the meek will inherit the earth" sort of)

And, of course high pressure is kind of like one of the ten commandments.

Ernie

[Ernie Rogers]

Yes, Racer, I can see the triangle principle.

And, I think you have an excellent discussion here, that I can subscribe to. I appreciate your patience-- that's needed sometimes with me.

Ernie Rogers

Originally Posted by CapriRacer

Remember it's a triangle and traction is the third leg.

So it is possible to make a tire with good RR and good wear properties, but it will suffer somewhat in the traction department.

This might be a good example of the complexity.



When Michelin says these are good for RR, are they comparing these tires to regular replacement tires? If so, then they may get good wear, but their RR would be only be better than regular replacement ires, but not as good for RR as some OEM tires - which would have either wear or traction complaints (or both).

Also, keep in mind that most tire wear occurs in the cornering mode. So if most of your travel is in a straight line, even potentially poor wearing tires will wear well.



Again, keeping in mind that it's a triangle, harder rubbers tend to wear well.



I think that is a good rule of thumb. The problem would be comparing tires with different families of rubber chemistry.

For example, different manufacturers will have slightly different rubber formulations - and the rule would apply within that family, but will have some variation between families.

This also means that even within a given tire manufacturer, if different families of rubber compounds are compared, you'll get different hardnesses compared to the wear / traction / RR triangle - such as the difference between an all carbon black formulation vs a silica / carbon black mixture.

Another factor to consider is that there are tricks that can be employed to improve the wear. Tread elements using large blocks wear better than those with small blocks. But this hurts snow traction.

Another trick would be to use more non-skid depth. An increase in original tread depth from 11/32nds to 12/32nds appears to increase the usable tread aby 11%, but you will get something less than that (Wear rates are not linear relative to tread depth.)

[orange4boy]

Some interesting comments on efficient tire tread design from:Fuel efficiency: new tread design factors.

Q. What steer, drive and trailer tread design factors areaimed at improving vehicle fuel efficiency?

Graves: Much of the rolling resistance of a tire, about 35%to 50%, comes from the tire tread, so its design can have a significant impacton fuel economy. Typically, shallow treads are more fuel-efficient than deepones and rib designs tend to be more fuel-efficient than lug or block designs.But there are exceptions to the rib versus lug rule. With newer-generationdrive tires, incorporating continuous shoulder ribs, tire designers have foundthey can be a lot more flexible in selecting tread rubber compounds. The resultis that certain closed-shoulder drive tires offer overall fuel economy equal toor even better than some rib designs.

Miller: Fuel-efficient steer, drive and trailer tires haveunique tread designs and patterns. In particular, a fuel-efficient drive tire’stread is more rib-like than the tread on a standard tire, and while it may lookless aggressive it does not necessarily have less traction as many driversbelieve.

Willis: When designing a tread pattern for fuel efficiencyit is important to concentrate on reducing the deflection of the patternelements and the volume of the deflected rubber. This can be achieved in avariety of ways that include reducing the pattern depth and increasing thepattern stiffness. In addition, a base compound that is optimized for goodrolling resistance gives designers some degree of freedom when designing thetread pattern.

Baldwin: Tread designs with less movement in the featuresare better for fuel efficiency. Therefore, designs that use solid shoulders andare more “rib-like” are the most efficient. Block and siped designs tend to beless efficient, but to minimize this effect, sipes that are zigzagged in twodirections can allow for good traction while locking the block in place.

Possibly why the Nokian H can be such a good performer and still have low RR. Rib like...

Nokian H wins the German ACE tyre test: "Well-deserved test winner is the Nokian H" writes "ACE Lenkrad" as result of its latest summer tyre test.

I'm pretty sure I'm getting a set of these this spring.

[orange4boy]

Originally Posted by CapriRacer: The problem is that extremely low RR tires tires also don't have great traction and / or wear life. This is one of the reasons one hears lots of complaints about these properties on tires supplied to new vehicles. It is commonly thought the cost is what is driving this, but that is not the case. It's this technology triangle.

BUT:

Miller: A different tread compound is used in each tire toachieve lower rolling resistance and better fuel economy than on standardtires. A fuel-efficient compound typically has a higher rebound value. In thepast, rubber compounds with this property might not wear very well, butengineers have come up with ways to improve rolling resistance without asignificant loss in the other properties that are required of a truck tire.

Nokian uses the cap technology described here:

Graves: Some compounds, especially those incorporatingsilica or using special formulas that combine natural and engineered-structuresynthetic rubber, can affect rolling resistance significantly. In some cases, atwo-layer, or “cap-base” tread can be used. The cap compound, which is chosenfor high resistance to abrasion and high traction characteristics, tends togenerate more heat, so a base layer with a cooler-running compound is chosen toprotect from heat buildup. The result is lower overall tire temperature forlonger casing life, which also means lower rolling resistance and better fueleconomy because less energy is wasted as heat.

[moonmonkey]

the firestone or maybe its bridgestone ecopia tires have great specs all around and were #2 in the tire rack (rolling resistance road test) are they maybe not as good as tirerack says? reason im asking i need a set soon for my echo.

[orange4boy]

Unfortunately Tire Rack does not sell the Nokians. Tire Factory does though and they are bricks and mortar.

One of the reasons I love the Nokians, is the lack of toxic oils used in their tires. The EU is banning toxic oils soon and Nokian phased them out in 2004, far before they were required to. Michelin, BS, and most other manufacturers have been dragging their feet on this waiting for the deadline for profit reasons. The Nokians are a favourite over at Prius Chat too. And they are cheaper than Michelins.

It must sound like it but I really don't work for them. I just think their tires are really great.

A good tip is to get the extra load tires if they have them in your size because they often have a higher max psi.

[Vekke]

Found a calculator which can calculate fuel consumption effects when looking the Eu tire mark labels:
Energy: Tyres calculator - European Commission

Roughly difference is 2% between each letters...