choosing low rolling resistance tires

The rolling resistance of a car tyre has little or nothing to do with the hardness of the rubber. Tread and casing design play apart but the real difference comes from the rubber at a molecular level where by the molecules when the rubber is deformed produce less friction between each other and therefore less heat wasting less energy. I also believe if you go round putting knives to tyres on display you may be arrested very quickly, certainly hear in the UK it is an offence to carry a knife in a public place.

 

Epoch, you should try normal punctuation. Something like this is so much easier to read.

"Almost every tire manufacture has a low rolling resistance entry into the market. Every tire manufacture's top of the line low rolling resistance model will vary in the consistency of the rubber used in said tire. The first mix of rubber poured in a given day will have different consistency than the average mix of rubber, thus two top of the line tires same model and manufacture on different dates will have different hardness of rubber.

If the two tires being compared were produced back to back the consistency or rubber hardness will be nearly equal but not necessarily a low rolling resistance tire as advertized. The harder the rubber the less rolling resistance and better gas mileage but the rougher the ride. Manufactures advertize both low rolling resistance and soft ride have that special tire just for YOU. IT IS NOT LOW ROLLING RESISTANCE anymore if it has soft rubber.

The only way to be 100% insured that your getting a low rolling resistance tire is by trying to jam your thumb nail into the tires tread. If you cannot put a depression into the rubber with your thumb nail you have found the least rolling resistance tire and the longest lasting tire but the roughest riding tire. END OF STORY, NO EXCEPTIONS!!!

Whenever you find that hard rubber, long wearing (also almost puncture proof) tire that your thumb nail cannot penetrate, it will always have at least 80,000 mile warranty, but not visa-versa. About 20% of advertized low rolling resistance, high mileage warrantied tires are soft rubber and won't last 25,000 miles even though advertized with 50,000 mile or better warranty's. Again the only way to tell if it is truly a high mileage, low rolling resistance, good gas mileage tire is jamming you thumb nail into the tire's tread.

LADIES you might not have the strength needed to push your thumb nail into tire tread (or the nail strength). I would suggest you use metal nail file or switch blade knife instead. All Prius owners need to start today testing rubber hardness when walking by those tire displays at Wallmart, Pepboys, discount tire, Goodyear , Michelin, Bridgestone, etc.

NOTHING CAN BE MORE UPSETTING THAN LOOSING 10MPG ON EXPENSIVE NEW TIRES. Also with hard rubber tires you don't have to over pressurize the tire to get that ruff high mpg ride."

 

I agree. That casing material and design, as well as the type of rubber compound (eg silicon rubber) all have an effect on rolling resistance.

To simplify it all to super hard rubber is mistaken. Such a tire would probably have very poor traction too.

 

It is not quite as simple as that. you could argue that a hard rubber take more energy to deform therefore wastes more energy.

 

When I used to race bicycles, it was a soft supple side wall that was considered the mark of a good low rolling resistance tire. You cant make the rubber so hard that it wont deform at all, if you did then you wouldn't need any air in it, and the ride would certainly be objectionable.

So the design of the tire has to maximize the energy recovery after the inevitable deformation. The casing, the sidewalls and the compounds used in the rubber are all important here.

I know there are trade-offs in all designs, but I think the hard versus soft rubber thing is more about the tradeoff of grip versus longevity than it is about rolling resistance.

 

Can you explain why the soft Bridgestone EP100 gets better fuel economy than the hard Michelin Hydroedge?

 

Low traction can mean high ware. If rubber slides across the road surface no matter how small that movement is ware will take place and energy will be lost.
When a tyre tread meats the road surface it has to flatten distorting the tread blocks if these blocks are supple the rubber can compress and deform when it leaves the surface it springs back to shape and releases it's stored energy to tur the wheel.
If it is hard the blocks will move on the road surface instead of deforming, warring the tread and wasting energy, and then when they leave the surface have no stored energy to return to the wheel.