Tested: Enasave vs. Bridgestone RE92 rolling resistance

[Fummins]

3 min tire change? I don't see that being impossible if you use a decent floor jack and an impact. You can lift the entire side of the car with one jack.

[MetroMPG]

Tire change? - I want to know the trick/procedure that allows one to change all 4 tires in 3 minutes. Did you hire a pit crew for this test?

Ha... wondered who would catch that!

Big hydraulic floor jack so I could lift both wheels on one side at a time. And I was running only 2 lugnuts per wheel during the test.

So, like 10 times slower than a NASCAR tire change.

OK. So maybe it was 4 minutes.

[MetroMPG]

Are the tread depths close? You said "nearly new" but I am not sure if that means depth or physical age, or both?

Not sure on the age, but both have lots of tread, near max I think. I'll measure & report back.

I understand the reasoning for tread depth question: rolling resistance declines as treads wear down. (Or so I've read.)

Does tire compound aging affect RR as well? Think it goes up or down as the years go by?

[7milesout]

And I was running only 2 lugnuts per wheel during the test.

Forget it, the whole test is been rendered invalid now!

[Basic]

Not sure on the age, but both have lots of tread, near max I think. I'll measure & report back.

Excellent

I understand the reasoning for tread depth question: rolling resistance declines as treads wear down. (Or so I've read.)

Correct

Does tire compound aging affect RR as well? Think it goes up or down as the years go by?

This one could theoretically go either way depending on the oil and wax combo the manufacturer uses in their anti-ozonate package

[Eggman]

Don't tires harden with age?

[Basic]

Don't tires harden with age?

Ehhh... "Hardness" is such a difficult word in the tire world...

The real answer is "maybe" but not really... It is so complicated.

Tires STIFFEN with age. There are multiple reasons for this. But does a compound inherently HARDEN with a measurable Durometer reading over age? Not really.

The stiffening typically occurs due to that same leaching of waxes and oils to the surface. It forms a crust on the surface of the rubber that can be "hard" (stiff} it could be tacky, or it could be slippery (what killed Paul Walker) so so so many variables...

[Mark]

MetroMPG's test was done at 55psi / 3.8bar with Enasave 01A/S tyres.
Just to mention it, I have a set of "Dunlop Enasave EC300" and on the sidewall it says " never exceed 40psi / 275kPa (=2.75 bar). I run them at 2.8 bar.

Tne Dunlop Enasave 01 A/S & Bridgestone Potenza RE92 78S have a 44 psi maximum rating.

Is inflating these tires to 55 psi & rolling the car down a hill dangerous? Probably not!

It makes the test somewhat invalid for me, however. I'm not going to drive down the road with tires inflated to 55 psi.

I like inflating my pair of Kumho Solus TA31 (maximum 44 psi) tires to approximately 40 psi & my pair of Nexen N'Priz AH5 (maximum 51 psi) tires to approximately 46 psi. I have no problem adding extra air to my tires, but I am not driving with tires inflated beyond their maximum psi ratings.

Unless I have a statement in writing that states exceeding the maximum psi rating is safe, I am not going there. I don't even trust a Dunlop Enasave sidewall at normal psi.

I honestly sense very little difference between the Dunlop, Federal, Nexen, or Kumho tires I have tried (especially once they become worn down a bit) over the years. I must come clean in saying that, however. My Mirage has not seen 4 identical tires since losing a Dunlop tire to a sidewall issue in June of 2018. I've been buying tires in pairs ever since that time.

I know that makes Mark sound like he's really going through the tires, but @ approximately 82,000 miles on my Mirage I have used up two pairs of tires (factory pair of Dunlop tires & a cheap $40/tire pair of Federal tires) so far.

I see my currrent pair of Nexen & Kumho tires carrying me well past 100,000 miles. I've been very pleased with both! My pair of Nokian Nordman 7 snow tires have seen front axle duty the past 6 winters, & they will continue to be used, too.

I would have to see some really hard data to justify the pricing of the Dunlop & Bridgestone tires in America. Finding a great deal on a slightly used set for cheap is another story!

[MetroMPG]

The stiffening typically occurs due to that same leaching of waxes and oils to the surface. It forms a crust on the surface of the rubber that can be "hard" (stiff} it could be tacky, or it could be slippery (what killed Paul Walker) so so so many variables...

Basic: off-topic tire question...

A friend (mech engineer) who auto-crosses a Miata SWEARS that you should not let his special sticky performance tires freeze, because the cold permanently degrades/alters the compound.

Seems unlikely to me, but what do I know!

He is so picky about it, he won't buy tires that were made in the previous calendar year in case they were stored in an environment that where the temp might have gone below freezing before he gets them.

[Basic]

Basic: off-topic tire question...

A friend (mech engineer) who auto-crosses a Miata SWEARS that you should not let his special sticky performance tires freeze, because the cold permanently degrades/alters the compound.

Seems unlikely to me, but what do I know!

He is so picky about it, he won't buy tires that were made in the previous calendar year in case they were stored in an environment that where the temp might have gone below freezing before he gets them.

Like so many things that get tossed around and believed about tires, there are bits of truth here. As I mentioned before about aging bringing the oils and waxes to the surface, cold can do this as well, and as such the product could be compromised. I believe Hoosier made a point about this with one of their competition only tires some time back. So it is very possible, but I believe it would only apply to very specific products and certainly not every manufacturer. If he is doing it with a certain brand and product (say Hoosier for example who has recommended this procedure) then it makes sense. However if then applying this to any other tire just because it was correct for one doesn't necessarily make it so for all others. Does that make sense?

There is another concern in cold areas like Canuckia. All rubber has a "glass transition stage" where at a certain temp, the compound loses its elasticity to the point that when exercised it can "shatter." I have seen truck tires up on the Al-Can where the truck sat overnight in a rut and it froze and the next morning they went to leave and the truck had to break out of the ice. From that day on, the tire(s) kept losing PSI, but nothing appeared wrong, no punctures etc. Upon removing them when looking inside, the innerliner which has a lower glass transition temp than the tread was shattered like a piece of glass at that spot where it had been frozen to the ground.

Obviously that is an extreme case that most tires will not see, especially ones like his AutoX tires that get kept in storage until race day. Speaking of storage, ask him if he keeps them in bags when they aren't on the car. Because if not, he is kind of only being partially particular