Tested: Enasave vs. Bridgestone RE92 rolling resistance

[MetroMPG]

(I'm posting this in the fuel economy section instead of the tire section because this is all about figuring out which tire is better for MPG.)

Within the past year or so, I happened to score both a set of nearly new Dunlop Enasaves on alloys AND a set of nearly new Bridgestone Potenza RE92's on steelies.

Both are 165/65R14 size.



For those who may not know, the RE92 was the factory tire on the 2000-2006 Honda Insight hybrid, which still holds the crown as the most efficient gasoline hybrid sold. That tire is widely regarded in the Insight community as the best tire for MPG. (The Insight has very low aerodynamic drag, so reducing rolling resistance is key, because it makes up a higher proportion of total drag than the average car.)

I had a 2000 Insight for a couple of years. That's my car, above -- 1.0L engine, 5-speed. It was an absolutely amazing machine. Honda let its engineers go farther in pursuit of efficiency than any other production car except for the smaller, super streamlined VW XL-1 diesel hybrid. I could regularly get 100+ MPG tanks in mine, in summer weather. Eco-modified, of course.


Long story short: in my simple coastdown test, both tires rolled almost identical distances.



Testing details:

-- Ambient temperature: 24 C / 75 F

-- Tire pressure: 55 PSI / 3.8 bar

-- Tread depth: Enasave = 5.6 mm / 0.22", RE92 = 5.1 mm / 0.20"

-- Each set of tires got 4 coastdown runs, plus one last run after switching back to the first set.

-- The testing area is 2 blocks from where the car was parked overnight, so tire temperature should have been extremely close for both sets (but not measured).

-- The car was positioned at the same point on a slight hill, then allowed to roll out to a level section, where the distance was marked on the pavement.

-- To minimize the potential of brake drag affecting the results, the car was stopped/positioned using only the handbrake rather than the hydraulic (foot) brakes.



Results:

-- The average coastdown distance was around 34.7 m / 112 ft.

-- The end points for all 9 runs were clustered within the last 122 cm / 48 inches!

-- 34.6 m / 113.6 ft ... Ensave average coastdown distance

-- 34.7 m / 113.7 ft ... RE92 average coastdown distance


Conclusion?

How much faith would you put in this test? Enough to say that both tires appear to have similar rolling resistance? It sure seems that way to me.

I'd be interested to hear from our resident tire engineer on the test method.

If it's a valid & accurate test, then Insight owners should be happy to know the Enasave appears to be a viable alternative to the RE92 in terms of preserving MPG performance. (There are always fears in the Insight community that the RE92 is going to be discontinued soon. Although I it was still available as of a year or 2 ago as far as I know.)

I'm not sure which tire costs more, but that might be a consideration too.

[Basic]

How much faith would you put in this test? Enough to say that both tires appear to have similar rolling resistance?

I'd be interested to hear from our resident tire engineer on the test method.

It's about as good as you are going to get outside of a controlled environment...

There are a few minute factors you didn't mention that I would be interested in. Did you do the tests back to back in the same day? If so, how long did the tire swap take and did any variables change (wind, surface temp due to sun exposure or lack thereof) If not, were they done at the same time period of the next testing day and did any variables change (same ones.)

The only true concern for me is the wheels... I have never weighed them, but do the alloys offer a weight savings over the steelies? I feel that the Enasave could have gained a slight bump due to this, but I cannot say to what extent.

Overall, I think it is a good test outside of the "uncontrolled" environment, but that is what test labs are for after all!

Well done!

[Fummins]

I once weighed a few different wheel and tire combo's. Iirc the aluminum 14" 2014-15 wheels weighed about the same(or very close) as the steel oem wheel. I'll have to dig through my pics and see if I can find them.

[MetroMPG]

Thank you for the reply, resident tire engineer! What I was hoping for.

Did you do the tests back to back in the same day? If so, how long did the tire swap take and did any variables change (wind, surface temp due to sun exposure or lack thereof)

All runs were one after the other, same day. Tire change took about 3 minutes.

The only true concern for me is the wheels... I have never weighed them, but do the alloys offer a weight savings over the steelies? I feel that the Enasave could have gained a slight bump due to this, but I cannot say to what extent.

As Fummins said, I believe the wheel weights are the same. But I'm not sure about the tire weight - will check & report back.

Thanks for chiming in, Basic.

[Mark]

Thank you for the reply, resident tire engineer! What I was hoping for.

All runs were one after the other, same day. Tire change took about 3 minutes.

As Fummins said, I believe the wheel weights are the same. But I'm not sure about the tire weight - will check & report back.

Thanks for chiming in, Basic.

Tire specs -

Dunlop Enasave 01 A/S 79S (all-season) - factory stock LRR tire
340AB, 44 psi, 9/32”, 13 lbs, 22.4”, 4.5 - 6” rims, 6.7”**, ?? miles, Thailand

Bridgestone Potenza RE92 78S (all-season) - LRR tire that has been around for a long time
260AB, 44 psi, 9/32”, 13 lbs, 22.5”, 4.5 - 6” rims, 6.5”**, 40,000 miles, Japan


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?

[OrganicFoxes]

I actually got the RE92s on my mirage recently, only thing I notice is the road noise, def much better. The RE92s were cheaper then the dunlops in my area, like way cheaper surprisingly.

[Basic]

OOHHH... Mark's post here with the specs gives me another question. Are the tread depths close? You said "nearly new" but I am not sure if that means depth or physical age, or both?

Tire specs -

Dunlop Enasave 01 A/S 79S (all-season) - factory stock LRR tire
340AB, 44 psi, 9/32”, 13 lbs, 22.4”, 4.5 - 6” rims, 6.7”**, ?? miles, Thailand

Bridgestone Potenza RE92 78S (all-season) - LRR tire that has been around for a long time
260AB, 44 psi, 9/32”, 13 lbs, 22.5”, 4.5 - 6” rims, 6.5”**, 40,000 miles, Japan


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?

[foama]

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.

There are other good and even better tyres available in these parts, but this set was incredibly cheap because they came "used" off a brand new car. The first owner wanted all-season tyres rather than the stock enasaves on his Suzuki Celerio.

[MetroMPG]

Iirc the aluminum 14" 2014-15 wheels weighed about the same(or very close) as the steel oem wheel. I'll have to dig through my pics and see if I can find them.

Yup! Same...

Thread: Weight of stock Mirage wheel/tire combo? (Steel, alloy)

[7milesout]

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?

I was going to post, the same thing. WE WANT TO KNOW!

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.

You gonna die!