Testing rolling resistance of the Various Tires of the Suzukiclone Fleet (RE92 wins)

[MetroMPG]

Just a note: keep in mind that a 4-7 mpg difference on an Insight won't equal a 4-7 mpg increase on a different car (should you try those tires on something else).

If the Insight's baseline is, say 60 mpg, that 4-7 mpg increase represents about a 7-12% change.

If your baseline is 20 mpg, that 7-12% change represents 1.3 to 2.3 mpg.

Just putting that out there.

[deathtrain]

Damn you math!!!!!!

[niky]

Just a question... aren't donuts supposed to be inflated to about 50-70 psi anyway? So if you're using the other tires at their max sidewall rating, which is usually in the 45-50 psi range, wouldn't the equivalent for donuts be around 90 psi (my donut is)...

[CapriRacer]

Originally Posted by niky

Just a question... aren't donuts supposed to be inflated to about 50-70 psi anyway? So if you're using the other tires at their max sidewall rating, which is usually in the 45-50 psi range, wouldn't the equivalent for donuts be around 90 psi (my donut is)...

Except that donuts have a short designed lifespan - on the order of 50 miles - while regular tires are designed for a lifespan up to 100K miles. That means the casing for donuts is designed weaker and additional pressure is much more likely to cause fatigure problems.

[MetroMPG]

Also, the max sidewall pressure on the donuts is 60 psi. I should have posted that.

[steffen707]

Awesome work and results. Only problem I see is that you had 13 inch tires and 14 inch tires, leading me to believe you had to use different wheels.

My Civic VX wheels are super light 13", steel wheels are very heavy. For an apples to apples comparison did you use the same 13" wheels for each 13" tire, and the same 14" wheels for the each 14" tire?

Also what were the weights of said wheels?

Don't get me wrong, the work sounds awesome, and i'm super happy I bought insight tires for my VX swapped EK hatch ( I ended up using semi hollow miata wheels that are like 11-12lbs and 14", I couldn't find a set of insight wheels to use). Just curious on the wheels used.

[MetroMPG]

All were conventional steel wheels (all the 13's were in practically identical), except the RE92's which were on light aluminum wheels.

I didn't try to estimate how much of an effect this would have had, if any.

Keep in mind the testing: a couple of feet elevation change, meaning acceleration to & deceleration from a top speed of about a brisk walking pace.

[niky]

Originally Posted by MetroMPG

Also, the max sidewall pressure on the donuts is 60 psi. I should have posted that.

Ah. Ok. Mine are bigger (replacement for 195/50R16), so that may be a factor.

Again, great test. I've been meaning to suggest this to some friends doing official tests on a "fuel-saving" tire from another manufacturer. They measured consumption as the average consumption over dozens of (tightly-controlled) laps over a closed circuit versus a control tire. Was going to participate, but had prior engagements. Was thinking they could also test rolling resistance directly, too.

[Olympiadis]

Originally Posted by steffen707

( I ended up using semi hollow miata wheels that are like 11-12lbs and 14", I couldn't find a set of insight wheels to use). Just curious on the wheels used.

Steffen, could you please post an image of the Miata wheels that you are talking about there?
And do you happen to know the lug spacing on them?
Thank you.

[niky]

If these are the famous hollow-spoke Miata wheels, probably these:

Typically 100x4 lug spacing, full hollow spoke 14" are about 10 lbs, semi-hollow in the 11 lb range, solid spoke in the 12+ lb range.

Julian's Home Page - The secrets of the '94-'97 MX5 OEM Wheels: Hollow Spoke and Solid Spoke - November 13, 2002

ROTA also sells really light cheap wheels. They have a set of 15x6.5 wheels that are 10-12 lbs, called AutoX... but I doubt you can find them secondhand as cheap as Miata wheels.

If your PCD is the same as the Miata's, I've always found this page helpful:
http://www.miata.net/faq/wheel_weights.html