"MPGiata" modding thread: aiming for 50 MPG with a 1990 Miata. Update: success, 55 MPG!

[MetroMPG]

^ Someone's having a big birthday!

[MetroMPG]

The Miata is out of hibernation, and the irksome Metro winter beater is taking a rest after delivering a surprising 77 mpg US = 3 L / 100 km on its latest tank. Best ever tank for that car!

Getting back into the Miata is pure joy by comparison.

However... I forgot how to work the radio and the MPGuino since last year. I actually wrote up a little reference guide for both of them for next year.

---

I celebrated the car's return with the purchase of a pair of only half-worn-out Insight size RE92's for the front wheels:



Unfortunately when I got home, I discovered they are NOT Insight tires, despite what the ad says: they're 175/65 instead of 165/65.



When I bought them, I only looked at the tread condition (same exact pattern) and general sidewall condition for cracking (they're fine).


RE92's in 175 width were used on the original Prius, but never on the Insight. And from what I've read on Insight Central, there not as good in terms of rolling resistance. Bummer!!



I think the seller made an honest mistake - they came as extra tires with his new-to-him 2000 Insight, but he didn't want to keep old tires around. I'm giving him the benefit of the doubt.

Oh well.


I'll mount 'em anyway, and do a coast-down comparison against the 165/65 R14 Dunlop Enasaves currently on the front of the car.

[19bonestock88]

Oops lol... I doubt it would affect mileage by *that* much but it begs some instrumented testing

[California98Civic]

Bummer about the tire. But I'm pretty sure CapriRacer would insist that the bigger contact patch is better for CRR, though of course the wider tire will also have an aerodynamic penalty.

[MetroMPG]

Another tip-off that these tires may be quite different: every old Insight Re92 I've seen is weatherchecked. These aren't. Either they lived an extremely pampered life, or it's a different rubber compound.

[euromodder]

I can't really believe that the old , even ancient, RE92 tyre design hasn't been bettered yet on RR

Best (B-rating) rolling tyres in EU are
Continental ContiEcoContact 5 165/65 R14 83T XL
Maxxis Mecotra 3 165/65 R14 83H XL

without the XL rating, they drop down to C (ie one grade worse) for RR though


The bigger size has a far better choice of tyres though, with A rating on 1 in 175/65/14 for the
Goodyear EfficientGrip Performance 175/65 R14 86T XL

[MetroMPG]

No doubt there are better tires out there now.

The trouble is selection in Canada / US is almost non-existant in the original size. The only car left on the market which uses the original size is the Mirage (Space Star). It's one of the last (if not the only) new cars with 14" wheels.

[wdb]

Originally Posted by MetroMPG

No doubt there are better tires out there now.

The trouble is selection in Canada / US is almost non-existant in the original size. The only car left on the market which uses the original size is the Mirage (Space Star). It's one of the last (if not the only) new cars with 14" wheels.

What's the bolt pattern and offset? Cheap steel wheels should be easy to find in other diameters. So long as you know the specs to look for you can match them with other make/model vehicles. People mostly take off steelies and put on alloys so the steelies should be plentiful.

[mpg_numbers_guy]

Originally Posted by wdb

What's the bolt pattern and offset? Cheap steel wheels should be easy to find in other diameters. So long as you know the specs to look for you can match them with other make/model vehicles. People mostly take off steelies and put on alloys so the steelies should be plentiful.

But steelies are heavy, and hurt economy. Most Miata alloys are quite lightweight, and sets of OEM rims aren't that expensive since a lot of people go aftermarket.

[MetroMPG]

Ooof! Yeah - 18 lbs OEM steel vs. 12.3 lbs OEM 7 spoke 1990 alloy.