145/65R15 ContiEcoContact EP vs. 165/65/14 Bridgestone Potenza RE92

[BabyDiesel]

I'm not due for new tires for a while, but I would rather plan ahead than wait till mine wear out. I am looking at these two tires for my next set. They are both thin, LRR, and roughly the same diameter. The Continental tires come on SmartCars, and the Potenza's on the Insight. Now I do know that the RE92 is the king of fuel economy. However, the Continentals are 20mm thinner for better aero, so they might be a competitor to the RE92s. I do not mind getting new rims for the Continentals. I will get 15x4 spacesaver wheels for them if they are decided on.

So, what says you?

[oldtamiyaphile]

Originally Posted by BabyDiesel

Now I do know that the RE92 is the king of fuel economy.

They were ten years ago. I don't know if anyones ever tested them against Conti's or Michelin's latest. The VW XL-1 runs Michelin. Take from that what you will.

[RPM]

OP, please be mindful of the load index. Smaller sizes aren't usually made to carry high loads and therefore might not be appropriate for your vehicle. It is a safety issue.

Further reading: http://www.tirerack.com/tires/tirete....jsp?techid=35

[BabyDiesel]

Originally Posted by oldtamiyaphile

They were ten years ago. I don't know if anyones ever tested them against Conti's or Michelin's latest. The VW XL-1 runs Michelin. Take from that what you will.

Hmm. You do make me wonder about these newer tires. There might be another tire out there that is better than the Bridgestones.

The XL-1 runs 115/80R15 up front, which would be awesome to get hold of! However, I read that they cost over $1000 apiece

I see basjoos, MetroMPG and DonkeyCRX running RE92's, so it makes me think that there is something to them. Tygen1 put RE92's on his ZX2 and he spoke highly of them. Although, I am curious about the unknown Conti's... someone with a SmartCar needs to post up!

Originally Posted by RPM

OP, please be mindful of the load index. Smaller sizes aren't usually made to carry high loads and therefore might not be appropriate for your vehicle. It is a safety issue.

Further reading: http://www.tirerack.com/tires/tirete....jsp?techid=35

Absolutely, RPM. Safety is a high concern. The Conti's carry 783 pounds @ 44 psi. My car is around 2200-2300. So I still have ~750 lbs of wiggle room. And I would run them at 50-55 psi, just because I am a limit pusher

There will be handling differences with the skinnier width and thinner sidewalls. Whichever I get, I plan on finding a road with no traffic and testing them out at different air pressures, just to get a feel for them.

[Chrysler kid]

Michelin defenders hands down

They are dead silent at any speed.

They have outstanding ride quality at max psi

I have no reason to switch to another tire

[BabyDiesel]

Originally Posted by Chrysler kid

Michelin defenders hands down

They are dead silent at any speed.

They have outstanding ride quality at max psi

I have no reason to switch to another tire

Michelin Defenders are good tires, no doubt. However they are not offered in a thin enough size (175/65R14), they cost about $20 more apiece, and are quite a bit heavier.

Tire Rack reports the 175/65R14 M.D. weighs 18 lbs.
The 165/65R14 RE92's are 13 lbs.
The 145/65R15 EP's are 12 lbs.

I'm going to stick to the 2 mentioned in the title

Thank you for your opinion anyhow, Chrysler Kid!

[Chrysler kid]

Originally Posted by BabyDiesel

Michelin Defenders are good tires, no doubt. However they are not offered in a thin enough size (175/65R14), they cost about $20 more apiece, and are quite a bit heavier.

Tire Rack reports the 175/65R14 M.D. weighs 18 lbs.
The 165/65R14 RE92's are 13 lbs.
The 145/65R15 EP's are 12 lbs.

I'm going to stick to the 2 mentioned in the title

Thank you for your opinion anyhow, Chrysler Kid!

Rotational mass will increase your inertia and increase the time you can coast and maintain speed. Seeing how you primarily have a highway commute you may not see any benefit from narrower tires. There is a reason why the most fuel efficient vehicles on this site aren't running just 4 spare tires on all 4 wheels

I will also mention my wife's 99 zx2 sport automatic was a good car, but the damn thing shook so hard at idle that we had to get rid of it.

[Baltothewolf]

RE92's hands down for fuel economy. The tires were DESIGNED for fuel economy, Bridgestone designed them SPECIFICALLY for the insight, which has yet to be beat by any car out there in FE (by EPA ratings).

[2000mc]

Originally Posted by BabyDiesel

Absolutely, RPM. Safety is a high concern. The Conti's carry 783 pounds @ 44 psi. My car is around 2200-2300. So I still have ~750 lbs of wiggle room. And I would run them at 50-55 psi, just because I am a limit pusher

Maybe if you used the smart cars rear tires on your front, and their fronts for your rears

Wiki lists 2478lbs for a zx2. maybe a bigger factor would be weight distribution, which according to some less reliable sources is 60/40, which seems typical for a fwd. a pair of passengers could add 100-300 lbs to the front.

Using 2478 and 60/40 distribution puts 743 on each front tire before adding the weight of passengers.

For no other considerations but mileage, I doubt you're going to beat the re92's by much with anything. If you're thinking 15s my next idea would be energy savers

[BabyDiesel]

Originally Posted by Chrysler kid

Rotational mass will increase your inertia and increase the time you can coast and maintain speed. Seeing how you primarily have a highway commute you may not see any benefit from narrower tires. There is a reason why the most fuel efficient vehicles on this site aren't running just 4 spare tires on all 4 wheels

I will also mention my wife's 99 zx2 sport automatic was a good car, but the damn thing shook so hard at idle that we had to get rid of it.

ZX2's are bad for having an idle shake. It is usually a combo of the knock sensor and slack in the timing belt.

I would think I would see a greater benefit running narrower tires all around. Here is my logic - When starting out, there is less rotational mass to get up to speed, reducing fuel consumption. At speed, the narrower tire would have less of an aero penalty, helping fuel economy even more. Correct me if I am wrong!

If it affects my coasting any, I'll simply add more and better aero mods to raise my coasting distance back up

And the biggest reason we do not run spare tires is they are high RRC bias ply tires (usually). They simply kill coasting, MetroMPG did a write-up on their coastdown distance... not pretty.

Originally Posted by Baltothewolf

RE92's hands down for fuel economy. The tires were DESIGNED for fuel economy, Bridgestone designed them SPECIFICALLY for the insight, which has yet to be beat by any car out there in FE (by EPA ratings).

Thanks Balto! I have thought this about the RE92's since I got on Ecomodder by the number of peeps running them. I might need to stick with what is tried and true...

Originally Posted by 2000mc

Maybe if you used the smart cars rear tires on your front, and their fronts for your rears

Wiki lists 2478lbs for a zx2. maybe a bigger factor would be weight distribution, which according to some less reliable sources is 60/40, which seems typical for a fwd. a pair of passengers could add 100-300 lbs to the front.

Using 2478 and 60/40 distribution puts 743 on each front tire before adding the weight of passengers.

For no other considerations but mileage, I doubt you're going to beat the re92's by much with anything. If you're thinking 15s my next idea would be energy savers

I had not thought about running the tire's placement backwards, 2000mc

I may have flubbed a bit on my own cars weight I really should weigh this thing since I have done weight reduction. I'm soon to be removing the p/s and a/c and installing an underdrive crank pulley soon, so I will weigh it after that.

The weight distribution cuts it close, a lot closer than I realized.