[Skimmer]

Well, after reading a bunch of tire stuff on this site and elsewhere, I decided to get the Dunlop SP8000 tires in size 195/55/14 for my Insight. They seemed to be the best compromise between mpg and handling that I was looking for, and so far that has proved to be true.

I wanted to get the Sumitomo HTR200 tire because it is rated as a "low rolling resistance" tire by Green Seal, but nobody had it in stock in my area, and I didn't want to wait for shipping from Tire Rack. One of my OEM tires blew out, so I couldn't wait. So I settled on the Dunlop SP8000 because my local Big O Tires shop had it in stock and agreed to match the Tire Rack online price of $70 each.

Right away after getting the tires installed, I noticed a softer, quieter ride. I worried this would not be the case because of the low-profile 55-series size of the tires, but they ride much better than the OEMs, and the handling difference is huge. The car really sticks in corners now and is much more fun to drive. Somebody said these tires turn the Insight into a "normal car", and I'd have to agree. Also, it no longer gets thrown around by pavement grooves, a real plus for driving enjoyment.

Shortly after getting the tires, I made a 400+ mile round trip on interstates and two-lane surface highways. I got 53 mpg for the trip with speeds around 65-70 mph. This is probably a 10 percent penalty from what I would have gotten from the OEM tires -- about what everyone else has experienced with this tire. To me, that's really not bad considering all the benefits of these tires. My cold tire pressures at the start of the trip were 37 front and 35 rear. I'm going to boost these up to 40 all around and see what happens.

One other point: The tires fit fine, but this is definitely the widest tire you'd want to try to fit on the stock wheels. The wider tread width fills out the wheel wells nicely and makes the car look sportier, in my opinion.

 

[Guillermo]

Your observations are consistent with others that have switched to high performance tires.

 

[Jackmpg]

Hi Skimmer

Hi Skimmer,
The tires you put on your car you said were 55's, low profile. Is the car slightly lower to the ground now? And if so how much. I've been trying to find 165/55's with no luck. Something Willie told me about a year ago about the insight being a little over geared (and I agree). A tire with a smaller diameter may lower gear ratio slightly to improve this condition. I've seen that Bridgestone has a new model Glll 165/55 R14, but it's only available in South Africa that I could find. Any ideas? I did call the Tire Factory in W. Sacramento, CA-Spoke to Derrick there. He's looking into whats available from Sumitomo, Bridgestone and others with regard to low profile-stiff sidewall LLR that will fit on our rims.
Jack

 

[Guillermo]

195/55R14 tire has the same diameter as the 165/65R14 OEM Insight tire.
55 is the aspect ratio in ralation to the tire width, so it's only a lower profile if the tire width is the same.

195x0.55 = 107 mm sidewall height
165x0.65 = 107 mm sidewall height

You can only replace the OEM tire with a tire that has the same or higher load rating. The load rating of the 165/65r14 OEM Insight tire is 78.
The 165/55R14 tire you suggested has smaller diameter while maintaining the same width. This means it has a much lower load rating that is not sufficient for the weight of the Insight.

My race tires have a smaller diameter and it has a higher weight rating because it has a larger air volume.
185/60R13 has a larger air volume because it uses a smaller rim and the weight rating is 80.

I don't recommend getting a tire size to reduce the tall gears for street use. It increases the chances of getting tire damage in pot holes etc...
And the difference in gearing is not noticeable.

For racing it allows me to have a lighter weight rim and tire combo and improve torque. But tire width is more important for handling so my race tire this year will be a 195/55R14 Kumho 710

To compare the diameter of different tire sizes use this link:

http://www.miata.net/garage/tirecalc.html

 

[Skimmer]

Guillermo is right, the SP8000 195/55/14 does not appear to lower the Insight at all, which is good as far as I'm concerned, as the car is already quite low for practical day-to-day use.

I'm still really enjoying the tire. A real improvement in both the handling and ride comfort areas. It does seem to cause some extra drag, noticeable in the greater use of hybrid assist in most driving conditions. So you do have to be a little gentler on the gas pedal if you're striving for best mpg and state-of-charge.

 

[Jackmpg]

lower profile tire

Thank you both,
Yeah, we don't have much ground clearance to start with. Thanks for the link, I'll go there today. And thanks for tires 101, not one of my strong areas. Will learn more as I can, and thanks.
Jack