Tire Sizes

[Don]

For anyone wanting 'fatter' tires, it looks like the best way to go about it is probably to go with 14 inch wheels

For the front, the stock 145/65-15 can be replaced with a 165/65-14 and you wind up with a tire two sizes wider, but still the correct overall diameter and circumference, so no change to the revolutions per mile. You will need a 5 or 5.5 inch wide rim with an offset in the 35mm to 45mm range. The 165/65-14 tire is available in a low rolling resistance tire made by Bridgestone

For the rear, the stock 175/60-15 could be replaced with a 195/60-14 and again, you'd have a tire two sizes wider, but still with the same diameter and circumference, so the revolutions per mile and the gearing would remain the same . . . . no appreciable changes. You would need a 5.5 or 6 inch wide 4X100mm wheel and those are very common - Miatas and other small Japanese cars of the '80's and '90's used 14 inch wheels in that size. Early Miatas ('90 to '93') came with 5.5 inch wide 14 inch alloy wheels (steel too if you prefer) so a set of those may fit front and rear without any modifications

I have a set of the BBS forged 'basketweave' alloy wheels that I took off my Miata and I bolted them on the car the other day and they look great, but 6 inches is too wide for the fronts. For me to use these, 2 of them will need to be narrowed from 6 inches to 5, both to fit the car and to properly fit the 165/65 tire. I think I'll have an inch cut out of the rim and the lip welded back on. Should cost me less than $200 to do this

This is just an example of what would fit . . . . not an endorsement for anyone to do the same. Cutting and rewelding wheels to make them either wider or narrower is a pretty common practice in the motorcycle world. I don't see why cutting a 6 inch alloy wheel down to 5 inches shouldn't be safe and practical, but as with any other modification of this type, proceed at your own risk. When/if I get this done for my car, I'll post pics

If you decide to try something similar, try bolting the wheels on the car first to make sure you have enough clearance up front before you rush out and buy the tires. The 165/65 tires will fit in the front fenders fine. The 14 inch front wheels could rub the suspension unless the wheels are narrow enough to clear. It does depend on the offset as well, so try it before you buy it. No problems with the rear at all - 14 inch wheels of any width fit just fine

Don

 

[alohart]

The lowest rolling resistance 165/65R14 tire available seems to be the Bridgestone Potenza RE-92, the OEM tire for the original very fuel efficient Honda Insight. Note that no other size RE-92 is a low-rolling-resistance tire. The 165/65R14 RE-92 is also extremely lightweight which also helps increase fuel efficiency (lower rotating mass). The Insight uses very lightweight and aerodynamic 5.5 x 14 alloy wheels, but I don't know whether they would fit the i-MiEV.

It would be nice to be able to fit the same size wheel and tire front and back. I understand that wider rear tires were used to reduce oversteer potential, but couldn't a (larger) rear antiroll bar accomplish the same goal?

 

[Don]

Depending on the offset (and assuming they're a 4 X100mm bolt pattern) I wouldn't be surprised but what the Insight wheels would bolt on all 4 corners. I think the 165/65-14 on the rear would be a bit small though. It's quite a bit less in circumference than the OEM rear tire. so using that would change the gearing

You can bolt the iMiEV rear wheels on the front if you really wanted all 4 wheels and tires the same. The clearance on the front black plastic inner fender is touch and go with that big a tire on the front, but that wouldn't be a difficult issue to get around. Bolting any wheel on the front requires the removal of the silver aluminum ring Mitsu installed up front . . . . no other wheel will bolt there intil you remove those

Don

 

[archie_b]

Whenever switching from one wheel diameter to another it is good to check both the diameter and the width of the new replacement tire. In the case of going from a 145/65-15 to a 165/65-14 for the front, the tire width stays approximately the same, 5.0". On the rear going from the stock 175/60-15 to a 195/60-14 gains a modest 0.4" to about 6.2". Of note is that I could not find any LRR tires in a 195/60-14 at tirerack.com.

Here is a link to a tirerack article on minus sizing:
http://blog.tirerack.com/blog/make-driving-fun/downsizing-to-smaller-diameter-wheels

Ask anyone who has switched from the OEM LRR tires on a gen 1 Honda Insight to a wider diameter performance tire and they will tell you to get the extra performance and traction you sacrifice MPG (in this case MPGe).

 

[Don]

The width of both tires changes by roughly 20mm - About 3/4th of an inch

The 145 and the 165 are the width of the tire in millimeters, so the 165 is about 20mm wider than the 145. same for the 175 and 195 on the rear - About 3/4ths of an inch wider

Specific widths for the 145 are 5.70" and 6.49" for the 165. For the rear, the 175 is 6.88" and 7.47" for the 195

There are no LRR tires (that I know of) in 195/60-14. It's true that a non LRR tire would have some amount of greater rolling resistance than a true LRR tire would. Perhaps it would be enough to notice some small decrease in range or MPGe, but I believe for just the two tires, it would be pretty nominal

I've done this 'downsizing' on other cars with great success - The Mazda Protege 5 in my garage came with 195/50-16's on it and I've had 205/55-15's on it for over a hundred thousand miles. The smaller wheels with taller sidewalls rides better and the smaller wheel combo is significantly lighter than the stock wheels/tires

Don

 

[jjlink]

My 2002 Prius came with these RE-92 tires (Bridgestone Potenza P175/65R14 RE92 XL) and they we the worst tires ever. They blew-out with a golf ball size hole in the side wall with less than 20,000 miles on them. Also the car would drift all over the place when crossing the Dumb-bridge on SF bay. I've used Dunlop or Brigestore-Ecopia tires (P175/65R14) on the Prius ever since with excellent results compared to the RE-92. With the Ecopia tires It gets over or about 50mpg just like the RE-92 did.

 

[alohart]

My 2002 Prius came with these RE-92 tires (Bridgestone Potenza P175/65R14 RE92 XL) and they we the worst tires ever. They blew-out with a golf ball size hole in the side wall with less than 20,000 miles on them. Also the car would drift all over the place when crossing the Dumb-bridge on SF bay. I've used Dunlop or Brigestore-Ecopia tires (P175/65R14) on the Prius ever since with excellent results compared to the RE-92. With the Ecopia tires It gets over or about 50mpg just like the RE-92 did.

Despite having a similar name, the Potenza P175/65R14 RE92 XL is a very different tire from the Potenza P165/65R14 RE92. Many Insight owners inflate their RE92's to as high as 80 psi (44 psi is the max inflation pressure printed on the sidewall) without suffering blowouts, delaminations, or any other premature failure. No other P165/65R14 tire has produced comparable fuel efficiency which is probably mostly due to its low rolling resistance with some help from its very light weight.

But these tires do seem to follow rain grooves more than other tires. They also seem to be louder and harsher than some other tires. But with the limited range of an i-MiEV, I would be willing to accept these negatives if I needed greater range.

But while this tire might work on the front, it appears that it would be too small for the rear. So the search for the ideal tire continues…

 

[JoeS]

...Despite having a similar name, the Potenza P175/65R14 RE92 XL is a very different tire from the Potenza P165/65R14 RE92. Many Insight owners inflate their RE92's to as high as 80 psi (44 psi is the max inflation pressure printed on the sidewall) without suffering blowouts, delaminations, or any other premature failure. No other P165/65R14 tire has produced comparable fuel efficiency which is probably mostly due to its low rolling resistance with some help from its very light weight.
But these tires do seem to follow rain grooves more than other tires. ...

alohart, glad you clarified the exact Potenza part numbers. I'm quite happy with them on my Insights (running at 60psi). I replaced them at 70K miles due to their age and yet they still had plenty of evenly-worn tread left. It's my understanding that the slight wandering on ribbed surfaces has more to do with the Insight's zero toe-in (to minimize friction) than the tires themselves.