Finding tires for better fuel economy/range

Nashco · 07-28-2011, 02:44 PM

I got my Insight with the intention of converting it to a full EV someday. My first step to accomplish that goal is to optimize the fuel economy of the car as it is now with the obvious end being that the better the fuel economy is on gas, the better my range will be for a given battery pack size as an EV. Since I bought my car with some snow tires mounted to the car, I figure it makes sense to focus on replacing them before fooling with aerodynamics.

Many have claimed that the best we can do for rolling resistance on the Insight is the OEM specified RE92s. I'm just not satisfied with that, it's hard to believe that in over a decade nobody has come up with anything that offers lower rolling resistance than the OEM tire, even if willing to sacrifice traction, noise, etc. Perhaps it's true, but I still think that it deserves a closer look. To make things challenging, while I'm reducing rolling resistance, I'd also like to reduce weight, improve aero, and keep costs in check. After digging into it a bit, I am really interested in buying a set of these tires:

Continental ContiEcoContact EP 145/65R15

By being very skinny and (supposedly) low rolling resistance, my hope is that in combination with a narrower wheel, this would meet my criteria. These tires are made to fit earlier smart cars, as I understand it. The thing I'm really having a tough time tracking down is a 15" wheel with 4x100 bolt pattern that is narrow enough for this tire AND is alloy. Space saver wheels would get the job done, but I can't find any that are aluminum and the steel ones are much heavier than I'd like. As you know, the Insight 14x4" spare wheel is extremely light weight...I just can't find a similar 15" wheel.

Does anybody know of an Insight that has tested this type of setup? Anybody know of an alloy 15" diameter 4-5" wide wheel with 4x100 bolt pattern? So far, I have found a few 15x5 aftermarket wheels, but can only find them new at over $200 each...hard to justify. I have found some alloy 15x4 wheels that use a different bolt pattern, but of course this is less than ideal.

Thanks for any help you can offer.

Bryce

**freezin4** · 07-28-2011, 03:12 PM

Bryce,

I was VERY surprised to see that the Conti is actually 1 lb lighter than the RE92.

The tread width is 5.2 in vs the RE92's 5.0 in.

Conti is 22.4 in diameter vs RE92's 22.5 in.

Continental ContiEcoContact EP

Unsure about any MPG savings over OEM tire. And as far as $ savings, the $17 per tire cost advantage of the Conti will be eaten up with buying correct light, aerodynamic rims. I would do the math to see how many (if any) tire changes would bring you overall savings.

I'm curious what others think.

racer26 · 07-28-2011, 03:27 PM

STAR8 15x4, 4x100, 1.75 Backspace [STAR8-154Skny] - $335.00 : Exospeed Racing Products, Founded by Import Racers

option, if an expensive one.

racer26 · 07-28-2011, 03:28 PM

I think in a 15x4, the only thing you're going to find is wheels aimed at the drag racing market for non-drive wheels.

racer26 · 07-28-2011, 03:30 PM

How much do the OE Insight1 alloys weigh?

Eli · 07-28-2011, 03:42 PM

11lbs IIRC

Eli · 07-28-2011, 03:45 PM

Very interesting. I'm always open to new tires, but the need for a different sized rim does throw it all off.. Hmm.

I'm not sure how I feel about using a 145mm tire though. Might make the car even more squirrely?

racer26 · 07-28-2011, 03:57 PM

I could see 145's being more fuel efficient, given their smaller frontal surface area, though.

Eli · 07-28-2011, 04:07 PM

Yeah. I'd be willing to try them out for sure, if we could find a good way to fit them.

The Honda Civic Hybrid uses the same style wheels as the Insight, but in 15".. right? Or are they 14s too? Do they use the same bolt pattern too?

Eli · 07-28-2011, 04:26 PM

I have a pretty comprehensive list of aftermarket wheels at home, some of them much lighter than the stock Insight wheels, but the problem is that most of them aren't designed with aerodynamics in mind. They're usually spoked wheels, which would be extremely turbulent.

That said, if you could find a lighter wheel AND tire, it might offset any loss in aerodynamics. And, you could always install a set of pizza pans - though it would be kinda a shame to put screw holes into brand new and/or expensive rims.

I'll have a look when I get home to see what I see.