Tried a 17 inch wheel-tire package on my Prius. UGH!

Sorry to gear that you had such a bad experience. I suspect that the biggest problem you experienced could have been due to the high rolling resistance of the Kumho tires. The Prius was designed for, and comes with low rolling resistance tires. The more the tires resist rolling, the more fuel it takes to get them to roll.

Since you matched the tire size fairly well, and confirmed it with a GPS unit this seems the most likely factor.

There are other possibilities, such as increased aerodynamic drag due to the the wider tires, but I think that rolling resistance is most likely since Kumho is not known for having any low rolling resistance tires.

I have emailed Kumho to ask them what their lowest rolling resistance tire is, and what the value (coefficient) of rolling resistance for that tire actually is. If they reply with anything interesting, I will let you know.

In the meantime, you could try another tire with very low rolling resistance and see what happens to your mileage. I think that we should be able to find a wide, low profile tire that is also great on gas (I have a few ideas already, but am still working on them).

Good Luck.

 

no pics?????????

 

17" wheels

:roll:
hey gang,

I got the 17" wheel package from toyota. it is with pirrelli wheels and tires. really cool . i am averaging 48 to 50 mpg and this is mainly due to the fact that i am careful with takeoffs from the light and while your driving just ease off the accellerator and then touch back on it lightly and you will do a lot more traveling in "electric " mode. now i know my spelling is not that great but you get the idea.

 

I like the pic. Very nice. And, you're still getting good gas mileage. I am currently trying to use the same technique you hinted to. my mpg went up today by about 3 or 4 mpg. I was abusing speed on the first 65 miles of this tank, so i was getting 38.5 or so. Someone else mentioned this technique. when you take off, try to keep it above 30mpg. It all averages out better. I accelerate lightly till i hit mid 30's.. or low 30 mph.. and i get 30+mpg at this time. As i slowly accelerate up to 45mph.. i'm getting 60mpg.. at times ( like earlier today) i was getting 70. This morning i averaged 65mpg on my way to work. Only a 15-20 min drive.

:mrgreen:

 

That easing off and then stepping gently back is known as 'feathering' to many.

 

mpg and 17" wheels

:lol:
the mpg will come with practice. i get up to about 35 then take my foot off of the accerator then ever so slightly put my foot back on the accelerator. the best sceen is as far as i am concerned is the electric and gas motor screen. the other with the watts regenerated is handy also if you can try to keep that tricky vertical bar on the right between 50-75 but like i said before aggressive driving will do two things , kill the mpg and generate speeding tickets :lol:

 

I agree.. and it seems this is the way to drive the prius.. because i do the exact same thing at the exact same speed. the car seems to ge to about 30-35 very quickly.. with almost no effort.. which is nice.. but after that.. it's about a 1mph gain every couple seconds. about the flow of traffic in the slow lane up here in San Jose.

 

Well when I was getting my Prius, the dealer inform me average gas mileage will drop at least 2 to 3 mile if I choose Touring package. Which come with 16" wheel. But I grad choose Touring package, because much better ride over 15" wheel also stiffer spirng and spoiler package did the job.

 

roverman, that is one great looking set of wheels/tires!
art

 

Why do the Bigger rims make you get less MPG?

 

Larger wheels have a higher moment of inertia. this means it takes more energy to get a 17" wheel to roll than a 15", and also to stop. A wider tire will also have some more rolling resistance, but the biggest impact is from the increased moment of inertia as well as the increased weight of the wheel.

The general heuristic about wheel weight is that in terms of acceleration, adding 1lb per wheel is like adding 10 lbs to the car.

This is why if one wants to go with a larger wheel with a higher moment of inertia, it can be mitigated somewhat by choosing a much lighter wheel.

 

Kumho's are known to be noisy tires.

 

The 215/45/17 have an outer diameter that is about .4" smaller than the stock 195/65/15 setup making initial spin-up less stressful. I reckon this may somewhat offset the increased width (195 to 215mm). Also, the car will sit about .4" lower to the road; I reckon this aerodynamic will also help offset the increase in tread width.

I have my Prius on Michelin Defender 205/60/16 steelies with avg. @ 44mpg (car sits .7" higher that stock 15" setup)

I am about to throw on my Michelin x-ice winter tires 215/45/17 with some American Racing 17" rims. I was bummed to learn car will now sit 1.1" lower than stock 15" set up. SO I'm losing over an inch in ride height at a time when i could use it most; with all that snow on the roads. Oh well, that's what I get for not figuring it out before I mounted them.

 

dead thread, but you definitely need to do the math before changing tire size. btw, the oem tires are actually too short, so the speedo (and likely the mfd) reads high.

 

@Red_Prii Second gen stock size is 185/65R15 if I'm not mistaken.

 

i think the gen 3 comes with 195's. maybe Toyota figured out 185 is too small by 2010.