Prius 15's are better than aftermarket 17's! (Wrong wheels/tires can wreck your MPG) - Fuel Economy, Hypermiling, EcoModding News and Forum

wyatt · 10-01-2012, 01:16 AM

So, about a year ago, I broke down and purchased a "new to me" Prius. A 2004 with all the bells and whistles from that year. Among these was a set of 17" rims that I was never really crazy about (I just didn't think they matched my car). So after a year of driving and getting low to mid 40mpg's, I told to my wife I wanted to swap tires with her car (also a Prius, but an '05) so I could test what the difference in MPGs would be. She said she didn't care, so I could do whatever I wanted. I swapped them between vehicles. My MPG went up, hers went down. I had half a tank with the 17's, and half with the 15's, and my MPG went up to 52mpg! She took a 1000 mile road trip, and her interstate MPG went down to 38 (normally mid to upper 40's)! Apparently the rolling resistance of those 17's was terrible.
She really hated the tires, and told me to give hers back, so I did... but not before I found a set of 15" Prius rims (from a 2010) and mounted some Bridgestone Ecopias to them :-). My first tank with the Ecopias came in at a whopping 64mpg! I am going to have to check a few more tanks, since it was a half tank (~250 miles) on account that we would be leaving on a trip. We currently have my car and are traveling on twisty, turney mountain roads in the middle of nowhere, so the next couple fill-ups may not tell much, but so far, EVERYTHING is better than it was. Road noise is reduced, acceleration in increased, tire mass is down, MPG is up (20% or more), the wife is happy, and I like the look of the new rims/tires on my car a lot better. If you are running 17's, just know, you could be paying an awful price for it!

Mrwassman · 10-01-2012, 02:28 AM

I doubt it is all in the size of the wheel, but I can agree with taking hideous aftermarket wheels off of a purpose built car.

Piwoslaw · 10-01-2012, 02:31 AM

What tires were on the 17's? Maybe the tires were bad, not just the rim size?

user removed · 10-01-2012, 10:24 AM

My brother just put Ecopias on his 05 Prius and his average mileage went up 5 MPG, without a wheel change. The old tires were some cheap Dunlops put on by the PO.

regards
Mech

LeanBurn · 10-01-2012, 10:56 AM

Many factors make this totally understandable.
1) How much did the 17" wheel weigh in comparison to the 15"?...17" will typically weigh a few pounds more.
2) With wheel up-sizing, tire width almost universally increases as well. 195 -> 215+.
3) OE tires on most vehicles (even on a Hybrid) are bottom rung for performance or value, moving to a better LRR tire would decrease fuel consumption.

I run 15" Prius wheels on my Corolla. At ~14lbs, they are a full 5+ lbs lighter per tire than the stock 15" steelie, the 16" or 17" wheel options... and the tire width is definitely narrower than the latter two as well. Steering response is quicker, initial steer in is snappier compared to all other options. Consequently fuel economy is better.

rmay635703 · 10-01-2012, 11:12 AM

If you like being odd do what I did on the set of old suburbans and keep the crap tires on the back of both cars, if most of your weight is up front, the MPG hit from crap tires on the rear is much smaller than on the front and better still you don't need to buy new tires.

I've also found I can keep a HUGE amount of air in the rear without affecting ride. (even though it has less of an affect on FE)

Cheers
Ryan

wyatt · 10-01-2012, 11:58 AM

I will have to check what the tires were when I get back home, and report back. I do know the rims were 8" wide, vs the 7" wide Prius rims. The rim/tire combos are noticeably lighter when lifting. This is comparing between my wife's 15's and the 17's. I don't have a mass reading on both, so it's not a real comparison, but it is something I noticed.
Running the old tires on the back of the car would be an option, but we plan to sell off the 17" rims to someone looking to "upgrade" their ride. Anyone here looking for some 17's?

I agree, it could be a large number of factors that impacted the large change in FE. I am just glad it is up, way up

.

Arragonis · 10-01-2012, 04:27 PM

I know you posted on my Mrs A Prius Tyres thread - for info the 2010 model has 17s as a standard fit with 215/45 R17 tyres, standard fit is Michelin Energy - which I understand are forgiving enough for Toyota to fit them to the new GT86 Coupe, which seems to be proof that total grip != handling.

I would be careful of fitting "bad" or "crap" tyres on the back, even in an FWD car - the rear does a lot more than just being dragged along, and if grip is the issue then understeer is easier to handle for most drivers - lift off, brake etc. A lot of tyre places here (UK) will only fit new tyres to the rear, and move rear ones to the front and most cars are FWD, very few RWD (BMW/Merc mostly) and very few trucks.

Just my 2p.

Weather Spotter · 10-01-2012, 05:43 PM

the ecopia's I put on my car in July were good for +5 MPG as well!

thomason2wheels · 10-01-2012, 06:28 PM

I just looked up the available sizes inthe ecopias...its about like it used to be when buying a car. You can have any color you want as long as its black. Or in this case, u have a choice of two sizes...too bad, i would have like to try a set on my old wagon, but not by buying new wheels. Sheeeeeiiiiiiitttttt.