Huge loss in fuel economy with wheels

LOL

Please research the topic before you go about flaming those of us with knowledge and experience on the subject.

 

I think the person was referring to break in of the tires. Did you read Tire Tech Information - Tire Rolling Resistance Part 3: Changes to Expect When Switching from Worn-Out to New Tires that I pointed you to?

Toyota NEVER offered 17" wheels on the Gen 2 Prius.

Don't get so hung up only the weight. Besides odometer and speedometer error, there's the unknown rolling resistance of your tires, but likely greater than the OEMs. Did you ever look at Tire Test Results : When Round and Black Becomes Lean and Green, specifically Tire Test Results : When Round and Black Becomes Lean and Green or When Round and Black Becomes Lean and Green.?

 

I'm suspecting it's the tires. That's why I asked do note what tire you're using.

I also didn't say that OEM rims will improve it, I'm just noting my results along tires I have. From what I read of other's experiences, rims weight seem to have low impact but tires do.

 

BTW, you can see my Fuelly log for how I'm doing. On my latest tank, MFD shows 51.3 mpg so far.. with four bars of gas left.

 

It always amazes me, that every six months or so, a topic like this pops up, OP never looks before he leaps and posts! Then when told by people who have done it, I.E., F8L, who certainly is well qualified to lay out facts, only to be ignored!
Really?
Also...
The latest "I ran my tank dry on the last flashing PIP, and it's Toyota's fault" thread is also included. RTFM

C'est la vie!

 

To be fair and unfair at the same time, Kore971 did 813.4 miles on 17s @ 75.6mpg.
Let's ask him how he did it and what brand his 17s and tires are.

So I'm guessing it's just three major factors.

1. tires
2. driving style
3. he drove a GenIII

 

Aye, the OE Toyo Proxes A20 tires have crazy low rolling resistance so they are much more efficient than aftermarket 17" tires in the Prius sizes. That's why people with the OE 17s are only 1-2mpg lower than the OE 15s. However, once they swap to a different tire the FE drops further and you're back to the 3-4mpg loss (vs. OE 15s) I stated earlier. This is the case with the GenIII. The GenII dropped even further with 17" wheels (15lbs) and aftermarket LRR tires. I never got to test anything other than the Primacy MXM4 (LRR) and Kumho ecsta ASX on my GenII but both tires really crushed my FE even after the size difference was accounted for.

Unfortunately weight is not the only contributing issue. Tire hysteresis is the main culprit and 17" tires are just not designed for efficiency like their smaller brothers. Soon we will have 18-19" LRR super narrow tires. We will have our bling, handling and FE!

On the issue of weight. You can get lightweight 17" wheels but few affordable wheels are as light as the OE 15s AND look good. Even then you are stuck with a heavier tire. So go lightweight if you can afford it but don't break the bank to do so or you'll never see a return on your investment. Drag, Motegi and Enkei etc., make nice lightweight wheels that are affordable.

 

He is using the OE Toyo Proxes A20. I checked after starting at his post in amazement. LOL

 

Yes, but that's a Gen 3 Prius with a TON of other changes. You don't have a Gen 3.

 

There you go!

the culprit is driving style.. change driving habits a bit and the possibilities are endless!
Well, not beyond 75mpg though.

 

No one is saying you don't have car-related knowledge. However, there is a difference between typical racing knowledge and knowledge on fuel efficiency. You'd be surprised how many of us spent decades racing and how many still do.

Instead of being defensive simply take in the information being presented and use it to your advantage. This isn't your typical car forum. Most people here are a lot more civilized than you will find at LS1Tech.com or the VTech forums.

 

No, I meant Kore971 is using OE Toyos which explains his excellent FE despite 17s.

 

i realized that.. can't find the delete message button..

but still!

Out of curiosity, if someone can lend me 17-inch rims with super sticky tires, i'm up for a challenge to see how much % mpg loss i'll get with my current set up.

 

See post #27 regarding the OE 17" tires. Add in the fact that the OE 17" wheels are very aerodynamic despite being very heavy at 24lbs/ea. Still, it does suffer compared to the 15" tires but it is not as noticeable because of the super efficient tire. Unfortunately those tires are crap, prone to blowouts, don't last long and are expensive!

 

So to wrap things up let's summarize.

17s will negatively affect FE at this point in time.

Tires can have a big impact on FE. See this test as an example and note the almost 4mpg difference between tires. Tire Test Results : When Round and Black Becomes Lean and Green

If you're dead set on 17s or 18s then try to get the lightest wheel that is practical. Look for an aerodynamic pattern. Stick to a 7" wide wheel and keep the offset between 42-45mm or even 50mm if the back will clear the caliper. Then wrap it with a slightly taller LRR tire like the Ecopia EP422 or PureContact. Keep them well inflated and slow down!

 

Well said Justin!

 

Think Mooneyes. Anything that flattens the face of the wheel and has narrow gaps and rounded edges to reduce turbulence.

The GenII with 17s and easily get mid 40s if one doesn't drive too fast. Racing around will bring your mileage down.