205/55/15 MPG

[Tonavi]

I just got new tires last week. Since I have aftermarket DXR wheels that are 6.5 inches wide, I moved up to 205 series tires from the OE 185s. I got between 40-45 MPG in the summertime with the 185s aired up to 40 PSI. I currently have the new tires (Yokohama Avid V4s) at 42 PSI and have a hard time breaking 33. I know it's winter and the cold is hard on everything, but to compare the stock tire size with the Yokos, how much of a mileage drop is reasonable? Will I be able to stay in the 40s? This last week it hasn't been especially cold, maybe -10, and I haven't broken 26 today on a route that gives me 40 in summer.

[supmet]

new rim and tire weight would help answering your question.

You have bare minimum 10% more rolling resistance just from width. They are high performance, so they have even worse rolling resistance than stock. The tires weigh 21 lbs, if your rims are heavier than 12 lbs you've gained weight over the stock set up - more mpg loss.

Throw in the cold and its not surprising.

[Tonavi]

I went from 18 pounds each on the Potenzas to 21 pounds each with the Avids. I used my 15 x 6.5 rims with both, which are lighter than the stock steelies, so that can't be a variable. Maybe it's just me and the mileage will improve. 26 down from 40 sounded like a huge drop to me even if it is cold outside.

[ctrj]

Are you accounting for the speedo error? You're speedo/odometer is now reading slow.

[derickveliz2]

I have 205/50/15 and in winter I'm getting a good 41 mpg on the dashboard, doing math it's like 38 mpg; in summer it's about 42-43 mpg. 2 cts.

[1NZYaris1]

you might also find that the trip to work was 14.5 miles now is only 13.9miles , accordding to your speedo

[Loren]

As has been mentioned, check your speedo accuracy and correct for it. 205/55-15's are pretty tall.

Part of the rest could be "new tire syndrome". If you like the feeling of a nice grippy tire, you might be driving a little more aggressively without even realizing it.

For reference, my car is wearing 15x7's with 215/45-15's and I still get well over 40 mpg (corrected).

[derickveliz2]

Originally Posted by Loren

For reference, my car is wearing 15x7's with 215/45-15's and I still get well over 40 mpg (corrected).

Where did you get these tires? I can't find that size. (never mind, I found them) but what is the diameter?

Thank you.

[Tonavi]

The revolutions per mile are 850 for the 185s and 845 for the 205s. That's less than a 1% reduction in gearing. This is with discount tire's calculator. "When the speedometer says you're going 65, you're really going 65.38." The difference between heights is minuscule. On some web sites, people are saying that doing wider would improve mileage because the extra width makes the tires deform less over road imperfections and therefore cause less resistance. I thought that going 20mm wider would add resistance simply because of the added contact patch. Even so, it's only a 10% increase in resistance at the absolute most.

[MadMax]

Originally Posted by ctrj

Are you accounting for the speedo error? You're speedo/odometer is now reading slow.

That is assuming the speedo was correct in the first place, which it isn't.

The more accurate way to find your speed is with a GPS. I found that my larger tires made the speedometer on my Yaris more accurate (same happened with my Jeep), which means that your MPG probably wasn't as good as you thought with your stock tires if you used your speedo to compute it.

But expect to take a hit with the larger tires, I did and it is significant compared to the stock wheels. With my 215/45ZR17s Riken Raptors on my 08 auto hatch I get 36-38 MPG during the summer and 32-34 during the winter with easy driving. I was hoping for better, but that's not bad and I can live with it because I love my Yaris so much. Plus, it goes around corners like it's on rails so there is a lot of fun in driving it.

Cheers! M2

[Loren]

Originally Posted by derickveliz2

Where did you get these tires? I can't find that size. (never mind, I found them) but what is the diameter?

Yeah, it's an oddball size. I really just wanted to try the extra width. But, with the T1R, it really didn't make that much difference. T1R's run narrow, so, the 215 is really no wider than some of the high performance "195" tires (that are often closer to 205, sometimes more) like the Dunlop Star Spec. I'm going to stick with 195/55's from here on out.

The diameter of the 215/45-15 is very short. Another reason I won't be using this size again.