Touring - larger tires & mpg?

On my 07 Touring with 4800 miles I'm averaging between 48 and 51mpg.

 

Our '07 Prius Touring is still "new" with under 800 miles on it. My Wife is still getting used to the Prius's "different driving techniques", but her miles are mainly (over 90%) HIGHWAY miles here in the Tampa, Florida area. She is currently getting a little over 48.5 MPG, but remember, like I said, both vehicle AND driver are still "new" !!

I have "heard" (and read) that the "wider" (which is what I guess you mean by larger?) tires in the TOURING models, which are entirely different tire type, tread design, Manufacturer, etc. than on the non-touring, get lesser gas mileage ?? Maybe the Bridgestone Turanza EL400's are not LRR (Low Rolling Resistance) tires....... or NOT as low a LRR as the non-touring tires ??

One other thing to consider in MY particular situation... we are running STOCK (factory) tire pressure, that is 35F / 33R. This is due to the Prius poor handling in very heavy cross-wind on the highway (another forum thread) while we are waiting to install a new BT Plate (even another forum thread) !!

 

A vehicle's fuel economy is the direct result of its total resistance to movement. The wider the tire, the more surface area of the tire is in contact with the road. So, compared to the non-touring model, the wider tires on the touring model probably decrease your MPG somewhat. My guess would be 1-2 MPG at most, which is not enough to worry about.

One way to minimize this is to inflate the tires with a few pounds of additional pressure. That is why you will see so many Prius owners talking about running their tires at 42/20 on the non-touring model.

 

<div class='quotetop'>QUOTE(Swanny1172 @ Jun 7 2007, 01:03 PM) [snapback]457422[/snapback]</div>

Once I get the BT PLATE (sore subject, I know) installed, I will next "experiment" with tire pressures. Since the Touring has a lower profile (55 series aspect ratio) tire than the non, and a stiffer sidewall, I was quite hesitant to suddenly bring it up to 42F/40R, especially while the driver is still "new" and still "cautious" on very windy days on the highway (another sore subject!). BTW, we only have less than 800 miles on our new Prius as of this morning (6/7/07) in addition to us waiting for the plate........... everything is still "too new" to start experimenting, but once we have the plate installed and ready to move onto the next step, I am seriously thinking of trying 40F/38R !! One of the reasons I am hesitant of "over-inflating" past factory recommended is that I tried that on our Honda CR-V with Bridgestone P225/60R16 (factory spec. 29F&R) and pumped 'em up to 35 lbs. since we did lots of highway driving.......... upon the next rotation (I do myself) about 6,000 miles after this pressure increase, I saw rapid "wear" in the CENTER of the tires, all four. Brought 'em back down to 29 and wearing fine now, althought slight "damage" (center wear) that was done cannot be un-done............

 

<div class='quotetop'>QUOTE(FloridaWen @ Jun 7 2007, 04:27 AM) [snapback]457251[/snapback]</div>

I too, live in a windy area (SoCal),and I found that slightly increasing the tire pressures makes the Prius all-around more enjoyable. I bumped the pressures 5, then 10 psi, and finally added the BT Brace. Anyway, just try increasing the pressures and it should help your windy day driving, not hinder it. You can play with pressures during the 6 weeks or so it takes to get the BT. I increased the pressures more as a handling improvement, than to increase mileage. Extra mpgs are an added bonus!

 

<div class='quotetop'>QUOTE(subarutoo @ Jun 7 2007, 03:38 PM) [snapback]457527[/snapback]</div>

Thanks for the advice .... I am an "old timer" from "the old school" and a gearhead from the 60's and 70's !! When we used to "Autocross" in parking lots (weekend events during the Connecticut Summers) usually with our "street tires" (the rich$ kids had special rallaye tires) around cones and barriers, we would always DECREASE the tire pressure for better adhesion and handling.......... it sure beat the crap out of the tire sidewalls !! I was "afraid" for a lack of a better word, maybe "cautious", to "over-inflate" the tires on our brand new Prius and stray from the placard on the door pillar with factory specs. of 35F/33R.
Do you think I should try, at very least to "start", 38F/36R (adding 3 lbs. per tire?) and then see how this is (handling). Remember, we have the TOURING edition with the Bridgestone EL400's (55 series).

 

we are averaging 49 to 51 mpg at 7,000 miles and 7 months

 

<div class='quotetop'>QUOTE(Swanny1172 @ Jun 7 2007, 10:03 AM) [snapback]457422[/snapback]</div>

Resistance to movement, or load on the propulsion system (I can't say engine, because there is more than one and they are of different types)? If you accept my proposition regarding propulsion system load, there are other things that can be done to improve efficiency beyond reducing rolling resistance - one modification that I did was to reduce the rotational mass of the wheels. That got me an additional 2 mpg (and in the S.F. Bay Area with its leading the nation gas prices, the 2 mpg is looking like it will pay for the cost of the wheels over the life of the car)! And the car is not even near completing break-in....

 

Past Toyotas owners manuals recommended increasing tire pressure a few PSI when long highway trips were planned. The Prius manual doesn't mention this, but 3 PSI over recommended will not harm anything. Note that some owners of the Touring who previously had a "normal" Prius, complained that the ride in the Touring got too harsh when they bumped up the pressure - I think they went all the way to 42/40.

Internationally, the 16" wheels with slightly wider tires have more history. They are rated for lower mileage than the 15" wheels with 185/65R15 tires. It's about a 10% difference.

My Prius has the 15" wheels, and I'm currently running 40/38 PSI. Rides nicely, handles fine. It's new so I can't comment on mileage changes. It came from the dealer with 40 PSI all around.

 

<div class='quotetop'>QUOTE(Xabiche @ Jun 6 2007, 04:00 PM) [snapback]456823[/snapback]</div>

The tires on the touring are not any different in the circumferance than the regular tire. Touring tire is a 195/55-16 and the regular is 185/65-15. These tires are within one revolution per mile of being the same. One has 824 revs per mile while the other has 825 revs per mile.

Check this website. www.miata.net/garage/tirecalc.html

 

<div class='quotetop'>QUOTE(Xabiche @ Jun 6 2007, 11:00 PM) [snapback]456823[/snapback]</div>

Everything else being equal, wider tires have a lower rolling resistance. Because of the increased contact area, they don't flatten out against the road as much, which means that they don't have to flex as much when the tire is rotating.
But, because of the increased frontal area and surface area, wider tires have a higher air resistance that becomes significant at higher speeds.

So, assuming that Toyota optimized the tire size for somewhere between low and high speed, the wider tire will probably give you slightly higher mpg at low speeds, and slightly lower mpg at high speeds.

 

Just FYI...
Japanese Prius has different brand of tires from NA model.
15 inch:Goodyear GT3 185/65R15: 33.0 km/L Japanese 10-15 mode test
16 inch:Michelin Pilot Primacy 195/55R15: 30.0 km/L Japanese 10-15 mode test

The real life mileage is also reported the 16 inch Turing mode is 10% worse than 15 inch standard model.
However, we believe the difference is caused by the tire brand.

Ken@Japan

 

I've been averaging 55 mpg freeway on my Touring. Our gas contains ethanol only October thru March, so presumably my gas mileage will go down during those months. I have 4,100 on my Prius and drive the speed limit.

If you look at the EPA estimates, they are identical for the Touring and the non-Touring models.

 

<div class='quotetop'>QUOTE(westex39 @ Jun 8 2007, 11:20 AM) [snapback]458018[/snapback]</div>

The Good Year Integrity tires on the US standard Prius is rated at 855 revs/mile by Good Year. Revs per mile increase as a tire wears as well by about 1.5% by tire end of life so also take care in comparing MPG between worn out and new tires.

JeffD

 

I've owned both a 2005 and a 2007 touring, and now that I've had a few tanks in warm weather I'm finding virtually identical 50 mpg mileage on both cars. In fact, with less than 10,000 miles in the 07, it is getting the same mileage that the 05 was getting at 30,000. Of course, there was no "driver break in period" needed for the 07!