2007 Touring Edition - Wider Tires???

You want to keep the tire diameter the same.

There are various (semi-BS) tire diameter calculators on the web, and web sites.
For example, according to

Code:

https://tiresize.com/calculator/

Going to a 205/50/16 results in an ~1.2% smaller diameter tire (24.1" vs 24.4").
That would result in an ~1.2% higher speedometer reading.
And, ~1.2% greater miles traveled reported/displayed.

However, tires sizes are like dress/pants sizes. In the real world, they mean nothing.
The tire diameter is also dependent on the tire pressure, and the wheel width.

Therefore, if someone says that "size-xyz is x% different than size-abc", at best, it's a rough estimate.

Fwiw, on the 4th Gen Prius, it's possible to change the speedometer calibration with TechSteam.
Straight from the factory, my speedometer calibration was off by ~5%. Fwiw, that's not uncommon with new vehicles. It makes it look like the vehicle is getting better mileage. Iirc, Rivian trucks are also ~5% off from the factory.

Good Luck!

 

The Prius uses Low Rolling Resistance (LRR) tires.

Therefore, going to those tires, will likely result in an ~~3-7mpg decrease.
That my very rough guess, from decades of people reporting on MPG losses, using various non-LRR tires, on many hybrid/EV/PHEV vehicles (e.g. Prius and Tesla).

Now, Michelin offers a new LRR tire, which also has good road grip, and has a real (European) LRR rating.
In places in Europe, tires sold as LRR tires, must have an official LRR-rating (based on some standard).
Before, like with tire sizes, in Europe, any manufacture could call a tire an "LRR" tire.
I'm not sure if/when America will adopt the same/similar standard.

Regardless, don't expect to see LRR ratings on non-LRR tires. So, no way to even get a "very rough" estimate on the possible MPG decrease, going to some non-LRR tire.

Good Luck!

 

I have a 2009 Gen 2 Touring 204,000 miles with 16" rims that I use on a mail route. I have run 195/55/R16, 205/55/R16, and 215/55/R16.

205/55/R16 works great in my opinion. They are generally cheaper because they are a much more common tire size... The Prius handles and corners much more effectively with them... Protects the rims better when pulling up to a curb due to increased width... increases ride height slightly... Makes the speedometer more accurate to it's true value... and they last longer. MPG is negligibly affected and you make up any lost money with the 205 tires being cheaper and lasting longer.

215/55/R16 was to big. They'd rub over big bumps and definitely caused a larger hit to mpg.

205/55/R16 works perfectly and is even listed as an alternative tire size by Toyota. I think diameter increase is only 1.7% or so from the OEM 195's. Width is a non-factor for both the 215's and 205's. There was no rubbing on full steering lock. For the 215's there was rubbing over bumps due to the increased diameter.

 

I have 205/55R16 on my 2009 touring, installed by the prior owner. Mine are Nebula "Pioneer", not LRR as far as I can tell. I still get over 50mpg on the highway at 65, so they aren't killing me.

 

I recently had 4 new 205/55/R16 94V tires installed on my 2007 touring. They are Solarus Starfires (by Cooper) and were on sale at Wally World for $63 each (~95ish? normal price). I wanted to go one size up from stock to make my speedo exactly match real speed. They're great. IMHO, the extra expense of a LRR tire is unwarranted. Even with the lower mph reading, I'm still hitting 51.7 mpg on last 3 tanks of gas without trying really hard. Could hit around 54 with stock size tires, but with stock size tires (they were Falken ZE950s?), the indicated mph (and therefore mpg) was higher than actual mph.

Although LRR tires create their savings several ways, a main way is reducing tire deformation at the point of road contact. Energy spent when the tire deforms at the road surface and then "reforms" is wasted energy. Design the tire to minimize that and you save energy/mpg. A similar improvement can be made merely by increasing tire pressure, but usually results in a harsher ride quality. I follow the typical PC guidelines of 42 front and 38-40 back tire pressures.

 

While it is true the indicated MPH on the speedometer with stock tires is higher than the true speed that is by design (and the amount of the variation is different around the world depending on local laws), this indicated speed is not used to calculate the MPG. The car knows the true speed and this is what is used to calculate the MPG and the odometer for that matter.

When you put larger diameter tires on the car you not only lower the indicated speed, you lower the true speed and the miles driven by virtue of changing the relationship between the number of wheel revolutions to the distance traveled.

In likelihood, your car is just as economical as it always was, it is just the math that has been altered (downward) by the change in wheel/tire diameter.

You can verify the amount of the shift (displayed speed vs true speed) by going to the 'secret' screen on the MDF and selecting the "Vehicle Signal Check Mode" screen. One of the displayed outputs is the speed at the wheel sensors which would be the true speed with stock tires. Unfortunately for the USA, to get the speed in MPH it will involve a bit of math to divide the number shown (in km/h) by 1.6 to get MPH to compare with the speed displayed on the speedo.

 

Good to hear it's a perfect size for your Touring. We'll check this 2009 Touring and it's due for a new set of tires. It's getting around 45mpg and properly inflated tires might improve that. Seeing some good deals on tires at DT and 4Wheelonline and we'll consider that size.

 

I've had 205s and 215s now on my Prius. It was fine with both. A lot of factors go into how it'll effect your fuel economy including wheel size/weight. I have to say though that the 215s did quite positive effect the ride and handling. Much more grip and the larger contact patch I think made the ride feel less crashy. I'm on 205s now but I've considered going to 215s for summer and 205s for winter. I have a lifted Prius, so narrower isn't an option for me anymore.

 

Thanks I was wondering what the largest tire was, I am also on 205/55 and will move to 215's
Thanks

 

What did you use to measure the actual speed before changing it, GPS of some sort?