Yokohama S.drive 205/55/16 for Touring model

I'd like to start a thread on Yokohama S.drives.

First off, I do not work for Yokohama -- this review is my own personal opinion. Second, I drive the Prius as I would a normal car, and paid extra for the Touring because I wanted better handling than the standard model. Thus, don't flame me for getting an ultra high performance summer tire that is not a LRR model made of recycled orange peels.

The Bridgestone Turanza EL400s were down to 3-4/32, and 2/32 on the lateral grooves after only 25k miles. The car has undergone regular alignment, but still the lateral wear was apparent. I kept them inflated at least at 35/33 as recommended by Toyota. For a few months, I kept them at 42/40 but then noted excessive center tire wear, so I dropped them back to recommended pressures.

Here is the summary graph of mpg and total fuel consumed while running on the Turanzas based on a log I updated at each fill-up. The blue dots are mpg, the black line is the moving average, and the red dots are gallons fueled. The average was 39.5 mpg (Prius computer lists 40.4 mpg). The reason my average is lower than what others report is due to 1) my driving style (I drive it like a regular car), 2) it's darned hilly where I live and work, and 3) my work is very close, so the engine never gets a chance to warm up and become efficient.




Since I live in an area with no snow and only occasional rain, I decided to get some Ultra High Performance summer tires. The S.drives from Yokohama seemed rather inexpensive and the tread pattern looked cool, so I went with it. I got the upsized tires, 205/55/16.







First Impressions:
The ride is cushy like the Turanzas, but everything feels much more controlled. Turn-ins are accurate, and grip is much improved. The Mira Mesa onramp to I805S is a big oval. With the Turanzas, I would be limited to ~25-30mph, but with these new tires, I got up to 45mph today, no squeals. I always thought braking sucked because of the rear drum brakes. To my surprise, these new tires gave my brakes a whole new feel...I actually feel confident braking now, something that I don't think I ever felt with the Turanzas. The only downside that I've noticed so far is that these tires seem louder than the Turanzas, especially on grooved concrete. There's no noticeable tramlining, but the road noise is definitely intrusive. I plan on keeping the tire pressures at Toyota's recommended levels. I know I'm going to take a mpg hit, but I'm willing to live with it.

I'll post interim and summary updates with mpg. But so far, I'm quite happy with the S.drives.

 

the stock turanzas are 19 lbs and the s.drives are 23 lbs, significantly heavier.

 

So it's been about 10 fill-ups since switching tires -- time for an interim update.

The tires have transformed the driving experience of the Prius. Taking curves and corners are enjoyable nowadays, especially zipping past "performance luxury" cars on the 360-degree freeway onramp. Unexpectedly, braking confidence has also increased, which now makes perfect sense. We took the Prius to Yosemite NP, and it was so much fun driving the curvy roads at the speed limit and also knowing we weren't smogging up the valley.

What I did was to take the 10 fill-ups after switching to the S.drives and compare it to the 10 fill-ups immediately prior. This is not exactly scientific, since the pre-Sdrive data was basically all San Diego mesa driving, while the post-data has significant highway and altitude changes weighing the results. Again, I'm keeping the S.drives at the recommended tire pressures. I feel like there's a 2-3 mpg hit, but the paired t-test does not demonstrate significance:



P value and statistical significance:
The two-tailed P value equals 0.4452
By conventional criteria, this difference is considered to be not statistically significant.
Confidence interval:
The mean of Turanza minus S.Drive equals 1.1660
95% confidence interval of this difference: From -2.1377 to 4.4697
Intermediate values used in calculations:
t = 0.7984
df = 9
standard error of difference = 1.460

I'll post more data in a few months. So far, I remain thrilled with my decision to go with the wider and stickier S.drives.