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EDIT NOTE: Topic moved to General Discussion. Rob

I just replaced the tires on the Red, little engine Insight with Toyo 195/55-14" T1-R high performance summer tires. I am so impressed with how the road manners of the car are transformed that I will no longer be putting the stock Bridgestones tires back on unless I need to because of unforseen events (damage, theft etc). Many characteristics of the stock tires are gone. Now there is no grooving, there is enhanced traction on braking, accelerating and cornering and the tires are quieter. The only negatives are the decreased mileage, to the tune of 5-8 MPG or so on my CVT, and the danger of using these in cold, and winter periods. Of course spirited driving could widen this gap. The mileage gap may be more on a 4 speed due to being unable to get to "lean burn" mode as easily.

The place that mounted the tires said I should have the tires siped. http://en.wikipedia.org/wiki/Siping

My question is what can I expect from siping these tires? Namely what will happen to performance characteristics, adhesion, gasoline mileage, tire life etc? Some tires, especially winter tires come with the appearance of already being molded with siped features already on the tire. e.g. the Bridgestone Blizzak MZ-03. I am being told that siping should increase longevity because of better heat dissipation. It would seem that increase performance would translate into shorter tire life.
 

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Siping improves grip on ice by wicking water away from the ice. Water forms on ice under the tire when ice is compresed under pressure. Ice is most slippery when there is a layer of water on it.

Siping an all season tire can help improve wet traction because the tire compound is hard designed for long mileage. Siping a hard compound tire makes the tire conform better to the irregularities of the road and grip better.

But the Toyo T1R tire is a soft compound tire that grips dry and wet roads very well as is. The reason it does not have sipes is because siping causes the tire surface to flex more and more heat is produced. During high performance driving siping decreases grip in dry conditions due to tire flex, and this also causes the tire to wear out more quickly.

Toyo T1-R ultra high performance tires are designed for summer only use.
In rainy conditions the massive water evacuations thread pattern of the T1R tire greatly increase the speed at which the car would hydroplane compared to all season tires. Because the T1R tire uses a soft compound designed for warm to high temperatures it grips wet roads very well and adding sipping would not make a noticeable improvement in the wet.

There is a reason race tires and ultra high performance summer tires never have siping. Even the special race compound tires designed only to be used in the rain do NOT have sipes!

Siping is essential for winter and ice tires. Siping does help the already highly compromised hard compound all season tires in wet conditions.

Dedicated high performance summer tires should not have siping.
Most race car drivers know a lot more about tires then tire store employees.
 
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