There was an era when bike tyres were marketed for both applications and said so, with direction arrows for both wheels. However that is a long time ago! Personally I wouldn't swap tyres, not least because I don't have odd tyres lying around looking for a home! Another reason for not using a narrow rear tyre on the front is load rating, as narrower tyres often have a low rating.

As for running a 150/80 with a narrow belt, you should have plenty of room. I've used one in my bike with an '07 s/a and wheel and been able to fit the stock belt guard.

 

For those who have tried a rear tire on the front and reversed the rotation: Why? I understand that the main job of the front tire is braking BUT my understanding of the tread pattern direction is for water flow. Spinning the tire in the designed direction should flow water away from the contact patch more efficiently than running it in the opposite direction, or is there something else to consider?

 

Front or rear fitment

 

Care to share why Sir??? Very curious!!!

 

I tried it once and my bike started to go backwards.

 

A rear MC tire is built to react best to acceleration forces. A front MC tire is built to better handle braking forces. So if you are installing a rear tire on the front reverse the rotation.
Most modern MC tires are built with a randomized tread pattern to cut down on noise and rpm induced vibrations. A lot of older tires have a symmetric tread pattern, and have the same foot print both directions. Not to many with a directional tread pattern.
I wouldn't run a tire with a directional tread pattern reversed on my bike.

 

Mostly because the size I want for the front is only made in a rear fitment.

 

Thanks.