I put the heavy in my new bike last year because of the inherant "diving" I got when slowing down rapidly from anything over 40 mph. In the warm summer months it is fine, but when it starts to get colder, it rides stiffer than a lumber truck. It is noisier too. I even thought my neck bearing might be getting looser so I raised the bike up and did the swing away test. That heavy oil in colder weather is just is going to give us a stiffer ride.

 

Rather have a stiffer ride than a bad nose dive in panic situation .. 15W works for me ..

 

I must have had the high quality Canadian Pacific salmon oil installed in my front forks cause they don't dive at all and are quite firm, my rear shocks however bottom occasionally when 2 up even at higher air pressures.

 

A heavier oil will make your front end firmer and reduce brake dive, but will also compromise the forks' ability to keep the tire on rough roads. You will be better served with adding a product like Intiminators and running a 5wt.