There seems to be some confusion about fork oil weights. Here's a list of them and the associated weight of the oils. If you want to make your front end firmer, you can go to a heavier weight oil.

Fork Oil - 16oz. Type E 5wt. Type E is for "Showa" forks.Part # 99884-80

Fork Oil - 16oz. Type B 10w. Fork Oil - See owners manual for recommended style. Part # 99880-73

Screamin’ Eagle® Performance Fork Oil - A heavier oil (15wt) provides extra damping in performance application. Part # 99881-87

Screamin’ Eagle® Racing Fork Oil - Designed and blended for the severe conditions on the race track (20wt). Not intended for street use.
Part # 99909-93R

There are also other options for tuning the forks on your bike. Bel Ray makes a host of different weight oils to do this also available in 5wt, 7wt, 10wt, 15wt, 20wt and 30wt.

http://www.belray.com/consumer/productpages/hpfo.html



Donated by: JamieWG

Stiffness of forks is purely personal preference. A heavier fork oil will not create a stiffer fork, but it will slow down the damping response. This is good for handling, up to a point. A fork with heavier oil won't dive as quickly when you grab a handful of front brake heading into a turn. It also won't wallow as much in a fast turn. All this is good, up to a point. A fork that's too heavy provides a harsh ride and can cause a loss of traction over stutter bumps in a turn. You need to decide what's best for you. If you're happy with the way the bike handles now, then stick with factory recommended weight of fork oil.