Looking to make your trail or enduro mountain bike just a bit slacker? And do so without any major mods and for only $20? The Niner Slacker Puck lower headset bearing cup lets you do just that, and it ships with their RIP9 and JET9 models but can be ordered separately for other bikes.
Niner introduced the current generation RIP9 and JET9 in summer 2016 as their first 29/27.5+ bikes able to run both wheel and tire sizes. The bikes were designed around 51mm offset 29er forks, which were still the norm at that time. If you opted for the 27.5+ wheels and tires, they simply spec’d a fork with 10mm more travel to match the 29er’s geometry.
Along with mid-term updates to those bikes’ cable routing, Niner also started shipping the bikes with a 15mm lower headset bearing spacer they called the “slacker puck”, which was designed to let you adjust the geo yourself if you wanted to swap in 27.5+ wheels and tires without having to buy a new, longer travel fork.
Now, with more 29ers coming stock with 44mm offset forks (Niner included, thanks to a rolling spec change this past summer) and more bikes pushing the front end slacker, the slacker puck can also be used to update your RIP9 or JET9 geo as needed.
The effect is that it’ll make the head angle about 0.5º slacker. For the RIP9, it goes from 67º to 66.5º, and ships with the bikes (but not pre-installed, even though their geometry charts show the numbers with it). By itself, it’ll increase trail slightly, and it’s meant to be paired with a shorter offset fork, which will also increase trail. But, the combo will help limit wheelbase growth, and the overall effect should be more stability on the descents and high speeds.
The tradeoff? As with any slack bike with lots of trail, handling might be a bit slower in the tight, twisty stuff or want to wander on the climbs. It also raises the BB about 3.5mm, too. Do you need it? Depends on the type of riding you’re doing. If you’re doing more down than up, it might be a nice upgrade.
The Slacker Puck is a lower headset cup that pushes the bearings out by 15mm and works with their ZS56/40 lower bearing. Those numbers mean a headtube with a 56mm internal diameter, and a standard 1.5″ tapered lower fork steerer tube. If those numbers match your bike, chances are it’ll work. Link below goes straight to the product page.