K9 Angle Reducer Cups
Having fitted the K9 reducer cups my first impression was an increased feeling of confidence on the bike. My initial few runs felt a little awkward: the front wheel was further ahead than I was used to and I ran too high on a berm and caught stumps/rocks that I thought I was turning inside of. The steering felt a little numbed, especially on flatter ground and tighter slower sections of trail. The front fork was not as responsive on smaller bumps particularly on shallower gradients (this was mainly down to running too stiff a spring). However the bike immediately felt far more predictable in a drift, I could confidently hold stable drifts far easier than before.
I had just fitted some 2010 Boxxer Teams and the soft spring was not soft enough, especially with the slacker head angle. The slacker head angle necessitated a slightly softer spring as the vertical force acting up from the ground has a smaller component force acting in line with the fork than with a steeper head angle.
The component of a force = Cos (angle between force and component of force) X force
Therefore the greater the angle between the vertical force and rake of the fork (slacker the head angle) the smaller the component of the vertical force acting in line with the fork for the same vertical impact.
The effect of head angle on correct spring weight is small, and for some impacts (more longitudinal forces) a slacker head angle may allow the spring to be compressed more easily. Nonetheless when in the riding position on flat ground there was less sag on the front fork after fitting the cups, and it was not until a softer spring was fitted that the desired amount of sag was reached.
After fitting an extra soft spring to the forks I had approximately 30% sag on my front forks; this matched my rear shock. The bike sat nicely in the suspension and felt well balanced. Running this much sag on the front would previously have made for a very steep head angle. However with the cups the bike maintained a confident and predictable ride.
On flat out sections and steeps the bike inspired confidence and felt much more stable. What was particularly noticeable was the ability to plough through steep rough terrain without the fork diving in sumps and catching on edges: the bike maintained speed far better. When riding ‘in deep’ on the Garbanzo in Whistler there were sections where I had hit sumps on steep gradients, and had been unable to hold on to the bars through the compression going chest first into the bars and crashing. Although this cannot be entirely credited to the steep head angle and diving of the fork I think its fair to say a slacker head angle has helped! The ability of the bike to carry momentum over bumps could be attributed to the more rearward axle path of the front wheel due to the slacker head angle, which improves the forks ability to absorb impacts that induce a longitudinal force (e.g. objects hit at speed/ square edge hits).
It was only the initial few runs when I had too stiff a spring in the forks that the cups felt a little awkward. Having just come back from Silverstar and Sun Peaks I’m incredibly pleased I had them fitted in time, especially at Sun Peaks where the tracks are flat out and steep, I don’t think I would have felt very comfortable riding without them! The slacker head angle inspired confidence on the rough steeps and the high speed bermed corners. The bike corners better, especially at speed, it drifts incredibly predictably, due to the lengthened wheelbase and lower BB. There was a section of drifty berms in Sun Peaks (it appears on Sam Hills section in Clay Porter’s film The Tipping Point); I don’t think I’ve ever had that much fun on a bike, the bike really came into its own. I was unsure if the cups would be so well suited to UK tracks as they tend to be slower, more awkward and tighter. Having done a few races at Caersws I have had no issues and the benefits of the cups still apply.
The slight numbing of the handling on slower, flatter tighter tracks is something I forgot about and got used to after a few runs. The slight loss of responsiveness of the front forks on smaller bumps, on flatter gradients was barely noticeable, especially once the correct weight spring was in the fork. Both of these characteristics are far outweighed by the benefits of being able to run greater sag at the front of the bike without creating a very steep head angle, the ability to carry speed over rough ground, the improved cornering and the general confidence inspiring and predictable ride feel given by the lengthened wheelbase, lowered BB and slacker head angle. Overall I am extremely pleased with the improved handling and performance of my bike with the cups and have no intention of returning to the old set up.
Written/Tested by Joe Taylor Photos by Harry Charnock (unless mentioned)