Fork pressure spring rate down and preload up:

There is a new pressure spring that has a softer rate and more preload on it, we measured 22N/mm for the 2024 bike and 20N/mm for the 2025 bike which has an increase in preload of around 5mm, what does that mean to you??? From a hydraulic point of view the pressure spring’s role is to help reduce or eliminate cavitation and the choice of the rate and preload are tied to the suspension setting, they work hand in hand. As a rider you can feel the pressure spring choices so the tuner needs to keep the rider happy while maintaining a healthy damping system.

Although not the exact pressure springs from the Yamaha fork, we took a picture of two different length pressure springs for a visual connection to what has happened.

New delta shape rebound shim:

There is a new rebound shim shape for 2025, by going to a delta style shaped shim the inlet flow to the compression side of the main shaft piston is a straighter path. This is a much deeper damping/tuning discussion that we won’t get into here, we did want to share some of the finer details with you though as to what has changed for 2025.

The 2025 fork gets a new rebound face shim change. The inlet flow to the compression port is less restricted with the new shim shape.

Front Engine Mounts:

The new front engine mounts are a 1-piece design with a new shape that are 8mm thick now. These new mounts compliment the feel of the frame to help achieve the overall performance of the bike. Yup that is the day and age we are living in, tuning the feel of the frame can be felt by you the rider and it matters. We have seen a couple of variations of these front engine mounts over the last couple of years and models, see the pictures below.

The new engine mount is a solid 1 piece versus 2 thinner mounts making up the same total thickness, the flex characteristic of the frame will be different…

Linkage:

The new motion ratio (linkage ratio) is reported by many to be firmer. The motion ratio affects both the load at the rear axle coming from the spring and the damping force of the rear shock, basically the linkage acts as a multiplier, if you use the linkage “more” you put less in the shock and use smaller spring rates, “less” linkage and you use bigger spring rates and a beefier shock. The designer makes these choices and needs to come up with the sum of the parts to find good feel and performance.

By changing the dimensions of the linkage (red lines are the delta and black line is the pull rod), you can change the motion ratio of the rear suspension, this basically makes things firmer or softer and is part of the rear suspension package. The spring rate and shock setting work with the linkage to create the performance at the rear of the bike.

Spring rate:

Due to the new motion ratio being “firmer” the rear spring rate has been reduced for 2025, the standard spring rate is now 56N/mm (White paint mark) compared to the 58N/mm (Gold paint mark) that it was in 2024.

Damping characteristics:

From our standard rear shock dyno captures the compression is softer and the rebound is quicker in 2025. The changes fit with the new motion ratio coming from the change in the linkage. Did they get the sum of parts right with the new linkage and damping curves?

In the above graph the red trace is the 2024 rear shock dyno curve and the black trace is the new 2025. The new 2025 shock has less damping force in both compression and rebound.