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Hi guys, I wanted to give anyone a heads up on some mods I have tried on the wp AER48 forks. Bike is a 2017 450sxf, I weigh 93kg and race mainly intermediate cross country and some b grade mx. First thing I did was a revalve. I increased the base valve stack and reduced the mid valve. After some riding I tweaked this abit by going from an 11mm clamp to a 12mm on the mid stack. I then updated the air piston and top out spring to the 2018 parts. Next stop was a krooztune mid valve piston to replace my plastic stock one. It took some convincing for them to send me one with out a bleed hole pre drilled in it. I fitted my mid valve stack that I had on the OEM piston which had 0 float, but by the following weekend I had gone back to a 11mm clamp on the mid compression stack to allow for the reduced port edge on the new alloy piston. Plenty of riding followed Then what if? I got hold of a donor set of AER cartridges from a 2017 350 which I had fitted kyb sss internals into a few years back. I disassembled the damper cartridge and air cartridge to swap them around. I had a 48mm nylon spacer made to eliminate the top out spring on the air side. I fitted the air piston (old x ring style) and air side seal head into the damper unit body with the bleed hole at the top welded up and caps changed over. This gave me air cartridge with no bypass dimple and independent positive and negative chambers. I did one track session and a xc race I didn't complete. I knew I was in trouble right at the start of the race but lessons were learned. Back to the old traditional air chamber with more riding, a 4th in the iron man open class at the Pirini 4 hour and won my intermediate class in the 3 round belray 2 hour series. More what if? Ok I thought, best of both worlds. I reduced my nylon spacer to 40mm, 12x18x40 to be exact. Under that I fitted 11x5mm cross section oring. The oring is essentially my bump stop. So we have 2018 u seal style piston with nylon stem, custom spacer and oring then seal head. Why did I remove the top out spring? Because I wanted to add preload to my air spring to eliminate the vague feeling caused by the fact that for approximately 11mm of stroke (due to the bypass dimple) the air chamber has neutral force. After doing this I refitted the unit and added a extra valve to the fork cap so I can pressurize the outer chamber. You cant achieve the same thing with the stock setup because you would be working against the top out spring and until you bottomed that out you would still technically have zero preload. FYI I don't run a top out spring in the shock. So I've done approximately 100km of trail riding with some tinkering. Running 155psi inner and 5psi outer 10 comp 16 rebound 175ml of oil. Definitely worth the effort, plenty of front end bite, I was looking for holes and it was eating them up. More refining this weekend and I'll get the data logger out again I think. There is so so so many mis perceptions around suspension function and some of it comes from guys who own big businesses. If we look at a air spring curve against our desired coil curve we see the issue isn't ramp up but in fact the flat mid stroke support which causes the fork to collapse faster which essentially makes your valving "stiffer". Shim stack A with a 4.4N spring is stiffer than shim stack A with a 5.2N spring if the same force is applied, not because it's "riding in the soft part of the stroke" but because spring rate relates to spring frequency. I checked, even with a theoretical 0psi in the outer chamber of a fork at full travel 175ml of oil (had 0psi inner) you get 45psi at the bottom of the stroke on that outer chamber, so for anyone to say coil springs dont ramp up, well they need a slap. 5psi in the outer is 48N of preload this also adds support in the flat mid stroke area. Anyway sorry for the long winded post.
I've been fighting harshness in my airfork for almost a year now. I started with settings in the book of 154 psi, and comfort settings for my fork clickers. It was very stiff, so I got on the internet and started reading. Everyone goes on and on about how plush this fork was and I just wasn't feeling it. Seems the consensus was almost always "let some air out." I did in small increments until I ended up at 118 psi, still on the comfort setting of 20 clicks out for rebound and compression. I rode on those settings for a full season and felt the aer fork was pretty over rated. I had a harsh feeling in most slow speed Rocky sections, and also in high speed light front end situations (accelerating out of corners, tapping tops of bumps) as well. It blew through the midstroke on hard hits and would bottom harshly. I knew there had to be a better way to setup these forks. I recently read an article about the 2019 SX-F bikes and how the light riders had gone out to 35 clicks on compression to get a plush fork! What?! 35 clicks out? For some dumbass reason I had this mental road block that comfort setting was as far out as I should go, especially since I had been blowing through the stroke and bottoming hard so often...Around the same time I listened to a podcast about relating suspension sensations into setup adjustments. I started over and set my PSI WAY UP to correlate to the spring rate through the race tech calculator. I then turned my clickers all the way out.... 38 clicks!!!! I had only been using a little over half of my clickers range! After riding and messing around with clickers I have finally found the amazing plush aer fork everyone was raving about! It has an amazing intial stroke that flows progressively into an amazing bottoming resistance!!! I have been running way too low of psi, running in my midstroke instead of my initial stroke! DON'T LET AIR OUT CHASING THAT PLUSH FEELING! Race techs calculator is dang close for a start, once you find your psi (usually within 3 psi up or down, 2-3psi is equal to about 1 spring rate.), just keep clicking those compression and rebound clickers out until you find that sweet spot! There is a ton of adjustment!!!! I'm a 150lb b class Enduro rider. Here is my bike setup. 145 psi, 29 out compression, 30 out rebound, lowest line in triple clamp (3rd line), SDI linkage, stock spring, 105mm race sag. Hopefully someone that is struggling with the wp aer 48 fork will read this and hopefully it will be helpful.