So I bought this FZR400r swingarm, and it came with this Yamaha shock. What the hell is the thing I circled for?
damping adjustment. take spring off and adjust that screw, you'll feel the difference in the shock resistance at different settings. usually like that they work a small set of gears that control a tiny shaft in the main rod that threads in and out of the orifice of the inside of the shock body, like a metering valve, to control this. :twocents:
Thanks! So you figure turn to the left, less dampening, turn to the right, more dampening?
not sure. is there a + and - on it? wire wheel the housing, they usually have some faint marking on it. but not always. :twocents:
And a damping adjuster at the bottom of the shock will control rebound.
Wade is correct. That is what is known as a shaft adjustment. Basically it controls a needle that opens or closes and orifice. Though it could be a simple barrel type adjuster as well. If the adjuster turns indefinitely without stopping it is a barrel type, but if it stops it is a needle type. Rebound is the most used adjustment, and it is rather critical, so many manufacturers make these adjusters do very little. It is a slow speed adjustment, meaning it does not change how the piston functions. Generally clockwise will mean more damping, i.e. a slower shaft movement.
:jacked: sorry peaky! Chris, please elaborate on the rebound adjuster not changing how the piston functions; you bumped up against the edge of my understanding there :umm:
:patriot:
i knew it was something like that. compression is usually at the top then I guess.
You guys are the best! I turned it clock-wise. I turned and turned and it finally stopped. There are no "+" and "-" marks on it. Just a punch-dot on the adjusting screw. More to come. I'm not done messing with this thing yet.
Slow speed rebound like this generally has a port through the center of the shaft that leads above the piston. Just below the piston are the inlets, so it actually bypasses the piston all together. On the top side there is a check valve that only allows fluid to flow through the center of the shaft in rebound. When you turn the adjuster it adjusts a needle up and down inside the shaft and that opens/closes the ports below the piston. The more you close the ports the more slow speed rebound damping.
The reason this works only on slow speed is because 1) once the shims on the piston open the pressure below the piston is low enough that not much oil passes through those ports/shaft, and 2) because in high velocity movements those holes tend to "pack up" and won't pass a significant enough volume of oil to make a difference in the high speed damping character.
Keep in mind low speed rebound is like when you come off the throttle or brake, high speed rebound is like when your wheel drops into a pot hole. The maximum velocity of the rebound movement is directly associated with the spring rate. The spring can only move the damper so fast. Compression gets a lot more tricky.
For Peaky, there is some chance that adjuster works backwards on account of the bevel gears, but there is also some chance they threaded the needle left handed and it works normally. I have seen both. Personally I'd set it in the middle and just forget about it. It doesn't likely change much anyways. Ever OEM shock I have ever seen the adjustments were damn near just for show.
Got it, thanks for the explanation :thumbs: