WP 43mm forks explained, want to understand revalving

[hannesd]

hey guys,
i'm looking for a vid or tutorial of how the oil flow goes in a WP 43mm (open chamber?) forks goed and how valvind can be altered to obtain a smoother or harder ride.
i don't just want to try and copy some one elses shim stacks, i want to understand this somewhat, so i can alter my own suspension to my taste.
i've got on leg apart now and can't see clear enough how and where oil flows on up- and downwards strokes of the fork.

thanks in advance guys.

[GMP]

Same as any open chamber cartridge fork, but actually easier to work on than most. Plenty of info on the web.

Basically its like this:

Compression

Base valve check plate forced closed, oil displaced by damper rod entering cartridge forced through ports, controlled by compression stack, and exits cartridge. Rebound stack forced closed, remainder of oil in cartridge forced through ports, opening check plate(mid valve) and flows to top side of rebound piston in cartridge.

Rebound

Base valve stack forced closed, base valve check plate opens allowing a volume of oil equal to the damper rod exiting the cartridge to enter the cartridge below the rebound piston. Rebound check plate forced closed, remainder of oil above rebound piston forced through ports, controlled by rebound stack, and refills remainder of cartridge volume below rebound piston.

Two things you must understand are that the pistons are bi-directional with two sets of ports, and only the volume of oil equal to that of the damper rod moving in or out of the cartridge changes in the cartridge.

[Simmo737]

Buy the racetech suspension bible, by Paul Thede and lee Park. It does crap on about racetech gear a bit but it gives you a clear understanding of suspension in a global sense, and from this you can make informed choices about what you want verses what you need.

It also has good sections on fault tuning and workshop guides for all types of forks and bladder shocks.

Suspension is quite simple in theory, but has so many variables and so many ways of doing the same thing the you need a peg in the sand to start from, something like this book will start you off.

http://racetech.com/html_files/SUSPENSION%20BIBLE.html

[GMP]

A basic understanding of flow dynamics is essential when you really get into it. Thats why most of the top suspension guys are sharp, technical people. They don't earn their money pulling stuff apart and swapping shims, its all in the anaylsis of the setup, requirements of the rider, and fine tuned by experience. Its fun to play with and learn, but you will have that fork apart a lot before you get where you want to be. Good thing its easy to work on.

[swazi_matt]

Originally Posted by GMP

A basic understanding of flow dynamics is essential when you really get into it. Thats why most of the top suspension guys are sharp, technical people. They don't earn their money pulling stuff apart and swapping shims, its all in the anaylsis of the setup, requirements of the rider, and fine tuned by experience. Its fun to play with and learn, but you will have that fork apart a lot before you get where you want to be. Good thing its easy to work on.

I (being an engineer myself) have often wondered if the suspension experts actually calculate the shim stacks or use their experience + academic training to come to an "educated guess" of what to put in. (i have seen that quite a few of the tuners mention that they have a degree in mechanical engineering)

I have cme to the conclusion that since the terrain we ride is so varied it comes dwn more to the educated guess option than to number crunching on a pad of paper!

[GMP]

I agree on the educated guess, although guess might be too loose of a term. That would be a very difficult calculation to make, with many factors. Only fairly recently has that Stacker software been available to make things easier. With a good knowledge and understanding of engineering principles, you can visualize the situation, take into consideration the riders problems and requests, and arrive at a reasonably accurate solution. This is then refined by rider feedback.

[hannesd]

http://www.shimrestackor.com/

just found this site... this might teach me something