Posts
360
Joined
3/28/2015
Location
Ashville, OH
US
Edited Date/Time
1/26/2019 9:48pm
How many Socal riders have used mainstream suspension services and think they're too expensive and replace parts "just to CYA" during a basic service job? Would you use a friend instead to do the work at a much lower cost if you knew they had the competence/tools BUT you had to supply the parts/liquids? Besides a real good price, what other expectations would you have (besides doing what was contracted and things not falling apart)? Things like turn-around, support, availability, LIABILITY, etc. Not sure this is the proper forum, I'm just trying to gauge reaction.
Obviously, this would apply to the person without the time/knowledge/tools to do it themselves but informed enough to properly select springs and/or replacement parts (seals/wipers/bushings/valves, etc). This would also not apply to the guy wanting a major setup change (new valving baseline). Minor tweaks to existing setup (assuming the person can communicate the issue) would probably be included.
Obviously, this would apply to the person without the time/knowledge/tools to do it themselves but informed enough to properly select springs and/or replacement parts (seals/wipers/bushings/valves, etc). This would also not apply to the guy wanting a major setup change (new valving baseline). Minor tweaks to existing setup (assuming the person can communicate the issue) would probably be included.
Call the shop, get a recommended spring rate and setup for what you are looking for, tear the assemblies apart and send them the assembled stacks on the rods, have them mail it back with springs to match what they did and reassemble everything back yourself and add the recommended oil height.
It requires very basic tools to do this. Only thing speciality you'll need is an inch pounds torque wrench and a spring holder.
Service/oil change - do in your garage or have a friend do it.
The Shop
About 10 years ago when I raced a lot a guy named George who has esp suspension used to do revalves fairly cheap.
Rees firestone at pro action used to do cheap revalves too.
This was just oil and revalving as I would have new bushings and seals already. This was awhile ago and I don’t know what these guys would charge now or if theyre still in business.
Whatever he did it worked well for me! I think he’s in NJ now.
ESP was too soft on spring rates on the forks for me. I’d always put a heavier weight set in place of his recommendation.
Dealing with the local 3 tuners was a negative experience to say the least with 2 mediocre results after a couple of revavles. The 3rd tuner resulted in worse suspension feel than what the factory started with.
The 7 reputable tuners have been good experiences with FC having the best results for me.
I believe suspension is a science & not any ordinary Joe or backyard mechanic can achieve the results of many hrs. R&D put in by the reputable well known companies. That being said most on here including myself at this stage in my life would just benefit from having the right spring / sag set up.
Here is a good read on suspension for those that like to get into the intricacies & details of it. It sure appears to be a science & it shows it's more than just moving shims & oil heights around..
https://thumpertalk.com/forums/topic/1264005-baseline-suspension-setup/
Thanks for the nice words Bryan. As mentioned, I try to take a very scientific approach to a discipline seen as more art than science. I've tried all the typical approaches, including "re-stackor" and as an engineer was frustrated when the actual results didn't match the tool/theory. My current process is very time consuming and involves measuring the bike very accurately (within .005") using a portable CMM arm to determine the kinematics, and scales to determine the mass properties (both by component and in total). I then build a CAD model that mimics these.
Once I have a CAD model I import it into ANSYS, a very sophisticated simulation software. In ANSYS I assign initial damping curves to shock/fork (generated in re-stackor), spring rates to same (including the effects of fork air pressure and shock gas pressure and bottoming systems), preloads, friction tables for any moving part, chain torque table, tire data, and of course an articulated "rider" with proper kinematics and mass properties.
There's a whole process for determining the proper dynamic front/back spring rates (with no damping). After that I'll apply the damping and do more simulations while tweaking the damping curve. Finally, I'll put the entire COUPLED system (most math models do not couple front and rear) through some simulated track conditions where the rear tire is actually driving the system (traction coefficients added) through the chain.
There's literally hundreds of outputs calculated by ANSYS during a simulation of this type. From forces, to velocities, accelerations, elongations (travel), attitude, etc. The trick is identifying the ones that affect the two biggies, comfort and control. Damping changes are just one variable I can alter. Note, I'm currently using Re-Stackor to generate valve stacks required for desired damping curves. Since I can create ANY (ie, physically impossible to achieve) damping curve I want in ANSYS, Re-Stackor keeps me within the limits of current damping control technology, almost! My next level process step is to model the actual valving using CFD to validate damping curves.
Here's a slow motion clip showing shock velocities in one condition (low amplitude, high speed, high frequency).
But like others here, I have done the re-valve on my last few bikes and was really happy with how it came out. For sure it took some time reading up and taking notes but I enjoy that part.
What drives me nuts is in bike tests they say the cliche- "Sent the suspension to PC or whoever..." What I'd like to see is them take the stock stack apart and list it, then take the PC stack apart and list it.
Pit Row
I've recently run FC on an RMZ & they did a REALLY super-good job. And that's on The Big Piston Super Blow-Thru shock! They've done miracles with Yamaha suspension for Rockstar/OTSFF in Canada, also.
I've had Enzo more than a few times and they're awesome...often asking to have it back if it's not quite right...this is after talking to me about what I feel the suspension is doing versus what they feel it SHOULD be doing. Boom! They take another swipe at it...no charge.
I've had PC KX-Fs and they've always worked better than expected and they make AMAZING PSF-1 parts that turn those forks into simply "unbelievably smooth".
There's a forum member, here, "SlipDog"...& he can just "service" your forks or shock for a pretty damn good deal and he has ALL the correct tools and parts.
Very recently...I tried a Murietta 'local', JBI...I was stoked on his ability to give me EXACTLY what I asked for and the dude was very reasonable on price. On KTM/Huksy...he's got ALL the good parts options to make your stock stuff stellar. I'll have a Bike Build with more info about his stuff VERY soon.
After that, I'm doing a KX450 with Race Tech stuff.
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We also did an enormous of testing and re-valving by seat of the pants riding and sometimes videoing the bike while it is being ridden.
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I know some of the top suspension design guys in the moto biz. A good friend of mine ran the power sports division for Fox Racing Shocks for over 20 years. After having my stuff serviced by a known local guy.... I went to visit my buddy at Fox and spent 15 mins in his office asking him a few questions about stacks. That's all it took.... haven't paid someone to touch my stuff since then.
It is NOT rocket science. You need some basic valve stack lessons (what does what), then you need to experiment from there. If you are mechanically inclined... go for it! It's not very difficult. It does take sometime but is rewarding. And once you learn what does what, and what you like, you'll be able to tune your stuff to do what YOU want it to do. Not what someone tells you it should.
My 3 cents..... )
Now, take a situation where you're swapping forks/shock from a totally different bike with no baseline. Simply using percentages or scaling probably wont be nearly as successful.
An interesting side note on PT and Racetech. His "claim to fame" was/is the gold valve and it's huge compression ports which allowed his shim stacks almost 100% control over the damping curve. Now that most mfgs have done the same he's switched back to ultimately restricting flow through a "virtual" fixed orifice. Funny how things just go round and round!
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