Factory suspension outer tubes

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1/12/2018 2:47 AM

Kind of a dumb question, but are the top tubes of factory suspension billet or cast? I could see it being billet and the factories adjusting wall thickness to allow for certain flex characteristics. Although I’m sure that would be super expensive. Aren’t stock just cast and then the outers cnc’d?

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1/12/2018 4:43 AM

These days they are laser printed

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1/12/2018 6:11 AM

One thing I have never seen in all my decades of MX is an interview with a Kayaba or Showa tech explaining what goes into works suspension units and how they differ from OEM, beyond the coatings and tolerances and billet lugs that we all know. I never see anything about the differences in the valve shim stacks or the complete separation of compression and rebound dampening circuits in works shocks. I find suspension the most interesting of all parts on an MX bike. It would make for a really interesting interview/ article.

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1/12/2018 7:47 AM

Tokyo_Tiddler wrote:

One thing I have never seen in all my decades of MX is an interview with a Kayaba or Showa tech explaining what goes into works suspension units and how they differ from OEM, beyond the coatings and tolerances and billet lugs that we all know. I never see anything about the differences in the valve shim stacks or the complete separation of compression and rebound dampening circuits in works shocks. I find suspension the most interesting of all parts on an MX bike. It would make for a really interesting interview/ article.

Would definitely be something worth reading. I wonder if Showa or KYB would be willing to share much? Maybe interview someone like George Quay instead?

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1/12/2018 9:30 AM

Tokyo_Tiddler wrote:

One thing I have never seen in all my decades of MX is an interview with a Kayaba or Showa tech explaining what goes into works suspension units and how they differ from OEM, beyond the coatings and tolerances and billet lugs that we all know. I never see anything about the differences in the valve shim stacks or the complete separation of compression and rebound dampening circuits in works shocks. I find suspension the most interesting of all parts on an MX bike. It would make for a really interesting interview/ article.

X100. Completely agree and I would love to learn some suspension tech as well. I’m not asking for proprietary info but I would like some basics about what their stuff does and why.

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1/12/2018 9:33 AM

Race Tech offers classes.

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1/12/2018 9:52 AM

Tokyo_Tiddler wrote:

One thing I have never seen in all my decades of MX is an interview with a Kayaba or Showa tech explaining what goes into works suspension units and how they differ from OEM, beyond the coatings and tolerances and billet lugs that we all know. I never see anything about the differences in the valve shim stacks or the complete separation of compression and rebound dampening circuits in works shocks. I find suspension the most interesting of all parts on an MX bike. It would make for a really interesting interview/ article.

Jmicmoto13 wrote:

X100. Completely agree and I would love to learn some suspension tech as well. I’m not asking for proprietary info but I would like some basics about what their stuff does and why.

Send me your email address and I can send you a comprehensive paper I wrote on this very subject. It's too long for a forum type format. Mark at maxvonauto@aol.com.

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Retired Mechanical Engineer, published technical writer, mscperformance.com, Bisimotoengineering.com,

1/12/2018 10:02 AM
Edited Date/Time: 1/12/2018 10:08 AM

Tokyo_Tiddler wrote:

One thing I have never seen in all my decades of MX is an interview with a Kayaba or Showa tech explaining what goes into works suspension units and how they differ from OEM, beyond the coatings and tolerances and billet lugs that we all know. I never see anything about the differences in the valve shim stacks or the complete separation of compression and rebound dampening circuits in works shocks. I find suspension the most interesting of all parts on an MX bike. It would make for a really interesting interview/ article.

What's to know? Less friction, less deflection, less dynamic deformation. That's it. This allows the dampening to do more of the actual absorption of movement, instead of movement being absorbed by flexing parts and the friction between the parts. The idea is that removing friction and flex allows more precise damping control. (This principle is observed in cars as well with chassis and control arm flex). Friction and flex are not consistent at dampening movement, and introduce uncontrollable dampening forces. Because those forces can spike at times, the actual dampening baseline has to be softer. With more rigidity and less friction, damening tuning can be much more accurate and consistent. And because there is less harshness, the suspenion can be stiffer without sacrificing comfort. This means you can go harder, faster, longer...and dial your suspension in with more accuracy.

This is litterally why they turned forks upside down. Less flex = less friction. Less Unsprung weight was just a byproduct of the inverted fork. Not the reason like many have suggested over the years.


Fluid dampening designs come and go, so they are sort of irrelevant. Factory suspension is really all about the manufacturing...materials, coatings, fitment, tolerences, and assembly...not dampening designs. I will say this though- the larger you make valves and orifices in your dampening design, the more consitant the dampening will be, so thats the trend in suspension design- move larger volumes of fluid per action.

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1/12/2018 10:04 AM

mark911 wrote:

Send me your email address and I can send you a comprehensive paper I wrote on this very subject. It's too long for a forum type format. Mark at maxvonauto@aol.com.

Cool, will do.

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1/12/2018 11:24 AM

Tokyo_Tiddler wrote:

One thing I have never seen in all my decades of MX is an interview with a Kayaba or Showa tech explaining what goes into works suspension units and how they differ from OEM, beyond the coatings and tolerances and billet lugs that we all know. I never see anything about the differences in the valve shim stacks or the complete separation of compression and rebound dampening circuits in works shocks. I find suspension the most interesting of all parts on an MX bike. It would make for a really interesting interview/ article.

ga_pike wrote:

Would definitely be something worth reading. I wonder if Showa or KYB would be willing to share much? Maybe interview someone like George Quay instead?

I know KYB is very protective over any information regarding factory or works parts. Most suspension guys never have and never will see the inside of a set of factory KYB stuff. From what I hear it was a pretty big deal for KYB to allow Racetech to service the suspension for the Motoconcepts bikes.

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1/12/2018 10:12 PM

To answer the OP's original question. The outer tubes of works and production forks probably both start out as extrusions. On works stuff the ID is probably precision honed and of course the OD is machined. Making a part like that from billet, although technically feasible, wouldn't make a lot of sense unless for some reason the factory part couldn't be made out of the raw extrusion that the factories already have.

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1/13/2018 12:46 AM

Tokyo_Tiddler wrote:

One thing I have never seen in all my decades of MX is an interview with a Kayaba or Showa tech explaining what goes into works suspension units and how they differ from OEM, beyond the coatings and tolerances and billet lugs that we all know. I never see anything about the differences in the valve shim stacks or the complete separation of compression and rebound dampening circuits in works shocks. I find suspension the most interesting of all parts on an MX bike. It would make for a really interesting interview/ article.

Katoomey wrote:

What's to know? Less friction, less deflection, less dynamic deformation. That's it. This allows the dampening to do more of the actual absorption of movement, instead of movement being absorbed by flexing parts and the friction between the parts. The idea is that removing friction and flex allows more precise damping control. (This principle is observed in cars as well with chassis and control arm flex). Friction and flex are not consistent at dampening movement, and introduce uncontrollable dampening forces. Because those forces can spike at times, the actual dampening baseline has to be softer. With more rigidity and less friction, damening tuning can be much more accurate and consistent. And because there is less harshness, the suspenion can be stiffer without sacrificing comfort. This means you can go harder, faster, longer...and dial your suspension in with more accuracy.

This is litterally why they turned forks upside down. Less flex = less friction. Less Unsprung weight was just a byproduct of the inverted fork. Not the reason like many have suggested over the years.


Fluid dampening designs come and go, so they are sort of irrelevant. Factory suspension is really all about the manufacturing...materials, coatings, fitment, tolerences, and assembly...not dampening designs. I will say this though- the larger you make valves and orifices in your dampening design, the more consitant the dampening will be, so thats the trend in suspension design- move larger volumes of fluid per action.

What's to know? How about all of the above...

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1/13/2018 4:15 AM

leighracer wrote:

To answer the OP's original question. The outer tubes of works and production forks probably both start out as extrusions. On works stuff the ID is probably precision honed and of course the OD is machined. Making a part like that from billet, although technically feasible, wouldn't make a lot of sense unless for some reason the factory part couldn't be made out of the raw extrusion that the factories already have.

Thanks for the response!

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