Re-valving shocks

[ben]

Does anyone out there have a Fox Vanilla rebuild manual (does such a thing exist?) or a procedure they've developed themselves for doing this?

Ben

University of Birmingham
www.ubracing.co.uk (http://www.ubracing.co.uk)

[ben]

Does anyone out there have a Fox Vanilla rebuild manual (does such a thing exist?) or a procedure they've developed themselves for doing this?

Ben

University of Birmingham
www.ubracing.co.uk (http://www.ubracing.co.uk)

[jack]

im pretty sure that fox requires you to send the shock to the factory for a rebuild--your not "supposed" to do it yourself. other than that, i would go ahead and yank 'em apart if i was you. just make sure you can get the pressurized nitrogen back in when your done...

jack @ WWU
http://www.etec.wwu.edu/

[Brent Howard]

What about risse shocks? We want to re-valve ours, but are not too sure where to do it or how to spec the damping rates. If anyone could point us in the right direction it would be appreciated.

Brent

www.ucalgary.ca/fsae (http://www.ucalgary.ca/fsae)

[ben]

I might just buy a spare and open it up without hhaving to worry about knackering the one's bought from our budget http://fsae.com/groupee_common/emoticons/icon_smile.gif

As for damping setup, Mr Rouelle suggested that a linear damper with equal coefficients in bump and rebound would be a good start. This is with the coefficient set at 70% critical based on the sprung mass acting on the damper.

To get linear I assume you would need very little low speed bleed?

Ben

University of Birmingham
www.ubracing.co.uk (http://www.ubracing.co.uk)

[Schumi_Jr]

Brent- you should read "The Shock Absorber Handbook" by Dixon. It's published by SAE so you will probably find it on their website. It covers a bit of everything from ride and handling to valve design. By the way, I'm in Calgary right now- are you guys in the shop at all over the holidays? If you don't mind I'd like to check out your shop and see how the new car is going... let me know off the forum.


Ben- Pressure drop with turbulant flow is a quadratic function of velocity, so your orifice area must increase with piston velocity- that is where your shim-stack comes in. From talking to engineers at Dynamic Suspensions, damper valving is a little bit of theory and a hell of a lot of testing...

Aaron Johnston
University of Waterloo FSAE

www.eng.uwaterloo.ca/~fsae (http://www.eng.uwaterloo.ca/~fsae)

[Brent Howard]

Hey Schumi,

Do you have that book in calgary too? I'm not actually a suspension guy, but I will pass the title onto him. Also, we are in the shop, If you are interested you can give me a call and I could show you around this weekend, or any weeknight. I'll e-mail you my phone numbers.


/Edit Or I won't because your e-mail isn't listed. E-mail me at howard_brent@hotmail.com and I will send you my numbers.

Brent

www.ucalgary.ca/fsae (http://www.ucalgary.ca/fsae)

[ben]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Schumi_Jr:
Ben- Pressure drop with turbulant flow is a quadratic function of velocity, so your orifice area must increase with piston velocity- that is where your shim-stack comes in. From talking to engineers at Dynamic Suspensions, damper valving is a little bit of theory and a hell of a lot of testing...

Aaron Johnston
University of Waterloo FSAE

http://www.eng.uwaterloo.ca/~fsae<HR></BLOCKQUOTE>

That's what I was alluding to, i.e. if the bleed is minimal the shim stack blows off earlier and you then have the linear characteristics desired.

I would also recommend Dixon's book. I'm currently taking one of our third years through it so we can start some work on custom dampers for 2005 (when I shall be long gone I hasten to add).

Ben

University of Birmingham
www.ubracing.co.uk (http://www.ubracing.co.uk)

[Brent Howard]

Aaron, check your private messages. I send you my phone numbers.

Brent

www.ucalgary.ca/fsae (http://www.ucalgary.ca/fsae)

[leclercjs]

Hi ben,

just to let you know, Fox doesn't want us to do the maintenance on the shocks. You have to send them to your country supplier or any other certified Fox reseller to have it done. Once you've opened it, they are the only to have all the stuff and equipement to rebuild it. This is the case for us since we have 2003 Fox Vanilla RC. Also, you have to place the exact amount of oil without having air trap inside!!

Here are the owner's manual for Fox shocks:

http://www.foxracingshox.com/website/OwnersManuals.asp?Market=MBike


Maybe it will help you

Jean Sébastien Leclerc
Dir. Formule SAE Poly 2004
http://www.fsae.polymtl.ca

[clausen]

Hi,

I would say a Fox would be very similar to my late model Rock shox pro deluxe (external reservior). I rebuilt it myself and we refilled and gassed it at a race team that uses Ohlins dampers. The guy there had no trouble with it because it all came apart in exactly the same manner as his proper race shock and used the needle gassing system the same as his shocks.

Hope this helps,

Regards

Paul Clausen
Uni of Adelaide

[FPV_GTp]

Hi , this might be useful , "Finally software to tune a shock absorber shim stack " http://www.shimrestacker.com/


cheers

[Jersey Tom]

I'm sure Ben will be pleased. If only you had been more prompt!