Motorcycle/bicycle fork lubrication... how does it work?

[Warprpl]

Hi all!

I'm trying to figure out why bicycle (mainly) and motorcycle fork manufacturers use very little amounts of oil in the non-damping leg of a convetional (not upsidedown) fork.

I figure the lower seal gets lubed easily with each rather deep stroke and the agitation of the oil with the bumps on the trail/road.

But what about the upper bushing? How does oil get there. Some mfgrs' use hydrodinamic lubrication and use grooves on their bushings, but others just don't.

Anyone has an insight on the matter.

 

[Fabrico]

What non-damping leg of a motorcycle fork? Upside down or conventional, both legs dampen.

On motorcycles, the oil level might not be as little as you think. It is usually just a few inches from the top of the upper tube in the fully collapsed condition, with the spring installed.

 

[Warprpl]

Thanks...

Ok. For a bicycle fork... most have a damping leg and one non-damping.

The non-damping one usually carries less than 50cc (50ml) of oil for a 28 to 36mm OD stanchion.

The damping leg is as a motorcycle one. The oil sits just shy of two inches from the top of the stanchion when fully compressed and the "air chamber" helps to prevent bottom out.

 

[Heckler]

I'm trying to figure out why bicycle (mainly) and motorcycle fork manufacturers use very little amounts of oil in the non-damping leg of a convetional (not upsidedown) fork.

Because they use high performance self lubrication bushings/bearings

http://www.ggbearings.com/literature.asp

Best Regards,

Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
XP Pro SP2.0
NVIDIA Quadro FX 1400
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Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.

 

[evelrod]

Gee, maybe we should have a bicycle engineering forum. If I had an interest in finding out 'why'...I might just ask the mfgr. of the thing, or a shop that works on them, or a really fast competitor that uses one of them. A post in the 'motorcycle engineering' forum might be a good starting point. The subject has little application in 'automotive engineering', IMO. Oh, bye the way, my son in laws mountain bike (high dollar) has both forks with seals and dampers!

Rod

 

[Heckler]

There is a bicycle engineering forum forum664. Some forks are "open bath" (Rock Shox) and some are cartridge (Fox).

Best Regards,

Heckler
Sr. Mechanical Engineer
SW2005 SP 5.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
XP Pro SP2.0
NVIDIA Quadro FX 1400
o
_`\(,_
(_)/ (_)

Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.