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Girdraulic Spindle Bushes

Hugo Myatt

Well Known and Active Forum Website User
VOC Member
I notice the VOC Spares Co. still lists synthetic (Nylon?) bushes for the fork spindles and eccentrics. Does anyone have any experience of these? Would they need reaming or fettling in some way? Or is the whole idea a No-No?
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Trevor Southwell fits them. If you were to get a set of, say, Manx Norton forks done by Maxton Engineering (suspension gurus to the stars, and to ordinary mortals too) then you'd find the slider bearings were PTFE, to reduce initial stiction. It works. Given the potential of Girdraulics for stiction, I would have thought them an improvement on bronze - which is what my Manx forks had pre-Maxton. When I get round to starting "the great Comet rebuild", the forks will go to Trevor to be so fitted.
 

Ken Tidswell

Well Known and Active Forum Website User
VOC Member
I fitted some over 20 years ago with gease nipples to keep the water out. The spindles polish nicely, You need grease nipples for the bronze bushes to keep out the moisture, stainless spindles are the only material to use. The old sintered bronze /steel arrangement is the worst .the water displaces the oil . corrosion sets in . the iron oxide produced works as a lapping compond, more wear more rust . a nice negative feedback system.
 

vince998

Well Known and Active Forum Website User
VOC Member
I notice the VOC Spares Co. still lists synthetic (Nylon?) bushes for the fork spindles and eccentrics. Does anyone have any experience of these? Would they need reaming or fettling in some way? Or is the whole idea a No-No?

After an incident involving a ditch (50 MPH, Sky-groung-sky-ground-ambulance!) i found that the nylon bushes i´d fitted had all compacted (well, the impact was hard enough to shear the eyebolts).
Moral:
If you misjudge the corner, and pick your run-off, check whats between you and the target area first ;-)

After stripping and checking alignment of everything, i fitted new standard sinter bronze bushes (just in case)
 

fgth130

Active Forum Website User
VOC Member
I'm pretty sure that the Spares Co. bushes are made from an 'engineered' nylon impregnated with Molybdenum Disulphide, the 'moly' is to minimise stick-slip in an oscillating bearing. If you're going to keep them on the shelf for some time before fitting, it's best to stop the nylon absorbing moisture and thus swelling, just dip them in grease.

Frank
 

rickgardner

New Forum Website User
Non-VOC Member
I am yet to run my bike with the plastic bushes. I am 95% certain the bushes are made from Acetal and not Nylon or PTFE. I have had experience of PTFE not working well on stainless shafts. Nylon is not a good material because it absorbs water and expands - so making the bush sieze.
Acetal is a great bearing material on Stainless, becausewhen it get wet the water acts as a lubriucant! -I found this many uyears ago when testing a bearing combination in a high humidity environmental chamber.

I was initially cautious about using the plasitc bushes, but they have more than enough compressive strength, so I am more than happy to fit them. I had a very poor experience with phosphor bronxze bushes on stainless spindles.
 

Tom Gaynor

Well Known and Active Forum Website User
VOC Member
Doubtless Clever Trevor knows, since my forks are with him to have plastic bushes fitted. The reason I'm doing it in plastic is that when I sent my Manx teleforks to Maxton for rework, they replaced the bronze slider bushes with plastic, and explained why: because the enemy of fork compliance is stiction, and plastic bushes have much less of that undesirable quality than bronze. See also Laney Thornton's remarks in February MPH about the transformation he wrought by cleaning up his front spring boxes. And note that the man who pointed him in that direction was John Renwick. Who knows a thing or three.

I am yet to run my bike with the plastic bushes. I am 95% certain the bushes are made from Acetal and not Nylon or PTFE. I have had experience of PTFE not working well on stainless shafts. Nylon is not a good material because it absorbs water and expands - so making the bush sieze.
Acetal is a great bearing material on Stainless, becausewhen it get wet the water acts as a lubriucant! -I found this many uyears ago when testing a bearing combination in a high humidity environmental chamber.

I was initially cautious about using the plasitc bushes, but they have more than enough compressive strength, so I am more than happy to fit them. I had a very poor experience with phosphor bronxze bushes on stainless spindles.
 
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