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FF: Forks Fork Travel

Bowsh

Active Forum User
VOC Member
#1
Hi All. Having only ever ridden bikes with modern front forks, I have no gauge as to whether the Girdraulics on My Rapide C are setup correctly. I’ve ridden a couple of circuits around the block and the front end is incredibly stiff. I’m no lightweight at 16 stone, if I sit on her the forks barely move. If I apply the front brake and try to pump the front end, again very little movement. Any help would be appreciated.
 

vibrac

Well Known and Active Forum User
VOC Member
#2
sounds like they need attention and we need some answers
Do you have any instruction books ?
Do the forks have any grease nipples?
What do you know about the forks?
The end caps (you can only see about 1/8" of shiny ring) at the fork blade link junctions do any turn with your fingers?
Are the ends of the spindles rusty -or do you think they are stainless steel?
Does the damper behind the headlight have a brass hexagon plug into the alloy?
 

davidd

Well Known and Active Forum User
VOC Member
#4
If I had a stiff Girdraulic I would drip some oil on the moving joints of the links. Maybe a few days in a row. Then, one day I would put the floor jack under the engine while it is on the rear stand and lift the front end off the ground just a bit. Look to see if the front mudguard or the mud guard stay is too close to the mag cowl for comfort. Assuming the clearance is fine, you will be able to move the bike up and down to check that it is attaining full droop (the fork droop is limited by the damper travel) and that it settles down well when you let the jack down. You should get maybe 3 inches of jack movement.

If the fork looks and feels like it is still resisting settling down, it is probably the springs that are too stiff. They were pretty much too stiff from the factory and yours may have settled a bit over the years.

The answer to the questions in Vibrac's post will lead to much more specific advice.

Ultimately, I like the fork to settle down a total of about 1/3 of its movement, which I measure on the damper, when seated on the bike. The damper moves about three inches, so an inch of travel on the damper is the minimum. I have run my racer at about 50% of travel, but the tracks are smoother than the streets. Anyway, the less loaded sag you give the fork the taller the bump you can absorb. That is the compromise you are trying to negotiate. This is pretty much the same as a modern tele fork. The travel is longer, but the percentages of travel and sag should be about the same.

I put a zip tie around the damper rod to measure the movement. At some point you will want to see if your front damper is functioning, and you can do the same by leaving the damper cover off after you have removed the damper to test its resistance.

It takes a while to make friends with the Girdraulics. Even with problems, the forks will probably work around town, but the lack of comfort may be the limiting factor. A photo of the links and damper would be helpful.

David
 

MartynG

Well Known and Active Forum User
VOC Member
#5
Hi All. Having only ever ridden bikes with modern front forks, I have no gauge as to whether the Girdraulics on My Rapide C are setup correctly. I’ve ridden a couple of circuits around the block and the front end is incredibly stiff. I’m no lightweight at 16 stone, if I sit on her the forks barely move. If I apply the front brake and try to pump the front end, again very little movement. Any help would be appreciated.
Applying the front brake LOCKS up the front suspension - its part of the 'anti-dive' design that is also a major contributor to tank slappers for the unwary
 

Bowsh

Active Forum User
VOC Member
#7
I’ve taken a few pics. I know very little about Vincent’s in general. I’ll take a few more shots later.
 

peter holmes

Well Known and Active Forum User
VOC Member
#8
To at get an idea of the general condition of your forks I would remove the wheel and detach the spring boxes, using various methods, I use the windlass method and detach from the top, detach or remove the, in your case, Armstrong damper, they are normally regarded as a Series D damper, and normally pretty soft so should not be the cause of any stiffness (unless faulty) now you should be able to lift to check the rise and fall of the fork blades, there should be no discernible stiffness, just the weight of the forks as you lift, now is also a good time to check your headset bearings for fore and aft movement, just hold the forks where the wheel spindle hole is and pull/push back and forth to detect any movement, a bit of help is good here, sometimes a finger placed across the joint line of the top bearing cups will detect movement the eye struggles to see.
 

greg brillus

Well Known and Active Forum User
VOC Member
#9
If it's like most Vincent's out there, the front end will be way over sprung. But you will need to remove the upper spring cases either side at the front to see what is lurking within, the inner springs can be removed and this will soften the ride quite a bit.
 

Hugo Myatt

Well Known and Active Forum User
VOC Member
#10
Somebody told me this years ago. A quick way to check fork movement is with the bike off the stands - stand left of bike, apply rear brake with right foot and pump up and down on handlebars.
 

peter holmes

Well Known and Active Forum User
VOC Member
#11
Hugo, sounds a bit precarious to me, but I totally get the logic as you are not preventing the front wheel from rotating, which it tends to do quite a lot with the Girdraulic fork, hence the John Emmanuel mod.
 

davidd

Well Known and Active Forum User
VOC Member
#12
Very good with the photos.

The damper looks like an Armstrong, which was stock on the Series D, but not the Series C. It looks like you have the short eyes at the bottom, which are usually not paired with this damper due to the Armstrong being a shorter damper than the stock Series C. The longer eyes offered on the Series D are usually paired with it.

You have a Series D breather on the Ex spring. It is OK if you are not having oiling problems.

The eccentrics look fine and they are in the solo riding position. I would drop some oil in the cracks.

It looks like you have Vincent Speet's brake on the front wheel. This is a very good after market brake.

It looks like it may be over sprung, as we guessed. It may be that you can get away with some softer or shorter springs. Ideally, with you sitting on the bike the lower fork link should be parallel to the pavement.

A shot of the whole front end would show its attitude.

David
 

Hugo Myatt

Well Known and Active Forum User
VOC Member
#13
Hugo, sounds a bit precarious to me, but I totally get the logic as you are not preventing the front wheel from rotating, which it tends to do quite a lot with the Girdraulic fork, hence the John Emmanuel mod.
Pete,
Never had a problem doing it until I reached 70 - years that is not MPH
 
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