Help Needed with Girdraulic Research.


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Could you help me with some information about your Girdraulics?

It would be extremely useful to me and I hope interesting to you.
It should help with understanding and improving these forks.

I will of course publish the results, so that anyone interested in Girdraulics can also use the info.

What I need is two measurements and some related information.

To take the measurements, proceed as follows:


With the bike on the stand, attach a cable tie as shown in picture 1 tight enough so that it stays in place but so that it can just still slide. Do both sides if you like for extra accuracy.

Take the bike off the stand and gently sit astride with feet lightly touching the ground.
Then carefully put the bike back on the stand and lift the front of the bike so that the forks are fully extended.

With the forks fully extended, measure distance “A”. (picture 2)

Leave the cable tie(s) in place until you have ridden the bike such that it feels as if the forks have bottomed out. If this doesn’t occur, just take the measurement when the bike has had enough usage to be representative of how you ride the bike.

Lift the front of the bike so that the forks are fully extended.

With the forks fully extended, measure distance “B”. (picture 3)

Post here or PM me as much as possible of the following information:-

  1. Measurement “A”
  2. Measurement “B”
  3. What damper you have fitted?
  4. Short or long eyebolts?
  5. What springs and inner springs are fitted?
  6. Length of any spring spacers/packers?
  7. Original or replacement spring cases?
  8. Rough idea of how heavily the bike was loaded? If possible, approximate weight of rider and passenger, if carried.
  9. Single or twin?
  10. Any comments about how the bike was ridden or how hard the forks bottomed out?

Measurement “A” gives the solo static ride height.

Measurement “B” gives the maximum suspension compression that occurred.

(B-A) gives the actual bump travel.

(Damper stroke – A) gives the available bump travel.

The most important and interesting information is measurement “B”.
If “B” is less than the available damper travel, the forks are not bottoming out.

(I should add that there is an outside possibility that if you have short eyebolts and very very thick packers, it may just be possible for the springs to bottom out before the damper.)

All info greatly appreciated.


greg brillus

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Hi there Rob, Well just as a starter, and playing around in the shed I was able to achieve the following....this on a C Rapide with original D type Armstrong shockers front and rear, and with a set of the blue 110 lb's springs as per David Dunfey's design and with no packers inside the front spring box's. So from rest on the stand to me siting on the bike, the spring box's compressed 10 mm, then whilst bouncing the front end up and down as much as normally would be expected over vigorous bumps, i was able to see 25 mm of movement....this from the starting point at rest. I could not and have not at any stage of riding felt the front end bottom out either via the springs or the front shock inner bump stop......remembering that i am only around 70 kg's. And that is the reason why i needed to change something in the front to stop it being so stiff ( this with it's original duel front springs within the box's). Also, so far, as per the mods i am carrying out with the bearings in the links is pretty straight forward, as i was able to find small torrington type needle rollers for the front spindles with the same length as standard and the same 9/16 ID to suit the spindles, but the OD is larger due to the rollers ( to be expected i guess) and the outer housing being about 1/16 th larger in size than the bore in the link needs to be enlarged a little, this being reversable if only larger bushes made to suit. The large eye end where the eccentric normally is....I found a sealed bearing with nearly the same width as the eye, an OD slightly larger than standard, so only needing enlarging slightly, but the ID is 15 mm requiring a larger spindle to be made.....this is only a minor set back as all of this is to go on a twin racer. The upper link mods could be as per the lower links front spindle. As for side thrusts, I will do as per the thrust washers on Bramptons between the links and the FF 10 thrust cups. The other major mod for me is to do away with the shock and spring box's, and fit a modern type coilover adjustable unit, and beef up the upper attachment point on the front of the FF 1 where the original shocker upper mount is. I am going to lower the bottom link by making up a bolt on alloy block to attach bellow the standard stem and drill through the 15 mm hole down and aft to suit the new larger spindle......I am hopefull i can make all of this work successfully, but am still a way off form anything being finished just yet.........Cheers for now........Greg.

Bill Thomas

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Hello Rob, A=32mm B= 64mm Spax Damper Long eyebolts, Springs D/D T/T "Blue" Packing=5 2p coins each side, Original Spring Cases, 110kg Fully Kitted with 20lb tank bag, C Twin, Forks don't Bottom or Top Good Luck, Bill.