FF: Forks Fork Travel

[Bowsh]

After oiling the joints, new Avo damper with short eyebolts and new std C springs the difference amazing. The feedback from the front has increased dramatically, the ride is smoother and I’m a happy bunny. I’m still considering the modified head, which will be a job for the winter.

Thanks to all for your help. Paul

 

[kettlrj]

it is imperative that the forks move freely. John Sherratt from our section was thrown of by a nasty tank slapper due to forks that were not moving at all. It was his first Vincent and he was not used to the idea of the front end moving up and down and so thought nothing of it. Another friend had the same problem many years ago in IoM, so it is a well known fact that stiff forks will lead to trouble.

 

[vibrac]

With the new steering head fitted and initially the fork is not moving as much as I expected, we have reduced the springs to 30lbs and I think the culprit is the 'stiffer' AVO damper that seems too stiff even at lowest setting (adjuster fully anti clock) without the damper the forks fall freely I will continue to monitor and may resort to trying other dampers once I feel the inital run in period is over.
I am 12 stone and the Comet has a coil over rear end it has been suggested that the selected damper may have been arrived at by a heavier rider Hadronuk tells me that reducing the dampers effect past the low setting is a factory job
To quantify the front damper to obtain a start and maintain a slow continuous movement I need to apply a 28lb pull one way and a 14lb pull the other
I cannot praise time traveller for his help in getting this project underway please help him by feedback of your progress

 

[davidd]

it is imperative that the forks move freely.

It is imperative that the forks mover freely, but even Paul's front end can revert momentarily back to the stiff condition that was causing so many handling issues if the fork tends to extend under braking. The two easiest ways to avoid this is to: 1. make sure the when you are riding the bike that the lower link is parallel to the road, or 2. change to a modified steering stem.

The new stem is the "idiot proof" way to solve the problem, but, as Paul notes, if you can get the fork in shape and keep it from favoring full extension when braking, the bike will work fine. A Vincent with a stiff fork will definitely seize when braking because its sorry state of stiffness is already promoting seizure of the fork. Add some braking and you have the front wheel bouncing off ripples in the road.

David

 

[vibrac]

Not much chance of the front brake doing any damage at the moment, I have just fitted new linings to a cast ally set of plates and they gave me atrocious performance, so bad that during my first test ride I rode in third gear with brakes fully applied for 2 or 3 hundred yards! hopefully that will have 'marked' them up now off they come and into the lathe I find this more effective than doing it before I have fitted them the first time.

 

[timetraveller]

AVO will increase or decrease the damper settings for a cost of about £30, maybe plus carriage. However, by the autumn Bowsh might have decided to go for the John Emanuel steering head and if so, on his twin he will need the stiffer damper. You both might be able to do a swap at zero cost.

 

[vibrac]

I will bear that in mind
I estimate my top link is pointing downwards about 8 degrees I have the longer eye bolts as specified
To illustrate the damper in use if I take it off the DH stand there is 1/8" between damper shroud and top link if I climb on gently it remains at that distance. if I push down hard at the front the gap increases to 1/4" and then if I get off it remains at 1/4 ", only when I put it back on the stand will it revert to 1/8" (remember sans damper and springs the gap is a piece of A4 thick) I reiterate have checked the free movements of the forks and oiled them.

 

[oexing]

There´s a fraction too much friction - I´d say. You don´t have any friction discs on your fork anywhere? So there must be some place that is a poor (tight) fit or poor lubrication. I would not go for needle bearings in the linkage - water ingress waiting to happen - but fit minimal friction teflon/graphite based maintenance free bushes. Or the types from IGUS that you can line-ream after pressing in. With the girdraulic I see an additional friction source in the telescopic spring boxes, well greased or not, a bit of half-bred design, at that time little choice of course.
I have to deal with Bramptons otherwise I´d be looking into fitting gas struts there, could be shrouded and no stiction with them. The monoshock to go with them could be fitted with a lighter spring then. Just thinking . . . .
Vic
Link IGUS : IGUS bushes

Link gas strut: Gas strut

 

[timetraveller]

The horizontality of the lower link is when the bike is fully loaded, with either you or you and your wife. If it is slightly down at the front, say five to ten mm, then that is not a problem but more than that means that you could be into the original problem of the bike trying to ride up over the forks when braking. Vibracs experience typifies why we need more feedback which can be exchanged between us all. For example, why has he got clearance between the damper shroud and the rear of the top link? Also why do some people have to worry about clearance between the mudguard and the front of the engine while with others there is absolutely no problem? I do not believe that any of this is due previous damage. When experimenting with this I spent a lot of time plotting out the front wheel spindle path and showed that path in MPH or/and on this forum. I am completely confident that I know the path on my bike but John Emmanuel demonstrated to me on his bike that the path was different with his, supposedly identical set up. He was sufficiently concerned that he got me to send one of the newly manufactured stems to him so that he could compare the original with the new. In one direction there was zero difference, while in the other ten thou. Feedback and the exchange of ideas is what is needed.

 

[Bowsh]

it is imperative that the forks move freely. John Sherratt from our section was thrown of by a nasty tank slapper due to forks that were not moving at all. It was his first Vincent and he was not used to the idea of the front end moving up and down and so thought nothing of it. Another friend had the same problem many years ago in IoM, so it is a well known fact that stiff forks will lead to trouble.

Although I didn’t have a tank slapper, there was very little front end movement. My suspicions were confirmed when the Ammeter fell apart on a mid sized pothole. You could argue that with the state of our roads, some mid sized potholes would swallow a bike and rider. I’m going to try removing the inner springs with 1 inch of packing next, to see what differences I can feel.