FF: Forks Re-made (by Maughans) original Vin front damper

[fogrider]

The longer eye bolts make better use of the available travel for the shocker and the springbox cases, if you use the short ones, the issue of the guard/wheel hitting something on full bump will be worse. So long as it clears everything with the wheel in the straight ahead position you should be ok. I too have had the set up where it will clip the front exhaust pipe, but the chances of having the bike with that much steering lock whilst hitting a savage bump is extremely unlikely. If you think of how much you actually turn the bars when riding, it is very little.

My C twin has a re-made (by Maughans) original Vin front damper and had the short eye bolts. After the Bawtry meet I was motivated to check the lower link and damper travel. With the link level, there was almost no travel left on the damper ( fully extended.) So, put in shorter springs to make the rear of the lower link lower than the front, still well extended. Fitted long eye bolts and it now sits in the middle of the damper travel. What it will ride like, I've yet to discover, but reading this forum it seems the lower link should be pretty well level.
The occasional "clonk" I was hearing was clearly the damper topping out. Looking at other bikes they all seemed to have well extended dampers, as if lower link down at the back should be right.
All very confusing !
Regards, Terry
(I AM a member, the system says I'm not, more confusion).

 

[greg brillus]

What front springs are you using..........?

 

[Bill Thomas]

So

My C twin has a re-made (by Maughans) original Vin front damper and had the short eye bolts. After the Bawtry meet I was motivated to check the lower link and damper travel. With the link level, there was almost no travel left on the damper ( fully extended.) So, put in shorter springs to make the rear of the lower link lower than the front, still well extended. Fitted long eye bolts and it now sits in the middle of the damper travel. What it will ride like, I've yet to discover, but reading this forum it seems the lower link should be pretty well level.
The occasional "clonk" I was hearing was clearly the damper topping out. Looking at other bikes they all seemed to have well extended dampers, as if lower link down at the back should be right.
All very confusing !
Regards, Terry
(I AM a member, the system says I'm not, more confusion).

Sounds like there is something wrong with that Damper, Forgetting the springs, Just think of the link movment with the damper, The damper controls how much travel there is, You have changed it with the long eyebolts. Cheers Bill.

 

[greg brillus]

I should ask the obvious........Is the front end standard, or does it have the modified stem kit installed.......?........ Just so I know we're on the same page.

 

[timetraveller]

It is not just the angle of the lower link which is important. The whole point of making the new steering heads is to change the pivot position of the lower link so that it moves, more or less, parallel with the top link. It is that which changes the path of the front wheel spindle as the wheel deflects over bumps. Shorter, or worn out springs will move the movement path of the front wheel to the more or less vertical part of the original wheel movement, but it will not do the job of the modification discussed here. If one has the standard set up and worn out springs then you can certainly get the front of the lower link to be higher than the rear. Many years ago when impoverished many of us had bikes like that and eventually packed up the springs some way or bought new springs. That is absolutely not what this is about. If you are going to test ride the bike like that be careful.

 

[davidd]

Fogrider,

If you have a standard steering stem, the fork and braking action works much better on compression than extension. Thus, it is a good thing to stay away from having the Girdraulics fully extended while riding and better to have them nearer full compression, where they act better. Looking at the lower link is a useful way to see if your fork is near compression or nearer extension.

If you have a modified steering stem, none of the above really matters. This is because the geometry is changed. You could ride around near full extension or full compression, and when you grabbed the brake the front end would still go up and down, as much as it is allowed. I would recommend that you set up the ride height of the bike in a more conventional manner by checking the ride height, sag and preload, but the fork will work safely with the brakes applied no matter what you do.

On the contrary, with the stock steering stem the fork will only work safely under braking if you stay away from full extension, where it is inclined to go by the bad geometry. Hence, the use of short springs and no preload with the stock stem to make it harder for the bad geometry to force the fork to full extension.

The short eyebolts should work properly with a damper that has a 3 to 3.25" stroke, which is roughly what the stock Series C damper had. The long eyebolts were used on the Series D dampers which were supplied by Armstrong and the Armstrongs had a shorter stroke. Thus, the extra length of the eyebolt tended to compensate for the lack of shock stroke. As Bill said, the shock stroke determines the total movement of the fork, up and down and the Factory wanted it to be similar to the Series C in terms of extended length.

With the modified steering stem you can run any spring with any preload you want and you will not have any problem with applying the brakes and having the fork go up and down during that braking. Of course, there are limits usually dictated by comfort and handling that will dictate how wild you want to get with springing and preload.

With the stock stem you need to be more careful about springing and preload, because too long a spring or too much preload will cause the fork to snap to full extension and stay there under braking.

It would be good to know how much damper travel you have.

David

 

[fogrider]

Well, what a response! The damper is an original Vincent re- made by Maughans ( upgraded internals ). Travel 2,6" plus 3/16" bump, so around 2.3/4"total. I took it out to check, seems it has a bit less travel than the originals. Springs are 15" outers with a 1.1/4" spacer. No inners. All else bog standard. I made a check on the trail, stood at the loaded ride height it 's pretty well 3.1/2".
That doesn't seem too unsafe ? At least the damper is in a working range now, I note that Thorntons recommend their damper is set to sag in the middle which is how mine is now.
Thanks all, I will have a run tomorrow, hopefully, and will report.
Regards , Terry.

 

[Bill Thomas]

Well, what a response! The damper is an original Vincent re- made by Maughans ( upgraded internals ). Travel 2,6" plus 3/16" bump, so around 2.3/4"total. I took it out to check, seems it has a bit less travel than the originals. Springs are 15" outers with a 1.1/4" spacer. No inners. All else bog standard. I made a check on the trail, stood at the loaded ride height it 's pretty well 3.1/2".
That doesn't seem too unsafe ? At least the damper is in a working range now, I note that Thorntons recommend their damper is set to sag in the middle which is how mine is now.
Thanks all, I will have a run tomorrow, hopefully, and will report.
Regards , Terry.

A few things to check, With the weight off the front wheel make sure the top link is not touching the damper shroud, I have just built a set of forks, And had to put short eye bolts in with standard Damper, And also the Mudguard is not touching the Mag' cowl.
If you check the trail with the forks Blades up high, Standard Forks, You won't sleep tonight !!,
Know thy Beast says always use inner springs, To help stop the blades coming up too high.
And I say, Fit an Hydraulic steering damper. Good Luck, Bill.

 

[fogrider]

Thanks Bill, just checked and front off the ground ,the damper is topped out but the shroud is 1/32" short of touching the top link. At the same time, the back of the mudguard is 3/8" short of touching anything. So far so good.
I had been running it with the outer springs only (with 1.1/4" packers) and the spring rate seemed OK. I guess there's a lot of stiction in the spring boxes and eccentric bushes.
Have'nt had chance to ride it yet, we'll see !
Regards, Terry.

 

[Bill Thomas]

Thanks Bill, just checked and front off the ground ,the damper is topped out but the shroud is 1/32" short of touching the top link. At the same time, the back of the mudguard is 3/8" short of touching anything. So far so good.
I had been running it with the outer springs only (with 1.1/4" packers) and the spring rate seemed OK. I guess there's a lot of stiction in the spring boxes and eccentric bushes.
Have'nt had chance to ride it yet, we'll see !
Regards, Terry.

As you say, They have rebuilt the damper slightly different.
I use a standard headstocks.
I run a Twin and a Comet on Short single springs, Specials, Done by Timetraveller/Davidd, Which are for having the fork blades higher than standard, I also have them packed out a bit, Because I am aware of not letting the blades come up too high, They work well on my Twin, Not so much on the Comet.
My new Comet will run cut down standard springs, With cut down inners, But it's not on the road for a while, It feels better in the garage, But that might not mean much !.
A hydraulic steering damper, Is such an improvement, Well worth doing, About £50 for the damper plus 2 homemade brackets. Cheers Bill.