• Welcome to the website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Hon. Editor and Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this website.

    If you have previously registered to use this forum, you should log in now. CLICK HERE.

    If you have never registered to use this website before, please CLICK HERE.

FF: Forks Girdraulic Springs


druridge

Well Known and Active Website User
VOC Member
I removed the spring boxes on my Series C Rapide to a) get the spring case bottoms FF16AS rechromed; and b) work out what is going on with the springs.
Bike is a Touring Rapide, with 19" front and 18" rear wheels, its got a twin disc set-up on the front. I ride solo at a reasonable pace rather than insane, and am just under 12 stone before I put the bike kit on.
The bikes handles great, very precise and predictable etc, until I hit a bump in the road when I get a bad shock through the bars.
I presumed I had 'hard' springs.
Once apart I found the 2 outer FF13 springs to be slightly different lengths (15.25" & 15.5"). No inner springs at all, but the outer springs were packed out with a spacer of about 1.25" sat in the bottom of each spring box. the Girdraulics move freely with the springs off. No play detected. Grease in all the right places, I can feel and hear the oil within the damper moving. The damper appears 'standard' but seems to work. In the past, the bike had a sidecar fitted and rode distances over bad roads.
I now assume I have two 'tired' C springs. These appear to have been 'firmed up' with a couple of spacers, this having the effect of pre-loading the springs. Odd why there are no inner springs; or ( unlikely) have I got 2 very tired D springs?
Anyway; the Spares Co. stock inner & outer springs for small money, so one option is just to buy the 4 and fit.
My question would be if this is the best option? KTB mentions the option of discarding the inner springs; would fitting D springs be an improvement?
I've read a bit and there doesnt seem to be a concensus ?
Any thoughts?
Many thanks
 
Last edited:

timetraveller

Well Known and Active Website User
VOC Member
Oh Dear! you have opened a can of worms. A complete solution to your problem is to fit the John Emmanuel steering head, complete with my springs and an AVO damper. This is written about in great length in the thread 'Modified Steering head'. It is a long and convoluted read and if you are interested I can send a pdf to your email address which is a much shorter read and gives you the all the details and fitting instructions.

The mod you have found in your forks is typical of what people were doing several decades ago when it was realised that the longer, softer 'D' springs gave a better ride and people chose the cheap way of updating by taking out the inners and packing the outers. What it did not do was to remove an inherent design fault in the geometry of the girdraulics.

If you are interested you can either put your email address on here or send me a private message (PM) and I will communicate in private. The front end can be made much better than the one you have now.
 

davidd

Well Known and Active Website User
VOC Member
Druridge,

The stock spring is 15.5" long and produces 68 lbs/in. The stock inner spring produces another 9.5 lbs/in. This made the total stock twin spring rate 77.5 lbs/in, while the stock single rate was 68 lbs/in.

The Series D sported a 16" spring that produced 63 lbs/in. Hence it was the lowest rate of the stock springs.

Here is what I would propose for the consensus:

With a stock Girdraulic and brake it is best to run springs that are short enough to be adjusted so that you can make your lower link parallel to the pavement as you sit on the bike.

With a stock Girdraulic and an improved front brake a modified FF2 should be installed. Once done, almost any spring that is comfortable should be fine, including stock springs.


I think that the "Oh Dear!" part of the conversation is that it is difficult to have consensus on properly setting up a front end with a known defect that has not been minimized or remedied in some manner.

I am a little surprised that you have noticed the how strongly the chassis moves upward when your disc brakes are applied, but you may be accustomed to it.

David
 

MartynG

Well Known and Active Website User
VOC Member
I had the understanding that the inner springs were only used if there was a sidecar fitted
 

macvette

Well Known and Active Website User
VOC Member
When I got my D about 15 yrs ago, I was new to Vincents. It ran but was in need of a lot of TLC. I rode it a few hundred miles to see what was needed and did a lot of reading. Very early in its life, it had a side car ( listed in the original log book). I found that it had C springs fitted i.e inners and outers. These were replaced with the series D single springs. They did improve the ride. I ride solo. There were many issues with the bike so I completely rebuilt it over a period of 3 or so years and used the D springs.
The bike was quite compliant for a bike of that era and I had no handling issues. I weigh about the same as you but have the standard drum brakes. I'm not a hooligan but ride quite vigourously.
Last year, I put the JE MOD on the bike with ball bearings in the lower link and fitted a hydraulic steering damper. The front end is more compliant but most noticebly, it now compresses when the front brakes are used, it didnt before.
I would put series D springs in as a first step and see how it reacts, read up on the JE mod, and do that if you feel its needed after you have tried the D springs.
 

timetraveller

Well Known and Active Website User
VOC Member
The inner springs were not fitted just for sidecar work but were fitted to all twins. It was rotating the clever eccentrics which altered/compressed the springs for increased weight resistance when a sidecar was fitted as well as altering the trail.
 

Bill Thomas

Well Known and Active Website User
VOC Member
I would first fit an Hydraulic Steering Damper, Then play with what ever you want, Different people want different things.
I would agree with David about, Lower Link Parallel to the pavement at rest, As we are seeing from
Older Photos, Don't know how they seem to have got longer Springs over the years !. But if they are standard forks, You don't want them to go too high or too low, Just my thoughts.
I am not a Hooligan but I like to push on sometimes !.
Cheers Bill.
 

macvette

Well Known and Active Website User
VOC Member
The inner springs were not fitted just for sidecar work but were fitted to all twins. It was rotating the clever eccentrics which altered/compressed the springs for increased weight resistance when a sidecar was fitted as well as altering the trail.
Hi Norman,
I was only trying to give my experience in comparing tired C springs with new series D springs and I understand the function of eccentics. In KTB, however, you will find a reccomendation to use inner springs to Ds when fitted with a sidecar.
 

druridge

Well Known and Active Website User
VOC Member
Many thanks all for your replies - yes I now do feel like I've just kicked over the can of worms!
However.....
Davidd : I've looked at a couple of photos of the bike on the(central) sidestand, and all show the front lower link FF3 tilted down at the leading edge. I now see I should have checked this more carefully before it came to bits (leant against a wall under its own weight, me sat on it etc).
Timetraveller : I clearly need to read and absorb the 'modified steering head' thread, I have seen some of the posts already but hadnt linked my problem to that.
I honestly haven't noticed any chassis lift when the brakes are applied (but would have said it doesnt squat either), it's fitted with two Grimeca calipers and they work well.
I've never had any head shake or nervousness so have never thought of a steering damper.
Macvette :Once I've checked the lower link for horizontal, then I agree any mods should best be done one at a time and checked out on the road. I'm thinking a new pair of D springs might be in order as Step1
Much appreciated!
 

timetraveller

Well Known and Active Website User
VOC Member
I think that when you have fitted the 'D' springs you will find that the front end is higher. Then when you brake hard I think you will find the effect that David mentioned, that is the bike will try to rise up over the forks. After that you might want to consider what to do next. Good luck with it.
 

everiman

Active Website User
VOC Member
My easy way of finding spring rates for anonymous springs, find a round bar or tube that will fit inside the spring, about 6" longer than the spring. Clamp tube in vice, put spring over the tube, measure spring length

Get some barbell weights, if you don't have any, your local thrift store will. Slip at least 25 kg, or 50 pounds whatever will fit, onto the tube so the springs are compressed, measure the length, you might need a large washer for a skinny spring. Lets say that 25 kg compresses the springs 3/8 inch, convert kg to pounds, 25 X 2.2 = 55 pounds (55/3) X 8 = 147 pounds per inch. Not extremely accurate, but accurate enough.
 

MartynG

Well Known and Active Website User
VOC Member
I think that when you have fitted the 'D' springs you will find that the front end is higher. Then when you brake hard I think you will find the effect that David mentioned, that is the bike will try to rise up over the forks. After that you might want to consider what to do next. Good luck with it.
what to do next? First Panic, second release brake, next panic, repeat sequence
 

Bill Thomas

Well Known and Active Website User
VOC Member
Anybody know Paul Norman, He has his own web site, He has just rebuilt a Comet, And did an 1/2 hour road test Video, His forks worked very well for a Comet, I thought, I think it was Standard front end, He did not say.
Warning, It made me ILL, I suffer from Motion sickness. Cheers Bill.
 

Old Bill

Well Known and Active Website User
VOC Member
Big Sid used to set up girdraulics using two outer C springs and one inner. Rider sits on bike and observes lower link; aim as david says is to get the link parallel with the pavement. To adjust add spacers such as old coins ( not ideal but once the desired ride height is achieved a spacer of a suitable material can be made) to the one spring case, should produce a good compliant front suspension. Another tip passed on re brakes; when applying brakes apply rear first, then front firmly, front suspension will compress and front brake becomes very effective; ie ploughs the road up, as the man said, try it!! Please note, this is all with standard set up except for the spring spacer. No doubt others will have different views, each to there own.
 

vibrac

Well Known and Active Website User
VOC Member
'Ploughing up the road' a good point often overlooked. When PCV got his magic 30ft from 30mph stopping distance it was on a rough road surface. I dont think we shall see that sort of large granite chipping very much in the future,. smoother and smoother asphalt seems to be the order of the day. Rough surfaces upset the precious tin box pilots and spoil the music and in car entertainment.
 

Bill Thomas

Well Known and Active Website User
VOC Member
I find with a Twin, As long as the springs are not too strong, Just closing the throttle, A nats before braking sorts the forks out, On the road and on the Track, For me, Not so much a Comet !. Cheers Bill.
 

Old Bill

Well Known and Active Website User
VOC Member
Agreed Bill, closing the throttle has a very similar effect especially from high revs, the rear brake trick is really for those oh poo moments ! Helps on a comet if hail mary fails !
 

Top