F: Frame Best Front Damper for Series 'D'

[kerry]

Can anyone tell me please the best front damper for a series D, also are they the same as a C, thanks, Kerry.

 

[Marcus Bowden]

I'd fit a Koni on lowest setting, then I have new ones ib stock.
bananaman.

 

[Peter Holmes]

The Series D was fitted with Armstrong dampers front and rear, but a very different unit for both, the front damper was very well suited to the Girdraulic fork, but had to be used with longer bottom eyebolts than the Series C damper, although sometimes the Armstrong damper shows up in for sale adverts, they will be 65 years old, and to the best of my knowledge are unrepairable or serviceable.

As Marcus says a Koni will do the job, they did manufacture a damper specifically for the front forks which was a little softer than the rear unit, documented in KTB, but even that is normally considered a bit too hard in use to get the best Girdraulic fork action.

Works Performance was good, but no longer available, Spax had a try, but one or two snapped the damper rod in use and consequently was withdrawn.

So you are left with AVO, which is very good, readily available, and, pretty much made to any specification that you require as far as firmness is concerned, and has adjustable damping in situ, which is convenient, it is the damper that is supplied with the Emmanuel/Walker fork mod, but is also available for standard set up Girdraulic forks.

Or newly manufactured Series C damper, or an old one with newly manufactured updated internals available from VOC Spares or Maughan and Sons.

I have been using an AVO for the 6-7 years without any complaint or issues.

 

[kerry]

Are they the same on a D, I have fitted an Avo on the rear but fitted a Avo front one on a D last year but had problems.

The Series D was fitted with Armstrong dampers front and rear, but a very different unit for both, the front damper was very well suited to the Girdraulic fork, but had to be used with longer bottom eyebolts than the Series C damper, although sometimes the Armstrong damper shows up in for sale adverts, they will be 65 years old, and to the best of my knowledge are unrepairable or serviceable.

As Marcus says a Koni will do the job, they did manufacture a damper specifically for the front forks which was a little softer than the rear unit, documented in KTB, but even that is normally considered a bit too hard in use to get the best Girdraulic fork action.

Works Performance was good, but no longer available, Spax had a try, but one or two snapped the damper rod in use and consequently was withdrawn.

So you are left with AVO, which is very good, readily available, and, pretty much made to any specification that you require as far as firmness is concerned, and has adjustable damping in situ, which is convenient, it is the damper that is supplied with the Emmanuel/Walker fork mod, but is also available for standard set up Girdraulic forks.

Or newly manufactured Series C damper, or an old one with newly manufactured updated internals available from VOC Spares or Maughan and Sons.

I have been using an AVO for the 6-7 years without any complaint or issues.

Hello Peter,
Many thanks, this really helps, we fitted an Avo on the front and rear on a D 18 months ago the rear was not reamed the correct size the front touched on the fork top as you say due to having longer eye bolts which we also had to re-machine.
This month I fitted a rear to another D and I mention the reaming to them on ordering but it was supplied correct and fitted fine in just a few minutes, It looks like this D has the shorter eye bolts already so I will order an Avo for the front, I do feel it is a better ride on D's and better bikes all round in my opinion, the only thing that spoils them is the ugly seat, I have seen a picture of one made to look better like the C and I hope to see if I can get one made. All the best for 2021 riding. Kerry.

 

[Peter Holmes]

The Avo front damper should be installed using short eyebolts, not long, it is not clear to me what you had to re-machine, short eyebolts are available from most Vincent spare parts suppliers, if you specify the damper without a top shroud it should not foul any of the fork components.
I think the D seat was more than just a design exercise, I think it also created a bit more space for the increased suspension travel, having said that you might be able to successfully craft a B-C seat to fit somehow, but I think you will have to sacrifice something along the way, maybe increased seat height or drastically reduced squab/foam depth and therefore comfort.

Good Luck

Peter

 

[timetraveller]

Kerry, see if you can get someone with an AVO on the front of a 'D' to respond. I have fitted a large number of these to John Emmanuel steering heads and they seem to suit that system very well. However, the 'D's were fitted with longer and softer front springs and have a very nice soft long movement compared with the 'C's but the AVO is significantly stiffer than both the Vincent and Armstrong dampers and it might not suit the original geometry and spring strengths of the 'D'. I am not saying that they don't but feedback before purchase would be useful. You also need to sort out the length of the AVO compared with the Armstrong when it comes to the length of the lower eye bolts. The Armstrongs were shorter than the Vincent dampers and required the long eyebolts. The AVOs require the long eyebolts with the JE steering stems but remember that the overall length of damper and eyebolts controls the range of movement of the forks and you don't want to get into a poor part of that range.

 

[kerry]

The Avo front damper should be installed using short eyebolts, not long, it is not clear to me what you had to re-machine, short eyebolts are available from most Vincent spare parts suppliers, if you specify the damper without a top shroud it should not foul any of the fork components.
I think the D seat was more than just a design exercise, I think it also created a bit more space for the increased suspension travel, having said that you might be able to successfully craft a B-C seat to fit somehow, but I think you will have to sacrifice something along the way, maybe increased seat height or drastically reduced squab/foam depth and therefore comfort.

Good Luck

Peter

Attached is my bike which years ago the owner had on it a good looking seat ! I have never seen another on any D., I might first have a strap made up like Triumphs have just to break up the long flat image.

On the last one we had to shorten the existing long eye bolts as the front of the damper jammed against the curved inner on the front of the top of the Girdraulic forks, this part also has to be filed to stop the damper touching it when on the stand or riding, I have seen others that had to be filed out too ! to sum up after reading time travellers really helpful advice I am now not sure what to do, this bike has a new modern better rear and needs similar on the front ! ironically this D already has shorter eye bolts the same as a C. ?

 

[timetraveller]

This problem of the AVO damper hitting the rear/underside of the top link is something that crops up with the JE steering stems. On my own bike, the ex-Cecil Mill 'C', I had to grind a lot of material out of the link. Some other bikes don't even touch. I have no idea why. I can't believe that the distance between front and rear hole centres on either the top or bottom links can differ. The same problem arises with the front mudguard hitting the front of the engine. Some do and others do not. Before starting the production and supply of the JE steering heads I spent a lot of time measuring the front wheel spindle movement. I even got AVO to send me an empty damper so that I could make a scale on the outside to compare damper movement with spring box movement. I found, and John probably knew this before me, that the allowed range of movement is important. If the lower link starts off with the front too low then the wheel path is forwards to start with which is what the system is intended to prevent. The standard Vincent fork geometry gives a wheel movement from the lowest position which is forwards, then upwards more or less vertically, and then forwards again at the top of the travel The combination of damper and eyebolt length need to be such that one does not get into the most rearward of this travel. It is time consuming but not too difficult to plot out the front wheel spindle movement once the spring boxes have been released. Exactly how you do it will depend upon what you have lying around to make use of.
Is there no one out there with a standard 'D' front end and an AVO who can tell Kerry if they are happy with this combination?

 

[kerry]

Thank you, I am really grateful for your and others help, on the last D we were a bit concerned grinding out the top link and had to shorten the links a bit more than standard which was also a worry in case it weakened things. Regarding the mudguard touching the engine I have seen this on C series fitted with the nice Dave Hills centre stands but others have not touched, as you say it's odd. I think maybe I should order an Avo and set on it's softest setting, On the D we done previously with Avo front and rear it really gave a very nice ride as good if not better than any other classic in my opinion.

 

[Chris Launders]

Is there any difference other than the springs between the C and D, there must be many out there with Cs fitted with D springs, I understood this was a common thing, I know mine was but I had a Koni on it and went the JE route before changing to an AVO.

 

[kerry]

I have ordered an Avo for the front, after everyone's kind help and advice it seems the most suitable.
I will follow up once fitted and tried out
Kerry.

 

[highbury731]

I have ordered an Avo for the front, after everyone's kind help and advice it seems the most suitable.
I will follow up once fitted and tried out
Kerry.

You will need softer springs to go with the AVO front damper
Paul

 

[kerry]

Hi Paul, I am told the D's have softer springs already but I am sure you are right, from trials this is a report 'The Avo front damper is superior to all older alternatives and is likely to at least be the equal of more expensive modern replacements, Unlike the rear a change of damper and springs cannot dramatically transform Girdraulics but can be improved by choice of damper'

 

[timetraveller]

If it turns out that you do need softer springs then the ones for the JE system will probably be too short. They are 16.5" long in 30, 33, 36 and 45 lbs/inch strengths. That it a lot shorter than the 'D' springs, but if you do need specials then I can put you in touch with people who would probably make them.

 

[kerry]

Thank you very much, the one we done last year gave a really nice ride but who knows I may need your help, thanks. Kerry.