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Suspension - please explain.

Howard

Well Known and Active Website User
VOC Member
I may have been in the VOC a very long time, but until I bought the Comet 7 years ago I've had nothing to do with standard cycle parts.

My Comet does about 500 miles a year ( Egli does most of my miles), it gets ridden and put away until it's needed again and only needs minimal maintenance. So during lockdown it's become my quest to change as many things as possible (as you do) and look how things work, rather than just putting them back as they were.

The rear suspension has always been a pain in the neck, and all points south, so that's got a good looking at. Everything seemed ok, apart from a bent damper rod and the stud that goes through the top damper eye was also bent - so I made a new stud and damper rod complete with Paul Ennis mods.

Now then, can someone explain to me why the damper has 2" of travel, plus 1/2" each end of hydraulic bump stop, but the spring will only travel 2" and is coil bound before it reaches the compression bump stop? Or is there something wrong with my suspension.

I feel the suspension is missing a trick. Using a spring with more travel, and longer threads on the eye bolts would (I think) allow a less vicious stop at the end of travel, and would allow pre load adjustment.

As they say in exams - discuss.

Cheers
Howard
 

timetraveller

Well Known and Active Website User
VOC Member
Pettiford springs allow more travel but you might have to compress them in order to fit them even with the damper fully extended. Are you sure that there is a hydraulic bump stop in the damper? I am not saying that there isn't but I have never noticed it and how would a hydraulic bump stop work? Is that part of the Paul Ennis modification? Fully sprung is a major improvement, hence the Series 'D's. AVO coil overs are a good way to go. At the front then the John Emmanuel mod with my mod for the springs and the Greg Brillus mod to the Oilite bushes makes a dramatic difference to front end comfort and I am currently out of stock so I am not trying to sell you anything.
 

BigEd

Well Known and Active Website User
VOC Member
VOC Forum Moderator
The original damper has a hydraulic stop created by the porting being closed as the damper nears the end of the stroke.
 

Bill Thomas

Well Known and Active Website User
VOC Member
The Comet rear springs were thinner, A lot of them have been changed to Twin ones over the years.
Maybe OK with a fully floating seat ?.
I like to keep my Old Comet looking Standard, Don't Laugh,
So have kept the seat stays, But changed one spring to a Twin one, I am about 200 lb without all the riding gear = Rides not too bad.
Are the bearings in the RFM OK ?, Free ?,
And the seat pivots free ?
I also don't like high tyre pressures, I run about 26 lb.
I now put oil or something on the lower rear seat pivots, No tension on the knobs, Bit of loctite to stop them from coming off !, Because we now have the hydraulic damper we don't need anymore stiffness.
 
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Howard

Well Known and Active Website User
VOC Member
Pettiford springs allow more travel but you might have to compress them in order to fit them even with the damper fully extended. Are you sure that there is a hydraulic bump stop in the damper? I am not saying that there isn't but I have never noticed it and how would a hydraulic bump stop work? Is that part of the Paul Ennis modification? Fully sprung is a major improvement, hence the Series 'D's. AVO coil overs are a good way to go. At the front then the John Emmanuel mod with my mod for the springs and the Greg Brillus mod to the Oilite bushes makes a dramatic difference to front end comfort and I am currently out of stock so I am not trying to sell you anything.
Maybe I'm reading too much into it, but the ends of travel look like they could be intended as a primitive bump stop. If I was using the Comet regularly and for a reasonable mileage, I'd have all the great mods you suggest, but I'm just trying to get the best out of the original setup with a few tweaks - A bit of improvement and a bit of DIY hobby while all our lives are restricted.
 

Howard

Well Known and Active Website User
VOC Member
Bill, Can't remember the wire diameter now, but apparently the Comet had two spring sizes and the first ones were superceded by thicker ones, mine are the later ones and they're 6 3/4" long so I assume (hmmm? ) they're still good. Oiling a friction damper is the last thing I would ever think of doing, but I see where you're coming from and I'll have a shot at that. All pivots are now good - can't vouch for how they were, because I wasn't looking for problems when I dismantled them.
 

Bill Thomas

Well Known and Active Website User
VOC Member
It was not me Howard, I think I got the idea from Vincent Speet, He does a nylon insert, But it's a Turning job and He's too far away, It just made sense to me, I am always willing to learn new tricks !.
 

Howard

Well Known and Active Website User
VOC Member
Nylon insert? Now you're talking. That's a lockdown DIY job, I might even have some HDPE bearing material big enough.
 

Albervin

Well Known and Active Website User
VOC Member
I assume you now have spacers between the springs and damper on the lower mount. When you rebuilt the damper what oil did you use? This can be critical to a good set-up. Most suspension tuners say " soft springs and firm dampers" and that has worked for me for forty years. The friction seat stays are a hangover from Series A and B bikes. Light machine oil on the damping fabric stops squeak, judders and still gives a smooth damping for the passenger. You say you have 1/2" each end of bump stop. That doesn't sound right. There should be a bump stop at the top of the piston but not 1/2". With modern oils I use a 3/8" Nylothane bump stop. IF the damper is compressing to full travel then you have to do a few things; but one at a time. First I would put heavier oil in the damper. Then I would think about changing one spring to a heavier one. Before doing anything you need to measure suspension sag; both static and with you sitting on the bike. This is critical for a comfortable ride. Cable ties are your friend here. Happy days.
 

vin998

Well Known and Active Website User
VOC Member
VOC Forum Moderator
Howard, I have done the nylon inserts on my C Shadow seat stays and it improved the rear suspension feel a lot. Think of it this way:
Series B usually had no rear damper (I think the last of the B's may have though) so the only rear damping is the friction damping in the rear seat stays. Series C's had a hydraulic damper but kept the seat friction dampers as well which defeats the point of the hydrauic one and they end up fighting against each other. When you fully spring a rear of a Vincent most owners first comments are the rear suspension suddently came alive and worked a lot better, my C Rapide did.
On my C Shadow I fitted bearing grade nylon ring instead of the friction material and so the seat stays move easily but most important don't flop around sideways as that will allow the seat to move sideways and put strain on the seats front mounting brackets. Result is the rear suspension is now controlled by the hydraulic damper.

Simon
 

Vincent Brake

Well Known and Active Website User
VOC Member
Don't know where i got them from anymore. Howard.

Later i went to works performance.
Coil over.
Better and way lighter.
But no, not looking standard...
 

Ken Tidswell

Well Known and Active Website User
VOC Member
Pettiford springs allow more travel but you might have to compress them in order to fit them even with the damper fully extended. Are you sure that there is a hydraulic bump stop in the damper? I am not saying that there isn't but I have never noticed it and how would a hydraulic bump stop work? Is that part of the Paul Ennis modification? Fully sprung is a major improvement, hence the Series 'D's. AVO coil overs are a good way to go. At the front then the John Emmanuel mod with my mod for the springs and the Greg Brillus mod to the Oilite bushes makes a dramatic difference to front end comfort and I am currently out of stock so I am not trying to sell you anything.
Many decades ago a young J Surtees suggested that that the handling of a Vincent would be improved by lenthening the rear spings by 11/2 inches . Since PCV was not good at receiving suggestios about his product it never happened. However the heretics among you did just this i am one. Fitted longer rear springs and aKoni and went fully sprung fot touring and the ability to carry luggage. The longer springs sharpen the steering and fitting a19 inch rim makes it better. Where's the bonfire.
 

Howard

Well Known and Active Website User
VOC Member
Longer spring box inners help alot to prevent thespring boxes fouling on extension
Ken, I'm not a purist. The Comet I raced had coil over damper front and fully sprung rear, I 'd love to build one like it, but it's not what I need, and it's not what my current Comet deserves, I'm trying to keep it standard/useable (if that makes sense). I love the work that's gone into some of the unnecessary art, like chain adjusters and friction dampers, and removing things like that take me further from the essence of Vincent. If it has to stay bumpy, so be it, but if I can make it a bit more comfortable and look the same, all the better. I had heard PCV didn't take criticism well. :)comet.jpg:)
 

vibrac

Well Known and Active Website User
VOC Member
At least if you have the Paul Ennis mods you are well on the way to getting the best out of a standard damper I know a standard set up can be made to work well (heck I raced on one long enough even if I had a broom with a short handle) however nowadays with todays roads I am glad I have coil over AVO and coil over Bramptons. When we were finally were allowed out last week and I tested out my brood after the winter, I found bumps on my test loop road on the 35 KSS Velo and 52 Trophy that I had not felt on the Comet something must be working right.
 

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