Comet Rear Suspension

[Howard]

Following the long running, on-going thread on front suspension, how about ideas on rear suspension.

My Comet is fine on smooth bends, but bordering on dangerous on bumpy bends. I should point out at this point it has a 90/90 19" rear tyre, which I will replace asap, because it seems much too small.

I've only just bought it, so I'm still finding the good and bad bits. I want to make it a rider's bike, but keep it looking standard and keep the engine characteristics of a 1950 Comet, but not to the detriment of rider safety/pleasure, so I've converted to 12 volt and indicators, it's got a B-TH, I'll fit modern tyres and brake linings and a steering damper.

I know of AVO, Koni Thornton etc, but I like the idea of keeping the Vincent dampers and I can modify them myself if that's the route to take.

So......... all sugestions gladly accepted, can a Vin damper be made acceptable, or is it essential to change to A N Other?

H

ps Urgent responses required - following winter I'm running out of smooth roads!!

 

[hadronuk]

Following the long running, on-going thread on front suspension, how about ideas on rear suspension.

ps Urgent responses required - following winter I'm running out of smooth roads!!

Howard,
I spent a lot of time exploring the MPH search facility on the VOC website before embarking on the AVO project, looking for ways to improve the original dampers. There was at least one writer who concluded that further improvements to the original damper were not practical, so I eventually decided that as so many had tried, I was not going to be able to do any better, although it would have been an interesting project.
My Rapide as purchased was fitted with Vincent dampers front and rear that had been given the "standard mods" by Don Alexander, so they were probably the best. They are very oil tight. I would say the handling was quite good, and by the sound of it, much better than your Comet is at present! So perhaps just the standard mods would be enough? For what it's worth, my view is that a good original damper works well enough at the front, which it was designed for of course, but is less successful at the back, where there are appreciable gains to be had in both handling and comfort from fitting a modern damper, especially when encountering rough surfaces when cornering quickly.
Rob

 

[Howard]

Thanks Rob, having read the write up you PM'd me (I didn't know you were that Rob) I'm looking towards buying an AVO damper, it's a quick fix, all the work's been done and it's not expensive.

H

 

[Bill Thomas]

Hello Howard, What rear springs have you got, I didn't think standard comet springs moved very much, Have you got standard seat fittings or have you got stays like a D Cheers Bill.

 

[Howard]

Hello Howard, What rear springs have you got, I didn't think standard comet springs moved very much, Have you got standard seat fittings or have you got stays like a D Cheers Bill.

Bill, if it ain't on show, I don't know what it is yet. They've commandeered the bike for the Stafford Show, so I'm only playing with bits until then, I don't want to find something big and let them down for an exhibit. When I get the new tyre (hopefully from the show) I'll check rear brakes, bearings, damper etc and see what we can see.

H

 

[Comet Rider]

Howard,
On my dads Comet he has managed to kill so far a standard damper, a Koni damper and an Ikon damper.
After such bad failures I decided to take it all apart and I think I found the cause of his problems.

Originally as a solo there were no real problems other than the ocasional bottoming out, so dad decided to fit extended eye bolt to the rear spring boxes. Unfortunately when he switch to an outfit and fitted petteford springs he kept the extended eye bolts, and as a direct result the over extension of the damper has casued the resulting failures.

Following on from Rob's excelent work with AVO, we have just ordered up the extended travel version (TA1446) and standard eye bolts for the spring boxes (From Spares Co).

So to sum things up, check everything including what springs, what eye bolts are fitted, and spend some money with AVO who are actually holding stock of the TA1446.

Best of luck
Neil

 

[davidd]

I liked the Thornton rear springs very much for the street. They provided a lot of comfort and travel. The stock spring boxes could not cope with the increased spring length. I made a new longer inner spring box for the racer to cope with the longer springs, but after the first practice I noticed the left spring box had come completely free and cocked upward at quite an angle. I set it straight and checked the other spring box carefully. I found a ridge on the outer spring box. It was raised from the inside where the inner spring box had repeatedly rubbed and was about to break through the outer spring box. I came up with a fix, but decided to use it on the street bike rather than the racer. On the racer, I decided to get rid of the whole mess and do a coil-over. When I made it, I bought a 200 lb. single rear spring to fit over the damper.

For the street I made stainless steel boxes with a plastic bushing that worked quite well at stabilizing the spring boxes. Many in the U.S. bought these from Justin MacKay-Smith who made these pieces for a few years.

I think the Comet rear suspension may suffer from the lack of suitably light springs.

David

 

[vibrac]

Banana man made some very nice rear units with standard springs and internal sliders so we could throw away the covers and excess weight full seasons racing on the Comet very good stuff

 

[Howard]

Banana man made some very nice rear units with standard springs and internal sliders so we could throw away the covers and excess weight full seasons racing on the Comet very good stuff

Don't get me started, you don't know how hard I'm fighting my natural instincts with this bike. I have lightweight bikes and sports bikes, I bought it for a relaxed outing bike for club runs, something to tinker with and improve, and, I have to admit, something that won't lose money from my pension fund. Everytime I pass it, I think "that standard horn is heavy - I know where there's a lighter one" or "Why do I need 2 heavy brakes on the back?" I'm trying to keep it as standard as possible with improved rideability, and that's it (I keep telling myself!). The rear tyre gave up the ghost yesterday, cracks all over it, it must be older than I thought, and 700 miles in 7 years seems to have let it perish before it wore out, so it's new tyre this week, and then I'll have a look at the suspension setup while the wheel's out. H ps why can't I do paragraphs today?

 

[Hugo Myatt]

I liked the Thornton rear springs very much for the street. They provided a lot of comfort and travel. The stock spring boxes could not cope with the increased spring length. I made a new longer inner spring box for the racer to cope with the longer springs, but after the first practice I noticed the left spring box had come completely free and cocked upward at quite an angle. I set it straight and checked the other spring box carefully. I found a ridge on the outer spring box. It was raised from the inside where the inner spring box had repeatedly rubbed and was about to break through the outer spring box. I came up with a fix, but decided to use it on the street bike rather than the racer. On the racer, I decided to get rid of the whole mess and do a coil-over. When I made it, I bought a 200 lb. single rear spring to fit over the damper.

For the street I made stainless steel boxes with a plastic bushing that worked quite well at stabilizing the spring boxes. Many in the U.S. bought these from Justin MacKay-Smith who made these pieces for a few years.

I think the Comet rear suspension may suffer from the lack of suitably light springs.

David

Early Comets were fitted with 2 x 121 lb/in rear springs = 242 lb/in. I believe these were found adequate for solo riding but not so with a pillion passenger and so they quickly became obsolete. They were replaced with two Rapide springs at 189 lb/in = 378 lb/in. I have always felt that these were too stiff/ strong (?). I should like to have tried one original Comet spring and one Rapide spring, i.e. 121 + 189 = 310 lb/in