FF: Forks Fork Travel

[Bill Thomas]

Bowsh,

Those are the dimensions for the bulk of the production springs, so what you have is stock. That means that the outer springs provide 68 lbs./in each.

The inner springs provide 10 lbs./in or you can think of it as each spring supplies 78 lbs./in with the inner spring included.

That means if you wish to use stock springs you can run two Series D springs at 63 lbs./in each.

Two of your springs without inners at 68 lbs./in each.

Two of your springs with inners at 78 lbs./in each.

It is easy to see that the Factory felt that the bikes were oversprung if you see that they lowered the twins from 78 lbs./in each to 63 lbs./in in 1954. This in turn would imply that the Comet could be oversprung depending upon its use.

Greg mentions the short springs, some of which I designed at 14" tall so you could adjust your ride height. The lightest ones were red, then blue, then white for the heaviest . Norman was good enough to make some of these so owners could experiment with various spring rates. He also made a number of different spring rates and sizes.

For the best handling (not necessarily the best ride) the lower link should be level with the pavement when you are riding the bike. If I remember correctly, your link looked pretty good with you on the bike.

This information applies to bikes with stock steering stems. Both Norman and I have made modified steering stems that are less fussy about working well.

David

I have had to pack these Short ones out to get good results, I have a red and a blue on my Comet,
And a blue and white on my Twin. Cheers Bill.

 

[davidd]

Bill,

Yes, Bill has mentioned this before and the packing is fine as long as your lower link is parallel to the pavement with you on the bike.

David

 

[Bill Thomas]

Bill,

Yes, Bill has mentioned this before and the packing is fine as long as your lower link is parallel to the pavement with you on the bike.

David

If you look at the photo of my Twin, under, Thread, "Comet Handling", reply 39, They are not far out ?.
Cheers Bill.

 

[Bowsh]

Thanks to everyone for your input. I’m going to change to an Avo damper first then go for a spring change. One step at a time though! Paul

 

[greg brillus]

At the very least, leave out those inner springs, that will soften the ride straight away and no cost. While your at it, give the inner/outer spring cases a good clean (solvent and a bottle brush) then whilst empty assemble each pair and make sure they slide freely with no binding as this will affect how free the forks move. Due to the bushes and spindle set up the friction in the front end is quite high, so freedom of movement is important, and costs near nothing to check.

 

[Bill Thomas]

I don't think you should let the forks come up too high !!.
Does he need the long eye bolts with an AVO ??, That might help.
Cheers Bill.

 

[Simon Dinsdale]

The AVO is intended to be the same operational length (or very close) so needs to be used with the std eye bolts which is the shorter ones. If you use the longer eye bolts you may get the lower front mudguard stay dangerously close to the mag cowl or the exhaust.
Simon

 

[timetraveller]

But with the new steering heads you should use the long eyebolts with the AVO damper to get the right fork travel. The geometry is different.

 

[Albervin]

With all of these variables it is paramount that you read the literature and know the basics. This is not for beginners!. The lay of the links is everything. Too high or too low is a recipe for a calamity. Way back I was always told soft spring and firm dampener. Still works after 40 years. Now we have adjustment for compression and rebound!. If anyone wants to argue that then feel free.

 

[timetraveller]

I think that if the original geometry is kept then too soft or too stiff springs are not a safety problem but it is certain that too long springs with poor damping will cause problems. The new geometry is a major improvement and we should thank John Emmanuel for his generosity in allowing it to be copied. However it will still only be safe with the right springs, damper and paying attention to the angle of the lower link, which should be more or less horizontal with the rider seated.