FF: Forks Modified Steering Stem

hadronuk

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This might be useful:
damper%20lengths%20Small_zpsjggid91g.jpg


Obviously ride height depends on spring choice and preload, but damper lengths provide the limits.
 

hadronuk

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One other thing about springs and ride height. Ideally suspension should be set up so that with a normal load the suspension is 30% compressed, as this should minimised topping out and bottoming out. But I think the great majority of B and C Vincents are set much lower than this. With the original springs the figure is more like 70%! Although the AVOs have a shorter extended length than the other choices, with the suspension set to the magic 30%, the seat is too high for me, and I am 5 ft 11 inches tall.
 
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Bill Thomas

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I did mean compression, but I may have misunderstood Bill and I can't find the original quote in KTB! I assumed "the forks move too far up" meant relative to the rest of the bike, rather than the bike rising on the forks.
What's your view on the matter Vibrac? As a racer, you must have far more experience of Girdraulics under extreme conditions than us ordinary road riders.
Morning Rob, Page 30, " Whichever damper is chosen, It is worth while fitting the longer eyebolts, They also prevent the fork from moving too far up, Thus avoiding the fork position where the trail is smallest and the fork most prone to "Speed Wobble". "
I think this was the second edition of Know Thy Beast. Cheers Bill.
 

Martyn Goodwin

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Morning Rob, Page 30, " Whichever damper is chosen, It is worth while fitting the longer eyebolts, They also prevent the fork from moving too far up, Thus avoiding the fork position where the trail is smallest and the fork most prone to "Speed Wobble". "
I think this was the second edition of Know Thy Beast. Cheers Bill.
It's in the first edition of KTB as well -

Martyn
 

greg brillus

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I can't imagine the forks being at full compression long enough to cause a speed wobble.......Remember these were the same guys that got it wrong in the first place. These days a manufacture would have called for a major 'Recall" if such a bad handling issue existed on a modern machine.
 

hadronuk

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It's in the first edition of KTB as well -

Martyn
Aha! Thanks, I was looking in my 4th edition, as my 2nd edition is a bit delicate. Using that as a reference, as was able to find the rewritten section which is on page 39.
Referring to the long eyebolts, it now reads:
"They may also prevent the fork from moving too far up, thus avoiding the fork position where the trail is smallest and the fork, in theory, more prone to "speed wobble"."

Sound like he was less certain and doubt was setting in! :)

I agree with Gregg. Very little time for an oscillation to build up as the forks momentarily bottom, plus when trail is low, the self centreing action is weakest and less likely to drive a resonant oscillation.
 

Bill Thomas

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The thing is Greg, If you had ever had a " Full Blown Tank Slapper ", You would know that once it's going, It only stops after you have been thrown Off !!.
I will say that my Brother, Does not use the Standard Damper, And he has been riding longer than me, And on the road was faster than me !!.
I also rode for many years, Without any trouble, Most of my Racing was done without an Hydraulic Damper.
For years I had full faith in my bikes, And with Red Arrow tyres on my racer, I could do anything with it, It's just that my luck ran out !!. Cheers Bill.
 

greg brillus

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My guess is that if the front end hit something hard enough to compress the forks till they bottom out, the instant rebound would send the fork action to the other extreme. I have had various tank slappers on two different bikes, luckily none bad enough to toss me off. Though the one on my RZ 500 Yamaha was enough to strain both my wrists and scare the life out of me. I don't believe there is anyone on this planet that if they have ridden bikes hard long enough, sooner or later something will happen to them, though these bikes are prone to handling issues, some are lucky to escape it. I just prefer to do all I can so it doesn't happen to me .........That's why I went to so much trouble on the racer.
 

Bill Thomas

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The thing with the Vincent is there is so much weight forward of the steering head, I see the Ducati down tubes are almost in line with the Stering head.
Cheers Bill. Like a bloke on the T.V. said at the end of his prog', " May Your God Go With You ".
 
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