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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Modified Steering Stem
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<blockquote data-quote="hadronuk" data-source="post: 75775" data-attributes="member: 1866"><p>Ah, it's a Koni! I thought it might be because of the short dust cover, but I was fooled by the silver coloured body.</p><p>Anyone who likes the Koni damping characteristics should like the AVO front damper, as the Koni 76F we tested has a very similar bump characteristic to the AVO front. Assuming the recently rebuilt Koni we tested is representative.</p><p></p><p>As Timetraveller has mentioned, he and I have been discussing the possible spec for an extra long front damper, and I am happy to report that AVO emailed me yesterday to say they are willing to build it, in spite of the likely low sales volume.</p><p></p><p>Re the earlier subject of progressive springs. As the first part of their travel is soft, they usually require a higher preload if the correct ride height is going to be maintained. This is totally contrary to David's short and stiff spring approach, which was specificity designed to minimise preload. He and others proved the concept on the track.</p><p></p><p>Following on from that and also Bills observation that "Know thy Beast" comments that the forks can be dangerous at full compression because of low trail.</p><p>This is a debate that has raged since Girdraulics were first produced! I have read every thing I could find on the subject and I have four main reasons (plus my own theories) to side with the fully extended danger area theory:</p><ol> <li data-xf-list-type="ol">It is the view of two of the biggest beasts (Surtees and Irving) of the Vincent world.</li> <li data-xf-list-type="ol">The most up to date study of tankslappers by Cranfield and Imperial cited evidence that light riders and/or a lightly loaded front wheel were risk factors.</li> <li data-xf-list-type="ol">Some of the descriptions of Girdraulic tankslappers report they occurred after the forks went light, cresting a rise for example. I believe both of the Vincent accidents at Goodwood occurred at such a point on the track.</li> <li data-xf-list-type="ol">As I mentioned before, modern racers regard a high preload as dangerous because the sudden unloading of the front wheel as the forks extend under full acceleration has been shown to precipitate a tank slapper.</li> </ol><p>=========================================================================</p><p>Some general points about my contribution to these discussions. Whilst I frequently promote AVO dampers, it doesn't follow I think other makes of damper are poor. I do think the other manufactures made a mistake with their offerings for the rear damper. The key fact is that the Vincent damper was designed for the Girdraulics and I think fitting the same spec damper to the back was an economically necessitated compromise which everyone else unthinkingly copied. This is why I think the AVO may have the edge on other dampers at the back. </p><p>With the Girdraulics its a different ball game. The Vincent damper travel is unsurprisingly perfectly matched to the fork geometry, so unlike the rear, there is no benefit to be had in changing its dimensions.</p><p>In my back-to-back road tests, the AVO gave slightly better control than the Armstrong and was slightly more comfortable than the Vincent. But I certainly wouldn't suggest anybody should expect a dramatic improvement by changing to an AVO at the front unless the existing damper is knackered.</p></blockquote><p></p>
[QUOTE="hadronuk, post: 75775, member: 1866"] Ah, it's a Koni! I thought it might be because of the short dust cover, but I was fooled by the silver coloured body. Anyone who likes the Koni damping characteristics should like the AVO front damper, as the Koni 76F we tested has a very similar bump characteristic to the AVO front. Assuming the recently rebuilt Koni we tested is representative. As Timetraveller has mentioned, he and I have been discussing the possible spec for an extra long front damper, and I am happy to report that AVO emailed me yesterday to say they are willing to build it, in spite of the likely low sales volume. Re the earlier subject of progressive springs. As the first part of their travel is soft, they usually require a higher preload if the correct ride height is going to be maintained. This is totally contrary to David's short and stiff spring approach, which was specificity designed to minimise preload. He and others proved the concept on the track. Following on from that and also Bills observation that "Know thy Beast" comments that the forks can be dangerous at full compression because of low trail. This is a debate that has raged since Girdraulics were first produced! I have read every thing I could find on the subject and I have four main reasons (plus my own theories) to side with the fully extended danger area theory: [LIST=1] [*]It is the view of two of the biggest beasts (Surtees and Irving) of the Vincent world. [*]The most up to date study of tankslappers by Cranfield and Imperial cited evidence that light riders and/or a lightly loaded front wheel were risk factors. [*]Some of the descriptions of Girdraulic tankslappers report they occurred after the forks went light, cresting a rise for example. I believe both of the Vincent accidents at Goodwood occurred at such a point on the track. [*]As I mentioned before, modern racers regard a high preload as dangerous because the sudden unloading of the front wheel as the forks extend under full acceleration has been shown to precipitate a tank slapper. [/LIST] ========================================================================= Some general points about my contribution to these discussions. Whilst I frequently promote AVO dampers, it doesn't follow I think other makes of damper are poor. I do think the other manufactures made a mistake with their offerings for the rear damper. The key fact is that the Vincent damper was designed for the Girdraulics and I think fitting the same spec damper to the back was an economically necessitated compromise which everyone else unthinkingly copied. This is why I think the AVO may have the edge on other dampers at the back. With the Girdraulics its a different ball game. The Vincent damper travel is unsurprisingly perfectly matched to the fork geometry, so unlike the rear, there is no benefit to be had in changing its dimensions. In my back-to-back road tests, the AVO gave slightly better control than the Armstrong and was slightly more comfortable than the Vincent. But I certainly wouldn't suggest anybody should expect a dramatic improvement by changing to an AVO at the front unless the existing damper is knackered. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Modified Steering Stem
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