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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
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<blockquote data-quote="timetraveller" data-source="post: 120641" data-attributes="member: 456"><p>To avoid confusion here; we have found that to get the best our of the front end one has to pay attention to the weight of the rider and the bike. That is whether it is a twin or single. Both bike sizes have the same un-sprung weight in the front suspension and a pillion passenger and/or luggage at the rear seems to make very little difference to what i required at the front. Therefore it seems to be the mass, and hence inertia, of the centre of the bike which is important. Chris is one of the heavier riders and did most of the test riding when the system was new. Before he changed the rear bearings in the lower link he had 36 lbs/inch springs and the standard AVO damper. Once he changed over from Oilite bushes to the Greg mod at the rear (he used needle rollers rather than ball races) there was so much yoyoing at the front that his first impression was that the damper had failed. This was overcome by changing to 45 lbs/inch springs with two inches of preload from 36 lbs/inch springs with three inches of preload and getting AVO to build a stiffer damper. Eventually Chris had to pack the springs and the lowest setting on the stiffer damper might not be very different from the stiffest setting on the original AVO damper. Greg has long maintained that stiffer springs and a softer damper are the best combination and yet here in the UK people who have started off with the stronger springs and a variety of dampers, all weaker than the AVOs, have all found that the front is not as comfortable as they would like. In Europe, Canada and the USA people seem to be happy with the longer travel of the weaker springs and cut down spring boxes rather than Greg's recipe but Greg has fitted more of these than any other person, he has had about fifty kits, and he has raced very successfully with his combination. This has left me with a problem. Is there a single best option or can both options be made to work? That is; stiffer springs and a soft damper or weaker springs and a stiffer damper. Note that the AVO dampers are adjustable and feedback from various parts of the northern hemisphere suggest that most people are using the AVO at about, or less than, half the maximum stiffness. Even with the AVO damper turned down to the minimum stiffness all the mid weight riders to whom I first supplied the 45 lbs/inch springs have asked for them to be changed to the 36 lbs/inch ones, or even 33s, or even 30s on the stripped down singles. Greg does not cut down the length of the spring boxes and my understanding is that his method of checking the front suspension is to run the bike down a slope without the engine on and with no damper and then once up to, say, 30 mph to slam on the front brake and to determine how much movement there is. Remember that Greg is a competent racer and so I value his views but that is not what I was trying to achieve with the combination which I normally supply. I wanted a system in which the damper modifies the spring pressure/movement; a little on the compression and more on the extension. This seems to be acceptable to most of the people who have provided me with feedback. I would have absolutely no problem with supplying people with stiffer springs but where a weaker damper could be found I don't know. The AVO turned down to a minimum is certainly not what I would call stiff but then I do not pretend to be a suspension expert. My impression from reading around this subject is that for comfortable road use the combination of softer springs and stiffer dampers are preferred. Do we have a suspension expert who reads this who could give us professional level information?</p></blockquote><p></p>
[QUOTE="timetraveller, post: 120641, member: 456"] To avoid confusion here; we have found that to get the best our of the front end one has to pay attention to the weight of the rider and the bike. That is whether it is a twin or single. Both bike sizes have the same un-sprung weight in the front suspension and a pillion passenger and/or luggage at the rear seems to make very little difference to what i required at the front. Therefore it seems to be the mass, and hence inertia, of the centre of the bike which is important. Chris is one of the heavier riders and did most of the test riding when the system was new. Before he changed the rear bearings in the lower link he had 36 lbs/inch springs and the standard AVO damper. Once he changed over from Oilite bushes to the Greg mod at the rear (he used needle rollers rather than ball races) there was so much yoyoing at the front that his first impression was that the damper had failed. This was overcome by changing to 45 lbs/inch springs with two inches of preload from 36 lbs/inch springs with three inches of preload and getting AVO to build a stiffer damper. Eventually Chris had to pack the springs and the lowest setting on the stiffer damper might not be very different from the stiffest setting on the original AVO damper. Greg has long maintained that stiffer springs and a softer damper are the best combination and yet here in the UK people who have started off with the stronger springs and a variety of dampers, all weaker than the AVOs, have all found that the front is not as comfortable as they would like. In Europe, Canada and the USA people seem to be happy with the longer travel of the weaker springs and cut down spring boxes rather than Greg's recipe but Greg has fitted more of these than any other person, he has had about fifty kits, and he has raced very successfully with his combination. This has left me with a problem. Is there a single best option or can both options be made to work? That is; stiffer springs and a soft damper or weaker springs and a stiffer damper. Note that the AVO dampers are adjustable and feedback from various parts of the northern hemisphere suggest that most people are using the AVO at about, or less than, half the maximum stiffness. Even with the AVO damper turned down to the minimum stiffness all the mid weight riders to whom I first supplied the 45 lbs/inch springs have asked for them to be changed to the 36 lbs/inch ones, or even 33s, or even 30s on the stripped down singles. Greg does not cut down the length of the spring boxes and my understanding is that his method of checking the front suspension is to run the bike down a slope without the engine on and with no damper and then once up to, say, 30 mph to slam on the front brake and to determine how much movement there is. Remember that Greg is a competent racer and so I value his views but that is not what I was trying to achieve with the combination which I normally supply. I wanted a system in which the damper modifies the spring pressure/movement; a little on the compression and more on the extension. This seems to be acceptable to most of the people who have provided me with feedback. I would have absolutely no problem with supplying people with stiffer springs but where a weaker damper could be found I don't know. The AVO turned down to a minimum is certainly not what I would call stiff but then I do not pretend to be a suspension expert. My impression from reading around this subject is that for comfortable road use the combination of softer springs and stiffer dampers are preferred. Do we have a suspension expert who reads this who could give us professional level information? [/QUOTE]
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