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Rudyís thread was becoming badly contaminated by extraneous off topic chatter.
Rudyís thread was becoming badly contaminated by extraneous off topic chatter.So hereís the thing.Tris noted that every time it started to gell for him, it drifted off. Start by separating the spring from the damper.Realise that the damper has two functions.1.To progressively dampen the oscillations of a given spring when deflected from rest.2.To give a top and bottom limit to the maximum and minimum length of the captured spring in the assembled unit.Next..The load is supported by the spring, not the damper....(ignore for now any pressurised shocks).Consider a 200 mm spring at rest on the bench.Now assemble the shock with no preload.When you sit on the bike, you are effectively sitting on the spring. That un preloaded spring will compress until it reaches itís compressed length for that load.Can we call that length 150 mm....(it has compressed 50mm). Remember it has no preload yet.The spring compressed, (sagged) 50 mm under the combined weight of rider and bike. You will perceive a certain ďsoftnessĒ that you associate with that spring.Now put the bike back on the centrestand with the rear wheel off the ground...The shock is now ďtopped outĒ against itís top stop, like it was on the bench.Wind on 25 mm of pre load...Now your spring is 175 mm long.Roll the bike off the stand and jump back on.The total LOAD has not changed, so itíll come as no surprise that the spring compresses back to....?...150 mmThe same as before the preload, but it has only compressed 25 mm under the effect of the load to get to that 150 mmhowever it will perform the same as the unpreloaded example, because it has still only been compressed to the same length as the first example (150mm).Hereís the crunch though.Because you have only compressed the spring 25 mm in the second example, the eye to eye length will be more than the unpreloaded example and therefore the ride height will be greater...(the damper rod is 25 mm further extended).But the spring performance will not have altered.For Tris...
Like a dog on a bone, just gotta make it hard eh?
Thanks for posting that. Took a bit of thought but I think I get "the crunch" now. Spring is compressed the same but the shock rides higher in it's travel due to preload on the spring.
......Hereís the crunch though.Because you have only compressed the spring 25 mm in the second example, the eye to eye length will be more than the unpreloaded example and therefore the ride height will be greater...(the damper rod is 25 mm further extended).But the spring performance will not have altered.For Tris...
Without wishing to rain on anyoneís parade, research into these subjects may help in understanding motorcycle suspension and the effect of adjusting preload1/ Progressive springs2/ Rising rate linkage (n/a v85 but relevant to most monoshock Guzzis)3/ Angle of shock absorber (very relevant to v85 and noticeable difference on 21 V7 compared to prior)To understand the latter read up on 60ís Velocettes with adjustable top shock mount position.Happy reading, no debate, it is what it is
Cheers Huzo - this is good of you Firstly GOT IT ... I think In my words If you changed the spring for a solid tube (spacer) the preload adjuster just changes the relative position between the top and bottom mounts as they slide on the damper that controls the max and minimum stroke (ignoring the damping effect)So when I raise the preload to carry my lardy ass the prime objective is to maintain the suspension (say) midway through its travel (I know that's a simplistic position)Is that right?
Great explanation, thanks
ďThe bike was too soft in the arse end through turn 4, so I wound on a bit of preload to stiffen it up a bit..Ē
In between working I've been pondering this!Should he have a) gotten some springs at a higher rate to cope with his weightb) wound the compression damping up to slow the rate the suspension got to full travel?
Itís not hard Bulldog.But that was a bit prolonged because it allows people who are coming to terms with the concept, to work methodically through and identify where their misunderstanding begins.You start with the bit thatís easy to understand and work your way through. Caffeineo in the previous post, indicated that there was a light beginning to appear for him. My post was to help people who are on the cusp of getting it, not people such as yourself who (apparently) already do.How would you have explained it more briefly without leaving out an important aspect ?I could have done it in two lines to someone who already understood, but Iíve been trying to learn the stuff Beetle does and I like the way he patiently leads the beginner along.BTW.I donít know what the emoji is supposed to convey, can you enlighten me ?Please donít make it too hard....
I heard the same thing Saturday when a local rider was checking the suspension & preload on my Ducati. Nor sure I still understand it. The bike "feels" stiffer with more preload. But it does sit up higher with more preload, no question.BTW- he was impressed that the suspension had so little stiction but the rear shock is too stiff (high speed) compression. we didn't change anything, it was close enough other than the "Stiff" rear shock.
I suspect that part of my confusion was the use of the word "Preload". Am I right to say that the objective is NOT to pre load the spring it is to just shift the mounting point of the springIf the shock wasn't there limiting movement then ride height would simply increase However we have a shock limiting the movement so the spring is compressed, and mechanically compressing the spring by 1 inch is the same as applying a mass that compresses the spring by one inchPhysically ride height can never exceed the max travel of the shock however the spring doesn't know that so doesn't react until the travel created by the travel created by the mass exceeds the compression applied by the "pre load" adjuster (I'm assume simple static loads at this point)Am I still on the right track?Cheers TrisPSMy second-hand Roamer came with Hagon Nitros fitted and 17GKg springs IIRCI wrote to Hagon last night to see if I have the right springs for my mass
When are we going to get to the "shocking" part?
Well...?The thread hasnít been nuked and a fight hasnít broken out yet. Thatís a bit of a shock isnít it ?
I read somewhere that Henry Ford grabbed the first model T off the line and took it for a spin across a lumpy field. His debrief note read "Needs shock absorbers." Some say he specified hydraulic, some say he was not specific. It doesn't matter. The point is that springs and shocks are two different components of a suspension system, and they have been forever. With that said, I'd like to offer how I understand them. Maybe it will help. Keep in mind that I'm speaking in generalities.,,,,,,,,,,
Nobody has yet brought up the touchy subject of the flux capacitor's part in all this. I do know this much. I am short, at 5'8 on a good day. Cranking up the preload for me to carry a passenger has always made it harder for me to swing a leg over the bike & reach the ground. Regardless of the science involved.
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