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Fork Springs
Posted: Fri Nov 02, 2012 10:58 pm
Author: Rhencullen
Can anybody clarify which way in that 'progressive' fork springs go in the stanchion
There is currently a debate on the GPZ forum regarding this, as the generally accepted norm, is to have the 'tighter coils' at the top of the fork leg...... but nobody has come up with a convincing reason why this should be, and confusion reigns
Why do you think that the force comes up from the bottom of the spring? Surely the force equally comes down from the top compressed by 300kg+ of motorcycle and rider
Also lets imagine the spring compressing... Do you think that force of the spring compresses one coil at a time before being passed onto the next coil or is the force spread evenly throughout all the spring coils at the same time.
And finally let's imagine compressing a spring in a giant bench vice. Would the spring compress from the moving jaw end of the vice or the fixed end? Or would it be both ends at the same time?
Posted: Fri Nov 02, 2012 11:09 pm
Author: Z903
I've seen this debate before....
but I've put mine tight coils to the top, whatever that's worth
Posted: Fri Nov 02, 2012 11:18 pm
Author: z1000puddin
Tight rings to top - me also
stu
springs
Posted: Sat Nov 03, 2012 7:24 am
Author: tricky
hi rhen, i am running koni shocks, and koni front progressive springs, as the tight coils were at the bottom on the rear shocks, i put the front springs in the same way, with the tight coils to the bottom.
i wish there was some company that made linear springs for these old bikes, suited to you body weight, as i think these progressive things, are all made at the same place, somewhere in tingtong land, and packeged up for different brands.
as there is no indicated spring rate they must be a compromise/ or wrong all together. bye for now tricky
Posted: Sat Nov 03, 2012 8:41 am
Author: Z1parR
Always tight to your bottom
Posted: Sat Nov 03, 2012 9:05 am
Author: Pigford
The tight coils are at the top - as the metal
mass is denser - so in theory (mine) there's less "unsprung weight"
If the mass is lower down, it's near the wheel centre
Posted: Sat Nov 03, 2012 10:44 am
Author: zed1015
Common engineering practice dictates that the tightest coils should be furthest away from the compressive force ( i.e at the top of the fork ) as they would be the last ones to compress.
However in reality the compressive force is spread equally from both ends and they will work just as well no matter which way they are installed. .
Posted: Sun Nov 04, 2012 9:40 am
Author: Rhencullen
Thanks for the info guys - although I think we'll leave it as we found it..... ie most people put the tight coils at the top, but in the real world, it doesn't really matter.
Posted: Tue Nov 13, 2012 7:16 pm
Author: gray
An engineer once told me that the tight coils should go at the stationary , not the moving side. - like pigford says , it's an inertia issue
Posted: Tue Nov 13, 2012 8:29 pm
Author: Pigford
gray wrote:An engineer once told me that the tight coils should go at the stationary , not the moving side. - like pigford says , it's an inertia issue
....but I suppose in reality, it won't make the slightest difference either way
Posted: Tue Nov 13, 2012 9:37 pm
Author: Rhencullen
Pigford wrote:....but I suppose in reality, it won't make the slightest difference either way
To be fair guys, I posted this issue on a couple of forums, and got this response from my VFR friends
Alan wrote:What does the manual say? Or are these after market replacements for original linear springs? In which case what do the fitting instructions say?
The argument that having the tighter coils at the top will reduce the unsprung weight sounds right but I'd be surprised if you can actually notice the difference in the real world. Something that you're more likely to notice though is messing up the air gap. Because the oil level is usually set without the springs in it relies on the the springs displacing a certain amount of oil to give a certain air gap. The oil level is therefore specified for the springs being in a particular way up and I suspect a messed up air gap will be more noticeable than a couple of ounces of extra unsprung weight.
The VFR has progressive* springs fitted as standard. The 750 and 800 have the tighter coils down but the VTEC has the tighter coils up according to the service manuals. So it obviously depends on how they're designed to go and that's probably connected to oil level
* Strictly two-rate linear but one end is wound tighter than the other.
I think that this is the best point , as they are aftermarket springs and the fitting instructions are fairly vague and don't specify fitment .
tricky wrote: i wish there was some company that made linear springs for these old bikes, suited to you body weight, as i think these progressive things, are all made at the same place, somewhere in tingtong land, and packeged up for different brands.
as there is no indicated spring rate they must be a compromise/ or wrong all together.
Fair point though Tricky........
Posted: Tue Nov 13, 2012 10:11 pm
Author: pertonpc
My Z1-B had the tighter coils to the top when I stripped it down.
I'm pretty sure I was the first one since the factory to disturb them judging by the rest of it.
So that's how I replaced them. Can't remember seeing any tighter coils on my 650 springs but that was a while back.
from Mark