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FZS600 Fazer / Fork springs - cutting them makes them stiffer, no need for aftermarket springs?
« on: 06 August 2013, 01:58:22 pm »
OMG here he goes again I hear you cry 
Fork springs, we all know FZS600s have a mushy front-end. Indeed, the springs seem to be set up for an eight stone rider, and anyone heavier can bottom them out under moderate to heavy braking. This offsets the advantage of those monster blue-spot calipers more than a little.
But why this setup on this bike? The forks contain dual-rate progressive springs to give the one-spring-suits-all-riders and helps with budgetary constraints of Japanese motorcycle suspension. The solution to this cost-cutting exercise is usually expensive for us; people order replacement springs from aftermarket manufacturers to compensate, from £60-120 (just look at Hyperpro's bargain kit prices on ebay).
But there is a cheaper way, as reducing the length of the fork spring makes it stiffer. Cheaper as in £0 (although you will have to replace or lengthen the hollow metal spacers inside the forks, say £10 for replacements). If you're big-boned, cutting coils away means the spring can be set up much more closely to your weight and such adjustment allows jumping from the standard 0.7kg/mm rate up to 0.95kg/mm, therefore covering most riders weights.
There is a calculation that can be performed to estimate how many coils should be removed. Normally it's easy to work out for a linear spring, progressive springs are harder but hey, there's bound to be some braniacs out there who can provide the solution for our springs?
Calculation below:
http://www.strappe.com/spring_rate.html
And here's the application of it, admittedly on an SV650:
http://www.strappe.com/suspension.html#rate
Admittedly the mod requires longer fork spacers, an angle grinder, blowtorch and bravery. Chopping off the tightly-would coils reduces comfort, whereas attacking the other end has a stronger effect on the overall spring-rate. I guess it depends how you want the bike to feel (I've removed the comfort coils, although admittedly I have VFR750 springs inside my forks).
Discuss.
EDIT: For anyone who thinks shortening fork springs doesn't make them stiffer, the following link addresses such concerns:
http://www.thumpertalk.com/topic/889824-shorteningcutting-front-fork-springs/
Fork springs, we all know FZS600s have a mushy front-end. Indeed, the springs seem to be set up for an eight stone rider, and anyone heavier can bottom them out under moderate to heavy braking. This offsets the advantage of those monster blue-spot calipers more than a little.
But why this setup on this bike? The forks contain dual-rate progressive springs to give the one-spring-suits-all-riders and helps with budgetary constraints of Japanese motorcycle suspension. The solution to this cost-cutting exercise is usually expensive for us; people order replacement springs from aftermarket manufacturers to compensate, from £60-120 (just look at Hyperpro's bargain kit prices on ebay).
But there is a cheaper way, as reducing the length of the fork spring makes it stiffer. Cheaper as in £0 (although you will have to replace or lengthen the hollow metal spacers inside the forks, say £10 for replacements). If you're big-boned, cutting coils away means the spring can be set up much more closely to your weight and such adjustment allows jumping from the standard 0.7kg/mm rate up to 0.95kg/mm, therefore covering most riders weights.
There is a calculation that can be performed to estimate how many coils should be removed. Normally it's easy to work out for a linear spring, progressive springs are harder but hey, there's bound to be some braniacs out there who can provide the solution for our springs?
Calculation below:
http://www.strappe.com/spring_rate.html
And here's the application of it, admittedly on an SV650:
http://www.strappe.com/suspension.html#rate
Admittedly the mod requires longer fork spacers, an angle grinder, blowtorch and bravery. Chopping off the tightly-would coils reduces comfort, whereas attacking the other end has a stronger effect on the overall spring-rate. I guess it depends how you want the bike to feel (I've removed the comfort coils, although admittedly I have VFR750 springs inside my forks).
Discuss.
EDIT: For anyone who thinks shortening fork springs doesn't make them stiffer, the following link addresses such concerns:
http://www.thumpertalk.com/topic/889824-shorteningcutting-front-fork-springs/
.
. Comes with preload adjustment spanner & original box.
