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Offline zed9

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Pending Suspension Upgrade
on: January 26, 2019, 03:26:11 PM
Cabin fever is setting in and I'm thinking of upgrading my suspension sooner rather than later.

Fork Springs?
I weigh 185 pounds (84 kg) in my undies. Has anybody resprung their forks for this weight class and what rate did you go to? I'm not going to race or do track days. I mainly ride spirited back roads and I don't want an overly stiff front end. I would like to set the sag/preload in the first 25-35 % of its adjustment range (which will allow me some room for weight gain and tank bag).

Revalving is happening as well. I will also be dealing with the shock at the same time.

Any info as to ride quality will be a help as to my decision with what springs I go with.



Offline JohnCW

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Re: Pending Suspension Upgrade
Reply #1 on: January 27, 2019, 06:36:51 AM
*Originally Posted by zed9 [+]
Cabin fever is setting in and I'm thinking of upgrading my suspension sooner rather than later.

Fork Springs?
I weigh 185 pounds (84 kg) in my undies. Has anybody resprung their forks for this weight class and what rate did you go to? I'm not going to race or do track days. I mainly ride spirited back roads and I don't want an overly stiff front end. I would like to set the sag/preload in the first 25-35 % of its adjustment range (which will allow me some room for weight gain and tank bag).

Revalving is happening as well. I will also be dealing with the shock at the same time.

Any info as to ride quality will be a help as to my decision with what springs I go with.

At 84Kg undressed you'll be over 90 Kg in gear, and certainly with a tank bag just about the same 95Kg as me.  Now my bike is not a Z900 but virtually identical weight.  After experimenting with several  different weight springs I run 0.90 Kg/mm in the front. 

0.85 gave a beautiful plush ride on bad back roads, but lacked high speed stability.  0.95 give great high speed stability and corner control on track smooth roads.  But you get beat to death on bad roads.   So that is why I found the 0.90 Kg/mm's a good compromise for a road bike riding a range of conditions.

At the end of the day don't sweat too much as springs are relatively cheap.  Also, just be aware there is nothing stopping you running different rate springs in each fork.  For example if you found a pair 0.90's just a tad soft, and 0.95's too harsh, nothing stopping you sticking a 0.90 in one fork, and a 0.95 in the other to give you a combined 0.925 spring rate.
Last Edit: January 27, 2019, 06:38:40 AM by JohnCW

Offline Cazzy_R

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Re: Pending Suspension Upgrade
Reply #2 on: January 27, 2019, 08:24:42 AM
Are the stock springs linear or progressive?
Judging by the way they (it) responds to adjustment I feel they are progressive.
Anyone know for sure?
Tighten it 'til it strips then back it off half a turn.

Offline Marco

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Re: Pending Suspension Upgrade
Reply #3 on: January 27, 2019, 11:28:01 AM
Linear.  I've been speaking to Ktech about their fork piston kit and they reckon 9s are right for me .
I'm 95kg in riding gear.
Z1000.  I had a 900 so you'll never get rid of me. NEVER!

Offline Cazzy_R

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Re: Pending Suspension Upgrade
Reply #4 on: January 27, 2019, 04:36:04 PM
*Originally Posted by Marco [+]
Linear.

Thanks. Another theory out od the window.  :034:
Tighten it 'til it strips then back it off half a turn.

Offline zed9

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Re: Pending Suspension Upgrade
Reply #5 on: January 27, 2019, 05:03:33 PM
*Originally Posted by JohnCW [+]
At 84Kg undressed you'll be over 90 Kg in gear, and certainly with a tank bag just about the same 95Kg as me.  Now my bike is not a Z900 but virtually identical weight.  After experimenting with several  different weight springs I run 0.90 Kg/mm in the front. 

0.85 gave a beautiful plush ride on bad back roads, but lacked high speed stability.  0.95 give great high speed stability and corner control on track smooth roads.  But you get beat to death on bad roads.   So that is why I found the 0.90 Kg/mm's a good compromise for a road bike riding a range of conditions.

At the end of the day don't sweat too much as springs are relatively cheap.  Also, just be aware there is nothing stopping you running different rate springs in each fork.  For example if you found a pair 0.90's just a tad soft, and 0.95's too harsh, nothing stopping you sticking a 0.90 in one fork, and a 0.95 in the other to give you a combined 0.925 spring rate.
Great info. This is what I need. I'm sending my suspension out to have it modified. I'm using Dohearty Motosports in Indiana, he specializes in suspension and worked wonders with my other bike for not a lot of money.
 
We have only emailed thus far but he told me the shock is worth modifying. When I talk with him over the phone I'd like to have some input as to what others have experienced so far with this bike. He hasn't yet worked on the z900 suspension yet but does the mt09.
My forks bottom out even with preload full tight using a zip tie to monitor it. I'm guessing lack of compression valving over bumps.

I would have guessed the factory fork springs were 80-85 kg. He uses a spring dyno so maybe he can tell us for sure.

As I said, I'm not racing but would enjoy stability in higher speed sweepers and back road bombing which includes rough surface tight corners.
My style is I pretty much like to connect a bunch of tight corners then lay back and make believe Valentino Rossi couldn't have done any better (LOL).
I'm not one to ride constantly on the bitter edge while keeping up a blistering pace all day. I've done that in the past, too risky. It usually only happens when I ride with a certain couple of guys. I keep up no problem but am becoming more cautious as time goes by. Not scared just cautious. I speed when it safe to.




Offline zed9

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Re: Pending Suspension Upgrade
Reply #6 on: January 27, 2019, 05:13:20 PM
*Originally Posted by Marco [+]
Linear.  I've been speaking to Ktech about their fork piston kit and they reckon 9s are right for me .
I'm 95kg in riding gear.
Same here, especially in my Vanson jacket. The thing weighs a ton.
I'm thinking 90 as well but will know better when I talk to Jamie at DMr.
He put 1.0 kg fork springs in my other bike but that bike has a wet weight 80 pounds more than the z900.

Offline zed9

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Re: Pending Suspension Upgrade
Reply #7 on: January 27, 2019, 05:58:04 PM
*Originally Posted by Cazzy_R [+]
Thanks. Another theory out od the window.  :034:
What theory?

Offline Marco

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Re: Pending Suspension Upgrade
Reply #8 on: January 27, 2019, 06:06:34 PM
Standard fork springs are 8s
Z1000.  I had a 900 so you'll never get rid of me. NEVER!

Offline Cazzy_R

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Re: Pending Suspension Upgrade
Reply #9 on: January 27, 2019, 07:52:39 PM
*Originally Posted by zed9 [+]
What theory?

 My theory that the stock springs may be progressive.
 When I adjusted the front preload I did not find that the rider sag altered in proportion to the amount of turns I was adding.
 It was only when I got to around 12+ turns in that they started responding as I expected.
 Also I noticed that adding preload made the forks feel stiffer when suspension theory, preached by the all knowing, say that adding preload only affects ride height and not stiffness with linear springs.
 But Marco has changed his springs and says stock are linear.   :006:

 Glad you asked?  :164:
Tighten it 'til it strips then back it off half a turn.