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le druide

shock spring free lenght

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le druide

Hi all,

Is somebody can give me the length of the rear spring when it is not installed on the shock ( free length) 

I want to replace the MT07 spring with a FJ09 spring if the dimensions are the same, I think the Mt07 spring rate is 625 lb/in

vs the 560 lb/in for FJ09,  I need a softer spring to have the correct 35mm sag , actual sag is only 10mm at the lowest preload !

Thanks! 

 

 

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AP996

Just measured mine 193mm about 7 and half inches.

Hope that helps

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le druide
4 hours ago, AP996 said:

Just measured mine 193mm about 7 and half inches.

Hope that helps

Thanks for your help , same length as the FJ09 spring , that's good news !

 

 

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RalphG

Can someone enlighten me as to why the 430# FZ/MT-09 with an full tank weight of about 430# should have a softer rear spring than a 403#  07?.  Seems inverted...

Thanks, Ralph 

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blackout
16 minutes ago, RalphG said:

Can someone enlighten me as to why the 430# FZ/MT-09 with an full tank weight of about 430# should have a softer rear spring than a 403#  07?.  Seems inverted...

Thanks, Ralph 

It's a different linkage design.  A linkage with more leverage on the shock will need more shock spring rate to counter the weight of the bike and rider.  The FZ-07 has a poor motion ratio so it needs rear spring rates higher than most bikes.   


Craig Mapstone
Upstate New York

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mossrider
Just now, RalphG said:

Can someone enlighten me as to why the 430# FZ/MT-09 with an full tank weight of about 430# should have a softer rear spring than a 403#  07?.  Seems inverted...

Thanks, Ralph 

Magic.  Seriously, leverage ratios. Linkage, lever and fulcrum lengths. There are as many mounting configurations as there are motorcycles. With proper physics I suppose you could use an ink pen spring in a semi.

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RalphG

Thank you for the enlightenment.  When I began riding, bikes had rigid rear sections (not choppers, came OEM from the factory this way) or had sprung hubs or twin Girling shock absorbers at the rear.  Admittedly, I am a dinosaur.

Ralph

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twf
3 hours ago, blackout said:

It's a different linkage design.  A linkage with more leverage on the shock will need more shock spring rate to counter the weight of the bike and rider.  The FZ-07 has a poor motion ratio so it needs rear spring rates higher than most bikes.   

Actually FZ07 is pretty much in the middle. Most bikes are from 500-800.

For example on some Triumphs, Kawasaki 650, Yamaha R3 we use springs over 1000#.

 

 

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blackout
23 minutes ago, twf said:

Actually FZ07 is pretty much in the middle. Most bikes are from 500-800.

For example on some Triumphs, Kawasaki 650, Yamaha R3 we use springs over 1000#.

 

 

Over 1,000 on a R3.   Wow, must be a short stroke shock.  Makes valving trickier as the piston moves less per wheel travel, but I guess the shock guys have that figured out.


Craig Mapstone
Upstate New York

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twf
3 minutes ago, blackout said:

Over 1,000 on a R3.   Wow, must be a short stroke shock.  Makes valving trickier as the piston moves less per wheel travel, but I guess the shock guys have that figured out.

One of my guys runs 1100 on his race bike. There is no linkage, shock is direct frame to swingarm.

On Kawi 650 we run 1200. I was running 1300 on my old Honda hawk. :)

Valving is easy.

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blackout
23 minutes ago, twf said:

One of my guys runs 1100 on his race bike. There is no linkage, shock is direct frame to swingarm.

On Kawi 650 we run 1200. I was running 1300 on my old Honda hawk. :)

Valving is easy.

Is his bike a KTM?


Craig Mapstone
Upstate New York

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twf
2 hours ago, blackout said:

Is his bike a KTM?

R3

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