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weight scaling suspension

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I ride a YZ250FX 2016 and i beefed up the springs to 5.2N in front and 65N in rear and I use stock valving. I understand and feel that the valving are no good for this springs and i need to beef up the rebound damping. But how does it work with the compression valving, should it be softer or harder to work properly with these stiffer springs. And is it low speed or high speed that need some changes, both reb and comp.  A Suspension-guy told me that stock valving only work properly with one or two step up or down in spring rate and if you go beyond that you need to revalve. So if anyone have some good ideas I will be very thankfull for that.

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You often need a revalve when making bug jumps in springs

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You often need a revalve when making bug jumps in springs

I understand i need revalve the rebound to take care of the increased stored energy in the spring when it returns. But how is it with compression, should it be stiffer so it can take care of the higher mass of the rider when it compress.

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Comp much less changes,sometimes a tad softer

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The hard part of suspension tuning is getting the right low speed damping to control the chassis, the right high speed to control the wheels and the right transition between the two so the shock works across the speed range. Yamaha worked all of that out in tuning the stock suspension. The idea of weight scaling is to preserve the tuning work the factory did and simply scale damping to correct for the spring rate change.

To keep the suspension response Yamaha intended for the stock setup you have to increase both compression and rebound damping. By weight scaling the increase needed is equal to the square root of the spring rate ratio and that increase is needed across the speed range - both at low speed and at high speed. That's the physics of it. The hard part is figuring out how many shims to add and where to add them in the stack to get that damping force increase.

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So if'n the valving in your fork is speed sensitive, suspension speed that is, then why would there need to be a change in damping to accommodate more spring rate?  More spring rate will keep the fork higher in the stroke, less sag, higher ride height.  I'd think you should be able to make any and all necessary adjustment with the low speed clickers. 

According to the rules, spring rate is what controls SAG, the installation of new springs will change your SAG measurement.

 

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When changing springs you don't have to change damping, it's not like the wheels are going to fall off.

But stiffer springs drive the suspension into an under damped condition. Closing the clickers helps but that just changes the bleed. To restore response of the suspension you have to go to a stiffer shim stack. That holds the stack closed longer so that the clickers make a difference and increases high speed damping to get control of the stiffer spring.

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