NC 700X shock adjust ratio

[gbony]

Hello,
I am trying to adjust the rear rider sag on my 2012 NC700X. After futzing around trying to do it with the shock on the bike I pulled the shock out (about a half hour job) and cleaned it up and put some penetrating oil on the adjustment threads. I want to gain about a half inch of ride height by adjusting the shock preload before I reinstall it. Anyone out there know about how many adjuster rotations would get me close to that so I minimize the adjustment needed with the shock installed?

Thanks,
Guy

 

[jeremyr62]

I should know this but I don't. It's normally a question of suck it and see. Half an inch is not a lot so about two full turns would be my best guess. I can understand why you took it off the bike to adjust it. I found it almost impossible to turn when installed. However if you are OK with marking and slightly deforming the adjuster rings, a long thin drift and a big hammer worked for me.

 

[dduelin]

Here is a NC700X shock removed at 1,800 miles. The preload is where the factory set it. The length of the threaded area on the shock body is 1 1/8" and the factory preload setting leaves about 9/16" of additional preload if the threaded ring is turned all the way to the end of adjustment - using all the available threads to compress the spring as much as is possible. I extrapolate from the exposed threads below the ring that 4 turns of the ring adds 1/4" of preload so the desired increase of 1/2" in ride height of half an inch would be about 8 turns.

 

[jeremyr62]

Does that answer his question though? He is asking about ride height. I think you have done the calculation for the shock but he wants to know how that translates into ride height. Unless I am being thick.

 

[dduelin]

Does that answer his question though? He is asking about ride height. I think you have done the calculation for the shock but he wants to know how that translates into ride height. Unless I am being thick.

The shock has a straight rate spring therefore 1/2" more of preload raises ride height 1/2".

All preload does is affect where the shock rides or operates in it's available range of travel. It does not make the spring "stiffer."

Thanks for the Q, I edited post #3 to clarify.

 

[jeremyr62]

We will get there in the end
He is asking if you change the preload 1/2 inch on the spring does that translate to 1/2 inch on the ride height after you go through the linkage.
If what you suggest is true then the travel on the shock is the same as the suspension travel? I don't think that's the case.
Velocity ratios and all that stuff..

 

[670cc]

We will get there in the end
He is asking if you change the preload 1/2 inch on the spring does that translate to 1/2 inch on the ride height after you go through the linkage.
If what you suggest is true then the travel on the shock is the same as the suspension travel? I don't think that's the case.
Velocity ratios and all that stuff..

I wondered this, too, but then I realized that adjusting the rings is basically the same as adding or removing a spacer at the top shock mount. If you change the point the spring is mounted on the shock body, the only thing it does is raise or lower the bike height as measured at the point of the upper shock mount. The linkage doesn’t matter. It may be slightly different than 1:1 only if the shock is not truly vertical.

 

[jeremyr62]

Suspension really is the gift that keeps on giving. I get it now..

 

[gbony]

Thanks for all the info. I put it all back together and this is what I found. In short, each full turn on the shock preload raises the ride height and reduces the sag by 0.20 inches. In other words, 5 full revolutions of preload raises ride height and reduces sag by an inch. To verify this, I added 2.5 turns of preload and got the 1/2 inch of sag reduction I was looking for. If you are up for some math I can explain why this is. To start with, the thread pitch on the shock is 1.25mm. I measured the shock travel at 1.5 inches and the wheel travel is 5.9 inches, so close enough to a 1:4 ratio. Multiplying the 1.25mm by 4 gives 5mm of wheel travel for each turn of preload at the shock. An inch is 25.4mm, so every turn of the preload gives 5/25.4 of an inch or close enough to 1/5 or 0.20 of an inch.

 

[jeremyr62]

And just when I thought it was safe to go back in the water. Without feeling smug at all, as I guessed 2 turns, how is what the OP has just posted consistent with the observation that adding preload is equivalent to a spacer sat on top of the shock and the linkage doesn't matter? He appears to have just confirmed that adding 3.125mm of preload to the shock does get magnified by the linkage and results in 3.125x4=12.5mm of ride height. My way of thinking about it is it depends where you put the spacer. If the suspension can be simplified to a pair of scissors then if the spacer sits outside the arms the scissors if does not encounter the fulcrum so the ride height increase is the same as the spacer. But if the spacer sits inside the scissor arms (akin to the shock and preload) it does encounter the fulcrum and the linkage ratio is applied. Make sense?