Static sag

[bicyclist]

I replaced the stock shock with a Hyperpro. Static sag with the new shock is only about ⅛". That is the difference between a measurement with the bike on the centerstand and with the bike unladen on the wheels. That's obviously not correct. Anyone know what the static sag should be?

edit: Answer and info appear in post #11.

 

[Phil Tarman]

I don't know this, but it seems like I've read somewhere that it should be 25-30% of the available travel from the static unladen position to full compression. Sure seems like it ought to be more than 1/8".

Seems like Hyperpro ought to be able to tell you the answer.

 

[DirtFlier]

The laden sag should be 25-30% but the static sag should be much less.

On my NC700X with a HyperPro shock, they recommend 15+/-5 mm of static sag but that bike has progressive linkage and is not direct like the NT shock.

 

[bicyclist]

On my NC700X with a HyperPro shock, they recommend 15+/-5 mm of static sag but that bike has progressive linkage and is not direct like the NT shock.

OK, found the sticker that says 12mm +/- 5mm.

Now the question is how much should I back off the spring adjustment to get that 12mm since the shock is at a pretty good angle. I don't want to strain my aged brain trying to figure out the geometry. I think that a little too much is better than not enough because I don't want to have to remove and replace the shock more than once since it's a major PITA. If it's a little too much, I can compensate by cranking up the hydraulic preload.

 

[DirtFlier]

It's not so much about the angle of the shock as it is how much one turn of the preload adjuster will reduce static sag. And I would suggest painting a white reference line on the adjuster so you'll know when you've made 1/4 turn, 1/2 turn, full turn, etc. Without a reference mark, it's pretty hard to tell!

ps. Is the preload adjuster inaccessible with the shock mounted on the bike?

 

[bicyclist]

ps. Is the preload adjuster inaccessible with the shock mounted on the bike?

Totally inaccessible. And you have to remove the wheel to R/R the shock. I don't want to have to do it more than once. The angle of the shock complicates things. If the shock were vertical, at the end of the swingarm, it would be simple. You need another ⅜" of sag? Crank the spring adjuster ⅜". With the NT setup, a small adjustment will have a large effect. Guess I'm going to have to call them for advice.

 

[Frosty]

In an earlier lowering link:
http://www.nt-owners.org/forums/showthread.php?6819-Yet-Another-Lowering-Thread-via-a-shorter-Rear-Shock-Eye

Dirflier posted:
"The HyperPro shock eye is only 10 mm shorter than the original but because of the leverage ratio of wheel travel-to-shock travel (approx 3.6 to 1), this results in the seat being lowered 35 mm (1-3/8")."

That was my experience as well, but that also includes raising the fork tubes in the clamp 12 mm. I don't think this ratio will give you the number that you are looking for, but it may confirm the number from HyperPro. It is no fun to R/R that shock and it is not a simple geometry problem. Let us know what they say.

 

[bicyclist]

Thanks. If that leverage ratio is correct, i should need to back off the nut by 2.5 mm to get 9 mm more sag. I shot off an email, waiting to hear what they say.

 

[DirtFlier]

[Totally inaccessible (preload adjuster). And you have to remove the wheel to R/R the shock. I don't want to have to do it more than once.]

When I ordered a custom-made shock from Works Performance for my NT, I specified it must have the preload adjustment at the bottom for that very reason. That was something unusual for them so it took a while but I'm still happy with the results. It now has nearly 30k miles on it so I plan to send it to them over this coming winter to have it rebuilt which means new oil & seals. That usually costs around $100 but I feel it's worth the expense.

The HyperPro shock on my NC700X came with a coupon for a free rebuild!

 

[bicyclist]

Klaus at EPMPerformance says that each revolution of the adjustment nut equals 1.5 mm of movement. If I back off the nut 2 ? turns, that should give me 17 mm of static sag, which is at the limit of the recommended 12 mm +/- 5 mm. I could then crank the hydraulic adjuster to get 12 mm. He's waiting to hear what HyperPro has to say and I'm waiting for cooler weather to do it.

Klaus also said that the hydraulic adjuster is good for 9 mm of travel.

 

[bicyclist]

I heard from Klaus, who forwarded a reply from HyperPro. They said that the shock travel to wheel travel ratio is 1:3.62 and suggested that I back off the nut 2.5 to 3 revolutions and compensate for too much sag with the hydraulic adjuster, verifying my thoughts. So, I backed off 3 revolutions and cranked the adjuster a couple of turns to get what I wanted.

To repeat above info, each revolution of the nut equals 1.5 mm of spring movement. The hydraulic adjuster is good for 9 mm of spring movement. Static sag should be 12 mm +/- 5 mm.