China's finest rear shock

[kaz]

I offered 75$ for this nice RSV shock on ebay -
APRILIA RSV4 RR RF 2016 REAR SUSPENSION SHOCK ABSORBER SACHS LIKE NEW 900 MILES | eBay

Made a mistake with the shipping method, it stopped in customs and I'm unlikely to ever see it (Used suspension not allowed into Israel).

Prices for new / aftermarket shocks aren't reasonable to my sensibility (#itsaspring), but google offered this NC700 specific Aliexpress listing -
Rear suspension shock absorber 310mm For HONDA NC700X NC700S NC750X 2012 2013 2014 2015 2016 2017-in Covers & Ornamental Mouldings from Automobiles & Motorcycles on AliExpress - 11.11_Double 11_Singles' Day

Says it has this and that adjustment, but I don't see the gas tank thingie like on my (never to actually be used by me) Sachs.

Then there's these -
Universal 320mm/340mm/355mm Motorcycle Air Shock Absorber Rear Suspension For Yamaha Motor Scooter ATV Quad Black & Gold-in Falling Protection from Automobiles & Motorcycles on AliExpress - 11.11_Double 11_Singles' Day
With the tank and everything, but not bike specific.


So, how bad of an idea is it to use Chinese suspension? What's the worst that could happen?

 

[1wiseguy2]

That tank thingy holds hydraulic fluid. Not gas. Don't know the answer to your question.
Feel for you losing your shock. That just has to hurt.
Good luck finding what you need.

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[TacomaJD]

That tank thingy holds hydraulic fluid. Not gas.

I'm pretty sure there is both gas and oil in the piggyback reservoir, but mostly gas. The oil in performance shocks is most always pressurized by a nitrogen gas charge to help stabilize the oil during extreme use and heat to keep it from cavitating (creating air bubbles). The shock body itself should be completely full of oil barely up into the piggyback reservoir (or remote reservoir, if applicable), where there is then a floating piston that separates the oil from the nitrogen charge on the other side of it. If the reservoir was full of oil too, that would mean the entire shock system was full of oil and it would hydrolock and fail.

The standard shocks on our NC's that do not have a reservoir are likely emulsion shocks. An emulsion shock has no dividing piston between the oil and nitrogen charge, which is why they should not be installed upside down. They are built to function in an upright position. The nitrogen gas is suspended on top of the oil, but under extreme use of the shock, emulsion shocks can still cavitate even though there is a nitrogen charge present. This is why higher performance shocks have either piggyback or remote reservoirs. They allow the shock system to contain more volume of oil for damping through the full stroke of the shock, and a charge of nitrogen divided by a 2nd piston in the reservoir that keeps the gas and oil separate. This system allows the shock to endure much more extreme use before reaching the point of cavitation.

 

[1wiseguy2]

So it acts as an accumulator for the shock then. I understand about the hydro lock. Makes sense.

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[TacomaJD]

So it acts as an accumulator for the shock then. I understand about the hydro lock. Makes sense.

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I don't know if that is the term I would use, but think of it like this. Often times in suspension setups, even on long travel rock crawlers, which is where most of my suspension knowledge derives, there is always a length limitation between point A and point B aka upper and lower shock mounts. It's entirely possible to build a motorcycle shock that has no external reservoir, but has more oil and a 2nd piston toward the top dividing the oil and nitrogen. Problem with that is that it would be too long of a shock to cram in between a swingarm mount and a frame mount on a motorcycle. A reservoir acts as an extension of a shock so that it can perform better, but off to the side. A piggyback style if there's room to fit it, or remote reservoirs if room is tight and you need to mount the reservoir in a spot that allows for easier access for tuning purposes.

 

[kaz]

Didn't notice the shipping is another 80$. Too much for a Chinese susp., guess I'm ordering a Tuono shock every couple of months until one gets through.

I do wonder whether the Chinese variants are worth their relative cost - Is a Chinese shock 1/4th the shock a 600$ shock is?

 

[potter0o]

Have you looked into any of the YSS shocks? I was researching this as a reasonably price option should mine fail. I have the "S" model so I think the shocks size is slightly different.

 

[kaz]

I saw them mentioned here, but I think(?) a used sportbike shock would be a better performer for the value.

Saw our shocks' specs in this thread:

1. Eye center to eye center length of the shock. 12 5/16" 315mm
2. Outside diameter of the spring. 3.125" 80mm (distance between linkage arms is 90mm).
3. Free length of the spring. At least 9.5" 240mm -still on the shock.
4. Width of the upper mount (through which the mounting bolt goes) ?
5. Width of the lower mount. 1.58" 40mm
6. Shock travel. 1.63" 41.5mm (used a telescope gauge - should be very close)
7. Spring wire diameter. 0.5" 12.80mm

Which ones are critical when looking for an alternative shock? There are many sportbikes out there