Bladders or no shock bladder? For most trucks, it’s pretty simple…build your shocks the way the manual says. The subject can get you scratching your dome, however, when you’re shopping for aftermarket shocks or if your stock shocks, such as with the Team Associated SC10 4×4, allow you to build them with or without bladders.
What’s in a Name?
Shocks without bladders are called emulsion style shocks which simply means the shock fluid and air inside the shock mix. Shocks with internal bladders are called, get this, bladder shocks.
Silicone shock fluid doesn’t compress well, so shocks need air in the shock body–it either needs to be mixed in with the fluid or separated from the fluid by a bladder. Let me explain. If the shock body was completely full of fluid, the shock would lock up (hydrolock) as the shock was compressed. This is because as the shock compresses, more of the shock shaft enters the shock body, and the shaft takes up an increasing amount of space as the shock compresses. In other words shock fluid gets displaced. The air compensates for the volume of fluid displaced by the shaft as the shock is compressed.
Which is Better?
In theory, for club racers running on typical rough off-road tracks that have jumps, bumps, ruts, dips, etc, emulsion shocks can work best as they tend to feel softer through compression and rebound. Again, in theory, smoother tracks with high traction call for bladder shocks. Does this mean bladder-style shocks won’t work on rough tracks and emulsion shocks won’t work on a blue groove track? Absolutely not.
It’s important to note that as the fluid and air mix in an emulsion, the shock fluid will feel lighter. That said, this difference may not even be detectable in most cases, but it is important that all four shocks are built with the same amount of fluid or you could, in theory (there’s that word again), have one shock that feels like it has 30 wt fluid, one that feels like it has 28 wt fluid, one that…well, you get the idea.
The main advantage of the emulsion design is that it is easier to avoid hydrolock and this type of shock won’t pack up (get significantly stiff) during fast compressions and during the final amount of compression. That’s the long winded way of saying trucks with emulsion shocks often land smoother. Improperly building either design can lead to hydrolock, but if you bleed the excess fluid out of an emulsion shock with the shaft fully compressed, hydrolock should be next to impossible.
Converting Bladder to Emulsion
Just about any shock can be converted from bladder style to emulsion. The converse isn’t true, however. To convert a bladder shock to emulsion, simply use a sharp hobby knife to remove the domed part of the rubber or silicone shock bladder. You’ll essentially create an O-ring to use in its place. Make sure you can find replacement bladders before performing this mod so you can go back if you decide to.
Team Associated’s SC10 4×4 Shock Building Tips
Team Associated factory driver Richard Saxton