Bilstein: Monotube vs. Twintube Shocks

Bilstein: Monotube vs. Twintube Shocks


Next we’re going to talk about the
difference between a monotube shock and a twintube shock. Now every shock absorber offered by Billstein for a light truck application is a mono tube high-pressure gas shock. And here’s the mechanical differences between the two. From the outside you could say they look relatively similar, but as I start taking these apart you’ll notice they are actually rather different. When I pull out the guts of both of them you’ll see the mono tube shock, you see a piston, and a piston rod. But, when I pull out the guts of the twintube you see another
tube, which hence the name twintube. When I take the actual piston or rod assembly out of the twintube it will reveal what’s going on between the two. As
you will see, just in diameter is a lot larger in the monotube shock. The oil
capacity in the monotube shock absorber is obviously a lot more as well,
but Billstein, as I said before, was a monotube high-pressure gas shock. Most
people think that when they hear gas shock that they’re full of gas but that
is not actually true. Every shock works on a hydraulic principle where a piston
travels through hydraulic fluid. In a monotube shock what Billstein has
created is a gas chamber and a dividing piston that separates the gas from the
oil. So you can see it is a hydraulic operated shock, except for the oil’s
placed under direct pressure. What this does it keeps the oil consistent.
Now if I remove the pressure this will demonstrate what’s going on in a
hydraulic twintube damper and as you see as I cycle the piston rod in and out
the oil that is not placed under pressure cavitates. When the shock is
cavitated your performance loss is exponential and obviously you’re going
to have a lot flow to your feel out of the vehicle and no consistency
whatsoever. Now, if I pump this up you can see how
quickly the cavitation goes away this demonstration what I’m using air in
Bilstein shock absorbers we use nitrogen gas. As you can see as I cycle it a few
times, the air bubbles essentially go away.