Which Shock is right for me?
Author: Nick Date Posted:5 April 2023
We represent five suspension companies in Australia: KYB, Showa, TracTive, TFX & Yacugar. We resell YSS and Wilbers too.
We service all the above plus WP, Ohlins, Sachs, Boge, Soqi (Soki) and many more.
There are basically three types of motorcycle shock absorber available from most manufacturers: emulsion type, internal floating piston type (IFP), and reservoir (piggyback) type.
Emulsion Shocks:
Emulsion means the nitrogen gas and shock oil are allowed to mingle. There are a few reasons why emulsion designs are common. First, they cost less to build so they generally have a more attractive retail price. Secondly, in very short shock builds there may be no room for a separation piston without significantly reducing stroke so it is built as an emulsion instead. Thirdly, in some applications such as the front shock on a BMW Telelever equipped street bike, the leverage ratio is lower and the spring rate and damping forces are light. Moving the mass of a separation piston in an IFP design requires some energy and this can make the shock less responsive. Plus, with the low spring rates on these front Telelever emulsion shocks, overheating and cavitation is typically not a concern.
When they are adjustable, these simpler shocks are often fitted with 1-Way Adjustability; when you turn the clicker you are adjusting both the compression and rebound damping at the same time.
The emulsion design can be problematic however when used as a rear shock if shock temperatures climb from riding on roughs tarmac/dirt roads for extended periods. The oil cannot dissipate the heat to the cylinder wall as effectively when it has gas molecules in it, and the vapor pressure drops as the oil temperature rises. Under these conditions the oil cavitates which means you're pushing foamy oil through the valving which leads to damping fade. If the shock gets hot enough, seal failure can occur.
In short, emulsion shocks work fine on street bikes where high shock temperatures are generally not an issue. They are not recommended for adventure bikes however, which might be ridden off road or where riding on rough asphalt or dirt roads for extended periods is common.
IFP Shocks (Internal Floating Piston):
IFP shocks are the next step up. An additional piston is added to the assembly to keep the oil and gas separate. Because the oil is just oil with no gas molecules in it, it can shed heat to the cylinder wall better which gives better thermal stability. These shocks are usually produced with a 6082 heat treated aluminium cylinder which conducts heat better than the steel cylinders commonly used with emulsion shocks. They are a middle ground of both cost and sophistication.
Being an intermediate step, these shocks are mostly available as either 1-Way or sometimes 2-Way adjustable, where the compression and rebound can both be adjusted separately via 2 different clickers.
Reservoir Shocks:
Reservoir shocks are at the top of the list in terms of adjustability, performance and heat management. By adding a reservoir (either riding piggyback on the main shock tube or via a separate canister mounted remotely via a hose), the nitrogen is no longer inside the shock, it is contained in the reservoir. This means that instead of the shock being only half full of oil as is the case with emulsion and IFP designs, the shock is now 100% full of oil.
With this additional oil capacity and the increased surface area of the shock created by the added reservoir, overheating is rare regardless of terrain. In addition, a reservoir shock typically has a more advanced compression circuit.
In the case of the common high/low speed design, the compression stroke is valved based on the velocity of the oil. Low speeds of compression are handled by the low speed path which has an adjuster, high speeds of compression are handled with an additional circuit that opens when there is high velocity demand, and it also has an adjuster.
These reservoir shocks are ideal for adventure bikes which are ridden off road, and will give any rider the best ride quality over the roughest roads. Reservoir shocks also give you ultimate adjustability due to the 3-Way damping adjusters (rebound, high and low speed compression) provided. Even if you never touch the clickers, the more advanced design will do a better job of smoothing out the biggest bumps.
In Conclusion:
If all the shocks were all the same price, we would only sell reservoir shocks because they are superior to the other designs. But they are not all the same price and frankly not every rider needs a reservoir shock. You have to look at your budget and your needs.
Most of our street bike customers are delighted with the improvements that they enjoy from upgrading to something like the Wilbers emulsion shocks; model 630 front and 640 rear, or the TFX IFP shocks model 130 front and 140 rear.
Most add a hydraulic preload adjuster to the rear shock making it easier to adjust sag when your loads change. If your loads don't ever change, you could omit the HPA and save your pennies by buying the rear shock with just the threaded preload ring adjuster.
Due to the fact that we carry and upgrade so many brands, we offer unbiased recommendations based on your budget and riding conditions. In many cases the standard shock can be repaired and modified to better suit your needs for cheaper than a new coilover setup - see our Featured Bikes Pages to get an idea of how much better a stock suspension can be made.