Tinker Tuesdays #3: How to Install/Set Up a Rear Shock

There are a plethora of rear shocks to choose from on the market and with prices coming down lower and lower, upgrading can be very tempting. Rock Shox and Fox are leading the market in affordable, high performance shocks and have great ranges to choose a shock from. If you find yourself with a shiny new (or second hand!) shock on your doorstep but realise you've never fitted one before, don't stress! Here's a helpful guide to the basics of fitting and setting up a rear shock.

There are a wide range of shocks to choose from, so do some research to find the right one for your needs.
Photo by Steven Rummukainen

1. Make sure you purchase the right size shock for your bike. There are two measurements you must take note of - the eye to eye length (overall length of the shock) and the stroke length (the distance the shock compresses). These two measurements must be identical to your old shock.

Remember to hang onto the bushings from your old shock as you'll need them when installing your new one!
Photo by Steven Rummukainen

2. Install the bushings onto your shock. Bushings can occasionally be removed by hand, or with careful use of a flat head screwdriver. Particularly stubborn bushings may need to be pressed or tapped out. Installing bushings is the reverse - simply push them back in, or tap or press in if they are a tighter fit. Each bike has its own set of specific bushings used to fit the shock onto the frame, and make sure you either use your bikes existing bushings or purchase the correct ones. You can find bushings on websites like chainreactioncycles.com, or if you want help, consult your local bike shop.

Don't overtighten those bolts! Also, make sure to check them over time as they can rattle loose.
Photo by Steven Rummukainen

3. Install the shock by doing up the mounting hardware on your bike frame. Bike frames can vary greatly and consult your owners manual if in doubt of how your hardware fits together. However, manufacturers usually aim to make this process as simple as possible and it should be straightforward.

Keep checking your shocks pressure over time, as they can slowly leak a bit of air.
Photo by Steven Rummukainen

4. Next, we have to set the shock up to your body weight. In this instance, we are installing an air shock. Air shocks are highly pressurized, so use a high pressure shock pump to start pressurizing the chamber. Spring coil shocks aren't so easy to adjust, as you must find and fit the correct spring for your body weight.

If you don't have an o-ring for measuring your sag, tie a cable tie around the shaft. Just remember to remove the cable tie after you're done, as the plastic could damage your seals if you use the shock continually with it on there.
Photo by Steven Rummukainen

5. This leads us to adjusting the sag. To correctly have the shock set up for your body weight, you should have about 25% to 30% sag. This means that the shock should compress about 30% when you have all your body weight on the bike. To check this, sit down slowly on the bike and lift your feet in the air. Then, hop off the bike slowly and avoid pushing down on it. Check the sag (fitting an o-ring on the shock shaft helps greatly) and adjust the air pressure until you get it to around 25% to 30%.

Rebound dials are usually red, however some manufacturers make them in blue. Photo by Steven Rummukainen

6. One adjustment that is present on practically every shock is rebound. The rebound speed determines how fast the shock 'rebounds' or returns after compressing. Generally, you don't want to go too far to either extreme. If the rebound is too slow, the shock won't return quickly enough after compressing and will 'pack down', never having time to return after compressions. On the other hand, if the rebound is too fast, the shock will return like a pogo stick and will buck the bike dangerously. It's good to set it somewhere in the middle, and make sure you experiment with different settings until you find the one that is perfect for you.

If your shock has a pedal platform, understanding how it works will help you get the best out of your shock.
Photo by Steven Rummukainen

7. Many modern shocks have a technology known as 'pedal platform'. Pedal platforms are a way of making shocks more efficient and to avoid 'pedaling bob'. Pedaling bob is when the rear shock compresses from the force of the rider pedaling and is a common problem on full suspension bikes. Pedal platforms work by keeping the shock 'locked out' over small bumps and pedalling movements, but still allowing it to compress over large bumps and impacts. This can detract from small bump sensitivity and as such, pedal platforms can usually be turned on or off. This is mainly done with a small lever, as seen above. Furthermore, some shocks allow you to adjust the tolerances of the pedaling platform for when its switched on. On this shock, this is done through the gold dial. By adjusting the dial, you can choose how large or small an impact needs to be to unlock the shock when the pedaling platform is active. This, combined with the lever, gives you a huge scope of adjustment. Just remember, you can always switch the switch to 'off' or 'unlocked' to ignore the pedaling platform altogether!

That's it, you've now installed your shock! Now go and enjoy your plush new ride.