ROUTINE SERVICING, AND WHY IT’S IMPORTANT

Just like your car, routine servicing is crucial to get the most out of your fork or shock. Most manufacturers will have routine service recommendations generally between 40 and 100hrs use which for most of us will be annually at the very minimum. Although it can cost more in the long run, regular servicing allows for many years of happy trails without spending up big on replacements and improves the performance of the fork or shock. And that’s a win!

‘My forks are working fine, they are just due for a service’.

It is quite common for a fork to come in for service that feels just ‘fine’, however the condition on the inside often tells a different story. It is not uncommon to find blackened contaminated damper oil, dry lower legs, perished seals, worn stanchions and so on. So whilst they may be working ok, it is quite possible they are working well below the performance potential. As you ride your bike, deep within the guts of your fork or shock is a complex array of seals, shafts, shims, pistons and bushings that allow for the complex damper systems within to work. Over time, in normal mountain bike use there will be contaminants such as dust that will make their way through the dust seals as they wear. Although it’s unlikely that dust will cause any major catastrophes within the fork or shock’s internals, it will almost certainly affect its performance by drying out the inside, and if dust can get in, it will allow oil to get out. Additionally, over time the seals or bladders containing the oil within the damper will perish, wear and flatten and in turn lose their ability to properly seal the oil within the damper body. Eventually, the oil within the damper becomes aerated and that can quickly translate to loss of functionality at the external adjusters. In rear shocks, this is sometimes referred to as cavitation i.e. when nitrogen or air from a shocks internal floating piston (IFP) chamber escapes and mixes with the oil, leaving you with that squelchy feeling and significant performance loss. (See images to left) The pic shows a cavitated shock damper that has also lost a significant amount of oil through the shocks main (but worn) seal head assembly and adjusters. As a result, there was little function in the lockout lever unit, and the shock rode like a ‘pogostick’. The second picture shows what the same shock damper body looks like during the reconstruction and pre bleed process, with a bubble free and clean oil ‹meniscus›. In forks, it is all too common to see severe damage to the stanchions, often referred to as the CSU - Crown Steerer Unit (See image to the left). This is usually a result of poor lubrication in the lowers, bushing wear and or seal/ foam ring contamination, most of which are avoided by regularly cleaning, inspecting and maintaining reasonable service intervals. Although these are all replaceable parts, the costs can sometimes get out of control when a fork may end up requiring a service, seals, bushings and new (CSU) stanchions just to get it trail worthy again.

SETTING UP AIR PRESSURES:

Correct suspension setup is vital to maintaining general balance, pedalling efficiency and to effectively achieve the full amount of travel in a fork or shock without the harsh bottom outs. So let’s go through just the basics with a few added tips to make live easier.

Sag - ‘The amount your fork or shock will move into its travel with just your ‘riding’ weight.’ To measure sag, you will need your bike, your riding gear and a shock pump. Make sure you set any adjusters on the bike to fully open. Unlock that lockout and or wind out any LSC dials on the fork or shock. Move your sag indicator o-ring as close to the fork or shocks dust seal. For the next part, set the bike up approximately 50cm from a wall running parallel so you can lean against the wall while seated on the bike. Whilst in your riding gear including the backpack (if you use one, see tips below for more on this) carefully climb onto the bike and rise up into a neutral riding position, which

is not seated, nor leaning over the front of the bike, It should be out of the saddle, arms bent and with your weight fairly central over the bike. Next up, have a friend help you here if you can, and examine where the little sag indicator o-ring moves to on the fork’s stanchion or shock’s damper body with your body weight centralised. Then, carefully climb off the bike, and measure the distance the o’ ring has moved as a percentage of the total stanchion or damper body length/stroke or travel. This part can take some patience and many attempts to really dial in the correct amount of sag, which for most of us will sit between 15 and 35% depending on the bike, rider, terrain and event.

Here’s a general idea of sag percentages:

15-25% Sag for the more XC type rider and bike 20-35% Sag for the more enduro/DH rider and bike Once you have ascertained your correct pressure settings based on sag, make sure you take a shock pump with you on that next ride or two just to make small adjustments if required. Keep in mind that this is just a ‘guide’ only, and is a really good starting point.

QUICK TIPS FOR THE ULTIMATE SAG SETUP:

1) Sag should be measured when you are in your common riding gear including your shoes, helmet, backpack and an average amount of water you would normally carry. If you carry a 2litre hydration pack, do your suspension setup with it half full, to achieve the happy medium with what becomes your ‘average riding weight’. 2) Full suspension bikes can be setup with slightly MORE sag in the rear shock than the front, sometimes as much as 10% extra (up to 35% total), but generally speaking - 5% is fine for the average rider. 3) Make sure your shock pump registers the current fork or shock’s pressure on the dial before you start pumping. If it doesn’t register the pressure and you have tightened it onto the fork or shock’s valve as much as possible, then it is possible that either there is an issue with the valve, or more commonly, the pump. 4) Many shock pumps will release a small amount of pressure during the removal from the valve process. This is normal, however it is important to work out exactly how much your pump is losing in the process. Once you have set the shock to 150psi as an example, remove the pump completely then reinstall it again until the pump’s gauge registers the current pressure. Then make note of the difference and keep this in mind next time you’re checking your pressures. 5) If you’re losing more pressure in the pump removal process than you think is acceptable, buy a $5 valve core tightening tool from your local servo, and check that the core is tightened firmly and not protruding from the top of the valve stem. Typically, the valve core will sit 0.5-1mm below the top edge of the valve stem.

THE TAKE AWAY

The suspension systems we have at our disposal can make the riding experience far more enjoyable with our wheels glued to the ground and traction for ‘days’ with care and attention to good setup and maintenance. And whilst not all forks and shocks are littered with external adjusters to make or break your ride characteristics, there is almost always a way its performance can be improved with relatively minor modifications to suit a rider’s needs. So I hope you have found some of that interesting, and are able to translate some of it to your own fork or shock to reach its full potential. Happy trails!