Some shock absorber parts may look worn, yet many are recoverable with mild polishing on a flat 200grit sheet
Whilst servicing is simple enough, the intricacies of each functional item is paramount, clinical cleanliness is vital
Like many parts that have been pushed to extreme, shock absorbers have a hard life, using the correct tools is vital
This image shows the valve head, barely noticeable, layers of wafer thin shims all sit on top of each other. Any change in stack height or diameter has massive consequences to the shock absorbers function
Just like the shim stacks in the shock absorber, forks have their own shim stacks. Changing from model to model, where the shock absorber has back to back compression and rebound, forks often have them in different places within the leg
Where some models have a base valve at the lowest point on a fork, others run damping at the top. This Kawasaki KX250 Kayaba fork has the damping stack all at the top of the leg, oil in the lower leg adds lubrication, and some damping assistance, although the damping is really controlled at the top of the leg
Modern suspension needs more than a screwdriver or adjustable spanner to keep it in good serviceable condition. Here at SWB Racing, we don't compromise on tooling, we have what we need, and as new tooling is required, we buy what we need, or have it made from our friendly machine shop neighbours. The inventory of special tooling and equipment grows almost weekly.
Factory produced items have a peening process, where threads are sealed to prevent them coming apart. Admittedly, it can be done by hand, slowly and painstakingly carefully. Any wrong gripping of suspension internals will have dire effects to the smooth action required from suspension. Here at SWB Racing, we machine the end threads from shock stems and base valves to cleanly access the internals so they can, once serviced be reconstructed to an OEM standard.
Call us pedantic if you wish, these parts are all changed or stripped for servicing on any pair of forks.
From the outside in, there are replacement dust seals, the first line of defence on any modern fork. The seals themselves, we use high quality OEM seals, avoiding cheap nasty on line items that are cheap for a reason. Two sets of bushes, one internal slider and one external slider, these do their best to keep forks running true and without stiction as the leg travels in and out. then the valve bodies, completely stripped and inspected. Not forgetting the suspension fluid!
Perhaps just two bottles, each containing a small quantity of oil. You're not wrong of course, but had you realised that dirty oil is the total contents of a shock absorber after one years use, and the clean oil is the quantity that will replace it. The service schedule on a car may be 10,000 miles, but that is typically five litres of oil, most sitting in the base of the sump ready to be used as the engine pumps it around. A shock absorber uses all the oil on a full stroke, changing compartments flushing through a shim stack. It goes through cycles between hot and cold, it needs all its qualities to perform its core function. Imagine each full stroke of the shock absorber moving such a small quantity of oil with every movement, and the big harsh bumps moving virtually all the oil as it circulates and blends as a dirty mess, losing its qualities to become less of a suspension fluid, and more of a weak dirty liquid with no damping qualities. As you would by now have figured, it wont last too long, yet so many people don't have a shock absorber serviced, and miss out on the plush action a well serviced shock absorber should give. You may also notice, the dirty bottle has less oil, part due to breaking down the structure of the oil, and part due to seepage. It may have taken a few months to reach this level so no trace of oil would be seen as a puddle on the floor, but the air space created can fill with water from condensation, power washing or rain ingress, or if dry air, it would be a percentage of the shock absorbers stroke that was ineffective. As a minimum, SWB recommend at least yearly servicing of motorcycle shock absorbers, and racers more frequently.
This state of the art piece of equipment is designed to evacuate all air from a freshly built shock absorber, creating a vacuum within the chambers, checking for and leakage before cycling fresh clean suspension fluid in the shock absorber.
It cycles oil, removes any suspended aeration from the oil, or more commonly known as 'bubbles'. With any fluid, shake it and the fluid mixes with air, air can compress, oil cannot. Our machine cycles oil, removes all air bubble and pockets from the fluid before charging the shock absorber with fluid.
Old practices used to depend on air bubbles making their way to the top of the bleed port, or chamber, probably only dependable if left 24 hours, and then not evacuating all trapped bubbles or pockets. This system means a shock absorber can be fully, and totally dependably bled in just 20 minutes, with all air removed as it creates a vacuum and sucks the filtered pure fluid into the shock body for the purest possible shock bleeding to take place. The consequences of aeriated oil are 'frothing' or 'cavitating' which will reduce effectiveness, thin oil as it friths and remove effectiveness of the damper. Air also condensates as shock bodies are not thermally broken, condensation can then turn to rust if it sits trapped between the shim stack. Technical? You bet!
The contents of one fork leg can be seen here. Metal fragments and dirt suspended in the oil have consequential effects on the damping provision of the whole sweep of the forks travel. Left to settle, it is evident these fragments will circulate in suspension within the fluid.
The fork that this oil came from had been serviced by others, a cheap £50 service! We have no doubt the oil had been changed, maybe the seals also, yet question if the fork had been separated, flushed, inspected and corrected if ingress should have any damaging effect. Just one fragment of this contamination suspended in the oil could be as detrimental as one full click on the compression adjusters, and the same again on the rebound. Have no doubt, that there are cheap services that merely change the oil, and then a SWB service, where each component is removed, inspected, cleaned and put back to give true damping.
We urge anyone to consider that a £50 service is not a service. Consider the time involved, at around an hour, consider the oil costs at over £10. Seals and dust seals another £20. Ask yourself if you do get a true service from the guy down the road who fixes bikes, or do you just get oil and a sticker on your fork legs that suggests it was serviced. We feel confident you will understand, there is no such thing as a £50 service. If the contaminates are left in the fork, you merely wasted £50.