Fork Servicing - A Performance Upgrade?

Motion Instruments Sensor

Suspension servicing is something we all know we have to do, but probably don’t do often enough. It’s seen as something that doesn’t drastically improve the ride of our bikes, instead merely maintaining the current level of performance and ensuring that expensive suspension components don’t wear out. But is this actually the case? Does a freshly serviced fork offer a quantifiable performance increase out on the trail, and if there is a difference, is it even noticeable? Tweed Valley Bikes’ Head Technician, Ady, and Retail Manager, Matthew, have both done back to back runs on their bikes before and after a lower leg service to try and answer this question as thoroughly as possible.

Matthew has been riding his Tallboy for the last 2 years and in that time the fork has never been serviced. Being long overdue a service, his Rockshox Pike Select+ is a classic example of neglecting the maintenance schedule of your suspension, but will he be able to feel a difference on trail?

Riding at Glentress

Ady’s Rockshox Lyrik Ultimate is also 2 years old, but has been regularly maintained in accordance with Rockshox service intervals. This is an ideal case of by the book servicing, we’d expect nothing less from our Head Technician, but will the regularly maintained fork perform any better than the unserviced fork once both have had a lower leg service?

Fork Seal Replacement

The Setup

In order to quantify what Ady and Matthew were feeling on the trail we used the Motion Instruments Fork Tracer. This sensor accurately tracks the movement, and shaft speed, of the fork as you ride down a trail. The parameters we were most interested in were:

  • Total fork movement 
  • Compression speed
  • Rebound speed
  • Average (Dynamic) Sag

These four parameters give us how much vertical travel the fork has used throughout the entire run, the speed at which the fork compresses, the speed at which the fork rebounds and its average ride position over the trail. 

Motion Instruments Sensor Data

The more a fork can move through its travel over a run, the more effectively it can do its job of absorbing the bumps on the trail. Overall travel used is obviously heavily influenced by air spring pressure so, to keep things consistent across the tests, we kept the air pressure identical before and after the lower leg service.

Compression and rebound speeds are driven by internal friction in the fork; the freer the stanchions are to slide through the seals, the faster compression and rebound speeds you will see. A faster moving fork gives a smoother feeling at the bar and increased traction, as the front wheel can more accurately follow the contours of the trail beneath the tyre.

This leads us to the last parameter, dynamic sag. If a fork can more effectively track the ground, the dynamic sag (or average travel position) can be higher in the travel. A faster moving fork is able to extend faster and is therefore able to ‘fill in’ the small undulations in the trail. This leads to a fork that feels more supple, gives more grip and has more travel in reserve at any given time. 

Each rider did six runs down the same trail with the Motion Instruments fork tracer tracking each run, three before a lower leg service and three after. In the name of consistency no changes were made to either fork between runs, both Matthew and Ady used the same air pressure, and compression and rebound dials were left untouched throughout the test. The track chosen was a mash up of some of the enduro trails at Glentress and is a favourite of both Matthew and Ady’s, with both riders being so familiar with the trail, line choice could be kept as similar as possible on each run. 

Glentress Mountain Biking

The Results

Pike Select+

After a simple lower leg service, Matthew’s Rockshox Pike Select+ was noticeably suppler and smoother throughout its travel. This led to a ride that was less fatiguing and offered more grip and inspired more confidence. Described as “immediately noticeable” after the service, Matthew found the final three runs significantly less tiring than those before the service. The increased suppleness offered by the freshly serviced fork calmed down the previously harsh front end on Matthew’s Tallboy.

The Motion Instruments data shows that what Matthew was feeling was no placebo; his fork increased its total movement by 12% after the service. This will have played a huge part in the smoother feeling at the handlebar he was experiencing. A faster average compression speed, increasing 9.9% over his first runs, and 12% faster average rebound speed, show that his fork is not only moving more but is able to move through its travel with far less resistance, and return to sag as quickly as possible. This allows the front end to ride higher, staying in the supportive mid stroke of the fork, rather than packing down into the firmer end stroke. This increase in rebound speed has led to Matthew using an average of 4.2mm less dynamic sag across his final three runs, meaning he has more travel in reserve at any given time and rides in the suppler beginning and mid stroke as much as possible.   

 Suspension Set Up Day

Lyrik Ultimate

Ady’s Lyrik has been well cared for over its 2 years of riding, but surprisingly he noticed similar results to Matthew, albeit a tad subtler. Overall he commented on the fork being less tiring to ride and felt the fork offered more grip, specifically in flat corners. 

These comments tie up quite nicely with his Motion Instruments data. 9% more total fork movement and an increase in rebound speed, 5.5% faster after the lower leg service, all suggest that what Ady is feeling is a fork that is more capable of absorbing the trail undulations and quickly returning to its sag position. 

Being a well maintained fork, Ady’s results have seen a smaller increase than Matthews, however what is surprising is that Ady was able to feel the difference between his fork before and after the service. Being able to back up that feeling with data from the fork tracer allows us to easily quantify the differences between the two forks. 

Fork Lower Leg Service


The main takeaway here is that an increase in shaft speed, and movement, from your fork leads to a more enjoyable ride. More grip and support and a noticeable reduction in fatigue all contribute to a ride that’s not only more enjoyable, but more comfortable and less tiring. 

The feeling from both riders, backed up with the Motion Instruments data, is that a lower leg service is not just a necessary part of bike maintenance, it actually offers a performance upgrade to your bike, gaining traction and confidence in your front wheel. 

SRAM Butter

If reading this has got you curious about your own fork, consider booking it in for a 50hr lower leg service or a more in depth full service if it hasn’t seen any love for a while. Call us on 01896 831 429 for more info. 

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