Monday Maintenance: VII Custom tuning forks - Bike Magic

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Monday Maintenance: VII Custom tuning forks

We’ve covered basic set up for spring rate and damping and we’ve covered basic maintenance. But what happens when you’ve twiddled your knob sore and your forks still aren’t doing what you want?

‘Custom’ suspension tuning can become a lifetime obsession (often linked to growing a mullet and racing dragsters) but there are some basic moves that you can do without voiding you warranty or boring the arse off your mates.
So part four of our beginner’s guide to forks deals with travel adjustment and what it means to your riding, plus how to change your damping without a drill.

Travel adjustment
Be prepared

Changing the travel of your forks seems to be this year’s big obsession. Rock Shox’s Psylo U-Turn and Manitou’s Black series make adjustment easy with an external lever or dial, but otherwise you’re going to have to get inside the fork to change it’s height.

Different forks achieve travel adjustment in different ways. Some use an additional spring section or longer replacement spring that can be added or removed, while others use a spacer that can be inserted on the spring rod to reduce or increase travel. Before you start pulling things apart, make sure you check the manual so you know exactly what’s involved. You will often need tools (big adjustable spanners, extra long Allen keys, rubber mallets) beyond the scope of the average bike tool kit, some oil forks will need refilling, while Pace forks will need fresh circlips to put them back together. You don’t want to find this out when your fork is in pieces in the kitchen after the shops have shut on Saturday and you’re riding Sunday morning.

Why change travel?

The marketing men suggest that the more travel you have, the taller buildings you will instantly leap over and the more girls (or boys) will throw themselves at your feet in adoration. They’ll even go so far as to try and make you feel like an inadequate social outcast if you have to ride up a hill with your fork at the same setting that you ride down the other side on.

Guess what? It ain’t that simple though.

Increasing the travel of your forks gives them more space to absorb an impact, so all other things being equal they generally handle big hits better. The extra length of the fork also tips the headtube back and slows down your bike’s steering, again this extra stability is good for high speed downhill sections.

Conversely, shortening the travel makes the fork less smooth through big hits but lets the bike steer faster with sharper responses for avoiding the rocks in the first place. Forks on shorter settings are also less likely to twang and flex than they are at max stretch as they have more slider overlap and less leverage on the tips.

If travel is externally adjustable, then trying out which suits you best is obviously no problem, but we thought you’d best mention that longer travel isn’t always a good thing before you get sucked in all the hype.

Changing damping
Change the oil to change the damping

If you’ve twiddled all the damping knobs (or maybe you haven’t got any) and still haven’t slowed the fork down (or speeded it up) as much as you’d like then it’s time to get internal with your damping.

Damping is generally controlled by oil being forced through a valve (or set of valves) as the fork compresses and extends. The larger the valve hole the faster the oil can get through the hole and the faster the fork can move. Most damping adjuster knobs work by changing the aperture size of these valves.

If the full closed or open position isn’t enough for your needs, the next step is to change the thickness and flow rate of the damping oil itself. This viscosity is generally described as oil ‘weight’ (which can vary from 2.5wt to 20wt) with different forks and damping systems using different weights.

Before you do anything check that the oil is actually part of the damping rather than a lubricant, or that opening a sealed damping cartridge won’t invalidate your warranty. All you have to do then is find out the weight of oil used as standard, pour that out of the oil bath or cartridge and refill with the exact same amount of new oil. Moving to a heavier weight (larger number) of oil will slow the fork down, while a lighter weight will speed it up, but a small difference in oil viscosity can make a big difference in the fork performance so try and follow manufacturer’s directions.

Where to look for more information

Different forks have widely different damping systems and particular tuning techniques and we recomend you use someone else’s experience wherever possible. Obviously the fork manufacturer should be the first port of call, but specialist fork tuners like TFTunedshox (who specialise in Rock Shox – old and new), CVI (who specialise in Manitou and Risse upgrade kits for older forks), or Mojo, (who specialise in Fox), all make a living out of suspension tuning and have got far more experience and know-how than most. The BIKEmagic forum can often be helpful, but there’s also a specialist fork tweaking forum on the Angry Asian website.


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