Suspension forks for idiots and experts!

Fork Suspension set up and care


As I get asked plenty of questions regarding fork set up and maintenance I thought I’d do a bit of a guide / pointers for the tech section to leave on the website.
I’ll break this down into set up and maintenance. Some of this info is fairly basic, but should cover most aspects / questions.



Forks

Rockshox
http://www.sram.com/en/service/

Fox
http://www.foxracingshox.com/fox_tec...er/manuals.htm

Magura
http://www.magura.com/en/service.html

Marzocchi
http://www.marzocchi.com/default.asp?idC=1592

Manitou
http://www.manitoumtb.com/index.php?page=forks

RST
http://www.rst-europe.com/manuals/Tools.HTM

Suntour
http://srsuntour-cycling.com/SID=sia...ormation&fid=5


The above list, with attached website links covers all main brands of front forks, on the various websites you will be able to find tech docs and set up guides for your particular fork.
Forks are broken down into air and coil forks, Coil use a coil spring for the suspension medium, and air forks use compressed air. To adjust the fork for different rider weights with a coil fork you need to swap the coil spring for a heavier or lighter weight spring, for air forks you need to add or remove pressure using a shock pump to adjust the springs performance.
Different resistance coils are available for most brands of forks from the likes of TF Tuned, however for some basic and budget forks; replacement springs may not be available.

http://www.tftunedshox.com/

What is Sag?

Sag is the amount the fork moves under the rider weight, and as a rule of thumb most forks are designed to run with between 25% – 33% of their travel as sag. What does this mean? Well when you sit on the bike in your riding equipment and pack and adopt a normal riding position the suspension should compress under your weight by that amount.

E.g. Fork travel = 140mm total travel, to run 25% sag you would need to do a bit of basic maths, 140 / 100 x 25 = 35mm sag. So you would want the fork to compress by 35 mm with your weight on the bike.

To measure this place a zip tie around the stanchion (the shiny bit) on your forks, sit on the bike with your normal riding kit on, have a friend push the zip tie down to the top of the fork lowers, and then carefully get off the bike. Measure the distance the zip tie has moved up the stanchion and this is the amount of sag you are currently running.

To alter this add / remove pressure for air forks until you obtain your required sag amount. If you fork is a coil and you fall outside the required sag range when you perform the above test you need a different coil spring for your fork these are readily available and easily swapped.

Getting the sag correctly set for your weight will mean the fork should track the ground and react to big hits as the manufacturer intended it to, this is the first most important aspect to getting your fork to run properly.

Rebound

Most forks have a form of rebound to adjust how fast the fork returns to full extension from compressing, so in layman’s terms how quickly it moves. This is normally controlled by oil flowing through a series of posts in the fork controlling the return stroke. Forks should be run with a reasonably quick rebound this avoids the fork “packing down” or getting shorter and shorter under successive hits. Rebound adjusters will have either a + and – or in Rockshox case a tortoise and hare.

Adjust your rebound fully to the plus / hare and compress the fork, it will return very slowly to its full length, now adjust fully the other way and the fork will return with lightening speed. Most forks are adjusted best with 1-3 clicks positive from the lowest negative rebound setting. This should mean the fork returns quickly but not so quick as to throw the rider upsetting balance.
Getting rebound set correctly is the second most important set up aspect of your front fork.

An easy way to test this is to stand off the bike and compress the fork heavily, then try and lift the front of the bike off the ground. The fork should just return to full length as you lift it off the ground.

Compression damping (high speed / low speed)

Most forks have factory set levels of compression damping but some have adjustments that can be made, these are however somewhat supplementary to sag / rebound and these are far more important settings to get right.

If your fork has compression damping adjustment have a play with the settings and see if you notice any difference in the forks performance, compression damping will affect the forks performance during the stroke and can make it more or less reactive under successive hits.

Travel adjust

Features such as U Turn, Talas, 2 Step air, all adjust the useable amount of travel on the fork to suit different riding situations, usually lower travel for climbing, and longer travel for descending. Your frame will have an optimum travel though so running the fork shorter or longer will affect the handling of the bike as a whole also. U Turn allows you to lower and raise the fork incrementally, whilst 2 step and Talas have defined travel steps that when the dial is adjusted and the fork compressed it will remain at the new travel setting. The idea with travel adjust is that the fork will perform as well during each of the different travel setting. Always ensure that set up for rebound and sag is done with the in the maximum travel setting.

Maintenance / Servicing

Cleaning

Forks are both expensive and exposed to all the filth we ride in and are subject to wear and tear. The most important part of a fork is the seal / stanchion area. The stanchions (the slidey up and down part of the fork) are either stainless steel on cheaper forks or coated aluminium on more expensive forks. This part of the fork is critical to keep clean as wear to the coating on the stanchions can lead to irreparable damage that can ruin your forks.
The stanchions enter the fork lowers from the upper seals; these consist of a series of rubber wiper seals and normally a foam lubrication ring. The seals job is keep the lubricating oil in and the dirt and grit out. Post ride cleaning of the fork stanchion and seal area should keep your forks running sweetly and avoid wearing out your stanchions.


To clean the seals / stanchions, I normally spray the area with Muck Off / Fenwicks and agitate the area with a large cleaning or paint brush all around the seal area. Then rinse and dry off, use a tea towel to get right around the seal area. Then spray the stanchions with a silicon lube spray, (just a little) like fork juice etc, then compress the fork vigorously 20 times, this in conjunction with the spray will lift any dirt from the seals, you should see a small ring of dirt on the stanchions, this will be dirt that was stuck under the seals, clean this off with a rag and you are done.

Servicing

Forks need regular servicing and fluid changes to keep them performing at their best and to stop them prematurely wearing out. Send away servicing is expensive and will mean you will be without your forks for a number of days. Expect to pay upwards of £90 for a full send away service from the likes of Mojo or TF Tuned, however home servicing with the right tools is easily achievable and much less costly.

I would recommend a strip down and service at least once a year to ensure that the internals of your forks are in good order and to fill with fresh suspension fluid and a thorough internal clean. Also when stripped down internal condition of other components such as damping cartridge and rebound assembly can be checked and serviced. If you ride all the time and are less scrupulous with your maintenance then more regular strip downs will be necessary.

The difference that fresh fluid can make to a forks performance should not be underestimated, as the fluid gets dirty and contaminated it does not perform as well and can foam up, causing suspension fluid to weep from around the seal area of the forks. Also as dirt and contaminants get into the oil, this is then used to lubricate the internal components of the forks accelerating wear.

If you run Fox forks the manufacturer recommends a strip down every 50 hrs of riding time, this is both ridiculous but is a way of getting around the warranty issue around premature wear of fox stanchions. Keep a close eye on Fox stanchions and at the first indications of any colour loss or marking on the gold legs, get them looked at.

As many of you may or may not know I have the tools and the guides to service Marzocchi, Fox, Rockshox, and Magura forks and am happy to service these for members for reasonable rates to cover materials and time taken, these rates are a fraction of what TF Tuned will charge and vary depending on the model of fork, pm me for more info.

Also I am more than happy to provide advice if you want to have a pop yourself.

Tools Required (not all required for all models)
Selection of sockets normally up to 26mm
Allen keys
Soft faced hammer
Dowel rod
Strap wrench
Vice
Drip tray
Syringes / measuring cylinder
Internal and external snap ring pliers
A pick
Workshop cleaning towel
Grease
IPA (Iso Propyl Alcohol)
Suspension fluid of correct weight (most forks require a number of different weights)
Float fluid (fox only)


Bushings

Forks use Bushings to hold the stanchions in place and they ensure a tight play free fit between the upper and lower legs of the fork. These are again a wearing part however normally last well. If play develops in the bushings these will need to be replaced and resized. This is a send away job; however I am looking into getting the tools necessary to do this DIY.
Forks have an upper and lower bushing. And if these do wear out they too can cause the anodising on the legs to wear out. So again keep an eye out for wear marks on the stanchions or for play in fork / front area of the bike that feels like a loose headset but isn’t.

Summary

1) Setting up and looking after your forks is no dark art and is both straight forward and saves heaps of money down the line.

2) Looking after and keeping your stanchions and seals clean is as important as looking after your drivetrain.

3) Most manufacturers’ websites contain a wealth of info on looking after your forks. A bit of research can yield great results.

4) Experiment with your setting and pressures so you know how they feel, when you find your sweet spot, be sure to make a note of your pressures and rebound settings.

5) If you notice problems get them looked at straight away, don’t put it off.