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Achieving Correct Air Pressure with Sag

The sag measurement is the amount that your fork, rear shock, or both will compress when you are positioned for riding on your bike, with all your riding apparel and gear. Adjusting air pressure until you achieve your target sag will help you determine the appropriate amount of air pressure for your fork or shock, or both.

To achieve the best performance from your FOX suspension product, the proper measuring and setting of sag is vitally important. As a starting point, set sag for your fork or rear shock to 25% of its available travel.

NOTE: While 25% sag is fine for most riders, you can experiment and vary your sag percentage to better suit your riding style, personal preferences of handling characteristics, and overall feel. For example, if your style is more downhill/shuttle, you can increase your sag percentage a few points (implying less air pressure) to add plush feel to your riding platform. If your style is more all-mountain/XC, you can decrease your sag percentage a few points (implying increased air pressure), to firm up your suspension.

New FOX suspension products typically have an o-ring on the rear shock body or fork upper tube, but if there is no o-ring, you can temporarily use a zip tie to aid your sag measurement.
- Turn off Propedal, compression damping, or lockout on the shock or fork before proceeding.
- Make sure your CTD fork, shock, or both are in descend mode.
- If your fork has the Terralogic® damper, turn the blue Terralogic® threshold adjust knob to fully counter-clockwise out. After achieving proper sag, be sure to return the blue Terralogic® threshold adjust knob setting to fully clockwise in.
You should be dressed to ride (including filled hydration bag, if you use one). Make sure that you are on a level surface and have an assistant hold your handlebars, or position your bike next to a wall or table to support yourself while getting into a riding position.
Mount your bicycle and bounce lightly while holding onto a single brake only, to compress both front and rear suspension slightly.
NOTE: Bouncing lightly will help free up any friction caused by sticky new suspension pivots or slack head tube angles. Holding onto both brakes at this point will prevent a good sag measurement.
Assume a normal riding position for 15-30 seconds, letting the suspension fully settle. Riding position will vary, based on the style of bike being set up:
- Measure sag on Freeride/DH bikes in a standing “attack” position
- Measure sag on XC/Trail/AM bikes in a normal seated riding position
While maintaining your normal riding position and without bouncing, reach down and slide the o-ring or zip tie against the scraper lip of your rear shock air sleeve, or the dust wipers of your fork or both, if your bike has full suspension.
This next step is critical for getting an accurate sag measurement: dismount your bike without bouncing, to avoid moving the o-rings or zip ties.
Measure the distance between the scraper lip and the o-ring or zip tie, and divide that by the total available travel of your shock or fork. For an example, your target sag percentage is 25% and your rear shock available travel is two inches (~50 mm); your target sag setting will be ½ inch (~12.5 mm), 25% of available travel (12.5 ÷ 50 = 0.25). Add or release air in 5 PSI (0.35 bar) increments with the FOX high pressure pump, and repeat the preceding steps until your measured sag equals 25% of total available travel.
NOTE: For the best TALAS performance, always set sag in the long travel position. Sag and spring rate will automatically readjust when you change to different travel settings.