Maintenance Tip of the Week: Set Your Suspension Sag for Summer Trail Riding

Welcome to our Maintenance Tip of the Week series — quick, practical advice from the mechanics at Brentwood Cycle to help you get the most out of every ride.

This Week's Tip: Set Your Suspension Sag

It's peak summer riding season in Victoria. Hartland is dry and fast, the trails at Bear Mountain and Gowlland Tod are in prime condition, and there's no better time to make sure your bike is set up to take full advantage. This week's tip is one of the highest-impact, lowest-effort adjustments you can make: setting your suspension sag.

Most riders never check their sag. Their fork and shock are either over-inflated (harsh, skipping over bumps) or under-inflated (wallowing, bottoming out), and they've just accepted that as how their bike rides. Five minutes with a shock pump changes everything.

What Is Suspension Sag?

Sag is the amount your suspension compresses under your body weight when you're sitting on the bike in your normal riding position. It's expressed as a percentage of total travel.

Why does it matter? Because your suspension needs to be partially compressed at rest to work properly in both directions — it needs to compress further when you hit a bump, and it needs to extend (drop) when the wheel falls into a hole or off a ledge. If your suspension is too stiff (too little sag), it can't absorb small bumps and loses traction. If it's too soft (too much sag), it wallows, feels vague, and bottoms out on bigger hits.

Correct sag puts your suspension in the middle of its working range, where it can do its job in both directions.

What's the Right Amount of Sag?

General guidelines for most trail and enduro bikes:

• Fork: 15–20% of total travel for XC/trail, 20–25% for enduro/all-mountain
• Rear shock: 25–30% of total travel for most trail and enduro riding

Always check your fork and shock manufacturer's recommendations first — RockShox, Fox, and other brands often publish specific sag targets for each model. These are a good starting point, but your ideal sag may vary based on your riding style and the terrain you ride most.

For Victoria's mix of technical climbing and rowdy descending at Hartland, we generally recommend sitting toward the middle of these ranges — enough sag to stay active on the climbs, enough support to handle the descents.

How to Check and Set Your Sag: Step by Step

You'll need: a shock pump, a zip tie or the sag indicator O-ring on your fork/shock stanchion, and a friend (or a wall to lean against).

For Your Fork

1. Slide the O-ring (or zip tie) down to the fork seal — this is your reference point. Most forks have a rubber O-ring on the stanchion for exactly this purpose.
2. Get on the bike in your normal riding position — sit on the saddle with your hands on the bars, feet on the pedals, wearing your normal riding gear (including a loaded pack if you usually ride with one). Have a friend hold the bike steady, or lean gently against a wall.
3. Gently bounce once and settle — let the suspension find its natural position without bouncing aggressively.
4. Carefully step off without compressing the fork further — slide off to the side rather than pushing down.
5. Measure the gap between the O-ring and the seal — this is your sag distance. Divide by total fork travel and multiply by 100 to get your sag percentage. For example: 30mm sag on a 150mm fork = 20% sag.
6. Adjust air pressure as needed — add air to reduce sag, release air to increase sag. Make small adjustments (5–10 PSI at a time) and recheck.

For Your Rear Shock

1. Measure the shock's total stroke — this is the distance the shock shaft travels from fully extended to fully compressed. It's usually printed on the shock (e.g., 55mm stroke on a 210x55mm shock).
2. Slide the O-ring to the shock body — most shocks have an O-ring on the shaft for sag measurement.
3. Get on the bike in your normal riding position — same as above. Sit centred on the bike as you would on the trail.
4. Step off carefully and measure the O-ring position — the gap between the O-ring and the shock body is your sag distance.
5. Calculate sag percentage — divide sag distance by total stroke and multiply by 100. For example: 15mm sag on a 55mm stroke = 27% sag.
6. Adjust air pressure — add air to reduce sag, release to increase. Recheck after each adjustment.

Fine-Tuning: Rebound Damping

Once your sag is set, take a minute to check your rebound damping — the speed at which your suspension returns after being compressed. Push down on the front of the bike and release quickly. The fork should return to full extension smoothly and relatively quickly, without bouncing back aggressively or returning so slowly it feels sluggish.

Most forks and shocks have a rebound adjuster (usually a red knob or dial). Turn it toward the – (faster) or + (slower) symbol to tune the return speed. For Victoria's rooty, technical terrain, a medium rebound speed works well for most riders — fast enough to track the ground, slow enough to stay controlled.

When to Check Your Sag

• At the start of each season — air pressure in suspension changes with temperature. Your summer sag setting may be different from your winter one
• After any significant temperature change — a hot summer day can increase air pressure and reduce sag noticeably
• If your bike feels harsh or wallowy — sag is the first thing to check
• After a crash or hard bottom-out — check that nothing has shifted
• When you change riding gear significantly — a heavy pack or different clothing can affect your sag

Not Sure Where to Start? Come See Us.

Suspension setup can feel intimidating if you haven't done it before, but it's one of the most rewarding adjustments you can make to your bike. If you'd like a hand getting your sag dialled in, bring your bike into Brentwood Cycle in Saanichton — our mechanics are happy to walk you through it or set it up for you.

We also carry shock pumps and suspension tools in the shop if you want to handle it at home. Stop by and we'll point you in the right direction.

Check back next week for another maintenance tip from the Brentwood Cycle team. Happy trails!