Dial in your ride.

Free, genuinely accurate tools to set up your bike like a pro — suspension sag, tire pressure, gearing, fit and chain length. No sign-up. Works on your phone in the trailhead car park.

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The toolkit

Everything you need to set up your bike

Tap a tool to get started. Every calculator explains the why, not just the number.

Suspension Calculator

Target sag, starting air pressure and rebound for your fork & shock — plus a sag checker.

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Tire Pressure

Front & rear PSI tuned to your weight, tire width, wheel size, terrain and tubeless setup.

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Gearing & Speed

Gear ratios, gain ratio, range %, and your real speed at any cadence for your exact wheels.

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Bike Size / Fit

Frame size from your height and inseam, with playful-vs-stable guidance at the boundaries.

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Chain Length

Exact chain length and link count from your chainstay, biggest ring and biggest cog.

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Why it's accurate

These use the same sag percentages, gear math and chain-length formula pro mechanics use — and every result shows its working so you can trust it and tune from there.

Start with suspension →

Stop guessing. Start railing.

Five minutes with these tools is worth more than any new part. Get your sag and pressures dialled first.

Set up my suspension
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Suspension Setup Calculator

Get your target sag, a starting air pressure and rebound guidance — or check the sag you already have. Sag is the king of suspension setup: it's the percentage your fork/shock sinks under your body weight, and it's the same on every bike.

Pressures are starting points to get you close, then you confirm with sag. Forks and (especially) shocks vary by model and frame leverage, so always measure.

How to measure & set your sag

  1. Push the rubber o-ring on the stanchion/shaft down against the seal.
  2. Gear up. Gently get into your normal riding stance on the bike (lean on a wall or doorframe — don't bounce).
  3. Carefully step off without compressing further. Measure how far the o-ring moved — that's your sag in mm.
  4. Compare to the target below. More air = less sag (firmer); less air = more sag (softer). Re-measure after each change.
  5. Set rebound so the bike returns quickly but doesn't kick back — roll off a curb: you want one controlled return, not a pogo.

Tip: for a rear shock you can also measure the shaft stroke and o-ring travel — the percentage is what matters.

Reference — typical sag targets

DisciplineFork sagRear sagFeel
Cross-country15%25%Firm & efficient, fast pedalling
Trail / all-mountain18%28%Balanced grip & support
Enduro20%30%Plush, planted on rough ground
Downhill20%32%Maximum traction & control

Within ±2–3% is perfect. These are widely used industry baselines — your perfect number is personal, so use them as a starting point and tune by feel.

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Tire Pressure Calculator

The single biggest free upgrade to grip and comfort. Front runs lower than rear because it carries less weight and needs maximum traction; the rear runs higher to protect the rim on square hits.

Numbers assume a gauge read cold. Adjust ±1–2 PSI to taste: lower for grip & comfort, higher for support & rim protection. If you're burping air or clanging the rim, add pressure.

Good to know

  • Wider tire = lower pressure. More air volume supports you with less PSI, giving a bigger contact patch.
  • Tubes need more. Without a tube you can run lower without pinch-flats — that's most of tubeless' magic.
  • Heavier & faster = more. Square-edge hits at speed spike pressure at the rim; a few PSI saves your wheel.
  • Test it. Drop 2 PSI at a time until the tire feels vague or you strike the rim, then add 2 back. That's your number.
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Gearing & Speed Calculator

See how your drivetrain actually translates to speed and climbing ability. Compare setups, work out your range, and find your top and granny-gear speeds at a realistic cadence.

Gear range tells you how wide your gearing is — a 520% range (10–52T) covers steep climbs and fast descents on a single ring.

What the numbers mean

  • Gear ratio — chainring ÷ cog. Higher = harder/faster.
  • Development — metres you travel per pedal revolution.
  • Gain ratio — accounts for crank length too; great for comparing bikes fairly (Sheldon Brown's metric). MTB ranges roughly 2 (granny) to 9 (top).
  • Range % — largest cog ÷ smallest cog. Bigger range = more versatility from one chainring.
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Bike Size & Fit Calculator

A solid starting point for frame size from your height and inseam. Modern MTB sizing leans on reach more than seat-tube length, so treat this as a shortlist — then test ride.

Measure from floor to crotch in socks, feet ~15 cm apart.

Brands differ — a "Large" from one maker can be a "Medium" elsewhere. Always check the specific geometry chart and, ideally, ride before you buy.

Reference — height to frame size

Frame sizeRider height
XS148–158 cm · 4'10"–5'2"
S158–168 cm · 5'2"–5'6"
M168–178 cm · 5'6"–5'10"
L178–186 cm · 5'10"–6'1"
XL186–194 cm · 6'1"–6'4"
XXL194–203 cm · 6'4"–6'8"

Between sizes? Size down for a playful, flickable bike; size up for stability at speed and on steep descents.

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Chain Length Calculator

Cut a new chain to the right length using the proven Park Tool formula. Too short can wreck your derailleur in the big-big gear; too long shifts poorly and slaps.

Centre of the bottom bracket to the centre of the rear axle.

The two trusted methods

  • Formula (this tool): L (inches) = 2 × (chainstay, in) + (largest ring ÷ 4) + (largest cog ÷ 4) + 1. We convert that to whole links and round to an even number.
  • Big–big wrap (cross-check): route the chain around the largest ring and largest cog bypassing the derailleur, pull snug, then add 2 links (1"). Use whichever method gives the longer result.
  • Chains come in even link counts so the quick-link can join an inner to an outer plate.