The Beginner's Guide to Motorcycle Suspension Revalving
Your motorcycle's suspension was set up at the factory for a 75kg rider on smooth pavement. If you're a 95kg motocross rider hitting whoops at race pace, those factory shim stacks are wrong for you. Revalving — replacing the shim stacks inside your forks and shock — is how you fix that.
This guide covers everything you need to know to get started, whether you're doing it yourself or working with a professional tuner.
Contents
1. What Is Suspension Revalving?
Inside every motorcycle fork and shock absorber is a damping valve — a piston with small holes covered by thin metal discs called shims. When the suspension moves, oil is forced through these holes. The shims bend to allow oil flow, and the resistance they create is what controls your suspension's damping.
A shim stack is the specific arrangement of these shims — their diameters, thicknesses, and order. Different stacks produce different force-velocity characteristics:
- Larger diameter shims = more resistance = stiffer damping
- Thicker shims = harder to bend = stiffer damping
- More shims = more material to deflect = stiffer damping
- Tapered stacks (decreasing diameter) = progressive damping that increases with speed
Revalving means disassembling your fork or shock, removing the existing shim stack, and installing a new one designed for your weight, riding style, terrain, and skill level.
Why factory settings don't work for everyone
Manufacturers set up suspension for the average rider in the average conditions. But there's no such thing as average in motorcycling. A 65kg enduro rider on rocky single-track needs completely different damping than a 100kg motocross racer hitting supercross-style rhythm sections. Factory clickers (compression and rebound adjusters) can only adjust damping by about 15-20%. Revalving gives you the full 100% range.
2. When Should You Revalve?
Before spending money on revalving, check your sag first. Incorrect sag (from wrong spring rate or preload) causes most of the same symptoms as bad valving. Fix sag first, then consider revalving if symptoms persist.
Symptom diagnosis table
| Symptom | Likely Cause | Fix |
|---|---|---|
| Harsh bottoming on jumps/bumps | Compression damping too soft or spring too soft | Check sag first, then stiffen compression valving |
| Fork dives hard under braking | Low-speed compression too soft | Increase low-speed compression (clickers first, then revalve) |
| Bike wallows / feels vague mid-corner | Rebound too slow or compression too soft | Speed up rebound, add compression damping |
| Suspension feels "springy" / pogo-sticks | Rebound too fast | Slow rebound (more rebound damping) |
| Headshake at high speed | Steering damper or fork/shock imbalance | Check fork/shock balance, oil level, revalve for stability |
| Excessive arm pump / fatigue | Suspension too stiff for terrain | Soften compression valving, check spring rate |
| Suspension "packs down" (gets shorter) | Rebound too slow for the terrain | Speed up rebound, reduce low-speed compression |
| Kick-back over sharp bumps | High-speed compression too stiff | Soften high-speed compression (revalve required) |
Good reasons to revalve
- Significant weight difference from factory target (more than ±10kg)
- Changed riding discipline (e.g., switched from trail to motocross)
- Upgraded springs — new springs without matching valving creates an imbalance
- Performance optimisation — you've maxed out clicker adjustments and want more range
- Suspension rebuild — if you're already doing seals and oil, revalving at the same time is minimal extra effort
3. DIY vs Professional Revalving
DIY Revalving
- Cost: $50-150 in shims + tools you already own
- Time: 4-8 hours first attempt, 2-3 hours once experienced
- Pro: Full control, learn your suspension deeply, iterate quickly
- Pro: No waiting for a tuner's schedule
- Con: Steep learning curve
- Con: Risk of assembly errors on first attempt
- Con: Need to invest in tools and shim kits
Professional Revalving
- Cost: $275-500 per end ($550-1,000 fork + shock)
- Time: 1-2 weeks turnaround typical
- Pro: Guaranteed expertise — they've done thousands
- Pro: Access to dyno verification
- Pro: They know the common issues for your specific bike
- Con: Expensive — $1,500-3,000/season if revalving regularly
- Con: Can't iterate quickly at the track
Where ShimCalculator fits
Whether you're doing it yourself or using a professional tuner, ShimCalculator helps you:
- Plan before you build: Enter your current stack and see the force-velocity curves before touching a wrench
- Communicate with your tuner: Show up with a printed build sheet showing your current setup and the recommended changes
- Benchmark your results: After revalving, enter the new stack and compare the predicted force curves against your target
- Validate with simulation: Run the recommended stack against track data to check for bottoming before you ride
Try ShimCalculator Free
Enter your shim stacks and see your force-velocity curves instantly. No sign-up, no software to install.
Try Free — No Sign Up4. Tools You'll Need
Physical tools
- Torque wrench — for valve nut and cartridge assembly (critical — wrong torque crushes shims)
- Fork/shock-specific spanners — cartridge holder, cap wrenches (bike-specific)
- Shim kit — assorted diameters and thicknesses (0.10, 0.15, 0.20, 0.25, 0.30mm)
- Suspension oil — correct weight for your application (ISO VG 3, 5, 7, or 10)
- Measuring tools — digital calipers for shim measurement, graduated cylinder for oil level
- Vise with soft jaws — for holding cartridge rods during disassembly
- Clean workspace — shims are tiny; a dropped shim on a dirty garage floor is gone
- Camera/phone — photograph every step, especially the original stack order
Software tools
- ShimCalculator — web-based, free preview, generates recommended stacks with simulation validation. Works on any device.
- ReStackor — Excel-based FEA analysis tool. Deep engineering depth but steep learning curve. See comparison.
- Race Tech DVS — proprietary Gold Valve sizing tool (only for Race Tech products)
- Motoklik — hardware sensor + app for data logging (€647+ for hardware)
5. The Revalving Process: Overview
This is a high-level overview — always refer to your OEM service manual for bike-specific procedures, torque specs, and assembly sequences.
Phase 1: Planning
- Record your current shim stacks (or get them from your tuner/OEM spec sheet)
- Enter stacks into ShimCalculator with your weight, spring rate, and discipline
- Review recommended stacks and run the simulation
- Print the build sheet — take it to your workbench
- Order any shims you don't have (allow delivery time)
Phase 2: Disassembly
- Remove fork/shock from the bike
- Drain oil, disassemble cartridge/damper
- Photograph everything — especially the existing shim stack order
- Record the exact stack: diameter, thickness, quantity of each shim, top to bottom
- Inspect all components for wear (bushings, seals, piston ring)
- Clean all parts thoroughly — any debris on a valve seat ruins the seal
Phase 3: Rebuild with New Stack
- Assemble the new shim stack on the valve — follow your build sheet exactly
- Verify stack order and taper before tightening
- Torque the valve nut to spec (too tight = crushed shims = wrong damping)
- Reassemble cartridge/damper
- Fill with correct oil weight and volume
- Set oil level (forks) or bleed air (shock)
- Charge gas (shock — nitrogen to specified pressure)
Phase 4: Testing
- Set static sag before riding
- Start with clickers at mid-range
- Ride at moderate pace first — feel for the baseline
- Fine-tune with clickers before deciding if the stack needs changes
- Record your clicker settings and riding impressions
6. Common Mistakes to Avoid
Over-shimming (too many face shims)
Adding more face shims makes the stack stiffer but also increases stack height. If the stack gets too tall, there's insufficient thread on the valve shaft to secure it. Keep within the original stack height + 1%.
Wrong oil weight
Oil viscosity has a huge effect on damping — especially low-speed. Changing from ISO 5 to ISO 7 can add 20-30% more low-speed damping. Always match the oil weight to your application; don't use whatever's on the shelf.
Ignoring spring rate mismatch
You cannot valve away a bad spring. If your sag is wrong (too much or too little), fix the spring rate FIRST. Then revalve to match the correct spring. Revalving with the wrong spring is like tuning an engine with the wrong fuel.
No photographs during disassembly
Shim stacks look simple until you've got 15 tiny metal discs on the bench and can't remember the order. Photograph each layer as you remove it. Some tuners use a dedicated shim tray with numbered slots.
Dirty valve seats
Even a tiny particle of debris on a valve seat prevents the shim from sealing properly, creating a bleed path that changes your damping. Clean everything meticulously. Use lint-free cloths and clean oil.
Wrong torque on the valve nut
Too tight = crushes the shim pack, preventing proper deflection. Too loose = shims shift during operation. Use a torque wrench and follow OEM spec. This is not a "feel" operation.
Ready to Plan Your Revalve?
Enter your current shim stacks and dyno data. Get three recommended stacks — baseline, softer, and stiffer — validated by suspension simulation. Print the build sheet and take it to your workbench.
Try ShimCalculator Free Compare ToolsNext Steps
- Try ShimCalculator Free — enter your stacks, see the force-velocity curves
- Compare suspension tools — ReStackor vs Motoklik vs ShimCalculator
- Subscribe for full access — recommended stacks, simulation, print reports