Project: DIY Build of a Rocker Plate

A rocker plate puts lateral movement between your smart trainer and the floor. It takes some of the rigid clamping out of the frame and noticeably reduces saddle discomfort on long sessions in our practical experience. For an honest breakdown of how much exactly, see the rocker plate overview page.

In this guide, I’ll walk you through step by step how to build a robust, functional rocker plate yourself. The principle is simple: two wooden plates, a rotation axis between them (rubber isolators), and air-filled rubber balls acting as progressive damping.

Benjamin from Hamm sent us his detailed build report — a great motivational nudge to get your own hands dirty: full PDF download

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1. The Construction Principle

Before we head to the hardware store, it’s important to understand why the rocker plate is built exactly the way it is. The setup consists of three core components:

1. Bottom and top plate: The stable foundation.
2. The rotation axis: Enables the lateral tilt.
3. The damping: Controls the motion and simulates the resistance of the road.

The literal German translation of “rocker plate” is “Wackelbrett” (wobble board) — but that only describes the function inaccurately. Many things can wobble. The rocker plate tilts along a defined rotation axis from left to right, actively supporting the out-of-the-saddle motion. Rider, bike and trainer swing evenly along — the balls cushion the lateral tilting gently and optimally support the return upward.

Excursus: Why we don’t use steel springs or tennis balls

During the development phase we tested a wide range of materials.

Steel springs have a linear rate — they produce instant counter-pressure and snap back hard. An air-filled ball, on the other hand, works progressively: it reacts softly at first to small movements and gets firmer the further you lean into the out-of-the-saddle position. This comes extremely close to real riding. A vendor on the market that uses only steel springs creates a much harsher ride feel, because the springs are installed with too much preload and give too much energy back into the upward motion.

Tennis balls are too small (too little volume) and offer no adjustment range. The small volume creates an uncontrollable “bouncing”, and because the pressure can’t be regulated, the flywheel weight can’t be balanced out.

Foam / camping mats underneath the trainer do dampen marginally, but the higher you stack them, the more spongy and uncontrollable the ride feels.

Inflatable rubber balls (the Kellersprinter standard): Over the years we’ve tested countless damping approaches – from springs through foam blocks to balls in every imaginable size and material. Our clear conclusion: Inflatable rubber balls from 15 cm diameter upward, made of double-layered rubber with no solid core, are by far the best solution.

Why? They offer a large air volume for extremely soft, progressive damping. That means: the further the plate tilts to the side, the softer — yet more deliberate — the swing is cushioned. The decisive advantage over all other systems: via a ball pressure gauge, the lateral tilt resistance can be adjusted to the tenth of a bar, matching your body weight, your core stability and your personal preference.

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2. Materials & Tools

⚠️ Note on sourcing parts: The pre-defined accessory kit from Kellersprinter is no longer available. However, all listed parts are standard items that you can easily source at hardware stores or online (e.g. eBay, Amazon). The parts list is based on the compact rocker plate. Deviations for building a large full-size plate (e.g. for smart bikes) are marked accordingly.

Tip before building: Before you start, it’s worth checking eBay Classifieds or other second-hand platforms. You’ll regularly find used rocker plates built exactly according to this guide. You can spot them by the three screws on the center axis — two sit closer together rather than being evenly spaced. Compare with our template.

The Wood (Base Structure)

Use plywood or phenolic resin panels with bond class BFU100 (waterproof per EN 636-3s). These are the only sensible materials for this purpose.

Phenolic resin panels have a clear advantage: the factory-applied phenolic film on both sides protects the wood against sweat and moisture out of the box, is abrasion-resistant and needs no further treatment. Plain plywood without coating works too — but should be sealed with clear varnish or wood oil, otherwise it will soak up sweat over the years.

Why no OSB: OSB panels swell in thickness up to 20 %, or 15 % for the better grade, within 24 hours of moisture exposure. Indoor sweat output produces exactly that kind of moisture exposure. Birch plywood BFU100, in contrast, holds 8–12 % panel moisture and is extremely dimensionally stable. In our tests, plywood plates have shown no visible deformation even after years in a sweat-soaked basement.

Why no MDF: MDF swells in thickness very heavily under humidity changes — about 3.5 % under normal humidity swings. An 18 mm MDF sheet can swell up to 0.7 mm in damp conditions — not acceptable for a load-bearing plate under your trainer. MDF also soaks up sweat like a sponge.

Thickness: 18 mm for both plates (bottom and top). That is our proven dimension — validated by years of use with riders up to roughly 110 kg system weight. For higher system weight, a thicker plate (21 mm or 24 mm) makes sense. This guarantees absolute stability even in dynamic out-of-the-saddle effort.

Hardware & Damping (The Motion Axis)

• Vibration isolators — standard: Type C 50×50 M10×10 (Schwaderer designation): 50 mm diameter × 50 mm height, M10 female thread on both sides (10 mm thread length), Shore A 55, natural rubber (NR is the standard material for this application).
  • Compact plate: 3 pcs
  • Full-size plate: 5 pcs (evenly distributed along the longitudinal axis)
• Variant for more travel — CT 50×50 M10 NR 56: The conical CT type uses the same thread (M10) and the same footprint as the cylindrical C, but its geometry allows more lateral and axial deflection. In practice: noticeably more dynamic ride feel, closer to a real out-of-the-saddle effort. Worth it once you have a trained core. Rule of thumb: C = quieter / more stable, CT = livelier / more agile. Same quantity as the standard.
• Countersunk screws: M10 × 40 mm, to fasten the isolators.
  • Compact plate: 6 pcs
  • Full-size plate: 10 pcs
• Inflatable rubber balls: 15–18 cm diameter, ideally double-layered with no solid core. We recommend ordering 3 directly (two for the left/right installation, one as a spare). Even on large plates, one pair in the rear area is enough. Good quality available e.g. at Betzold.

Mounting Hardware (Fixing the Trainer)

Depending on your smart trainer design, you fix it on top of the top plate:

• Hook-and-loop/strap variant: 2+ strong hook-and-loop straps or tension straps plus strap clamps to screw the straps into the wood.
• Bolt-down variant: Clamp fittings (pipe clamps), perforated metal strap plus matching wood screws and washers.

Tools & Aids Needed

• Saw: Jigsaw or circular saw (tip: having the rectangular cut done to size at the hardware store saves a lot of work).
• Drilling: Cordless drill with a 10 mm wood bit for the M10 isolator holes.
• Countersink bit: Sized for M10 countersunk screws. Extremely important! Only when the drill holes are cleanly countersunk do the screw heads disappear completely flush into the wood. Otherwise your trainer will wobble on protruding screws.
• Sanding: Sandpaper (e.g. 120–180 grit) or an orbital sander to ease all edges and smooth the surfaces. Saves sweat ingress into the wood later and prevents splinters.
• Measuring: Folding rule, square and pencil.
• Tuning: A precise ball pressure gauge (regular bike floor pumps are far too inaccurate for the low pressures in the balls of approx. 0.1 bar).

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3. Cutting and Shape

A small plate beats a big plate. Do not build a large, continuous rocker plate unless you want to put a KickrBike, NeoBike or another smart bike on it — they are simply too sluggish. With a small plate you get much better control and a more dynamic motion (plus: lower wood cost).

A good rocker plate always supports the trainer and the front wheel. If only the rear wobbles, an unnatural torsional moment develops in the frame that, over time, stresses the head tube.

Reference by trainer size (footprint with legs open):

Brand	Model	Width × Length
Tacx	Neo / Neo 2 / Neo 2T	75 cm × 57.5 cm
Tacx	Flux	65 cm × 67 cm
Wahoo	Kickr & Kickr Core	72 cm × 54 cm
Elite	Suito	67 cm × 59 cm
Elite	Drivo	57 cm × 64 cm
Elite	Direto / DiretoX / XR	65 cm × 84 cm
Saris / CycleOps	H2 & H3 & H4	79 cm × 50 cm

With a width of about 80 cm and a length of 65 cm, nearly every modern direct-drive trainer fits on the plate. Round the corners by approx. 2–5 cm so you don’t smash your ankles when mounting and dismounting.

Tips on measuring and shaping

1. Rough outline: Place your complete setup (trainer + mounted bike + front wheel block) on a large piece of cardboard or directly on the wood.
2. Mark it out: Trace the trainer’s legs and the front wheel block generously. Leave at least 5–10 cm clearance on all sides so the wood won’t split when you later screw in the clamp fittings.
3. Finding the axis: Mark the exact centerline under the bike (directly below the down tube). This is where the rubber isolators will later sit. The important center of gravity of the rider is approximately at 37.5 cm from the bottom edge — that’s where the middle isolator goes, the other two each 16 cm from the top and bottom edges.
4. Ball cutouts: Plan a cutout of approx. 8 cm diameter for the balls — only on the top plate. That’s enough to reach the valve comfortably and prevents the inflated balls from slipping. The horizontal position sits roughly at saddle height (approx. 50 cm from the bottom edge), laterally approx. 20 cm from the edge — this gives a slightly larger rotation radius.
5. Cutting: Cut both plates congruently. Whether you leave the edges square or round them is purely cosmetic and has no impact on function.

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4. Templates for Download

Templates & build phases

← Zum Scrollen wischen/ziehen →

Downloads

• PDF "Universal" template (80 × 65 cm) 2.7 MB · v2 Download
• PDF Template Tacx Neo Bike T8000 1.9 MB Download
• PDF Template XL for Kickr Bike / Kickr Shift / Zwift Ride 7.0 MB · v4 Download

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5. Mounting the Axis

Once the plates are cut, it’s time for the mechanics. The three rubber isolators form the backbone of the rocker plate.

1. Mark the drill holes: One isolator far forward, one in the center (below the bottom bracket / rider’s center of gravity) and one to the back (below the trainer) — exactly on the center axis.
2. Drill and countersink: Drill the holes through both plates. Extremely important: Countersink the holes on the outside faces of the plates deeply enough with a countersink bit. The heads of the countersunk screws must disappear completely into the wood — if they stick out, they’ll scratch your floor or damage the trainer.
3. Screw it together: First bolt the isolators firmly to the bottom plate, then lay the top plate on and screw it down from above.

Alternative: Rigid shafts / hinges instead of rubber isolators

For 90 % of riders, rubber isolators as the axis are the best solution: cheap, easy to mount and absolutely silent.

The only downside: by design, rubber isolators allow not only lateral tilting but also a minimal fore-aft movement (pitch) and a slight lateral shift (yaw). Some riders are bothered by this minimal “spongy” feel.

Anyone who wants a completely play-free movement, limited strictly to the roll axis (left/right), has to install hinges, pillow blocks or a continuous steel shaft. That requires significantly more craftsmanship, absolutely parallel alignment when screwing it down, and over time it often tends to creak.

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6. Fixing the Trainer and Offsetting the Front Wheel

Fixing the smart trainer

Place your trainer on the top plate. Align the bike (not the trainer!) precisely straight and centered on the rotation axis (the rubber isolators). Since every trainer is built asymmetrically, the trainer itself usually ends up offset on the plate – that’s completely normal.

Mark the spots where you want to fix the trainer. If you’re using hook-and-loop straps, either screw the strap clamps into the wood or cut narrow slots for the straps.

Note on securing the trainer: Hook-and-loop straps or strong cable ties are usually perfectly sufficient to hold the trainer in place. If you want to be extra safe (e.g. during extremely hard sprints), you can additionally lash the trainer down with tension straps.

Building the front wheel riser (height compensation)

The rocker plate now puts your entire rear setup (trainer + bike) significantly higher. Let’s do the math: bottom plate (18 mm) + rubber isolators (50 mm) + top plate (18 mm) = approx. 8.6 cm of added height.

To avoid the feeling of constantly riding downhill (and too much pressure on your hands), the front wheel has to be raised by exactly this amount.

The easiest way is to build a small, precisely fitting wooden pedestal from scrap wood:

• Bottom plate: 18 mm plywood
• Top plate: 18 mm plywood
• Middle piece: A wooden block approx. 5 cm thick (e.g. squared timber)

Result: 18 mm + 50 mm + 18 mm = exactly 8.6 cm.

Size of the pedestal: If you only want to rest your front wheel on it, a small pedestal of around 20 × 20 cm is perfectly sufficient. However, if you use steering accessories (such as the Elite Sterzo Smart), the area needs to be planned more generously (e.g. 35 × 30 cm). If you own a Wahoo Kickr Climb or an Elite Rizer, simply place the device directly on the pedestal. Important: Accessories like the Kickr Climb are not bolted down — they stand freely on the pedestal.

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7. Setup: Asymmetry and the Perfect Ball Pressure

Now for the centerpiece: the balls. They get clamped between the plates on the left and right. Position them exactly at the height of your trainer’s flywheel — not in the geometric center of the plate!

The flywheel problem (asymmetric load)

A direct-drive smart trainer (e.g. Wahoo Kickr) is massively asymmetric. The heavy flywheel sits far off to one side. Practical starting values from our tests:

• Heavy ball (on the flywheel side): carries the main load, gets more pressure — starting value approx. 0.15–0.2 bar.
• Light ball (opposite side): only stabilises the return movement — starting value approx. 0.08–0.1 bar.

There is no universal pressure that’s optimal for every rider. The widespread claim that pressure depends on rider weight did not hold up in our tests — what matters is core stability.

Approximate ball pressure in the right ball (opposite the flywheel) vs. annual km ridden.

→ LIVE TOOL

The Ball Pressure Calculator.

Ball pressure does not depend on your weight, but on your trunk stability — and that correlates strongly with your saddle time. Set the slider to your approximate annual kilometres.

MANDATORY

Use a ball pressure gauge. Floor pumps are too inaccurate for 0.1 bar.

Beginner Amateur Elite Pro

ANNUAL KILOMETRES / SADDLE TIME

8,000km

0 30.000+

RECOMMENDED BALL PRESSURE

0.17 bar

≈ 0.15 – 0.19 bar · average over 3 measurements

RIDE FEEL

Dynamic &
flowing

i

Your stabilising muscles are well trained. The perfect compromise between stability and realistic lateral movement during hard out-of-the-saddle efforts.

→ How do you train your core?

Fine tuning: Which pressure is the right one?

• For beginners / occasional riders: Start with more pressure (approx. 0.25 bar). The plate moves more sluggishly, resistance is higher and it gives lots of guidance and confidence.
• For ambitious amateurs: Gradually reduce the pressure toward 0.18 to 0.15 bar. Less pressure = more stabilising work for the core muscles = a more authentic ride feel.
• For elite & pros: From 12,000 annual kilometres on, you can drop the pressure to around 0.10 bar (or lower). You now balance the bike almost entirely through your own body tension.
• Important: A pressure difference of 0.02 bar already makes an enormous difference in the ride feel on these large balls. Use a precise ball pressure gauge — floor-pump gauges are too inaccurate for these low pressures.
• Counterweight: If, despite balanced ball pressure, you still notice a persistent left-heaviness, we recommend placing a weight of approx. 5 kg (e.g. a dumbbell plate) on the right side (next to the trainer’s leg). This offsets the flywheel more effectively than additional ball pressure alone and at the same time spares the left ball.

Note: Ball pressure gauges from different manufacturers are not calibrated consistently — there can be variations. Stick to the same gauge for all adjustments.

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Once everything is in place and the pressure is right: Ride On! 🚴

Show us your finished plate — via email to info@kellersprinter.de or on Instagram @kellersprinter / #kellersprinter. We’d love to see every DIY build.

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Comments from the community

“Hello Kellersprinter, the project is now finished on my end too. After the first 1.5 h on Zwift […]” — Oliver, Zeesen (10 Jan 2023)

“Worked out perfectly! Fast delivery, great with the pressure gauge. 10 out of 10 stars.” — Wolfgang Ulbricht, Meerbusch (3 Mar 2022)

“Great guide and your kit is the perfect complement for building the plate.” — Geppi (13 Sep 2021)

“Project complete. With your support it worked out smoothly.” — Wolfgang Paul, Hunsrück (17 May 2021)

The sketches created here are examples and are free for everyone to use for private DIY building. Commercial use is prohibited. If you post your plate on social media, a source credit is appreciated — thanks!

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Disclaimer

This guide is a pure experience report. Rebuilding and using the construction described here is expressly at your own risk. I accept no liability for property or personal damage. Check all screws regularly for tightness and always secure trainer and bike with additional tension straps.