Choose a different timber for each part of a wheel: elm for the hub because its interlocked grain resists splitting when the spoke mortises are cut and driven, riven oak, hickory or ash for the spokes where stiffness and straight grain along the spoke matter, and ash, elm or beech for the felloes where the wood must bend. All of it must be seasoned, because wood that shrinks 0.1-0.2% along its length after tyring gives up 3.8-7.5 mm of the 10-20 mm the tire was forged short.
Part of Wheelwright Craft
Wheel timber selection is the matching of wood species, grain direction and moisture to the very different loads on a wheel’s hub, spokes and felloes.
Each Part Fails In A Different Way, So Each Wants A Different Wood
| Part | Best wood (carrier) | What the wood must do | How it fails if wrong |
|---|---|---|---|
| Hub | Elm | take 12 square mortises without splitting | splits from mortise to mortise |
| Spokes | Oak, hickory, ash | carry load along the grain and absorb shock | breaks where the grain runs out |
| Felloes | Ash, elm, beech | bend, or be cut, to the rim curve without breaking | cracks on the bend, or at the tenon holes |
Hub. Twelve mortises leave webs of wood as thin as 1.5 cm between them (Hub Construction), and every spoke is driven in like a wedge. Elm’s interlocked grain, with fibres that change direction, is the carrier’s reason for choosing it: a crack that starts has no straight path to follow.
Spokes. A spoke is loaded along its length, so the strength that counts is along the grain. Oak, hickory and ash are stiff along the grain and tough under shock. Hickory is the toughest of the three and oak splits more readily than elm at the hub, which is why the hub and the spokes are not made of the same wood.
Felloes. The rim must take the tire’s squeeze and the bend of the curve. Ash, elm and beech bend well (Steam Bending lists all three as good bending species, ash and elm as excellent).
Grain Direction And Ring Orientation In A Spoke
A spoke breaks where its grain runs off the edge, so the grain must run the full length of the piece:
- Riven, not sawn. Splitting follows the fibres wherever they go, so the grain stays continuous even if the billet is not perfectly straight; a saw cuts across any fibres that wander, leaving a weak plane (Spoke Shaping).
- Check all four faces. Sight along each face of the shaped spoke and reject it if grain lines run out through an edge.
- Avoid the pith. The heart of the log is where the first cracks open as the wood dries; take spokes from the clear wood between the pith and the bark. (Recalled wheelwright practice; the carrier does not state it.)
- Rings. A riven spoke has its growth rings running along its length, the same way as its grain; do not cut across them. How the rings face relative to the load is a refinement the corpus does not source, so no rule is given here.
Seasoning: Green Wood Bends, Then Shrinks Away
The carrier requires all wood to be air-dried 1-2 years; green wood shrinks and loosens joints (Wood Seasoning). The exception is the bending stock, which bends best green or recently steamed, and must then dry on the form for at least 24 hours before it is drilled (Steam Bending Felloes).
How much does a green felloe cost? Wood shrinks little along the grain, taken here as 0.1-0.2% from green to air-dry (a recalled typical range, not measured). For a rim of circumference 3.77 m (a 120 cm wheel):
- 0.1%: 3,770 mm × 0.001 = 3.8 mm
- 0.2%: 3,770 mm × 0.002 = 7.5 mm
The tire is forged 10-20 mm short, so shrinkage along the rim alone uses up roughly a fifth to three quarters of the margin that grips it. Across the grain, wood shrinks many times more, about 4% from green to air-dry (also recalled): a 2 cm felloe hole closes by about 0.8 mm, and the green felloe’s depth and width shrink by the same percentage, which is how green rims lose their joints.
Strength Figures, Recalled
Air-dry oak and ash break in bending at very roughly 100 MPa, hickory higher, and elm lower than oak (recalled from handbook values, not measured here). Use them to rank the woods, not to design a spoke.
What You Need
- Elm blocks for hubs, oak, hickory or ash billets for spokes, ash, elm or beech for felloes
- A froe and maul to rive spoke billets
- A dry store with air movement (Wood Properties for species data)
Method: Select And Sort
Step 1: Sort by part. Mark each log with the part it will become before it is cut.
Step 2: Reject by defect. Discard hub blocks with end cracks, spoke billets whose grain runs out, and felloe stock with knots on the bend.
Step 3: Season each part for its time; keep bending stock green, but plan its drying on the form.
Step 4: Test. A spoke tapped with the knuckle should ring; a dull note means decay or a hidden crack.
Common Mistakes
- One wood for everything — a hub of oak splits; a felloe of hickory will not bend.
- Sawn spokes — the first hard blow finds the run-out.
- Green hubs or spokes — they shrink after the wheel is tyred and every tenon goes loose.
- Trusting the tire to cure bad timber — it only squeezes what is there.
Safety
A wheel built from bad timber fails under load
A split hub or a spoke that breaks at a run-out drops a loaded cart on that corner and can crush people and animals beside or downhill of it. Reject doubtful pieces, test a new wheel at half load, and never stand downhill of a loaded vehicle.
Four Other Articles Called “Wood Selection”
A short link such as wood-selection points to several unrelated pages. None is about wheel timber; go to them only for their own subjects:
- Wood Selection (wooden gears) — species and grain for mill gears
- Wood Selection (charcoal) — which woods make good charcoal
- Wood Selection (gunpowder charcoal) — charcoal species for powder
- Wood Selection (fire and smoking) — resinous versus hardwood for fire and smoking food
What’s Next
- Learn next: Spoke Making & Fitting — turning the billets into spokes
- Combine with: Engineering Principles — why the wheel is shaped as it is