What size tyres does the Brompton G-Line use?

It uses 20-inch ETRTO 406 tyres. The stock fitment is the tubeless-ready Schwalbe G-One Allround in 54-406 (20×2.10), and Brompton also sells a 50-406 Continental Contact Urban as the faster road option.

What is the widest tyre that fits the G-Line?

54 mm (the stock G-One) is the widest officially-supported width — Brompton publishes no clearance figure. Width is limited by the frame, fork and Roller Frame, not the 406 bead, so a wider 406 may not fit. Treat anything above 54 mm as a measure-it-yourself, at-your-own-risk choice.

Can you run the Brompton G-Line tubeless?

Yes. The G-Line rims are tubeless-ready and come pre-taped from the factory; you only add a tubeless Presta valve and sealant. The stock G-One tyre is tubeless-ready too. Most aftermarket 406 tyres, however, are not tubeless-ready — check the tyre, not just the rim.

Is there a tubeless knobby or gravel tyre that fits the G-Line?

Effectively no. The only true-tubeless folding knobbies that exist in 406 (Schwalbe Rocket Ron 57-406, Vee Crown Gem 70-406) are too wide for the frame. For a real off-road tread that fits you currently accept a wire-bead, non-tubeless tyre such as the Schwalbe Black Jack 47-406.

Tyre compatibility record

Brompton G-Line tyres: every 406 option

Short version: the G-Line runs 20-inch ETRTO 406 tyres, and the stock Schwalbe G-One is a 54-406 (2.1in), tubeless-ready. That ~54 mm is the widest Brompton supports, and the limit isn’t the 406 bead — it’s frame, fork and roller-frame clearance. So a 406 that’s too wide will share the bead size and still not fit. Check clearance, not just the number on the sidewall. Below: every 406 tyre worth knowing, by purpose, with an honest fit call.

Working record. Widths and specs are compiled from manufacturer and dealer data and are being source-verified entry by entry; anything wider than the stock 54 mm is owner-measured on the actual bike before it’s called a fit. Prices are volatile bands, never live figures.

A What actually gates fit

Every 406 tyre shares the bead — that’s the easy half. The real limit is the gap in the frame, fork and (tightest of all) the Roller Frame. Brompton publishes no maximum.

Bead / wheel sizeconfirmed: ETRTO 406 (20"), NOT 451 · source ↗
Stock rimconfirmed: Brompton proprietary, double-wall hooked clincher, tubeless-ready & factory pre-taped, 6mm Presta, front 24h / rear 32h · source ↗
Rim internal widthlikely: ~22.6 mm internal / 28 mm external (both wheels) — wide for a 406; owner to caliper-verify · source ↗
Stock tyreconfirmed: Schwalbe G-One Allround 54-406 (20×2.10), LiteSkin 127 TPI, tubeless-ready, max 55 psi / 4.0 bar · source ↗
Max tyre widthlikely: 54 mm is the highest OFFICIALLY-SUPPORTED width (the stock tyre), NOT a measured ceiling. Brompton publishes no clearance figure. Anything wider = owner-measure / at-own-risk. · source ↗
Roller-frame clearanceunverified: No published figure. 54 mm confirmed to clear (sold that way); anything wider unverified. Likely the tightest point on the whole bike — owner must measure. · source ↗

B The 406 tyre database

Schwalbe G-One Allround (stock, HS473)

54-406 · All-road / gravel

Fits tubeless confirmed

55 psi · €55–80

The stock fitment and the only confirmed true-tubeless all-road tread in 406 that fits. Seats on the pre-taped rim with a floor pump.

Schwalbe G-One Speed (Brompton 'G One for G Line', LiteSkin)

54-406 · All-road / gravel

Fits tubeless confirmed

55 psi · €55–70

Faster dealer-sold sibling of the stock tread; same 54-406 footprint, tubeless-ready.

Schwalbe G-One Speed (40-406, V-Guard)

40-406 · Mixed

Fits tubeless confirmed

€35–55

Narrower, faster all-road option with more clearance margin and tubeless capability.

Schwalbe Marathon Racer (HS429, RaceGuard)

40-406 · Touring / commuter

Fits confirmed

€25–40

Lighter, faster touring option than Marathon Plus; folding bead, less puncture armour.

Schwalbe Marathon (HS420, GreenGuard)

40-406 · 47-406 · Touring / commuter

Fits confirmed

€22–35

The default rugged commuter; wire bead, reliable, cheap, everywhere.

Schwalbe Marathon Plus (HS440, SmartGuard)

35-406 · 40-406 · 47-406 · Touring / commuter

Fits confirmed

€26–45

Near flat-proof SmartGuard belt — the bombproof commuter choice. Heavy, slow, peace of mind.

Schwalbe Marathon Winter Plus (studded)

42-406 · Touring / commuter

Fits likely

€50–65

Studded ice tyre — niche, for genuine winter/ice commuting.

Schwalbe Big Ben Plus (HS439, GreenGuard)

55-406 · Touring / commuter

Check clearance likely

€30–45

Balloon comfort at 2.15in — AT/above the 54mm ceiling; measure frame + roller-frame before buying.

Schwalbe Big Apple (HS430, balloon)

50-406 · 55-406 · Urban / road

Check clearance likely

€25–40

Cushy low-pressure balloon. The 2.00 likely fits; the 2.15 needs a clearance check.

Schwalbe Kojak (HS385, slick)

35-406 · Urban / road

Fits confirmed

€30–45

Lightweight pure-road slick; fastest tarmac feel, minimal puncture protection.

Schwalbe Black Jack (HS407)

47-406 · MTB / dirt

Check clearance confirmed

€9–16

The most credible knobby that stays within clearance at 47mm — cheap, easy to buy in Spain. Wire bead, not tubeless. Verify knob height vs the stock low-profile tread.

Schwalbe Mad Mike (HS137)

47-406 · 57-406 · MTB / dirt

Check clearance confirmed

€12–20

BMX/dirt knobby; the 47 may fit, the 2.125 is over the ceiling. Wire bead.

Schwalbe Rocket Ron (20in, EVO Super Race, TLE)

57-406 · MTB / dirt

Too wide (likely) tubeless confirmed

€35–55

The ONLY tubeless folding knobby Schwalbe makes in 20in — but at 2.25in it is too wide for the G-Line. Listed to explain why a tubeless knobby that fits does not currently exist.

Schwalbe One (HS464, road, tube-type)

28-406 · Urban / road

Fits likely

€25–40

Narrow performance road slick (28mm) — for riders chasing speed over comfort.

Schwalbe Pro One Tubeless (TLE, HS462)

28-406 · Urban / road

Fits tubeless likely

€40–60

The only other true-tubeless 406 besides the G-One family — but a narrow 28mm road slick, a very different bike than the stock 54.

Schwalbe Durano / Durano Plus (road, tube-type)

28-406 · Urban / road

Fits likely

€25–40

Durable narrow road tyre; Durano Plus adds a puncture belt.

Continental Contact Urban (Brompton G-Line)

50-406 · Urban / road

Fits confirmed

73 psi · €25–45

Brompton's own faster/harder-wearing road option, reflective sidewall + puncture belt. The default fast-commute swap; confirms a 50mm fits stock. Wire bead, not tubeless.

Continental Contact (classic city/touring)

47-406 · Touring / commuter

Fits likely

€18–30

Budget city/touring all-rounder.

Maxxis DTH

40-406 · 47-406 · 50-406 · 55-406 · Urban / road

Fits likely

€20–35

Fast folding BMX/street slick in several widths; pick ≤50mm for clearance margin.

Maxxis Hookworm

49-406 · Urban / road

Fits likely

€20–35

Thick urban slick (corrected from a mislabelled 2.5in — real 406 is 1.95).

Maxxis Holy Roller

53-406 · Mixed

Check clearance likely

€18–30

Semi-slick street/dirt; at 53mm it is right at the ceiling — measure first.

Maxxis Torch

44-406 · 49-406 · 56-406 · Urban / road

Check clearance likely

€22–38

BMX-race semi-slick; the 56 is too wide, the 44/49 are the usable widths.

Tioga PowerBlock (S-Spec, folding)

40-406 · 44-406 · 54-406 · MTB / dirt

Check clearance likely

€20–40

Lighter folding dirt-block; the 40–44 are the clearance-safe widths. Import-only in places.

Kenda Small Block Eight (K1047 / Pro)

40-406 · 47-406 · 50-406 · All-road / gravel

Fits likely

€15–35

Low fast-rolling all-road tread; a genuine gravel-ish option that fits at ≤50mm.

Kenda Kwest (K193, high-pressure)

40-406 · 47-406 · Urban / road

Fits likely

€12–22

Cheap high-pressure commuter slick.

Kenda K-Rad (K905)

50-406 · 54-406 · 58-406 · MTB / dirt

Check clearance likely

€12–22

Aggressive urban-MTB knobby; only the 50 is plausibly in clearance, and only with a check.

Vee Tire Co. Speedster

40-406 · 44-406 · 47-406 · 50-406 · 60-406 · Mixed

Fits likely

€15–30

Popular folding-scene slick-ish tyre in many widths; choose ≤50mm. The 60 is too wide.

Panaracer Minits Tough (PT)

32-406 · Urban / road

Fits likely

€15–28

Narrow tough commuter slick (Panaracer does NOT make GravelKing in 406 — see negatives).

Tyre	ETRTO / width	Use	Tubeless	Weight	Max psi	Fit on G-Line	Note
Schwalbe G-One Allround (stock, HS473) confirmed	54-406	All-road / gravel	✓	~493	55	Fits	The stock fitment and the only confirmed true-tubeless all-road tread in 406 that fits. Seats on the pre-taped rim with a floor pump.
Schwalbe G-One Speed (Brompton 'G One for G Line', LiteSkin) confirmed	54-406	All-road / gravel	✓	——	55	Fits	Faster dealer-sold sibling of the stock tread; same 54-406 footprint, tubeless-ready.
Schwalbe G-One Speed (40-406, V-Guard) confirmed	40-406	Mixed	✓	——	——	Fits	Narrower, faster all-road option with more clearance margin and tubeless capability.
Schwalbe Marathon Racer (HS429, RaceGuard) confirmed	40-406	Touring / commuter	—	——	——	Fits	Lighter, faster touring option than Marathon Plus; folding bead, less puncture armour.
Schwalbe Marathon (HS420, GreenGuard) confirmed	40-406, 47-406	Touring / commuter	—	——	——	Fits	The default rugged commuter; wire bead, reliable, cheap, everywhere.
Schwalbe Marathon Plus (HS440, SmartGuard) confirmed	35-406, 40-406, 47-406	Touring / commuter	—	——	——	Fits	Near flat-proof SmartGuard belt — the bombproof commuter choice. Heavy, slow, peace of mind.
Schwalbe Marathon Winter Plus (studded) likely	42-406	Touring / commuter	—	——	——	Fits	Studded ice tyre — niche, for genuine winter/ice commuting.
Schwalbe Big Ben Plus (HS439, GreenGuard) likely	55-406	Touring / commuter	—	——	——	Check clearance	Balloon comfort at 2.15in — AT/above the 54mm ceiling; measure frame + roller-frame before buying.
Schwalbe Big Apple (HS430, balloon) likely	50-406, 55-406	Urban / road	—	——	——	Check clearance	Cushy low-pressure balloon. The 2.00 likely fits; the 2.15 needs a clearance check.
Schwalbe Kojak (HS385, slick) confirmed	35-406	Urban / road	—	——	——	Fits	Lightweight pure-road slick; fastest tarmac feel, minimal puncture protection.
Schwalbe Black Jack (HS407) confirmed	47-406	MTB / dirt	—	——	——	Check clearance	The most credible knobby that stays within clearance at 47mm — cheap, easy to buy in Spain. Wire bead, not tubeless. Verify knob height vs the stock low-profile tread.
Schwalbe Mad Mike (HS137) confirmed	47-406, 57-406	MTB / dirt	—	——	——	Check clearance	BMX/dirt knobby; the 47 may fit, the 2.125 is over the ceiling. Wire bead.
Schwalbe Rocket Ron (20in, EVO Super Race, TLE) confirmed	57-406	MTB / dirt	✓	——	——	Too wide (likely)	The ONLY tubeless folding knobby Schwalbe makes in 20in — but at 2.25in it is too wide for the G-Line. Listed to explain why a tubeless knobby that fits does not currently exist.
Schwalbe One (HS464, road, tube-type) likely	28-406	Urban / road	—	——	——	Fits	Narrow performance road slick (28mm) — for riders chasing speed over comfort.
Schwalbe Pro One Tubeless (TLE, HS462) likely	28-406	Urban / road	✓	——	——	Fits	The only other true-tubeless 406 besides the G-One family — but a narrow 28mm road slick, a very different bike than the stock 54.
Schwalbe Durano / Durano Plus (road, tube-type) likely	28-406	Urban / road	—	——	——	Fits	Durable narrow road tyre; Durano Plus adds a puncture belt.
Continental Contact Urban (Brompton G-Line) confirmed	50-406	Urban / road	—	~420	73	Fits	Brompton's own faster/harder-wearing road option, reflective sidewall + puncture belt. The default fast-commute swap; confirms a 50mm fits stock. Wire bead, not tubeless.
Continental Contact (classic city/touring) likely	47-406	Touring / commuter	—	——	——	Fits	Budget city/touring all-rounder.
Maxxis DTH likely	40-406, 47-406, 50-406, 55-406	Urban / road	?	——	——	Fits	Fast folding BMX/street slick in several widths; pick ≤50mm for clearance margin.
Maxxis Hookworm likely	49-406	Urban / road	—	——	——	Fits	Thick urban slick (corrected from a mislabelled 2.5in — real 406 is 1.95).
Maxxis Holy Roller likely	53-406	Mixed	—	——	——	Check clearance	Semi-slick street/dirt; at 53mm it is right at the ceiling — measure first.
Maxxis Torch likely	44-406, 49-406, 56-406	Urban / road	?	——	——	Check clearance	BMX-race semi-slick; the 56 is too wide, the 44/49 are the usable widths.
Tioga PowerBlock (S-Spec, folding) likely	40-406, 44-406, 54-406	MTB / dirt	—	——	——	Check clearance	Lighter folding dirt-block; the 40–44 are the clearance-safe widths. Import-only in places.
Kenda Small Block Eight (K1047 / Pro) likely	40-406, 47-406, 50-406	All-road / gravel	?	——	——	Fits	Low fast-rolling all-road tread; a genuine gravel-ish option that fits at ≤50mm.
Kenda Kwest (K193, high-pressure) likely	40-406, 47-406	Urban / road	—	——	——	Fits	Cheap high-pressure commuter slick.
Kenda K-Rad (K905) likely	50-406, 54-406, 58-406	MTB / dirt	?	——	——	Check clearance	Aggressive urban-MTB knobby; only the 50 is plausibly in clearance, and only with a check.
Vee Tire Co. Speedster likely	40-406, 44-406, 47-406, 50-406, 60-406	Mixed	—	——	——	Fits	Popular folding-scene slick-ish tyre in many widths; choose ≤50mm. The 60 is too wide.
Panaracer Minits Tough (PT) likely	32-406	Urban / road	—	——	——	Fits	Narrow tough commuter slick (Panaracer does NOT make GravelKing in 406 — see negatives).

C Asked for, but not made in 406

The most-requested tyres that simply do not exist in this wheel size — so you can stop searching.

Panaracer GravelKing (SK/Slick/SS/X1)

Not made in 406 — smallest GravelKing is 650b/700c. The most-requested tyre that simply does not exist for the G-Line.

Rene Herse / Compass (Barlow Pass, etc.)

No 406 SKU — smallest Rene Herse diameter is 26in (559).

Soma Cazadero / Shikoro

700c/650b only; no 406.

Schwalbe G-One R / RS / RX (race treads)

The performance G-One patterns are 622/700c only — only the Allround/Speed exist in 54-406.

Schwalbe Marathon Almotion / Mondial / GT

No confirmed 406 SKU (Almotion smallest is 40-622; Mondial/GT are 622/559).

Maxxis Rambler (and Maxxis gravel treads)

Maxxis's gravel/CX treads are 700c only — no Maxxis gravel knobby exists in 406. The Torch in 406 is a BMX semi-slick, not gravel.

Vee Crown Gem 70-406 / Schwalbe Rocket Ron 57-406

These tubeless folding knobbies DO exist in 406 but are too wide (2.8in / 2.25in) for the G-Line frame — which is why a true-tubeless knobby that fits does not currently exist.

D Running it tubeless

The G-Line wheels are tubeless-ready and ship pre-taped. Tubeless is a four-part chain — all four must be true; never trust “it’s tubeless” alone:

1 Tyre is tubeless-ready (TLR/TLE) — stock G-One is; most 406 options are NOT.
2 Rim is tubeless-ready — G-Line rims are, factory pre-taped (hooked, not hookless).
3 Tape seals the bed airtight — re-tape if the stock tyre is removed or the bed is disturbed (~21–25 mm tape for the ~22.6 mm bed).
4 Tubeless Presta valve + sealant — ~40–60 ml per wheel (verify against the sealant maker chart).

For a conversion you only add valves + sealant (re-tape only if the bed is disturbed). The owner’s build uses a Muc-Off Road/Gravel 44 mm kit — the shallow-rim valve length that’s correct for a 406 rim; the 60 mm and MTB-width options are wrong for it.

Tyre FAQ

What size tyres does the Brompton G-Line use?: It uses 20-inch ETRTO 406 tyres. The stock fitment is the tubeless-ready Schwalbe G-One Allround in 54-406 (20×2.10), and Brompton also sells a 50-406 Continental Contact Urban as the faster road option.
What is the widest tyre that fits the G-Line?: 54 mm (the stock G-One) is the widest officially-supported width — Brompton publishes no clearance figure. Width is limited by the frame, fork and Roller Frame, not the 406 bead, so a wider 406 may not fit. Treat anything above 54 mm as a measure-it-yourself, at-your-own-risk choice.
Can you run the Brompton G-Line tubeless?: Yes. The G-Line rims are tubeless-ready and come pre-taped from the factory; you only add a tubeless Presta valve and sealant. The stock G-One tyre is tubeless-ready too. Most aftermarket 406 tyres, however, are not tubeless-ready — check the tyre, not just the rim.
Is there a tubeless knobby or gravel tyre that fits the G-Line?: Effectively no. The only true-tubeless folding knobbies that exist in 406 (Schwalbe Rocket Ron 57-406, Vee Crown Gem 70-406) are too wide for the frame. For a real off-road tread that fits you currently accept a wire-bead, non-tubeless tyre such as the Schwalbe Black Jack 47-406.