Dirt Bike Tire Hub
OEM sizes, terrain-specific tread guides, pressure charts, mousse vs. tube vs. Tubliss comparison, how to change a dirt bike tire, mini/youth bike sizing, and fitment tables for KTM, Honda, Yamaha, Kawasaki, Husqvarna, Suzuki, and Gas Gas.
All tire sizes, pressures, and recommendations on this page are for informational reference only. Always verify fitment with your bike's owner manual and a qualified mechanic. TireCalculatorHub is not liable for damages arising from use of this information.
Quick Reference
Common dirt bike tire questions answered in one line. Expand sections below for full detail.
Decode 80/100-21
80 = tread width in mm. 100 = aspect ratio (sidewall height is 100% of 80mm = 80mm tall). 21 = rim diameter in inches. This is the universal front tire for full-size motocross bikes.
Standard MX front tire
80/100-21 is the global standard for full-size MX/enduro front tires. Enduro trail bikes often run 90/90-21. Mini bikes (65cc–85cc) use 60/100-14 or 70/100-17.
Standard MX rear tire
110/90-19 (250cc soft) or 120/80-19 / 120/90-19 (450cc intermediate/hard) for motocross. Enduro and trail bikes typically run 110/100-18 or 120/90-18 on 18″ rims.
Motocross tire pressure
Typical MX: 12–14 PSI front, 12–14 PSI rear. Enduro: 10–12 PSI front, 10–13 PSI rear. Sand: 10–12 PSI. Always check cold — never exceed 20 PSI for off-road tires.
Mousse vs. inner tube?
Bib mousse = zero puncture risk, consistent feel, heavier (+400–700g), generates heat, needs replacement every 25–50 hours. Tubes = lighter, adjustable pressure, susceptible to pinch flats. Enduro racing favors mousse; recreational trail riders often prefer tubes.
Which terrain tire for me?
Soft (S): deep mud, loam — open paddle knobs. Intermediate (I/MX): most tracks, packed dirt — balanced knobs. Hard (H/MX33): rock, hardpan — short, dense knobs. Sand: pure dunes — long rear paddles, open front. Dual-sport/trail: mixed; look for "AT" or enduro compounds.
How to Read Dirt Bike Tire Sizes
Dirt bike tires use the metric sizing system: Width / Aspect Ratio – Rim Diameter. Unlike car tires (which use an "R" for radial construction), most off-road tires are bias-ply (cross-ply) — indicated by a hyphen before the rim size (e.g., 110/90-19) rather than "R19".
Decoded Example: 110/90-19
- 110 — Section width in millimeters (widest point)
- 90 — Aspect ratio: sidewall height = 90% × 110mm = 99mm sidewall
- 19 — Rim diameter in inches
- Hyphen (–) — Indicates bias-ply construction; "R" would mean radial
Decoded Example: 80/100-21 (Universal Front)
- 80 — Narrow 80mm width — cuts through loose terrain
- 100 — Tall 100% aspect ratio: sidewall = 80mm — absorbs impacts, allows flex
- 21 — Standard 21-inch front rim for all full-size MX and enduro bikes
Note on 90/90-21: Same 21-inch rim, but wider (90mm) and slightly lower profile. Used on enduro and trail bikes where a larger contact patch helps on roots and rocks. The 80/100-21 is the MX standard; the 90/90-21 is the enduro standard.
Older inch sizing: Some older bikes and catalogs list sizes in the legacy inch format (e.g., 3.00-21 or 4.50-18). See the conversion table below for equivalents.
Full Sidewall Markings Decoder
Directional arrow: Most knobby tires have a directional arrow molded into the sidewall. Mount so the arrow points in the direction of forward rotation. On the rear, the open (wide) end of the V-shaped knob pattern should face forward at the contact patch bottom — this is the drive face. Mounting backwards causes knobs to fold over under acceleration rather than bite, causing traction loss.
DOT code: A string starting with "DOT" followed by letters and a 4-digit date code. Example: DOT AB1C 2423— the last 4 digits (2423) mean week 24 of 2023 (June 2023). Some off-road tires are NOT DOT approved and display "NOT FOR HIGHWAY USE" — they cannot legally be ridden on public roads in the US.
NHS (Not for Highway Service):Tires marked "NHS" lack DOT approval for road use. Most pure motocross tires are NHS. For public road riding, you need a DOT-approved tire (e.g., Dunlop D606, Kenda K760 Trackmaster). EU equivalent: e-mark (ECE homologation).
Bias-ply vs. radial: A hyphen before the rim size (110/90-19) means bias-ply. An "R" would indicate radial. Nearly all off-road tires are bias-ply — the stiffer carcass handles rocks and rim impacts better than radials.
DOT date code & rubber age: Tire rubber degrades from UV, heat, and ozone even without riding. Leading manufacturers recommend replacing tires within 5 years of manufacture (10 years absolute maximum for stored tires). Always check the DOT date code before buying new-old-stock tires online.
OEM Tire Sizes by Make & Model
Factory tire sizes for current and recent dirt bike models (2021–present). Rim sizes and fitment notes included. Always verify against your owner's manual — sizes can vary by model year and regional market.
| Make | Model | Years | Front Tire | Rear Tire | Front Rim | Rear Rim | Notes |
|---|---|---|---|---|---|---|---|
| KTM | 125 SX | 2023–present | 80/100-21 | 100/90-19 | 21×1.60 | 19×1.85 | Junior MX; some prefer 100/90-19 rear upgrade |
| KTM | 250 SX / SX-F | 2023–present | 80/100-21 | 110/90-19 | 21×1.60 | 19×2.15 | OEM Bridgestone X30; 120/80-19 popular upgrade |
| KTM | 450 SX-F | 2023–present | 80/100-21 | 120/80-19 | 21×1.60 | 19×2.15 | Factory option: 120/90-19; avoid going wider on SX frames |
| KTM | 250 EXC-F / 350 EXC-F | 2023–present | 90/90-21 | 140/80-18 | 21×1.60 | 18×2.15 | Enduro spec; 18″ rear for trail; road legal in many markets |
| KTM | 500 EXC-F | 2023–present | 90/90-21 | 140/80-18 | 21×1.60 | 18×2.15 | Adventure/dual-sport use: 120/70-19 front common swap |
| Honda | CRF250R | 2022–present | 80/100-21 | 110/90-19 | 21×1.60 | 19×2.15 | OEM Dunlop MX3S; Geomax MX33 direct replacement |
| Honda | CRF450R | 2021–present | 80/100-21 | 120/80-19 | 21×1.60 | 19×2.15 | Factory Dunlop Geomax MX34; soft tracks: 110/90-19 |
| Honda | CRF450RWE | 2021–present | 80/100-21 | 120/80-19 | 21×1.60 | 19×2.15 | Works edition; DID Dirt Star rims; same tire spec as CRF450R |
| Honda | CRF250F (trail) | 2022–present | 80/100-21 | 100/100-18 | 21×1.60 | 18×1.85 | Trail/recreation; 18″ rear; tubeless option on some markets |
| Honda | CRF450X | 2020–present | 80/100-21 | 120/100-18 | 21×1.60 | 18×2.15 | Desert racing spec; wider 120 rear for sand/hardpack |
| Yamaha | YZ125 | 2022–present | 80/100-21 | 100/90-19 | 21×1.60 | 19×1.85 | Two-stroke; lighter rear (100) suits 2T power delivery |
| Yamaha | YZ250F | 2023–present | 80/100-21 | 110/90-19 | 21×1.60 | 19×2.15 | OEM Dunlop MX33; upgrade to MX34 for hard/intermediate |
| Yamaha | YZ450F | 2023–present | 80/100-21 | 120/80-19 | 21×1.60 | 19×2.15 | OEM Dunlop MX33; factory riders often on 120/90-19 |
| Yamaha | WR250F | 2022–present | 80/100-21 | 110/100-18 | 21×1.60 | 18×2.15 | Enduro/trail; 18″ rear; road-legal in many markets |
| Yamaha | WR450F | 2022–present | 90/90-21 | 120/90-18 | 21×1.60 | 18×2.15 | Wider tread for varied terrain; 90/90-21 on open trails |
| Kawasaki | KX250 | 2022–present | 80/100-21 | 110/90-19 | 21×1.60 | 19×2.15 | OEM Dunlop MX3S; 120/80-19 upgrade on hardpack |
| Kawasaki | KX450 | 2023–present | 80/100-21 | 120/80-19 | 21×1.60 | 19×2.15 | Factory option: 120/90-19 on sandy tracks |
| Kawasaki | KLX300R | 2021–present | 80/100-21 | 100/100-18 | 21×1.60 | 18×1.85 | Dual-sport/trail; 18″ rear with street-legal tread |
| Husqvarna | FC 250 / FC 350 | 2023–present | 80/100-21 | 110/90-19 | 21×1.60 | 19×2.15 | Shared KTM platform; same tire spec applies |
| Husqvarna | FC 450 | 2023–present | 80/100-21 | 120/80-19 | 21×1.60 | 19×2.15 | Factory spec follows KTM 450 SX-F; Bridgestone X30 OEM |
| Husqvarna | FE 350 / FE 450 | 2023–present | 90/90-21 | 140/80-18 | 21×1.60 | 18×2.15 | Enduro spec; 18″ rear; road legal in EU/AU |
| Husqvarna | TE 150i / TX 300i | 2023–present | 80/100-21 | 110/100-18 | 21×1.60 | 18×2.15 | Two-stroke enduro; lighter rear spec for 2T power |
| Suzuki | RM-Z250 | 2023–present | 80/100-21 | 110/90-19 | 21×1.60 | 19×2.15 | OEM Dunlop MX3S; intermediate compound standard |
| Suzuki | RM-Z450 | 2023–present | 80/100-21 | 120/80-19 | 21×1.60 | 19×2.15 | Factory Dunlop MX34; same sizing class as YZ450F/KX450 |
| Suzuki | DR-Z400S | 2021–present | 80/100-21 | 110/90-18 | 21×1.60 | 18×1.85 | Dual-sport; DOT tires required; 18″ rear for trail compliance |
| Gas Gas | MC 250F / MC 450F | 2023–present | 80/100-21 | 110/90-19 / 120/80-19 | 21×1.60 | 19×2.15 | KTM-platform bike; same sizing rules as KTM SX-F |
| Gas Gas | EC 250F / EC 350F | 2023–present | 90/90-21 | 140/80-18 | 21×1.60 | 18×2.15 | Enduro; same platform and sizes as Husqvarna FE |
Sources: KTM AG, Honda Powersports, Yamaha Motor Corp, Kawasaki Motors, Husqvarna Motorcycles, Suzuki Motor Corp, Gas Gas Motorcycles product specifications. Verify against owner's manual for your specific model year.
Mini Bike & Youth Dirt Bike Tire Sizes
Mini and youth bikes use entirely different tire sizes than full-size bikes. The 50cc–125cc class covers a wide range of rim diameters (10″ to 19″) and requires careful size matching. Using the wrong size can affect handling, safety, and AMA class eligibility.
50cc Tire Sizes
50cc bikes divide into two categories: balance/training bikes (Yamaha PW50) use 2.50-10 on both ends — a legacy inch size. Race-spec 50cc bikes (Honda CRF50F, KTM 50 SX Mini) use 60/100-14 front and rear. When replacing, always confirm the rim diameter from the tire sidewall before ordering.
65cc Tire Sizes
65cc race bikes (KTM 65 SX, Kawasaki KX65, Yamaha YZ65) use 60/100-14 on the front and a smaller rear — either 2.50-12 (Kawasaki) or 2.75-10 (KTM/Yamaha). The difference in rear size between brands is a common source of confusion when cross-shopping tires.
85cc Small Wheel (SW) Tire Sizes
The 85cc SW class uses 70/100-17 front and 90/100-14rear. AMA class rules cap the rear at 14" and front at 17" for SW eligibility. SW is suited for lighter, shorter riders who aren't yet ready for the larger BW wheel geometry.
85cc Big Wheel (BW) Tire Sizes
The 85cc BW class uses 70/100-19 front and 90/100-16 rear. AMA rules cap the BW rear at 16" and front at 19". The larger wheels give a geometry closer to full-size bikes, making BW the preferred setup for taller riders transitioning toward 125cc/250cc competition.
110cc–125cc Trail Bike Sizes
Trail bikes in this range (Honda CRF110F, Yamaha TTR125, Honda CRF125F) typically run 70/100-17 front and 80/100-14 or 90/100-14 rear. These are recreational sizes — riders wanting to step up to race compound tires will find limited options compared to the full-size 80/100-21 and 110/90-19 market.
Mini Bike OEM Size Reference
| Class | Make / Model | Years | Front Tire | Rear Tire | Notes |
|---|---|---|---|---|---|
| 50cc | Yamaha PW50 | 2023 | 2.50-10 | 2.50-10 | Balance/training bike; same front and rear size |
| 50cc | Honda CRF50F | 2022–present | 60/100-14 | 60/100-14 | Standard mini; identical front/rear sizing |
| 50cc | KTM 50 SX Mini | 2023 | 60/100-14 | 60/100-14 | Race-spec 50cc; OEM Dunlop MX53 |
| 65cc | KTM 65 SX | 2023 | 60/100-14 | 2.75-10 | Competitive 65cc; front and rear differ |
| 65cc | Kawasaki KX65 | 2023 | 60/100-14 | 2.50-12 | OEM Dunlop MX12 |
| 65cc | Yamaha YZ65 | 2023 | 60/100-14 | 2.75-10 | Mini motocross spec |
| 85cc SW | KTM 85 SX (SW) | 2023 | 70/100-17 | 90/100-14 | Small wheel class; AMA-legal rear ≤14", front ≤17" |
| 85cc SW | Kawasaki KX85 | 2023 | 70/100-17 | 90/100-14 | Factory Dunlop; small wheel for lighter/younger riders |
| 85cc SW | Yamaha YZ85 | 2023 | 70/100-17 | 90/100-14 | Standard SW spec for AMA 85cc class |
| 85cc BW | KTM 85 SX (BW) | 2023 | 70/100-19 | 90/100-16 | Big wheel class; AMA-legal rear ≤16", front ≤19" |
| 85cc BW | Yamaha YZ85 (BW) | 2023 | 70/100-19 | 90/100-16 | Big wheel setup for taller/transitioning riders |
| 110cc | Honda CRF110F | 2022–present | 70/100-17 | 80/100-14 | Trail/rec; durable stock tires for beginners |
| 125cc | Yamaha TTR125 | 2022–present | 70/100-17 | 90/100-14 | Trail 125; transitional before full-size 21" front |
| 125cc | Honda CRF125F | 2022–present | 70/100-17 | 90/100-14 | Rec/trail; good first upgrade: Dunlop AT25 |
AMA Youth Class Wheel Size Rules
- 50cc class: Typically rim sizes 10"–14"; check local sanctioning body rules
- 65cc class: Front max 14", rear max 12"; check regional series rules
- 85cc Small Wheel (SW): Rear rim max 14", front rim max 17"
- 85cc Big Wheel (BW): Rear rim max 16", front rim max 19"
- Note: AMA rules apply to sanctioned events; local club rules may differ. Always confirm with the event organizer before purchasing BW tires for your rider.
Metric ↔ Inch Tire Size Conversion
Modern dirt bike tires use metric sizing, but older bikes, some catalogs, and vintage parts still use the legacy inch format.
| Metric Size | Inch Equivalent | Common Application |
|---|---|---|
| 60/100-14 | 2.50×14 | Mini 50cc–65cc rear |
| 70/100-17 | 2.75×17 | 85cc rear / mini front |
| 70/100-19 | 2.75×19 | 85cc big wheel front |
| 80/100-21 | 3.00×21 | Full-size MX/enduro front (universal) |
| 90/90-21 | 3.00×21 (tall) | Enduro/trail front; taller sidewall |
| 100/90-19 | 4.00×19 | 125cc MX rear / 85cc BW rear |
| 110/90-19 | 4.50×19 | 250cc MX rear (standard) |
| 120/80-19 | 4.75×19 | 450cc MX rear (intermediate/hard) |
| 120/90-19 | 4.75×19 (tall) | 450cc factory / soft-intermediate |
| 100/100-18 | 4.00×18 | Trail / recreation rear 18″ |
| 110/100-18 | 4.50×18 | 2-stroke enduro rear (250cc) |
| 120/90-18 | 4.75×18 | WR-spec enduro rear (larger bikes) |
| 140/80-18 | 5.50×18 | KTM/Husqvarna EXC enduro rear |
| 120/100-18 | 4.75×18 | Desert / hard enduro rear |
Terrain-Specific Tire Guide
Matching your tire to terrain type is the single most impactful performance decision you can make. Running the wrong terrain tire can turn a fast bike slow — or a safe setup dangerous.
Soft / Mud (S)
Intermediate (I / MX)
Hard Pack / Hardpan (H)
Sand / Desert
Enduro / Trail (AT/E)
Hard Enduro / Extreme
Dual-Sport / Road-Legal
How Tire Size Affects Handling & Performance
Tire dimensions directly influence steering feel, cornering, weight, and traction. Understanding these trade-offs lets you make informed choices beyond simply matching OEM specs.
Going Wider: 110 → 120 Rear — Trade-offs
Swapping from 110/90-19 to 120/80-19 adds approximately 0.8–1.2 kg and increases the contact patch width. Benefits: more traction in loam, intermediate packed dirt, and soft conditions; preferred by most 450cc-class factory riders. Downsides: harder to tip into corners (more resistance to lean), slightly slower steering response. Most 450cc swingarms are wide enough for a 120 with standard chain clearance. According to Motocross Action Magazine, 120s can make bikes noticeably harder to roll over in tight corners — notable primarily at the 250cc level, less so on 450cc.
Going Narrower: 120 → 110 Rear — Trade-offs
Running a narrower 110/90-19 reduces rotating mass and improves tip-in speed. Benefits: easier to lean, better hook-up in ruts and soft/muddy conditions, lighter overall. Standard on all 250cc factory bikes for this reason. Downsides: slightly less footprint on flat hard-pack; minimal traction penalty in intermediate conditions. PulpMX notes that most AMA 250 pro riders prefer 110s for the faster cornering geometry they provide.
Front Tire Width: 80/100-21 vs. 90/90-21
The 80/100-21 is the MX standard — its narrow profile cuts through loam and MX ruts more effectively, contributing to straight-line stability under braking. The 90/90-21 is the enduro/trail standard — the wider footprint provides more contact patch on roots, rocks, and loose-over-hard terrain, improving front-end feedback at low speed. Switching from 80/100 to 90/90 on a motocross bike is uncommon and generally not recommended; going the other direction (90/90 to 80/100 on an enduro bike) is occasionally done for particularly rooted/technical terrain.
18" vs. 19" Rear Rim — The Enduro vs. MX Split
This is the fundamental divide between MX and enduro suspension philosophy. 19" rims (standard MX) give a shorter, stiffer sidewall — quicker steering response and rim protection at speed on groomed tracks. 18" rims (standard enduro — KTM EXC, Husqvarna FE, Yamaha WR) have a taller sidewall that acts as a secondary suspension element, absorbing rock and root impacts the suspension doesn't fully catch. Factory MX teams run 19"; ISDE and GNCC enduro teams universally run 18". You cannot mix rim sizes without changing the entire wheel.
Tire Pressure Reference by Discipline
Dirt bike tire pressures are far lower than road vehicles — low pressure increases the contact patch and compliance on uneven surfaces. Always measure cold (before riding). Pressure rises 1–3 PSI after a hot lap; this is normal.
| Discipline | Front (PSI) | Rear (PSI) | Notes |
|---|---|---|---|
| Supercross (indoor MX) | 13–14 | 13–15 | Harder surface, consistent; higher pressure for rim protection |
| Motocross (outdoor MX) | 12–14 | 12–14 | Standard outdoor track; adjust for wet vs. dry conditions |
| Enduro / Hare Scrambles | 10–12 | 10–13 | Mixed terrain; lower pressure increases traction on varied surfaces |
| Hard Enduro / Extreme | 8–11 | 8–11 | Very low for rock grip; mousse recommended at < 10 PSI |
| Desert Racing / Sand | 10–12 | 10–12 | Sand floats — lower pressure spreads load over more surface |
| Trail / Recreation | 12–14 | 12–14 | Conservative starting point; adjust ± 2 PSI per conditions |
| Dual-Sport / Road Legal | 19–23 | 21–26 | Road sections require higher pressure; check tire sidewall max |
Pressure & Rider Weight Adjustment
Adjust from the baseline above based on rider weight:
- Under 65 kg: Reduce 1–2 PSI from baseline
- 65–80 kg: Use baseline pressure
- 80–95 kg: Add 1–2 PSI
- Over 95 kg: Add 2–3 PSI (also consider wider rear tire)
Heavier riders risk rim strikes at very low pressures. If you're frequently denting rims, go up 1–2 PSI before buying a new rim.
Manufacturer-Recommended PSI by Tire Brand & Model
Each tire manufacturer publishes specific PSI recommendations for their models — these differ from the generic discipline ranges above and reflect the tire's carcass stiffness and compound design. Race-day setup should reference the brand recommendation first, then adjust ± 1–2 PSI for conditions.
| Brand | Model | Front PSI | Rear PSI |
|---|---|---|---|
| Pirelli | MX32 Mid Soft | 13.5 | 14 |
| Pirelli | MX32 Mid Hard | 13.5 | 13 |
| Pirelli | MX32 Soft (Scoop) | — | 13 |
| Dunlop | MX33 | 12.5 | 12 |
| Dunlop | MX3S | 13.5 | — |
| Dunlop | MX53 | 13 | 13.5 |
| Bridgestone | X30 / X31 | 13 | 12.5 |
| Bridgestone | X40 | 12.5 | 12.5 |
| Michelin | Starcross 5 Soft/Med | 13.5 | 13 |
| Michelin | Starcross 6 Soft/Med | 13 | 13 |
Source: manufacturer published race setup guides (Keefer Inc Testing, Pirelli, Dunlop, Bridgestone, Michelin technical documentation). "—" indicates front-only or rear-only tire model. Values are for intermediate MX conditions; reduce 1–2 PSI for softer terrain.
Inner Tube vs. Bib Mousse vs. Tubliss: Full Comparison
Three distinct philosophies for off-road tire setup, each with different trade-offs in weight, cost, puncture protection, and adjustability. Michelin invented the bib mousse in the 1980s for extreme enduro racing; the Tubliss system offers a middle ground.
| Factor | Inner Tube | Bib Mousse | Tubliss |
|---|---|---|---|
| Puncture risk | Pinch flats, thorns, rim cuts | Zero — no air, no flat | Zero — 100 PSI inner core protects rim |
| Weight | Lightest (150–300g tube) | +400–700g per wheel | ~800g per wheel (kit + bladder) |
| Pressure feel | Fully adjustable — fine-tune per terrain | Fixed ~12 PSI feel; not adjustable | Adjustable 0–13 PSI outer; inner core at 100–120 PSI stays fixed |
| Heat buildup | No heat concern | Generates heat at speed; lifespan affected | Minimal — no foam to degrade from heat |
| Lifespan | Indefinite if no puncture; cheap to replace | 25–50 riding hours (replace every season if racing) | Kit lasts years; replace bladder every 2–3 seasons |
| Installation | Standard tire irons; straightforward process | Requires mousse grease; more effort; curved irons helpful | More complex; may require drilling rim lock hole on KTM/Husq/Gas Gas |
| Cost | €10–€25 per tube | €40–€120 per mousse | $80–$100 kit per wheel; reusable indefinitely |
| Rim locks | Required; torque to 12–15 Nm | Still required to prevent tire rotation on rim | 1 rim lock still recommended; inner core adds rim strike protection |
| Best for | Recreational trail, MX practice, budget riders | Enduro racing, ISDE, extreme events, hard enduro | Enduro/trail riders wanting flat protection with adjustable pressure |
| Top brands | Michelin, Bridgestone, Dunlop | Michelin Bib Mousse, Nitro Mousse, Mefo Sport | Nuetech TUbliss Gen 2.0, Ride Engineering |
Mousse Installation Key Steps
- Apply generous mousse-specific mounting grease (NOT WD-40) to the mousse exterior and tire interior
- Stand the tire upright and push the mousse inside — work it around until fully seated
- Install rim lock and valve stem on the rim before mounting the tire
- Use curved tire irons; mount one bead, then work the mousse over the rim lip
- Mount the second bead — the last few inches near the rim lock will be very tight; use small "bites"
- Stand the wheel and bounce it to seat the tire fully; tighten rim lock to 12–15 Nm
- Inspect mousse and re-apply grease every 10–15 riding hours to prevent heat damage
Tubliss System — How It Works & Setup
The Nuetech TUbliss system replaces the inner tube with a two-chamber approach: a 100 PSI inner bladder (red) seats against the rim and acts as a structural bead-locking device, while the outer tire chamber can be run at any pressure from 0 to 13 PSI — giving mousse-level flat protection with tube-level pressure adjustability.
- Compatible rim sizes: 18", 19", and 21" (fits standard 1.85–2.15 width rims)
- Setup note: KTM, Husqvarna, and Gas Gas bikes require drilling/enlarging the rim lock hole to accommodate the TUbliss valve stem fitting
- Inner core pressure: 100–120 PSI (never vary this — it's the structural component)
- Outer tire pressure: 0–13 PSI — adjust per terrain like a normal tube
- Weight: ~800g per wheel — heavier than a tube, lighter than most mousse
- Ideal for: Enduro and trail riders who want flat protection on long wilderness rides where tube changes are impractical
Rim Locks — Setup, Torque & Common Mistakes
A rim lock is a metal clamp that bolts through the rim and bites into the tire bead, preventing tire rotation on the rim at low pressures. Without it, hard braking or acceleration at off-road pressures (8–14 PSI) will spin the tire on the rim and shear the valve stem — resulting in catastrophic sudden deflation.
- How many: Front: 1 rim lock (standard). Rear: 1 minimum; desert/enduro racers sometimes run 2 for extra security
- Correct torque: 12–15 Nm (9–11 ft-lbs). Under-torqued = tire spins; over-torqued = cracks rim lock or damages bead
- Position: Mount the rim lock directly opposite the valve stem (180° apart) to balance wheel mass and reduce vibration at speed
- With mousse or Tubliss: Always still required — rim lock prevents tire rotation regardless of tube/mousse setup
- Weight: Steel rim lock adds ~120–150g; aluminum aftermarket rim locks save ~60g — relevant for race builds
How to Change a Dirt Bike Tire
Changing a dirt bike tire is a fundamental skill every rider should know. With the right tools and technique, a tire change takes 20–30 minutes. The most common mistakes (pinching the tube, wrong rotation direction) are easily avoided with the steps below.
Tools Required
- ✓ 3× spoon-type tire irons (curved, 10–12" length)
- ✓ Rim lock wrench (10mm socket or open-end wrench)
- ✓ Bead breaker tool (or use body weight on the sidewall)
- ✓ Valve core tool
- ✓ Soapy water or dedicated tire mounting paste
- ✓ Torque wrench (for rim lock: 12–15 Nm)
- ✓ Stand, bucket, or tire changing stand to hold the wheel
- ✓ Rim protectors (optional but prevent scratching)
Removing the Old Tire (Step-by-Step)
- Remove the valve core with a valve core tool — let all air out completely
- Loosen (don't remove) the rim lock nut; push the rim lock body inward so it's flush with the bead
- Break the bead: stand the wheel upright, place your foot on the sidewall near the rim edge, and press down to push the bead off the rim seat. Repeat around the full circumference on both sides
- Apply soapy water to the bead to reduce friction
- Insert one tire iron at a point away from the rim lock. Lever the first bead over the rim edge and hold it; insert a second iron 10 cm away, lever again. Work around until the entire first bead is over the rim
- Remove the tube: reach inside, pull out the tube, remove the valve stem nut first
- For the second bead: insert irons again and lever the tire completely off the rim
- Inspect the rim tape and rim lock for damage before fitting the new tire
Installing a New Tire with Inner Tube
- Check rotation direction first — find the directional arrow on the sidewall; confirm it will point forward when the wheel is installed before mounting
- Apply soapy water to both tire beads and the rim edge
- Push the first bead onto the rim by hand — this should go on without tools
- Install the rim lock loosely; insert the valve stem through the rim hole and thread the nut finger-tight
- Inflate the new tube to just enough pressure to give it shape (2–3 PSI) — this prevents pinching
- Tuck the tube inside the tire; insert valve stem through the rim hole
- Mount the second bead: work by hand as far as possible. For the last section, use tire irons in small "bites" — push the mounted bead into the drop center of the rim to create slack before each lever
- Inflate to operating pressure. Bounce the wheel to seat both beads. Check both bead lines are evenly seated around the full circumference. Torque rim lock to 12–15 Nm.
Tire Rotation Direction Explained
Virtually all dirt bike tires are directional— mounting them backwards causes a significant loss of traction. Here's how to read the arrow correctly:
- The directional arrow on the tire sidewall indicates the correct forward rotation direction. Install with the arrow pointing forward (in the direction of travel when you look at the wheel from the side).
- Rear tire: At the contact patch (bottom of rotation), the open (wide) end of the V-shaped or angled knob pattern should be facing forward. This is the drive face — the knob digs in under power. Reversed, knobs fold backward under acceleration and you lose drive traction.
- Front tire: The arrow is equally important — the knob geometry is designed to self-clean and provide directional braking grip. A backwards front tire loses braking performance and mud-clearing ability.
- Quick check: After mounting, look at the bottom of the tire from the side while it sits on the ground — the V-pattern should open (face) in the direction you plan to ride.
Common Tire-Change Mistakes to Avoid
- Pinching the tube: Caused by too little air in the tube before mounting or aggressive iron use near the valve stem. Always pre-inflate the tube slightly.
- Wrong rotation direction: The most common mistake. Always check the directional arrow before mounting. Can't be fixed without another full tire change.
- Over-torquing the rim lock: Cracks the rim lock body or damages the bead. Use a torque wrench; 12–15 Nm is the correct spec.
- Skipping lube: Dry beads tear and refuse to seat properly. Soapy water is free and takes 30 seconds to apply.
- Not seating the bead: An improperly seated bead causes wobble, uneven wear, and potential blowout. Inflate to pressure, bounce the wheel, and visually inspect both bead lines before riding.
Top Dirt Bike Tire Brands
The off-road tire market is dominated by a handful of brands, each with distinct strengths across terrain types and rider levels.
Dunlop
Flagship: Geomax MX33 / MX34
Terrain: MX33: soft–intermediate. MX34: intermediate–hard
Rider level: All levels; most widely fitted OEM tire
Most MX race wins globally. MX12 for soft/sand. AT81 for enduro. AT81 EX for hard enduro/gummy.
Michelin
Flagship: Starcross 5 series
Terrain: Soft, Medium, Hard, Sand variants
Rider level: Intermediate to pro
Bib Mousse inventor. Desert Race rear for sand. Enduro series for trail. High compound quality.
Bridgestone
Flagship: Battlecross X30 / X40
Terrain: X30: soft–intermediate. X40: intermediate–hard
Rider level: All levels
KTM and Husqvarna OEM supplier. X10/X10S for pure sand. Strong durability on hardpack.
Pirelli
Flagship: Scorpion MX32 / MX32 Mid-Soft
Terrain: All-around MX and enduro
Rider level: Intermediate to advanced
Aggressive knob pattern. Very popular in European MX. MT16 for mud and intermediate.
Maxxis
Flagship: Maxxcross MX / IT / SI
Terrain: MX for hard-intermediate, IT for intermediate–soft
Rider level: All levels; great value
Strong value-to-performance ratio. Popular in amateur MX. SI for soft. Desert for sand/desert.
IRC
Flagship: VE-33 Gekkota / IX-09W
Terrain: VE-33: extreme enduro rocks. IX-09W: enduro mixed
Rider level: Enduro and hard enduro specialists
Cult following in extreme/hard enduro. Very soft gummy compound. Not for high-speed MX.
Mitas
Flagship: E-13 / EF-07
Terrain: E-13: enduro hard/extreme. EF-07: all-terrain enduro
Rider level: Enduro trail and competition
Czech brand; growing presence. Strong in European enduro. Good wet-grip compound.
Kenda
Flagship: K760 Trackmaster / K785 Millville
Terrain: K760: all-around trail. K785: intermediate MX
Rider level: Recreational and amateur
Budget-friendly option. Southwick II for sand. Popular for trail/recreation riders.
Tire Tier Guide by Budget & Skill Level
Not all riders need competition-grade tires. Matching your tire budget to your riding frequency and skill level ensures you get the right value.
| Tier | Budget | Best Brands | Who It's For |
|---|---|---|---|
| Entry / Recreational | Under $50/tire | Kenda, Shinko, Maxxis IT | Backyard trail riders, beginners, budget builds |
| Mid-Range / Club | $50–$85/tire | Maxxis MX, Pirelli MX32, Dunlop MX33 | Amateur MX, weekend enduro, club racing |
| Competition | $85–$130/tire | Michelin Starcross 5/6, Bridgestone X30/X40, Dunlop MX34 | Club racing, ISDE, MX nationals, hard enduro |
| Pro / Extreme | $100–$150+ | IRC VE-33 Gekkota, Mitas E-13, Michelin Enduro | GNCC, Erzberg-style events, extreme enduro |
Tire Wear & Replacement Indicators
Dirt bike tires wear faster than road tires — often without obvious visual cues. Use these indicators to know when to replace.
Knob height reduced by 50%+
Meaning: Grip significantly reduced — replace now for competitive riding
Action: Replace tire, especially for hard terrain where short knobs matter most
Knob edges are rounded/mushroomed
Meaning: Knobs have heat-cycled; compound hardened; traction lost in corners
Action: Replace — especially critical for rear MX tires after 10–15 hours
Chunking or missing knobs
Meaning: Carcass stress or hard terrain damage; structural integrity at risk
Action: Replace immediately — a missing knob can cause sudden grip loss
Cracking in sidewall or between knobs
Meaning: Rubber has aged (UV/ozone degradation) or been heat-damaged
Action: Replace regardless of tread depth — aged rubber loses grip in cold/wet
Continuous tire spinning / loss of bite in familiar conditions
Meaning: Compound has glazed from heat cycling — no visual sign needed
Action: Replace front if pushing wide in turns; replace rear if drive is washing out
Flat spot on rear crown
Meaning: Excessive rear brake use or slide-heavy riding style
Action: Safe to continue if knobs intact; replace if flat area exceeds 25% of crown
Tire Age, DOT Date Code & Storage
Reading the DOT date code:The last 4 digits of the DOT code molded into the sidewall = week + year of manufacture. Example: "2423" = week 24 of 2023 (June 2023). Always check this when buying new-old-stock tires from shops or online.
Shelf life: Even an unused, visually perfect tire degrades from UV, ozone, and heat. Bridgestone, Michelin, and Dunlop all recommend a maximum 5-year service life from manufacture date for actively ridden tires, and 10 years absolute maximum even for stored tires.
Soft gummy compounds age faster: Enduro and hard enduro tires (IRC VE-33, Michelin Enduro) use very soft compounds that degrade measurably faster than harder MX compounds. A 3-year-old IRC VE-33 sitting in a warm garage will have noticeably less grip than a fresh one even if it looks intact.
Visual aging signs: Fine cracking between knobs or on the sidewall = ozone/UV degradation. Replace immediately — aged rubber loses grip in cold and wet conditions regardless of remaining tread depth.
Recommended storage: Cool (below 25°C/77°F), dark, away from direct sunlight, electric motors, or ozone-generating equipment. Store flat or hung vertically — not compressed under weight. Avoid contact with solvents or petroleum products.
Buying tip: For competition use, avoid tires manufactured more than 2 years ago. For recreational use, 3 years is the practical limit. Always ask to see the DOT code before completing an online purchase.
Frequently Asked Questions
What does 80/100-21 mean on a dirt bike tire?
The three numbers decode as: 80 = section width in millimeters (how wide the tire is). 100 = aspect ratio, meaning the sidewall height is 100% of the width (so 80mm tall). 21 = rim diameter in inches. So an 80/100-21 fits a 21-inch front rim, is 80mm wide, and has an 80mm sidewall.
What is the standard front tire size for a full-size dirt bike?
80/100-21 is the near-universal front tire for full-size motocross (125cc+) and many enduro bikes. Some enduro/trail bikes use 90/90-21, which has a taller sidewall for better compliance on rocks and roots. Mini bikes (65cc–85cc) use smaller sizes like 60/100-14 (rear) and 70/100-17.
What rear tire size does a 450cc motocross bike take?
450cc MX bikes (KTM 450 SX-F, Honda CRF450R, Yamaha YZ450F, Kawasaki KX450) come from the factory with either 120/80-19 or 120/90-19. On soft tracks, some riders prefer 110/90-19 for lighter weight and better hook-up. Pro riders typically run 120/90-19 for maximum footprint on varied MX tracks.
What tire pressure should I use for motocross?
Standard outdoor motocross: 12–14 PSI front and rear (cold). Indoor supercross: 13–15 PSI (harder surface, more rim protection needed). Enduro trail: 10–12 PSI. Hard enduro/extreme: 8–11 PSI (very low for rock grip, use mousse to avoid pinch flats). Never inflate off-road tires above 20 PSI.
Should I use a bib mousse or inner tube?
Bib mousse is the choice for enduro racing, ISDE-style events, and hard enduro where flats are race-ending. It eliminates puncture risk but adds 400–700g per wheel, generates heat, and costs €40–€120 per mousse with a 25–50 hour lifespan. Inner tubes are lighter, pressure-adjustable, and far cheaper — the better choice for recreational trail riding, MX practice, and budget-conscious riders.
What does the terrain marking (S, M, H, MX) mean on a tire?
Tire manufacturers use different systems: Dunlop uses numeric suffixes (MX12=soft, MX33=soft-int, MX34=int-hard). Michelin labels directly: Starcross 5 Soft/Medium/Hard/Sand. Bridgestone uses X-series (X10=sand, X30=soft-int, X40=int-hard). Maxxis uses letters: SI=soft-intermediate, IT=intermediate, MX=hard-intermediate. Always match terrain codes to your local conditions.
Can I put a 120 rear tire on a bike that came with a 110?
Generally yes on most 450cc-class bikes — swapping from 110/90-19 to 120/80-19 or 120/90-19 is common practice. The 120 adds ~0.8–1.2 kg and creates a marginally larger footprint. On smaller 250cc frames, a 120 can impede cornering feel. Always check chain clearance and swingarm clearance before fitting a wider tire.
How often should I replace dirt bike tires?
Motocross rear tires: every 10–20 hours of hard riding (race-level). Front tires last longer — typically 20–40 hours. Recreational trail tires: every season or when knobs are worn 50%+. Enduro tires: every 30–60 hours depending on terrain. Visual checks: replace immediately if chunking, severe cracking, or knobs worn below 5mm height on rear.
What is a rim lock on a dirt bike wheel?
A rim lock (also called a rim clamp) is a metal clamp that bolts through the rim and bites into the inner tire bead. It prevents the tire from rotating on the rim when braking hard or at low pressures. All off-road bikes require at least one rim lock (front and rear). Without one at very low pressures, the tire rotates and shears the valve stem.
What is the difference between an 18-inch and 19-inch rear rim?
19-inch rims are standard for motocross bikes — they suit the taller, more flexible sidewalls MX tire sizes offer. 18-inch rims are standard for enduro bikes (KTM EXC, Husqvarna FE, Yamaha WR series). The larger sidewall on an 18″ rear provides better rock and root compliance. Trail and dual-sport bikes often use 18″ rear to accommodate enduro tires with gentler sidewall profiles.
What tire size does a 50cc dirt bike use?
Most 50cc bikes use 60/100-14 front and rear (e.g., Honda CRF50F, KTM 50 SX Mini). The Yamaha PW50 uses 2.50-10 on both ends — a smaller legacy inch-size wheel common on balance/training bikes. Always check the rim size molded into the current tire before ordering a replacement.
What tire size does an 85cc dirt bike use? Small wheel vs. big wheel?
The 85cc class comes in two wheel configurations: Small Wheel (SW) uses 70/100-17 front and 90/100-14 rear. Big Wheel (BW) uses 70/100-19 front and 90/100-16 rear. AMA-sanctioned class rules cap SW rear at 14" and BW rear at 16". SW is better for shorter/lighter riders; BW suits taller riders transitioning toward full-size bikes.
Which way does a dirt bike tire face? How do I read the directional arrow?
Most dirt bike tires have a directional arrow molded into the sidewall. Mount the tire so the arrow points in the direction of forward rotation when looking at the wheel from the side. On the rear: the open (wide) end of the V-shaped knob pattern should face forward at the bottom of the rotation — this is what drives the tire into the ground. Mounting backwards on the rear causes knobs to fold over under acceleration instead of biting, resulting in significant loss of drive traction.
How do I read the DOT code on a dirt bike tire?
The DOT code is molded into the tire sidewall. The last 4 digits are the manufacture date: the first two digits are the week number, the last two are the year. Example: "2423" means week 24 of 2023 (June 2023). Some pure off-road (MX) tires are NOT DOT approved and display "NOT FOR HIGHWAY USE" or "NHS" — these cannot legally be ridden on public roads in the US. DOT tires must carry the full DOT alpha-numeric code.
What is a Tubliss system and is it better than mousse?
The Nuetech TUbliss system uses a 100 PSI inner core that sits against the rim, providing rim protection, while the outer tire runs at a freely adjustable 0–13 PSI. Unlike mousse (which is a solid foam insert with a fixed pressure feel), Tubliss gives you adjustable pressure AND flat protection — but it costs $80–$100 per wheel and requires more complex installation. It's best for enduro/trail riders who want the flat protection of mousse with the pressure adjustability of tubes.
What is the difference between Dunlop MX33 and MX34?
The MX33 is designed for soft-to-intermediate terrain — it has a more open knob pattern with taller knobs for digging into soft dirt, loam, and mild intermediate conditions. The MX34 is designed for intermediate-to-hard terrain — it has a denser, shorter knob pattern that provides more contact patch on hard, packed surfaces. If you ride one type of track, pick accordingly. Many club racers keep MX33s for wet spring conditions and MX34s for summer hardpack.
Do I need a rim lock with a bib mousse?
Yes — rim locks are still required when running bib mousse. The mousse prevents flat tires, but it does NOT prevent the tire from rotating on the rim under hard braking or acceleration. Without a rim lock, the tire can spin, twist, and eventually shear off the valve stem area or damage the bead. Always install and torque the rim lock to 12–15 Nm (9–11 ft-lbs) regardless of whether you run mousse, Tubliss, or inner tube.
What tire pressure should I use for dual-sport / road riding?
Dual-sport and road legal riding requires much higher pressure than off-road use: 19–23 PSI front and 21–26 PSI rear for road sections. At typical off-road pressures (10–14 PSI), tires overheat and risk catastrophic failure at road speeds. Before a road section, always inflate to road pressures; reduce again before hitting trails. Refer to the maximum pressure molded into the tire sidewall — never exceed it.
How does tire size affect handling on a dirt bike?
Going wider (e.g., 110→120 rear) adds footprint and traction in soft terrain but makes the bike harder to tip into corners and adds weight — suited to 450cc class. Going narrower improves tip-in speed and suits ruts and soft/muddy conditions — standard on 250cc. On the front, 80/100-21 cuts better through loam and MX ruts; 90/90-21 has more contact patch for roots and rocks on enduro bikes. Rim size matters too: 18" enduro rims have more sidewall flex for rock compliance; 19" MX rims give quicker steering response.
What does NHS (Not for Highway Service) mean on a tire?
"Not for Highway Service" or "NHS" means the tire has NOT received DOT approval and cannot legally be ridden on public roads in the United States. Most pure motocross and MX competition tires are NHS — they lack the structural and safety requirements for sustained road speeds. If you need a tire for any road use, look for a full DOT code on the sidewall. In the EU, the equivalent road-legal requirement is ECE homologation (indicated by an e-mark).
Need to compare two tire sizes?
Use the Tire Size Comparison Calculator to check diameter difference, speedometer error, and fitment compatibility between any two sizes — including 110/90-19 vs. 120/80-19.
Open Tire Size Comparison →