The transmission is the link between your engine and your rear wheel. Wear signs, intervals, correct tension, and the kits worth buying.
Sommaire · 5 parties
01How long a motocross chain kit lasts
| Use | Average service life |
|---|---|
| Motocross racing (sand, mud) | 30-60 h |
| Enduro | 60-100 h |
| Road / trail | 200-400 h |
A motocross chain wears 3-5× faster than a road one: sand and dirt thrown up at it, brutal loading under acceleration and deceleration, and often not enough lube.
02The signs it needs replacing
The chain
- Tight spots: spin the rear wheel in the air and watch — if the chain binds at one point, it's finished
- Stretch: measure 20 links. New = 635 mm (pitch 12.7 mm × 50 = 635). Over 640 mm (+1 %) → worn. Over 645 mm → dangerous.
- Side play: waggle a link sideways. More than 2 mm means the pins are worn
The front and rear sprockets
- Hooked teeth (wave or shark-fin shape) → worn, replace them
- Pointed teeth instead of rounded → worn
- Golden rule: you ALWAYS replace chain + front sprocket + rear sprocket together. A new chain on a worn sprocket is destroyed in 10 hours.
03Maintenance to make it last
After every motocross ride
1. Low-pressure hose (keep the pressure washer off the chain) 2. Chain cleaner if it's really caked (WD-40 Specialist, Motul Chain Clean) 3. Lube with O-ring chain grease (Motul C2, Bel-Ray Blue Tac)
The correct tension
- Bike on a stand, rear wheel off the ground
- Halfway along the lower run (between the two sprockets): 40-50 mm of slack (3-4 fingers)
- Too tight → premature wear plus a broken output shaft
- Too loose → the chain jumps, chain and sprockets wear, and it's dangerous
04Chain kits worth buying
| Brand | Type | Average price | Durability |
|---|---|---|---|
| DID 520 ERV7 | O-Ring Gold | €150-200 | Excellent |
| RK 520 MXZ4 | Non O-Ring | €80-120 | Good (pure motocross) |
| Regina 520 ZRE | Z-Ring | €130-170 | Very good |
| Supersprox Stealth | Bi-metal rear sprocket | €60-80 | Excellent |
Sources: 24mx.fr and crossmoto.fr catalogues
05O-ring or not?
- Without O-rings: cheaper, lighter, less friction. Ideal for pure motocross (it's not going to last long either way).
- O-ring / X-ring: more expensive, longer-lasting, less maintenance. Ideal for enduro and trail.
The chain doesn't lie: lube it after every ride and keep the tension right, and it lasts twice as long.
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