The Front Brake Feels Wrong
You are about to set off on a 200 km ride. As you wheel the bike out, you squeeze the front brake lever and it comes back almost to the grip before feeling firm. The fluid level in the reservoir is at the lower mark. There is no visible leak, but the lever feel is spongy. The bike has done 18,000 km and the brake fluid has not been changed in three years. You also notice the chain has about 40 mm of slack at the midpoint, against a specification of 25–35 mm.
1. Diagnose the likely causes of the spongy front brake and decide whether to ride.
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Likely causes:
- Air in the hydraulic system - spongy lever feel is the classic sign. Air compresses, so the lever travels further before pressure builds.
- Old fluid - brake fluid absorbs moisture over time; three years is well past typical change intervals (often every 1–2 years). Moisture lowers the boiling point and can cause fade under hard use, and corrosion internally.
- Low fluid level - could indicate worn pads (as pads wear, fluid fills the caliper) or a slow leak. With no visible leak, worn pads are plausible, but the level should be checked against pad condition.
- Worn or glazed pads / contaminated disc could also reduce bite, but would not usually make the lever spongy.
Decision: do not ride. A brake that comes to the grip may not provide full braking in an emergency. The system needs bleeding, fresh fluid, and inspection of pads, disc, and lines. This is a safety-critical defect - fix it before the 200 km ride.
2. Assess the chain slack and explain the consequences of riding with it out of specification.
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Assessment: 40 mm slack against a 25–35 mm spec means the chain is too loose.
Consequences:
- Derailment risk: a slack chain can jump off the sprocket, especially under acceleration or over bumps, potentially locking the rear wheel.
- Wear: it slaps against the swingarm and wears the sprocket teeth and chain unevenly.
- Handling: snatchy drive and poor throttle response.
- Damage: it can damage the swingarm, chain guard, or case.
Action: adjust to the specified slack at the tightest point, check for tight spots and worn sprocket teeth, and lubricate. A loose chain is a warning sign that the bike has not been maintained - check the rest of the machine too.
3. List the pre-ride checks you would carry out before any long ride, and explain why each matters.
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A useful routine (often remembered as a 'power' or 'weekly' check):
- Brakes - lever and pedal feel, fluid level, pad thickness. Matters because brakes are your primary safety system.
- Tyres - tread depth, pressure (cold), cuts and bulges. Grip and blowout risk.
- Chain - slack, lubrication, sprocket wear. Drive integrity and rear-wheel lock risk.
- Controls - throttle, clutch, steering free play, cables. Control and response.
- Lights and horn - headlight, brake light, indicators. Visibility and communication.
- Fluids - oil, coolant, brake fluid. Reliability and safety.
- Mirrors - adjusted correctly. Observation.
- Fuel - enough for the journey. Avoid running out in a dangerous place.
Any defect that affects braking, steering, or tyres means the bike should not be ridden until fixed.