Unstable handling / weave on a KTM 125 Duke 2026

Incorrect tire pressure

Tires and handling are safety matters: at the slightest doubt, get it checked. The diagnosis is confirmed: incorrect tire pressure, which degrades handling (and wear). This is the most common cause of instability and the first thing to check, since it's free and immediate. Inflation pressure gives the tire its shape and stiffness; it's set by the manufacturer (often shown on a sticker near the swingarm or in the manual) according to load. An underinflated tire flexes, heats up, makes the bike feel soft, heavy to steer, and unstable, and wears at the edges; overinflated, it reduces the contact patch, feels harsh, and wears at the center. The fix, in principle: set both tires' pressure, always when cold (riding heats the air and skews the reading), to the manufacturer's values. This is a basic job, one to do regularly (at least every two weeks). Risk level: low. On budget: free (just a reliable gauge and a pump/station). Important: a tire that regularly loses pressure has a leak (valve, rim, puncture) that needs addressing; and if pressure is correct but instability persists, look toward tire wear/deformation, steering head bearings, or the chassis. Adjust pressure for load (passenger, luggage) per the specs. This tool helps you understand what's going on -- it doesn't replace a certified mechanic.

How to make the repair yourself

🟢 Within reach of any rider: no advanced mechanical skill or specialised tooling needed.

1. 1Get a reliable gauge (your own or a station's, but cross-check them, since some are inaccurate). Always work with COLD tires: the bike hasn't been ridden for at least 2-3 hours, otherwise heat skews the reading.
2. 2Find the manufacturer's specified pressures: on a sticker (often on the swingarm or under the seat) or in the manual. Note the front and rear values, which differ, and the loaded values (passenger/luggage).
3. 3Unscrew the valve cap, measure each tire's pressure, and compare against the target values.
4. 4Adjust: add air with a pump/compressor if pressure is low, or bleed a little out (press the valve pin) if it's too high, until you reach the correct value.
5. 5Recheck pressure after adjusting, and refit the valve caps (they protect the valve from dirt and help with sealing).
6. 6While you're at it, quickly inspect the tires: wear, deformation, embedded objects, cracking -- a tire in poor condition won't handle well even at the right pressure.
7. 7If a tire was very low, keep an eye on it over the following days: a steady loss points to a leak (valve, rim, puncture) that needs repairing.
8. 8Take it for a test ride: correct pressure often immediately restores sharper steering and a more stable bike. If instability persists, continue the diagnosis (tire wear, steering head bearings, chassis).