On a flat, straight road the bike wants to turn or lean one way, and you have to push on one side of the bar to go straight. The front and rear wheels may not be in line (often after a chain adjustment), the forks may be twisted, a tyre may be worn to one side, or a brake may be dragging. A bent part after a fall is also possible. Note: many roads slope to one side for drainage; test on a road that is truly flat, or ride the same road in both directions.
Is it safe to ride?
Ride with care if the pull is slight and started after a chain adjustment. If it started after a fall or crash, or is strong, do not ride until checked.
Quick checks first
- Check both tyre pressures.
- Look at both chain adjuster marks: same position on each side?
- Stand in front: is the front wheel straight when the bar is straight?
- Spin each wheel: any drag?
- Look at the tyres: worn more on one side?
Diagnose it step by step
1Does the pull stay the same on a flat road in both directions?
- No: it is the road slope. No fault.
- Yes: go to step 2.
2Are tyre pressures correct and wear even across the tread?
- No: set pressures; a tyre worn on one side should be replaced. Inspect tyres for wear and damage.
- Yes: go to step 3.
3Are the chain adjuster marks the same on both sides, and is the rear wheel in line with the front?
- No: realign with Check and adjust chain slack, then check with a string line as in Align the front wheel, forks and handlebar.
- Yes: go to step 4.
4Is a wheel dragging?
- Yes: Check for brake drag.
- No: go to step 5.
5Is the front wheel straight with the bar, and are both fork legs at the same height in the clamps?
- No: go to Handlebar is not straight when the wheel is straight and Align the front wheel, forks and handlebar.
- Yes: go to step 6.
6Is the steering tight or notchy?
- Yes: a tight bearing holds the bars off centre. Check the steering head bearings.
- No: go to step 7.
7Has the bike been dropped or crashed, or does the swingarm have play?
- Yes: Check the swingarm pivot and Inspect the frame after a crash. A bent fork, swingarm or frame is workshop work; see The bike has been dropped or crashed.
- No: have a workshop check frame and fork alignment.
Causes, most likely first
| Cause | How to confirm | Fix |
|---|---|---|
| Road slope | Pull changes with direction | None |
| Rear wheel out of line | Adjuster marks differ; string line | Check and adjust chain slack |
| Low pressure or uneven tyre wear | Gauge; one-sided wear | Inspect tyres for wear and damage |
| Twisted forks or bar | Wheel not straight with bar | Align the front wheel, forks and handlebar |
| Dragging brake | Wheel slow to spin | Check for brake drag |
| Tight steering bearing | Bars do not fall freely | Check the steering head bearings |
| Bent fork, swingarm or frame | After a crash | Inspect the frame after a crash |