Every chain adjustment ends with lining up the little stamped marks on the swingarm — and on a lot of bikes, those marks have been lying since the factory. Misalignment quietly eats chains and sprockets from one side. Here's how to check it for real.
What misalignment does
A rear wheel cocked even slightly runs the chain at an angle across both sprockets. The chain's side plates rub one side of the teeth, roller wear goes asymmetric, the slider grooves off-center, and the whole drivetrain wears faster in a pattern you can read: shiny wear on one inner face of the chain, sprocket teeth polished on one flank. Handling pays too — a misaligned rear steers the bike subtly differently left versus right. If your chain keeps developing one-sided noise or wearing unevenly despite good maintenance, check alignment before blaming the chain.
Why the marks lie
The stamped hash marks on adjuster blocks reference the swingarm's machined ends — and stack-up tolerance between stamping, machining and the axle slots means marks that match side-to-side don't guarantee a straight wheel. Treat marks as rough positioning, useful for keeping adjuster turns equal (the adjustment procedure), and verify with geometry when it counts.
Method 1: The string line
Loop string around the rear tire so two parallel lines run forward past the front tire on both sides, bike vertical and bars straight. Measure the string-to-front-tire gap on each side at the same points; equal gaps mean the wheels are in plane. It's free, surprisingly precise, and easier with a helper holding the bike.
Method 2: Direct measurement
Measure from the swingarm pivot center to the axle center on both sides — calipers, a stick with marks, or a purpose-made tool. Equal distances mean the axle is square to the frame regardless of what the stamps claim. Laser sprocket-alignment tools do the same job optically and are worth it if you adjust often.
When to bother
Full verification isn't an every-adjustment ritual — do it once to learn how honest your marks are (then trust or correct them accordingly), after wheel removal, after buying a used bike, and whenever wear patterns look one-sided. Between checks, the usual care carries the load: clean drivetrain (the CC360 minute), correct slack, and an occasional glance at the slider's wear pattern — an off-center groove there is misalignment writing you a note.
Quick answers
Are swingarm alignment marks accurate?
Often not — stamped marks can be off from the factory by a visible margin. Use them for rough positioning and verify with a string line or direct axle measurement when precision matters.
What happens if the rear wheel is misaligned?
The chain runs at an angle, wearing one side of the chain, both sprockets' tooth faces and the slider unevenly — plus subtle handling effects like the bike tracking differently in left and right turns.
How do you check chain alignment at home?
String method: run string from the rear tire's sides forward past the front tire and compare gaps. Or measure axle-center to swingarm-pivot distance on both sides. Alignment tools that clamp the rear sprocket work too.