Why no two wheel alignments ever match
Have your car aligned twice and you'll probably get two different printouts. That doesn't mean anyone did it badly. It's how measuring works at this scale.
How small is small?
Alignment is measured in minutes of a degree, written ′. Sixty of them make one degree. A difference of 7′ across a 60 cm tyre is only about 1.2 mm.
What's normal
- A shop's alignment rack is good to about 3′ on its own.
- Clamps, a steering wheel that slips off centre and the operator often add another 5 to 15′ between two checks.
- With the Slowmile app on a real 911, runs of an unchanged car repeated within about 4′ on toe totals and about 5 to 8′ on camber.
So the useful question isn't whether the numbers match exactly. It's whether they agree closely enough to act on.
How to get readings you can trust
- Park in the same spot every time. Mark where the tyres stand with tape.
- Set the same tyre pressures before each check.
- Wipe the rim lips clean.
- Touch the rim lightly. Pushing moves the wheel: on our test car it changed front toe by about 13′.
- Roll the car back and forth after every change.
- Measure twice before you touch anything. In the app, toe within 7′ and camber within 10′ count as repeating.
Before you pick up a spanner
Measuring is for anyone. Adjusting is for people who know suspension work. If that isn't you, take your numbers to a shop.