A lucky escape – a rim that is badly worn can collapse totally

The rims on a rim-braked bike wear out – inescapable fact. Grit, aluminium fragments embedded in brake pads, simple friction of a clean pad – all take their toll. How much and how fast depends, but it’s worth taking steps to minimise wear. What can you do?

  • use a good quality brake pad e.g. Swissstop (and of course, always use the correct compound for carbon rims!!)
  • clean the brake pads regularly, and dig out any bits of grit and metal embedded in them
  • for optimal rim cleaning, you could use a dedicated block such as this one. I use elbow grease, and occasionally wipe down with Isopropyl Alcohol
  • keep an eye on pad wear, change them in good time so there’s no risk of catastrophic wear from metal on metal contact if the pad surface wears out

There’s two general ways rim manufacturers indicate rim wear – a dimple or a groove:

Fairly worn Shimano C24 rim – dimple to right of brake pad
Groove wear indicator all around rim

Once the dimple or groove disappear – time to change rim.

It’s also possible to measure rim wear accurately – I’ve just bought myself a nice tool for this:

Iwanson Calliper

The Iwanson Calliper is a tool used by jewellers (and dentists!) that can measure rim wear to 0.1mm precision. When to replace? Accepted wisdom is <= 1.00mm. Rim strength is proportionate to the cube of the thickness, so small changes make a big difference to overall strength. Change at 1.00mm to be safe.

Rim wear