Regular brake drum inspection catches problems before they become dangerous — and expensive. Here is what to check and when to replace.

What to check

• Inside diameter: measure with a drum gauge. Compare to the maximum allowable diameter stamped on the drum (or in your manual).
• Surface condition: look for scoring, grooves, heat cracks or blue discoloration from overheating.
• Out-of-round: an oval drum causes brake pulsation and vibration.
• Runout: excessive lateral runout produces pedal pulsation and uneven lining wear.

When to machine vs replace

Light scoring can be corrected by machining (turning) if the drum stays within the maximum diameter limit. Deep cracks, heat damage, or drums already at the wear limit must be replaced — machining is not an option.

How often to inspect

Inspect drums at every brake service and at each scheduled maintenance interval. Heavy-duty fleets running mountain routes should inspect more frequently.

Quality matters

Replacement drums must match the OEM dimensions exactly. UIB Truck Parts supplies OEM-compatible cast iron brake drums — including 3721AX, 3600AX, 1599009 and 05255-E (WA-69170) — with strict quality inspection on every batch.