Pre-Trip Inspection: Wheels
6 questions in the bank cover this topic. Everything below is drawn from the sources those questions cite.
Sources: 49 CFR 396 Appendix A, 49 CFR 570.63
What you need to know
570.63(a) names all three.
Welding is a defect rather than a fix, because heating a wheel changes the metal's temper and the repair usually fails where it was welded.
A tire rim, wheel disc or spider shall have no visible cracks, elongated bolt holes, or indications of in-service repair by welding.
49 CFR 570.63
All of them, in place and tight.
A missing nut puts extra load on the rest and they tend to loosen in sequence, which is why wheel-off failures often follow one unnoticed missing nut.
All wheel nuts shall be in place and tight.
49 CFR 570.63
The clamp area is where a cast wheel is held, so wear there means the clamping force is no longer reliable even though the wheel looks sound.
Cast wheels shall not be cracked or show evidence of excessive wear in the clamp area.
49 CFR 570.63
570.63 covers all three.
Elongated bolt holes are the subtle one: they mean the wheel has already been running loose, so the damage is evidence of a fault you have not noticed yet.
A tire rim, wheel disc or spider shall have no visible cracks, elongated bolt holes, or indications of in-service repair by welding.
Cast wheels shall not be cracked or show evidence of excessive wear in the clamp area.
All wheel nuts shall be in place and tight.
49 CFR 570.63
All six conditions.
A lock ring under tension that lets go releases the whole assembly violently, which is why the list is so unforgiving.
Lock or Side Ring. Bent, broken, cracked, improperly seated, sprung or mismatched ring(s).
49 CFR 396 Appendix A
Any one of them, in any of those states.
The standard does not count how many: one ineffective fastener loads the rest beyond what they were designed to carry.
Fasteners (both spoke and disc wheels). Any loose, missing, broken, cracked, stripped or otherwise ineffective fasteners.
49 CFR 396 Appendix A
Check yourself
- What is it that puts your wheel out of service?
- Is a vehicle fit to drive with one wheel nut missing?
- What must you look for specifically on a cast wheel?
- What must you find before driving on a wheel is unsafe?
- What is the condition of a lock or side ring that puts a wheel out of service?
- What is the condition of wheel fasteners that is an out-of-service defect?
Answers are in the practice test for this topic.