Quick answer
Anti-roll bar links help control body roll and connect the anti-roll bar to the suspension. If a link is loose, snapped or badly worn, it can be an MOT failure.
A light knock may start as an advisory, but obvious play, damage or insecurity should be fixed before the test.
When an anti-roll bar link can fail MOT
Excessive play
Loose ball joints or bushes can cause failure.
Broken link
A snapped or disconnected drop link is a clear defect.
Insecure mounting
Loose nuts, bolts or damaged fixings can fail.
Split dust boot
Damaged rubber boots can allow dirt into the joint.
Heavy corrosion
Severe rust can weaken the link or fixings.
Suspension noise
Knocking may point to worn drop links or bushes.
Common symptoms of worn drop links
Common signs include knocking or rattling over bumps, clunking at low speed, noise on uneven roads and slightly less stable cornering.
Drop link noise can sound similar to other suspension faults, so inspection is needed before replacing parts.
What to check before your MOT
1. Listen over bumps
Rattles or knocks from the front or rear suspension can be a clue.
2. Check both sides
Drop links are often fitted on both sides of an axle.
3. Inspect rubber boots
Split boots may allow joint wear to develop quickly.
4. Look for looseness
Visible movement or missing fixings should be repaired.
5. Check related parts
Bushes, ball joints and shock absorbers can make similar noises.
6. Get it inspected
A garage can check suspension play safely on a lift.
Should you repair it before MOT?
Yes, if there is clear knocking, play or damage. Anti-roll bar links are usually not the most expensive suspension repair, and fixing them can remove annoying knocks.
If one side is badly worn, the other side may also be worth checking.
Related suspension and MOT guides
Frequently asked questions
Can drop links fail MOT?
Yes, if they are broken, loose, insecure or excessively worn.
Do worn drop links knock?
Yes, knocking over bumps is a common symptom.
Can a split boot fail?
It can, especially if the joint is contaminated or worn.
Are anti-roll bar links expensive?
They are often cheaper than many other suspension repairs, but costs vary.
Should both sides be changed?
Not always, but the opposite side should be checked for wear.
Best next step?
Have suspension play checked before the MOT if you hear knocking.