When is it time for new Motor mounts?

[Benny771]

Just getting some odd vibration on the wheel above 4k
Should these be changed everey so often?
What do they look like when it is time?

Thank-you

[JFairman]

When the rubber is dry rotted, cracked, or collapsing from the weight. You can't see all that while the big washers are covering up most of the rubber part.
The bottom side is especially hard to see until it's removed.

If they are 20 years old it's a good chance they should be replaced.

[Benny771]

Thank-you Fairman