If you have Danemann or Monington & Weston school piano (typical example makes), the chances are that your piano is fitted with the standard 'Homa' castors - gold/bronze bracket with a rubber tyred wheel.
Over the years, the liquids used on floor finishes can cause the adhesive, used to secure the rubber tyre to the inner steel core, to separate. That and age, plus the weight of a piano on a small bearing point for many decades cause the tyres to vulcanise (go hard) and split or have chunks come off it, or it disappears all together.

Does yours look like this?

Or this?
A new set can be fitted in about 30 minutes so it should look like this.
The cost is £48 complete.
Please e-mail me or call for more advice.