In article ,
geoff m wrote:

There is one on the Net which uses a car tyre. 2 plywood plates fill
in the hole in the middle and it ran on a couple of bits of shafting.
IIRC the tyres lasted for years, despite being worn from the inside

There is no need for anything in the hole with a car tire or tyre.
Simply keep the load size such that the fluid does not spew out the hole.