Aggregate roots are very likely to have dependencies. For example, if you have an Invoice aggregate root entity, it is likely going to have a LineItem collection. The only way to edit the line items is using the InvoiceRepository.
If the Invoice was not an aggregate root, invoice line items would have their own repository.
Your example looks fine if you never have to work with wheels outside the context of the car. The only question is can the car replace its own wheels? If not, the method is probably located in the wrong place.