How to add custom settings / attributes to a field I want to be able to add custom settings / attirbutes to field instances.

I can create a custom field with custom settings no probs, but is it possible to get rid of the custom field and just add the settings so that the settings are stored per instance?

For example:

I create a content type, let's call it vehicle. I add a field called wheels which is a basic textfield where you can specify the number of wheels. Now I would like to add a few settings to the wheels field such as brand, model, etc. These settings would be specific to the content type but if you re-used the field wheels on another content type the settings could have different values... now this is a bit contrived but you get the idea!

Any ideas on how this could be achieved? My current solution is to create a separate field called something like Wheels meta information with the settings but I would rather a cleaner solution.
Ok, this is done with third party settings in hook form alter:

function my_module_form_alter(&amp;$form, FormStateInterface $form_state, $form_id) {

  $entity = $form_state-&gt;getFormObject()-&gt;getEntity();

  $form['third_party_settings']['my_module']['my_field_setting'] = array(
    '#type' =&gt; 'textfield',
    '#title' =&gt; t('My custom field setting'),
    '#default_value' =&gt; $entity-&gt;getThirdPartySetting('my_module', 'my_field_setting'),
  );
}


...and that's it. So awesome.