Show field in frontend but not allow to edit by the user

Hello,

I have a proble using:
'disabled' => !is_admin(), // This disables editing in the front end.

With a meta box with:
'storage_type' => 'custom_table', // Important

Is that all fields are saved well in the custom table except the fields that I put 'disabled' => !is_admin()...

Have you detected if it is a general error? Or does it just happen to me?

I try to put this like this
'attributes' => array(
'disabled' => true,
),
But it doesn't matter, not save the value...

Thanks.