Just tested - doesn't work without the hidden fields. 
I believe the @ride variable from the new method is being overwritten when the create method is called. 

Here's a screenshot emulating it in the rails console:
![screen shot 2014-01-21 at 12 45 09 pm](https://f.cloud.github.com/assets/1820919/1966730/6a7ee458-82cc-11e3-8b5b-c45e19e6491b.png)