I've been curious about the real justification of using a rear frame rail kit on a high performance street car when it is tubbed for very wide tires with a narrowed rear-end other than it looks good.


Is there a need that I am missing?


Thanks

 

Absolutely! But most street cars don't need it. In the case of extremely radical street builds, with a lot of HP, and huge rear ties, there's no other way to fit tires that are very large without tubbing the rear and moving the frame rails in.
It's not something I'd do unless I wanted to run the largest tire, but it definitely is necessary when your engine and tires require it. I guess the option is let the tires hang outside the body, but that's 70's stuff. Many states wont allow that, so narrowing and tubbing is the only option.