On the face of it, not much.
When you dig a little deeper though, a few nuggets might turn up.
Biker culture has undeniable working class roots. Guys who wear patches and ride Harleys work in steel fab shops and truck repair joints and on construction sites large and small.
They're working folks.
Most so-called liberals consider "working folks" their grass roots.
Their bread and butter.
Unfortunately, those liberals also consider themselves "the vanguard of the proletariat."
The vanguard has to come FROM the proletariat, not out of sociology or poly-sci programs in Ivy League schools.
I'm sure Louis Proyect could set me straight on everything I've said here.
But at the end of the day, bikers and liberals are both dedicated to improving the lot of the working class.