Inverted Portal Axles for the Street

Surprisingly, portal axles have been mentioned only a very few times on the HAMB. The idea of turning a 4x4 portal axle upside-down to facilitate lowering the rear of a car seems such a natural that it's odd that more people haven't done that mental arithmetic.



Though, until recently, portal axles have tended to be either very heavy (e.g. Unimog) or possibly fragile (e.g. early VW bus). Some reversed rotation, and most featured wall-climbing reduction ratios. That has since changed, with new offerings beginning with units based on Humvee portal hubs, and later ones engineered from scratch by e.g. TRE and Proformance. These feature realistic reduction ratios for street applications, retain input rotation in the interest of bolt-on applicability, and are probably quite a bit lighter than earlier units.

Unfortunately they tend to be expensive. Still, as part of a thoroughly engineered build, they might be an option. A "free" extra 4-6" of lowering is not to be sneezed at.

The idea has been kicking around in my head for 30 years. In 1995 I was envisioning a build style inspired both by the then-current Pro-Street and by European Touring Car Racing: combining tubbed fats on the back with negative-cambered big-inch low-profile tyres on the front. And the cherry-on-the-top cool factor there would have been on-board tyre pressure control, with the hardware visible on the rear wheels.

It's stuck its head out again now in the course of a set-out-packaging-from-scratch exercise around the observation that 120" or 3m was a common wheelbase for what we'd call a medium-sized car in the Vintage era, and that led to an investigation of low-floor planning and, hence, inverted portal hubs, among other things like unorthodox IRS and whether you'd engineer a cowl fuel tank if you didn't have to. I'll post about the IRS elsewhere.