I took some time and made some measurements… did some calculations. For the most part, I’m into doing things by the book. Especially if the book I’m following isn’t fashionable, and is by some nerdy engineer or legendary builder. There are many reasons that small scrub radi are good. I think I’ve been there a few times, but the summary is less kick back at the handoru, better high speed stability, and reduced “scrubbing” in tight turns (aka auto-x and everyday driving). A car that’s easy to drive, is a car that’s easy to drive fast… And that’s where I want to be.
The word is that a negative scrub radius of 10% of wheel width is about the limit of what’s acceptable for auto-x. In some cases positive scrub radius is even preferred.
Good news AE86 drivers… your handicap just got higher! There is NO WAY to get a positive scrub radius with the factory strut/upright… and even the 10% of wheel width rule would take serious creativity and construction.
Of course, I’m overplaying the importance of scrub radius… lots of people probably operate at about 30% of wheel width, and are more than accomplished. The notable thing is… that my planned set up of 15 65J 15 up front, would have almost the exact same % of wheel width as the current 8J 0.
I guess I have to justify it all with weight savings. If your curious about your scrub radius, I made this excel spreadsheet for your reference.