NRCA or RCA? 1

More negative camber is always good right?

No… that’s not entirely the point. I started into this issue a couple of years ago, but I was reminded of it again by the fact that the in-term owner of my car swapped out my NRCA’s for RCA’s. Since I never really finished the thought last time… I’ll take another stab it it. Gonna be quick and brief though.

The negatives of NRCA’s are fairly clear. Bumping the hub location outboard without changing anything else has some negative effects on steering geometry. Scrub radius grows tremendously, especially when combined with gargantuan wheels, as is common. As does bump steer change with the new position of the steering arm relative to all other points. Now… scrub radius is easily fixed with some less negative offset wheels (probably quite easily and affordably) and some people place no priority on bump steer… but I guess ultimately I am not one of them.

In the end, only advantage that NRCA’s really offer over RCA’s is more negative camber without increasing kingpin inclination. More kingpin inclination is fundamentally bad, but with the mac strut suspension on our AE86’s all methods of adding negative camber EXCEPT FOR THE NRCA, also increase Kinpin Inclination. Back in 2003 I crunched some numbers and came up with the formula…

Camber Change = (KPI)*(1-COS(steering angle)) – (Caster Angle)*SIN(steering angle)

… and if that doesn’t make sense to you… I sympathize because 6 years later it barely makes sense to me. The gist of it though… is that Kingpin Inclination causes our outside tires to lose negative camber as we turn into a corner, but Caster in contrast allows us to gain negative camber. You can read the details of that discussion HERE.

Of course all this is contingent on … “TURNING INTO A CORNER.” If we’re not doing that (aka… drifting (バンザイ!)) then I guess the opposite is true, and more kingpin inclination and less caster is actually going to help keep our front tires flatter on the road. You decide if that’s a good thing or not…

…But I think… I just realized past error.

So perhaps more Kingpin Inclination is good for drifting… but certainly it is good for decreasing scrub radius when running big shoes. It is also good for raising front roll center height which was our intention right from the beginning when fitting either an RCA or NRCA. A higher front roll center offers some advantages for drifting which I have detailed in the past… and will eventually… hopefully get back up on the new site.

So… as brief as that was it wasn’t even as brief as I intended. I suppose I thought I had a point to made… and I would have if we all drove these cars like normal people. Instead… I suppose I should thank someone for longer control arms and garbaged NRCA’s… at least as long as I’m a drifter wannabe.