First Autocross of 2019! (BB comes into her own!)

As my (few but faithful) readers know, BB and I are on a slow journey of improvement.  We will morph BB into Chitty-Chitty-Bang-Bang and me into a rally class, autocross pilot!  Perhaps, I'll even learn something about invention along the way!

Over the Winter, I was faced with a tough decision...either have BB's paint job and rocker panels restored or go in for new wheels and tires!  This decision was eventually made easy by my chosen body shop's lack of a schedule date.  So I went nuts on wheels and tires!

Now, those are tires!  Any of you who are familiar with the size of an MGB will recognize that, if one lines them up side-by-each (as my Grandpa George used to say!) they are about as wide as the car.  Hmmm.  Can that really fit under fender?  After all, our job here is to build the ultimate "sleeper" (not the Woody Allen movie, a super fast car that no one can recognize from the outside).

Even after much research, there was some doubt on my part.  This is not a big car!  However, the trials worked out and the tires fit.

 

Now, the proof is in the pudding.  Do these new tires add any performance?  Much to the dismay (had they known) of my local law enforcement agencies, I set out to find out!

What follows is semi-scientific data collected on my neighborhood round-about.  This roughly approximates a skid-pad, which I read about with as much joy as a teenager!  When one is acquiring data, one needs a baseline.  For mine, I turned to the internet and was not disappointed.  It turns out, there was a test of sports car in the late 60's, which included BB's generation.  Cornering capability is measured by driving faster and faster in a circle until the tires start to slide.  The side force at which they slide is expressed in g force.  Getting above 1.0 is world class for production vehicles.

That respectable 0.8g is better than I remembered.  An MG has a near perfect 50/50 weight distribution between front and rear, which helps and is very low to the ground.  Basically, BB is a go-kart.  

In a former post, I showed the timelapse of rebuilding the front suspension, adding a competition anti-sway bar, and lowering the car 1".  I was curious how that had helped so I did a measurement with the upgrades but old tires and then one with the new tires.

The blue line is the old tires.  The lowest part of the valley is where the wheels started to slide.  So my suspension upgrades got us to 0.84g.  Not bad.  But truly impressive are the new tires, coming in 0.99g!  They on wheels from MGC which are 1" wider and 1" bigger in diameter.  The tires are Dunlop Direzza ZIII's at 195/50 R15.  They are extreme performance Summer tires, and can't be driven below freezing.  Great fun!

So, what did that do for us at the course?  We went from 7 seconds slower than the field, to 13th out of 24 cars, including beating a Porsche 911, a Subaru WRX, and a modified Firebird!  Very rewarding!