[Fot] Brake Bias

[Bill Babcock]

It doesn't change all that much track to track, unless a track has a really
special feature like a very slow corner after a long straight--like Road
America.

That's pretty much what I do--at the beginning of a test and tune day or first
practice on a track that I haven't had much experience with I'll try some very
hard braking while I'm on a straight section--after making very sure there's
no one behind me. Really stand on it and try to hold the brakes at the limit
of adhesion. If it tracks perfectly straight I know I can use more front bias.
I add it until the back end starts to get really light. How that manifests
itself is different on different cars. Peyote just gets tail happy but won't
spin usually, other cars I've tried this with can get into a spin pretty
quickly. Since you're going straight you can usually avoid a full spin by
easing off the brakes. If you just lift it will probably snap spin (one of
those left-right-left things that just get worse). Not that big a deal, get
both pedals in and ride it out. Try not to flat spot the tires and do the
entire maneuver in a place where a spin wont stick you into a rail.

I'd also do this if I'm changing tires for some reason. The exception is
Monterey or other General Racing events where I'm required to use Dunlops. I
don't bother trying to optimize Dunlops. there's never enough track time at
those events and the tires are so marginal that a little tweaking won't help.

Once you have the bias dialed in on the straight, try it in a fast corner. If
you have too much front bias the car will understeer when you are continuously
braking while turning. If trail braking is important for the track then it
makes sense to back off a little. Most tracks I race on, trail braking is not
important other than keeping the car settled. The exception is Sears Point
(Infineon) which has two turns that work best with late braking and a lot of
trail.

It's a little hard to work this out since a little sudden braking in a turn
will also stop understeer by transferring weight to the front wheels. What I'm
talking about is the braking that goes on after the weight has shifted
forward, in other words you brake hard to the turn in, ease off a little as
you start turning but maintain some steady braking as you head for the apex.
If the car understeers then, you might get some relief with less bias.

Winter's been great. A little tsunami scare this morning kept me from surfing,
but other than that...


On Feb 27, 2010, at 2:33 PM, Mark Eginton wrote:

> Curious how you set the brake bias on your car. Left to my own devices, I
would bias forward then add more rear till the back wants to pass the front on
corner braking and back off. How do you get it settled in? Does it change much
by track e.g. fast corners vs slow tight corner dominated tracks or do you set
it and forget it?
>
> Hope the winter is treating you well...
>
> Best,
>
> M