Understeer. Tires?

[Kurt Bogerman]

Dave,

My understanding is this:

Approaching corner.... Decelerating... Weight transfers forward... Turn right... RF tire pivots downward, while LF tire would rise off the ground... Kart tilts towards LF corner...

What happens to the RR corner?

I envision the RR lifting, while pivoting on the RF and LR corners.

I thought that the purpose of the exaggerated steering caster, and the resultant "chassis jacking", was to mimic a differential action in the solid rear axle, allowing the inside rear tire to lift, or, at least, slip while cornering?

I am completely open to criticism and new information, but I am uncertain of how to understand your explanation. I'm going to have to do some homework before I agree or disagree with your statements.

For what it's worth, my kart seems to handle much better with new spindles, 4.10x3.5 tires on Azusalite wheels, and 1/16" toe out ( rather than toe in). Too many changes at once, yes, but headed in the right direction, for sure. I wish I had the track time and space to be more scientific with these changes, but I don't.

Thanks,

Kurt

[David Luciani]

the easiest way to see if what i say is better is to try to stay with me on the track. 
sadly this year that isn't an option.

what your describing is called crow hopping and you REALLY don't want to do that.
crow hops usually finish in a flip.   

any way you're close on the front and lost on your rear lift idea.
the front lifts removing tire scrub from inside tire. 
the back tires, if you've set up your slide correctly , will go sideways around the corner thus the term REAR STEER.
the front outside tire acts more the pivot.

i'm gonna try to explain in general what you should be trying to do. 
this is for anyone running a rear kart that wants to utilize rear steer.
this may be open to dispute but it's more or less how i set up corners.
 
setting up for a corner goes like this:

• in practice you pick a brake point at the corner and mark it in your mind .
  

something like a painted line on the track works well or a cone or even a fair sized rock.
if there's nothing there to mark the corner i've been known to wander around the track with a stick or a big pebble and drop them near where i'd like to mark the corner!

• that point you pick is where you should apply braking every lap. 
  

if you find you're having issues in the corner you can adjust your brake point either deeper or further away depending on what you need to change in your line.
   
 at the braking point you need to do several things pretty fast some close together some at the same time.

• the first thing is tap/brake hard enough to break traction from the track. it's quick a hard jam and release.
  
• at the same time you twist your steering into the corner.
  

if you do it right the front outside tire digs in the inside tire lifts and the rear tires quit gripping the track and start a sideways slide.
the reason the front lifts is you added tire scrub to the outer most tire which also serves as braking force.
mean while the rear has gotten light and loose from the sudden braking.

this is a big reason why tire pressure matters.

• the rear tires being higher pressure are more inclined to slide.
  
•  the fronts need enough pressure to resist folding over 
  
•  12 to 15# front + 15 to 20# rear works pretty good.
  

when you've cleared the apex actually a little before you'll need to plant both front tires and release the tire scrub.

• this is done by steering into the skid basically reverse tire direction.
  

the tire drag releases and the inner front drops back in.

• at the same time you need to hit the gas full on depending on clutch engagement you might actually hit gas a microsecond sooner. this digs the rear tires in and the slid stops as you move forward.
  

the idea is to have the clutch hit exactly when you eliminate tire scrub.

• the steering wheel is then swung into line with the track .
  

either setting up for the next corner or following the straight.

if everything is really perfect you'll squirt outta the corner .
if you're running a pipe and it hits just after the wheels get straight you'll be flying.

this all happens in about 2 seconds but seems like a lifetime.

 

if you are slow doing these steps you'll spin out or scrub speed and bog down.
done right the steering is light and you blow through corners.

a good sign you're getting crossed up or trying to force the kart through corners is arm pain.
if you are arm whipped after a session around the track you are probably forcing corners and lines.

typically you'll know you've mis-cornered the kart when it wants to head to the wrong place like outside the track
you then have to try to correct by making the kart go against forward motion and direction. 
if you have to correct kart direction in the corner that indicates you aren't picking a line that works in that corner.

the idea is to flow smoothly through the corner with your initial set up controlling where you land on the other side
done right you are just pointing the kart where it wants to go and suggesting changes in direction.

braking in the corner also indicates alot of stuff like maybe you went in too hot or high in the corner.

if you are like me and like sliding you'll lose a ton of momentum screwing around with slides. 
they ARE FUN.
a correct rear steer slide barely registers before you release it. 
best cornering just a quick brake bump skid/steer hit gas steer into slid straighten gone

hope this clears it up a little
or not
d

[Kurt Bogerman]

Thanks, Dave and everyone, for your input here. I appreciate your efforts to explain both the mechanical side of the matter, as well as the driving techniques.

With each opportunity to practice, I am learning new techniques. With each event, the stress of learning the flow of these events has decreased and I'm more able to focus on the acts of driving and tuning. (I am way more confident mechanically, but I've also been taught quite a bit in that regard during this rookie season of karting.) A lot of my driving has been by random trial and error. A litmus test for me is when my wife, Natalie, comments whether I look "comfortable" or "uncomfortable" out there. With the advice I've been given here and at each event, I've started to look "more comfortable" at Oreville and Cuddebackville.

-Kurt