Someone talk Caster with me!

1fasttiller

Member
So we've been looking more into setup and trying things at tracks here across the SE in our '21 Pursuit. Our team owner asked me something the other day that made sense and I want to understand it better.

You can use caster to either plant the LR or take weight off it I'm told.

Typical dirt setting for caster on almost any kart is LF 8 and RF 10 or possible 8/12. But if you look at Pavement setup they suggest crazy numbers like LF 8 and RF 6. I'm told this is to free the chassis and cause the LR to "lift" allowing it to turn.

SO if running high bite "dirtphalt" tracks here in the SE, why wouldn't you run Asphalt settings especially if having issues like a push center off due to the kart staying on the LR?

I still can't really grasp what caster does and how it affects the kart. Its one of those things I've never touched on any kart.
 
Caster is to get you into the turn. It drops the outer wheel (RF) as it turns left
and shifts weight and unloads the LR in LTO. The LF loads the RR and the effect
is the kart pivoting/teetering across the LF and RR. Turn the steering with the kart
on a stand and you can see it. Turned to the left, the RF rises and the LF lowers,
this unloads the LR if you're going into a turn and also loads the RR.
Turned to the right the RF goes lower (same effect as if you moved washers and increased
the weight on the RF). This would load the LR. This is what you are doing when you are
about to spin out and turn into the spin, you are loading the LR. You can see it on the
scales as well.
We messed around with caster (outside of what was recommended)
and improved lap times. Driven style ? Wrong initial setup ? Don't know.
But we did get faster with just a change in caster.
The Sprint kart 8*LF and 6*RF is probably to make up for weight differences
side to side, is my guess.
 
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With Sprint kart racing, the karts have caster angle to lift the inside rear tire in a turn. Without it, the kart would go straight when you try to turn it.

I have trouble understanding what it does with LTO karts. Why would you want to lift the inside rear tire? That's the whole purpose of stagger, though both wheels roll around the corner rather than one skidding and one rolling. The more caster you have, the more you lift that the inside rear tires, this means less traction. Now I don't know if for a fact, but it appears to me, with the proper stagger, the kart would roll around the corner with no caster. Anyway, if it was me, I'd be experimenting with less and less caster, just to see how far we could go. Of course we have to get the stagger right for the track we are racing on.

I often wish I was still a young man and able to try my ideas out at the track.
 
caster does several things
1. it helps the kart track strait it i.e. if you let go of the steering wheel the wheels would would right themselves into a strait line.
2. positive caster will have the right front lift causing the right front of the kart to drop and unload the left rear.
the left front pushes down transferring weight to the left front right rear.
adjusting the caster will effect how much weight transfer and how rapidly it transfers the weight by how many degrees the steering wheel is turned.
 
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With Sprint kart racing, the karts have caster angle to lift the inside rear tire in a turn. Without it, the kart would go straight when you try to turn it.

I have trouble understanding what it does with LTO karts. Why would you want to lift the inside rear tire? That's the whole purpose of stagger, though both wheels roll around the corner rather than one skidding and one rolling. The more caster you have, the more you lift that the inside rear tires, this means less traction. Now I don't know if for a fact, but it appears to me, with the proper stagger, the kart would roll around the corner with no caster. Anyway, if it was me, I'd be experimenting with less and less caster, just to see how far we could go. Of course we have to get the stagger right for the track we are racing on.

I often wish I was still a young man and able to try my ideas out at the track.
hey Mr Nunley. you are correct. the answer is why we run different sized tires on left vs right. traction is not evenly split in an lto kart left to right wee need the bigger tire on the right because it does more work.
 
What Al is calling lifting, I am calling unloading. The LTO kart
is going thru the turn on almost 3wheels and I think the Sprints
are also. When you turn to the left entering the turn the RF
drops due to caster and the LR transfers weight off of it and
onto the RF.
I have seen a guy pull onto the track in turn 3 to line up and not
realize his steering lock was still in until the middle of the straight
between 4 and 1, so Al is correct that at least at slow speeds a staggered
kart will naturally go around a turn with no steering input.
 
Road course racers lift the inside rear because they don't run stagger. they are not necessarily lifting the tire with caster (although unloading it helps) they are doing it with a stiff chassis, and an upright seat and up to 3 sets of seat struts. the seat struts are welded to the frame. and then they add more they are using their bodies as leverage to lift the wheel.
 
So we've been looking more into setup and trying things at tracks here across the SE in our '21 Pursuit. Our team owner asked me something the other day that made sense and I want to understand it better.

You can use caster to either plant the LR or take weight off it I'm told.

Typical dirt setting for caster on almost any kart is LF 8 and RF 10 or possible 8/12. But if you look at Pavement setup they suggest crazy numbers like LF 8 and RF 6. I'm told this is to free the chassis and cause the LR to "lift" allowing it to turn.

SO if running high bite "dirtphalt" tracks here in the SE, why wouldn't you run Asphalt settings especially if having issues like a push center off due to the kart staying on the LR?

I still can't really grasp what caster does and how it affects the kart. Its one of those things I've never touched on any kart.
Reverse caster never for worked for us in 10 yrs of asphalt ovals. We normally ran 4/6 or 6/8 both blocks back. Now it does work on the indoor concrete depending on the track, but then again so does 0/0 0/2 2/0 2/2 and so on.
I've played alot at different tracks with caster on the Xpect & Pursuit on dirt (never had em on asphalt) and we're always fastest with both blocks forward, where as our PRC's have always been best with both blocks back.
 
You can use caster to either plant the LR or take weight off it I'm told
The short of it IMHO he is correct.

_______________________________________
Because IMHO changing caster per x degrees of turning lowers or lifts the RF tire.

Changing IMHO washers changes height at the RF.
Changing IMHO caster at the RF changes RF height variably per steering input.

______________________________________

EDIT: changing caster equally on both sides alters the over all resistance to turning using more or less grip when turning.
Therefore over all it can tighten up or free up the front end.
And as always use excessive resistance/grip to turn when the grip is not available, the fronts and it can push.
Use too little and it can push.
Use too much and there is still grip available it will eat speed and hp.

... and maybe???????? ... :)
 
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I have trouble understanding what it does with LTO karts. Why would you want to lift the inside rear tire?
It's not about lifting or lowering/planting/using the LR as a rudder AL.
It's about getting needed grip at the LR when and where you need it all around the track to make your staggered solid axle function as needed to go fast.

The ONLY problem using a Staggered Solid Axle Al is the LR entering and in a turn will ALWAYS loose weight.
Setup is about being able to minimize as needed the MUST HAPPEN unloading of the LR or delay it's unloading until the unloading is a mute point.
Al, the unloading can becomes a mute point because of and only if you travel to a place in the turn or the track, where it is no longer a problem to your speed.

... sorry Al about all the commas my mind is not as quick as your mind, not being able to grasp long unbroken sentences. ... :)
 
Make no mistake it's all about the set up and tires working in most perfect harmony to provide the most perfect forward drive, and lots of races are won where that harmony and forward drive is only 90 % perfect, very few times do you see everything is perfect when you do you'll know it.
 
Asphalt cars are always turning the wheel left. Dirt cars are always(or majority of time) turning right. If i've got the wheels turned left on dirt i'm not feeling fast.
 
I reversed my caster and found speed. Takes more front stagger. Also the steering is much lighter and easier to steer. No tired arms. Also helps you come out of the corner and be able to turn down to pass low without killing speed as bad as regular caster. I prefer the feel and steering comfort over regular caster.
 
There may be pros and cons on this subject, but I think the information supplied is worthy of experimenting. This forum is valuable, especially to new comers like myself. Great job.
 
I have one Question. What is a Staggered Solid Axle.
What we race has a solid axle with staggered rear tires.
This means usually there's a bigger tire on the right rear.

I call it a staggered solid axle.

... :) LOL don't know yet how to stagger a solid axle?
Maybe soak it in ethanol overnight?
 
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