Caster Question

Wacomike04

Wacomike04

Member
I have a 2017 PRC recon. Excuse my wording if I call something other than its actual name as I learn. RF caster block is on the forward pin, so i use the forward line. My LF caster block is on the back pin, so i use the back line on top.

I run on a.low/medium bite 1/8 mile track here in Michigan.

My question is....

Did the kart come with RF forward and LF caster block on the rear? Some guys faster run both on the front pin, then they scale/set-up the kart, some ride with both caster blocks on the rear pins. I saw a few posts on here where RF forward pin and LF back pin is correct.

What is correct, AND why? Is it different every chassis? Different for tracks? How do I find out what PRC recommends or had.it set at when it rolled out the door?

Thanks,
Me
 
I just called PRC today and asked for some guidance and they first asked me what gearing I was running and then gave recommendations that were a little different from the setup sheet that they provide for my chassis. They were great to talk to.
You can also go to their website and they have base setup sheets for every kart they’ve made.
 
Marcis71 said:
I just called PRC today and asked for some guidance and they first asked me what gearing I was running and then gave recommendations that were a little different from the setup sheet that they provide for my chassis. They were great to talk to.
You can also go to their website and they have base setup sheets for every kart they’ve made.
Click to expand...
I have the base setup sheet for my kart and year. Just talked to a local builder and wise owl and he said put both caster blocks on the rear unless at a 1 mile track....the fast track champ said both his caster blocks are on the front pin.

I am so lost....
 
PRC told me both caster blocks in the rear setting for a small track also. Are you racing Arthur, Owosso, or another small track?
 
I am interested to hear what makes a difference. I run one front one rear but can't remember which side is which.
 
Honestly I feel like this is an adjustment that does nothing.

You would think moving the entire wheel assembly forward/back in relation to the rear would make a big difference in handling.

We have run every combination of lead setting with the castor block on everything from tight indoor concrete to 3/8 mile super speedways. Won plenty of big paying races on both. My drivers, who arent any slouches behind the wheel, could not tell the difference from one way or another.

With all that being said, I typically run them both in the back setting.
 
i think as long as they are both in the same holes you will be happy either way. When we had the RF forward it didn't seem to stick the RF very well.
 
Wacomike04 said:
Owosso. Not racing Arthur until they allow prep and open tire rule.
Click to expand...
Not familiar with the track. Yes, every chassis is different. Some newer chassis have three settings on the RF. I'm on chassis with two RF caster settings and I always run the RF and LF in the rear position. The only time I would run the RF in the forward position is if I cared nothing about straight-line speed, so true bullring or indoor racing. There are a lot of factors when considering dynamic weight transfer. If you run the RF forward it takes slightly longer for the chassis to transfer weight LR-to-RF and back when turning... don't overcomplicate it both in the rear position sounds right.
 
My thinking is to run them both in the rear position for small or standard "oval" tracks. You can run the RF forward for big momentum "circle" tracks where you're not loading up the right front as much on entry and in the center of the corners. A lot of the adjustments on karts are for driver preference as much as anything else. Some may make YOU faster, some others may make another driver faster depending on how he/she likes their car to feel under them.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
www.youtube.com
34 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
JPMKarting said:
Honestly I feel like this is an adjustment that does nothing.
Click to expand...
IMHO you are correct.
Moving caster equally to the front or back only changes where weight of the kart is being projected forward or back.
Doing so is totally and only a driver feel thing.
Moving top to the back adds some feel to steering the fronts and may add in some driver security.
Moving top to the front will make if feel sort of quicker reacting or freer turning.

If moved top to the back the driver will feel the weight of the kart reaching out and engaging the bank of the track sooner.
If moved top to the front the driver will be a bit more into the turn before feeling the bank of the track.

Longer flatter tracks top to the front will make the front end feel lighter and make rolling thru a bit easier because there will be less input from the track to contend with.
Shorter more banked tracks where reaction time and feel is more important to the driver even if your over all going slower top to the back may help.

... maybe

Our early days on asphalt sprint course taught us equal movement of caster is a driver feel thing and only a feel thing.
... caster split may be the same of just a feel thing and because of it the reports of it making no difference
A difference in performance can come from either the driver and changing how the driver feels the track or something which allows what your racing to actually be able to go thru the turns faster. which is which is tough to call

It's about does maintaining the same grip level but changing how the right front leads the driver into the turn really make you faster or not.
Were also not talking about having a lot of hp and demanding the RF turn us while its being forced into the bank by the rears accelerating.
That's not the ball game were discussing.
Were talking about being at the limit of applying poser and trying to minimize the amount of speed the turn is stealing from us.

... maybe???
 
If we're talking "just" about caster, and not about wheelbase and lead in the front end, then consider that more caster does more than add "feel to the wheel." Increased caster increases weight jacking affect. You can see this on the scales, with or without turn plates. 10-15-20* of wheel input and see the weight moving across the car. Caster can be used to your advantage -- small bullrings typically require more front end grip, while big momentum tracks require less wheel input, and thus less weight jacking effect. As far as roll speed goes, less caster is faster...but you also loose grip and "feel" in the front end - if the car breaks loose, it'll be tough to save it from spinning if you are running very low caster as opposed to a higher caster setting. Higher caster can potentially scrub a lot of speed since you rarely hold the wheel perfectly straight. Even small bumps in the track (chunk of clay, rock, etc) cause the front end to jerk weight back and forth as one tire rolls over it.
 
CarlsonMotorsports said:
consider that more caster does more than add "feel to the wheel." Increased caster increases weight jacking affect.
Click to expand...
I don't think that is correct because weight jacking by definition is the result of the RF going up and the LF going down when the wheel is turned.
Changing caster the same on both sides will not change how much the RF goes up and the LR goes down.
It will change tire presentation to the track but the actual amount of travel up and down will not change.

You will see differences on the scales when caster is equally changed but it's not the result of changing weight jacking because changing caster equally does not change the amount of weight jacking.

Any change to grip changes driver feel and the limit of speed you can get in a corner because a change in grip effects your potential for speed at any given point on the track, how much hp you are able to use to accelerate and how quickly you can slow when needed.

For the same reasons changing caster equally does not change the amount of lead in the RF.

Both though do change how the front end grips with the track and how and when it engages the bank of the track.

... maybe????

I think changing caster is about tire presentation during camber gain, not about a change in weight jacking.
I do not disagree with all the stuff it does to grip and feel.
 
Last edited:
paulkish said:
Changing caster the same on both sides will not change how much the RF goes up and the LR goes down.
It will change tire presentation to the track but the actual amount of travel up and down will not change.

You will see differences on the scales when caster is equally changed but it's not the result of changing weight jacking because changing caster equally does not change the amount of weight jacking.
Click to expand...

Changing caster WILL result in a difference in how much weight jacking is created in relation to steering wheel input
 
Paul,
Absolutely increasing caster will increase weight jacking effect.
Consider how much weight is moving with 0* caster in both fronts. Now set the caster at 15* and it's easy to see the weight move back and forth in an "X" pattern through the car, even with a small amount of wheel input. Still not convinced?
Try it on scales.
 
From old time AI: ... :) (a simple google search for the definition of kart weight jacking)

There's a difference between mechanical weight jacking and mechanical and dynamic weight transfer.


"A lifting or lowering of a car or kart chassis in relationship to the ground is called jacking. The amount of jacking from steering geometry is directly related to the distance between the tire's contact patch and the steering axis as well as the angle the tire rotates about."

Read from the internet so it's got to be true. ... :)

edit: you all are correct. I was relating to lefty righty stuff with the same parts on both sides.
 
You must log in or register to reply here.
Back
Top