Sunday Morning crew chief

I think I’m a fast learner.....
I can’t get this stuff out of my mind
  • 17’ Triton Jr
  • 4th race ever for driver and crew chief
  • Two nights in a row finished 4th with a tight kart. (Different but similar tracks)
Ran a 300# class Friday and 320# class last night. The tracks have similar dirt, banking etc. both nights we had speed earlier then lost it.

I had to rescale and add 20#. Using bathroom scales, a 6’ level and printer paper to adjust.

In practice we used the tires we ran the night before and ran 13.80 lap times. Kart would’nt turn and get off the (Flat tight corners)

Heat race it was even worse. 14 seconds laps.
3.3 psi left
4.3 psi right
front stagger @1.25 inches was off. (math error) I may need to use mm’s to keep from doing this again.
Going into the feature, I knew my stagger was a problem. I raised my stagger to 1.5” front and kept rear at 1.0” rear. We hadn’t lost any traction all night. I didn’t add any bite. Zero but I wanted to free the rear end up.

Front psi raised from
3.3L > 3.5 right
4.3 > 4.6 left

rear
3.3 > 3.8L
4.3 > 4.8R

Started the feature 7th and raced up to 3rd before getting passed toward the end. The kart improved but was still not turning like the leaders.

Everyone says tires tires tires....

here are my numbers on the official track scales which am told are very accurate.

FL 65# FR 87# Front 47.6%

Left 57.7%__cross 64.6%__Right 42.3%

LR 119# LR 48#___ Rear 52.4%

PRC’s tech guys words are echoing in my head. PRC told me that if I got good bite, good tire program that I can run up 68%~70% cross.

I don’t know if I locked the kart up. I don’t know if I over prepped my tires, don’t know if my duro was too low? Punched .46

or should I have had more cross% and more weight on the front right?

or .....
 

Colt sr

Member
I would raise air pressure to 5 lbs left 6 lbs right... Also would keep 1.5 in front stagger and drop to 5/8-3/4 in stagger in rear... And go from there personally
 

mike97760

Premium User
What gears did you run at Rockport? And how many rpms were you running? Which way did you decide to go with prep?
 

CarlsonMotorsports

Premium User
OP,
Couple things:

I love PRC karts, and specifically the Triton Jr, for our midwest tracks.
But chassis manufacturers' recommendations are RARELY correct when using floppy sidewall Burris tires on the little paper clip oval dirt tracks we have here in the midwest, or up norf. Our tracks are good for growing corn, not necessarily the best for racing. Loose, black, organic dirt doesn't compact as well as good red clay, and results in a low/no bite track surface in comparison. Most all of the manufacturers' testing is on stiff sidewall plastic Maxxis tires with internal prep on good biting red clay big momentum circle tracks in the south.
Not saying that you can't get 70% cross to work up here, but I'm telling you that is not how I'd set a jr kart up to run @ Jennings or Rockport.

1st thing, is to increase your rear stagger. 1 1/4" in the rear. (maybe more on the tighter track.)
That will help free the kart going in (and keep it free all the way through the corner.)
Next, drop the cross to 60-62% as a starting point.
Go up on air pressure. 5/6 - again, as a starting point.
Add grip chemically, or decrease your split rather than dropping so low on air pressure.
Both fronts all the way in against the steering arms, RR all the way in. Set your rear tracking with the LR tire...and THEN scale to see where you're at. Moving the LR hub out will free up the kart some on corner exit, and also changes how the kart transfers off of the LR.

Now, if you run Maxxis at a big car count event down south - follow those factory numbers and you'll be real close.
At least a couple things to get you thinking the right direction. :)


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
31 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
What gears did you run at Rockport? And how many rpms were you running? Which way did you decide to go with prep?
I had a stagger problem. I was way off on rear stagger. I only had 1.0”. 6600 rpm and didn’t prep in the feature. I’d really like to know how to much better it would’ve been with proper stagger.
 
OP,
Couple things:

I love PRC karts, and specifically the Triton Jr, for our midwest tracks.
But chassis manufacturers' recommendations are RARELY correct when using floppy sidewall Burris tires on the little paper clip oval dirt tracks we have here in the midwest, or up norf. Our tracks are good for growing corn, not necessarily the best for racing. Loose, black, organic dirt doesn't compact as well as good red clay, and results in a low/no bite track surface in comparison. Most all of the manufacturers' testing is on stiff sidewall plastic Maxxis tires with internal prep on good biting red clay big momentum circle tracks in the south.
Not saying that you can't get 70% cross to work up here, but I'm telling you that is not how I'd set a jr kart up to run @ Jennings or Rockport.

1st thing, is to increase your rear stagger. 1 1/4" in the rear. (maybe more on the tighter track.)
That will help free the kart going in (and keep it free all the way through the corner.)
Next, drop the cross to 60-62% as a starting point.
Go up on air pressure. 5/6 - again, as a starting point.
Add grip chemically, or decrease your split rather than dropping so low on air pressure.
Both fronts all the way in against the steering arms, RR all the way in. Set your rear tracking with the LR tire...and THEN scale to see where you're at. Moving the LR hub out will free up the kart some on corner exit, and also changes how the kart transfers off of the LR.

Now, if you run Maxxis at a big car count event down south - follow those factory numbers and you'll be real close.
At least a couple things to get you thinking the right direction. :)


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
31 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
I learned a ton this week and honestly at points with a bad kart showed some speed. The driver has really improved. I think the a couple more improvements we’ll be competitive. On the drive home I had some good thinking time and realized that I had been thinking about cross weight “backwards”. Once I figured that out and confirming it with Ken I feel much better.

I may have to get some tires cut to get stagger how I want I want it. Jennings and Rockport clearly require and complete different stagger.
 

LynnRacing

Member
I learned a ton this week and honestly at points with a bad kart showed some speed. The driver has really improved. I think the a couple more improvements we’ll be competitive. On the drive home I had some good thinking time and realized that I had been thinking about cross weight “backwards”. Once I figured that out and confirming it with Ken I feel much better.

I may have to get some tires cut to get stagger how I want I want it. Jennings and Rockport clearly require and complete different stagger.
Cutting tires wont help with stagger
 

GClary

Member
Was the tracks smooth for the most part or bouncy ? I would suggest 5/4 split as a starting point , I think 6/5 would be a bit much with the weight classes your running . You also might try no split , or little split and see what that does .
 

mike97760

Premium User
I had a stagger problem. I was way off on rear stagger. I only had 1.0”. 6600 rpm and didn’t prep in the feature. I’d really like to know how to much better it would’ve been with proper stagger.
It's a fun, tricky track. I had 7/8 stagger in opens and wished I had even less.
 

95 shaw

Premium User
Because, contrary to what some may say, there is no universal correct stagger for a track.
The opens enter the corner with more speed, generating more g force, transferring more weight. Then they have more power to overcome drag for straight away speed, but need more traction to hold that power so less stagger is needed for both cases.
It's all a compromise for lowest lap times.
 
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CarlsonMotorsports

Premium User
Opens have surplus HP that can break the tires loose at any moment....they almost always run less stagger than stock class karts.

Cutting the tires isn't for the purpose of sizing -- you size tires by mounting them and stretching or shrinking them with heat/cold.
Take the valve core out of your left rear and place the tire in the sun until it is hot. The put it in the freezer for a bit. That'll shrink it some. Repeat if necessary to get desired stagger you want.
 
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