Cross for Jr2 Drivers

1fasttiller

1fasttiller

Member
What is the general opinion for cross with a Jr 2 kart? Higher cross, lower? 1/4-1/5th mile dirt ovals with low grip. We're on an 07 Prowler and I've been thinking of changing cross to get more speed. We just seem to be slightly off here lately. Driver weighs 60lbs and total kart weight is 280lbs.

I'm currently scaled close to the Prowler recommended base lines but wanted to experiment.
 
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Cross range is chassis dependent not driver
Higher the grip, higher in the cross range you can run
I would work the tires differently first.
 
General cross higher or lower is MORE chassis related and amount of grip in track than class related, 07 Prowler 62 would be considered high and pushing it, with everything else right cross is most important for corner Exit speed, cross only change is just to tweek it, normally it alone will not give speed lacking. If you had it and lost it I'd look to tires first.
Where is your cross now ?
 
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I run a 07 Prowler... but I cross the scales at 415lbs...with a yz144 at 35+hp...
I had go to 47-50% cross to make it hook up...
Don’t be afraid to try something outside the norm...
 
Sorry gents, been a LONG weekend.... we raced Friday night and I went ahead and took 2 washers of cross out (dropped LF) and the kart did seem faster but I missed the tires. Track was very sandy on top with lots of moisture underneath. It was bad fast for about 3 laps and then the 2nd and 3rd place karts caught him and went around him. He held on to third with it having a nasty push center off.

I put it on the scales yesterday morning and Had the following numbers:

Cross- 57-58%
Left- 55.5%
Front- 47%

Also found that my RF camber had mysteriously changed to barely -1.5. I don't recall ever changing it so I reset to -2.5. I'm thinking that was a significant part of my issue.
 
1fasttiller said:
Sorry gents, been a LONG weekend.... we raced Friday night and I went ahead and took 2 washers of cross out (dropped LF) and the kart did seem faster but I missed the tires. Track was very sandy on top with lots of moisture underneath. It was bad fast for about 3 laps and then the 2nd and 3rd place karts caught him and went around him. He held on to third with it having a nasty push center off.

I put it on the scales yesterday morning and Had the following numbers:

Cross- 57-58%
Left- 55.5%
Front- 47%

Also found that my RF camber had mysteriously changed to barely -1.5. I don't recall ever changing it so I reset to -2.5. I'm thinking that was a significant part of my issue.
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Changing cross effects more than you think, thats what reduced your camber, I still stand on my statement, should work the tires not the chassis
 
XXX#40 said:
Changing cross effects more than you think, thats what reduced your camber, I still stand on my statement, should work the tires not the chassis
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Yes sir, doing that now. We rolled them this weekend with some inside prep. As of current, I've only wiped the outside of the tires, never put anything in them. Am I correct is my thinking that the low RF camber could have also caused a push?
 
1fasttiller said:
Yes sir, doing that now. We rolled them this weekend with some inside prep. As of current, I've only wiped the outside of the tires, never put anything in them. Am I correct is my thinking that the low RF camber could have also caused a push?
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low camber put more tire on the track, lowered how much the kart would dewedge, it did contribute, push was more than likely the tires being wrong again and oveheated the RF with lower cross, chassis working correctly depends solely on the tires creating enough grip for the conditions
 
Interesting to note, I had reached out to Ed Kimble of Prowler about this and he suggests 62-65% cross on this kart. We are way down usually around 56-58%. Does it sound normal to you guys to be this low and out of the range of what is suggested baseline?

In practice I may start upping the cross just to see what happens to this thing. Any of you Prowler guys know if these are like a normal kart i.e. 1 washer is usually around 2% change?
 
I have no idea about a JR set up...

But at a heavier weight and high HP... I run -2 RF camber +1.5 LF camber... and 47-50% cross
8-10lbs air in RF tire and 5 lbs air in the rest...

Anything else in that year of Prowler always had a push in... and could not ever pull it down on exit...
 
I ran an 07 Prowler at that very same track, do what Ed told you. Get that cross up around 65, and get the camber up to no less than 2.75 on the RF. After you get the correct numbers in the kart then its tires.
 
SoCo Tire Treatments said:
I ran an 07 Prowler at that very same track, do what Ed told you. Get that cross up around 65, and get the camber up to no less than 2.75 on the RF. After you get the correct numbers in the kart then its tires.
Click to expand...

Earl,

I thought I remembered you saying you knew this track personally... I'd like to talk to you sometime about tires and preps here soon. Granted I'm sure the track has changed a ton since you last raced there.
 
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