Jr2 Driver needing more weight xfer to RR?

Hi guys, looking for a little feedback for my son's kart. We have almost always had a loose condition from center off and I've only been able to remedy it by going to low tire pressure, of course that hurts lap times. My son is very light, weighs 50lbs soaking wet. I have him setting up in the seat pretty well to gain as much transfer as I can (and so he can see, hes short lol)

Is it as simple as moving or putting some lead on the RR? we're barely at weight so adding some won't hurt us or is there a better way to get some weight to transfer to that RR on exit?

Kart is a 2006 Prowler on Vega MCS's
Scaled per Prowlers specs
track is a 1/4MI very soft dirt/sand track with almost no bite.

We normally are very fast and have won a lot of races but I know there is more in it and being in the infield last weekend, I could see exactly what the kart was doing. He's only 10 and this is his first season so I'm not 100% sure his feedback is accurate yet but Being in the infield at turn 1-2 watching closely showed me he was spot on!

Is it possible I need more left rear weight? These prowlers tend to push if you run much LR weight or over prep the LR tire I just didn't want to create a push and slow him down, as he can drive it well when loose.
 
Hi guys, looking for a little feedback for my son's kart. We have almost always had a loose condition from center off and I've only been able to remedy it by going to low tire pressure, of course that hurts lap times. My son is very light, weighs 50lbs soaking wet. I have him setting up in the seat pretty well to gain as much transfer as I can (and so he can see, hes short lol)

Is it as simple as moving or putting some lead on the RR? we're barely at weight so adding some won't hurt us or is there a better way to get some weight to transfer to that RR on exit?

Kart is a 2006 Prowler on Vega MCS's
Scaled per Prowlers specs
track is a 1/4MI very soft dirt/sand track with almost no bite.

We normally are very fast and have won a lot of races but I know there is more in it and being in the infield last weekend, I could see exactly what the kart was doing. He's only 10 and this is his first season so I'm not 100% sure his feedback is accurate yet but Being in the infield at turn 1-2 watching closely showed me he was spot on!

Is it possible I need more left rear weight? These prowlers tend to push if you run much LR weight or over prep the LR tire I just didn't want to create a push and slow him down, as he can drive it well when loose.
Just because it's set to Factory spec does not mean it's correct for track conditions, those specs are based on testing which is NOT done on a loose sandy NO BITE condition, For Anyone to give info with some confidence they would need to confirm more details like, What Class I see Jr 2 but what motor and weight are you currently running ? What are you normal Air pressures all 4 tires when you have the loose condition ? Do your tires have Internal prep & if so how much ? Are you prepping outside of tires & if so with what and how much ? What is your current base line numbers, Left %, Nose %, Cross %, Cambers, Toe out ? How far is LR tire out from inside of wheel to the cassette hanger ? How far out is the RR tire from inside of wheel to cassette hanger ? How much Rear Stagger are you running ? Is he running same line as experienced drivers ? I ask because MOST 1st yr drivers run low and box off corners some then the low entry causes little to much wheel in then loose off, OR if his entry is good line BUT turns to the bottom to quick on exit it will cause loose off. Are all the kids able to flatfoot the track ? if so is your driver doing the same ?
You answer is NOT just add weight to the RR, give these details and we can HELP !!
 
Thanks for the reply, I'll answer all I can. Sorry to be vague initially just know that many don't like to read a book when looking at a post....

Class- Jr2 Clone purple plate weight is 270lbs
Air pressure- 5psi right side and 4psi left, sometimes down to 4psi Right and 3psi Left
Tires are prepped very lightly internally and we use BTGP or real goat on the outsides with a wipe of black sand before features.
Current set up -
Left- 54%
Cross- 62
Rear- 52.5%
Stagger 1" front and rear
RF camber- 2.75
Rear width- tight to hangers both RR and LR

He does drive extremely smooth and follows a great line, like I said we are very fast and win most features by several kart lengths. He will box the corners some times.
I don't believe any others are able to flatfoot this track, it requires a throttle blip on entry and feathering in the center as it is very low bite, and wet usually.
 
Have you tried lower left? 50 pounds is very small for purple plate. Do they offer a green plate class that he can run? Reason I ask is my son ran both last year, and he says green plate is way easier on the driver.
 
No Haven't really tried lower left yet.

No green plate class really, maybe 1-2 kids if that. We went to purple mainly because his age, he's been racing motocross since he was 3 so I skipped rookie and threw him right in Jr2.
 

ColeAchey

Premium User
You can also take out rf and lf camber .25 at a time to try and slow down transfer that way to keep the kart under control rather than trying to simply plant the right rear. Possibly taking out some cross on the left front corner, along with neutralizing the right side with the spindle on the king pin as well would surely flatten things out and snug everything up without tightening the kart too much. If you go too far and slow down on the stop watch simply back up the adjustments one at a time.

Hope that helps,
Cole
 

RCJ

Member
Watch closely that the kart is not tight early in the corner and he is forcing it to turn, making it loose off.
 
That should confirm your thinking it's under loaded RR, When you can give LF camber, and spacings on rear tires from inside of wheels to cassette hangers because IF there out to far that's your first go to adjustment to try to fix it.
The spacing on the rear tires is as tight to the frame as you can go and still have clearance. We were told to do that by Prowler to maximize weight on the LR/RR.
 
Watch closely that the kart is not tight early in the corner and he is forcing it to turn, making it loose off.
I suspected that at first but after standing in the middle of the track and watching him very closely this past weekend I see that is not the case, the kart seems to turn in great with barely any movement of the wheel.
 
You can also take out rf and lf camber .25 at a time to try and slow down transfer that way to keep the kart under control rather than trying to simply plant the right rear. Possibly taking out some cross on the left front corner, along with neutralizing the right side with the spindle on the king pin as well would surely flatten things out and snug everything up without tightening the kart too much. If you go too far and slow down on the stop watch simply back up the adjustments one at a time.

Hope that helps,
Cole
Interesting thought... do you mean to drop the LF spindle therefore placing more load on the RR?
 
Interesting thought... do you mean to drop the LF spindle therefore placing more load on the RR?
When he say's make a cross adjustment taking some out on the LF yes that would drop the tire, However he's NOT saying for that to be the only adjustment that goes hand in hand with taking out camber on both sides.
 
The spacing on the rear tires is as tight to the frame as you can go and still have clearance. We were told to do that by Prowler to maximize weight on the LR/RR.
Ok the only thing we still do not know is where is your LF camber currently at ? , I've had a few Prowlers and IF I would of ever ran wheels as close to frame as possible on both LR & RR it would not rotate very well causing a push, I think you'll find you have an entry issue causing the loose off.
 
I hear the same thing about the rear end spacing, but many haven't had these working with 50lb drivers! lol...

Widening the rear (pulling either the RR or LR off the frame) would cause it to get even more lose would it not?
 
I hear the same thing about the rear end spacing, but many haven't had these working with 50lb drivers! lol...

Widening the rear (pulling either the RR or LR off the frame) would cause it to get even more loose would it not?
If indeed it's getting in real good and free now YES it would, however if the loose is caused by over steer of being to tight then NO.
 
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