Jr2 Driver needing more weight xfer to RR?

XXX#40

Member
You suggest this even though he told us previously the LR tire was in more then the manufacture recommended as a minimum?

"I went ahead and pulled the LR out last night to the MIN suggested spec from Prowler, moved it a total of 5/8"."


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just yada yada and proly more useless yada below because the response got me thinking about it. no argument intended, just offering what it made me think about which probably ain't right anyway.

IMHO the position of the tire in or out has nothing at all to do with the effects to rotation caused by stagger. The ONLY thing which effects how stagger will work, unless your traveling in a perfect circle is the loading of each rear tire and the direction forces act on the tire. Moving the axle out effected tire loading and because it slightly lowered the LR corner of the kart it effected the direction forces acted laterally to pull the LR tire to the right. The key IMHO is did moving the LR out cause an increase or decrease in the amount of slip at the LR.
Well you're wrong paul, its easy to prove drawing a line from the top of the right tire to the top of the left, then move the left tire out and draw the same line you see the angle of that line has changed where they intersect.
Moving the tire in increase the effect, and out lessens it
It didnt lower the left rear, it moved the left rear farther out from VCG which slowed weight transfer from and to the LR
 

paulkish

Premium User
Well you're wrong paul, its easy to prove drawing a line from the top of the right tire to the top of the left, then move the left tire out and draw the same line you see the angle of that line has changed where they intersect.
Moving the tire in increase the effect, and out lessens it
It didn't lower the left rear, it moved the left rear farther out from VCG which slowed weight transfer from and to the LR
Your right I was looking at it wrong. Moving the LR out raises the LR corner and does not lower it. thank you


corrected my reply with the words >raised< and >tire< it now reads:



IMHO the position of the tire in or out has nothing at all to do with the effects to rotation caused by stagger. The ONLY thing which effects how stagger will work, unless your traveling in a perfect circle is the loading of each rear tire and the direction forces act on the tire. Moving the >tire< out effected tire loading and because it slightly >raised< the LR corner of the kart it effected the direction forces acted laterally to pull the LR tire to the right. The key IMHO is did moving the LR out cause an increase or decrease in the amount of slip at the LR.

How's what follows? It changed the position of the karts rear roll center in relation to how it is working the LR tire. Not by lowering the rear roll center but by raising the point on the chassis which pulls or works the LR tire. You end up with not only a longer lever to operate but where the lever is operated is placed in a better position to be pulled downward. ... again not arguing, your letting me see it better and thanks.

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edit and added on: "it moved the left rear farther out from VCG which slowed weight transfer from and to the LR"

Weight created at the LR transfers instantly per g's created. Weight physically located at the LR cannot leave the LR without also having a loss of grip. It's how much you cause the LR to slip and loose grip that lets physical weight leave the LR tire. If the LR does not slip(loose grip) physical weight cannot leave. The only timing involved is with when you cause or lessen slip/grip. That is the only reason more grip/bite allows you to go faster. ... maybe???
 
Update: 3/15/19

We came to the track with the same setup as we've been running here and out of the gate the kart was pushing on entry VERY badly. My little guy had a terrible time. I chased it with minor air pressure adjustments which didn't seem to help in the heats so I pulled the RR hub out 1/2" and moved a 5lb lead puck to the nose for the feature. It took most of the push out but seem to "Lock" the kart down. He said he was running flat out and not lifting but the kart just wouldn't gain speed. Ended up running 5th out of 11 karts.

My question is how?? why?? RPM's were same as normal 5880-6000 peak. Same gear, same tires etc. We have had incredible luck at this track all season and know the setup we have on this kart works, I just can't see what caused such a drastic change.
 

flattop1

Dawg 89
My initial thought is . After all the changes on the left rear , you moved to the right rear for a fix.
The left rear seems like the logical place to start.
 
So you're thinking I should move the left rear hub back in to the frame as it was before? That thought has crossed my mind but all my knowledge tells me push on entry is solved with other means... I forgot how fun it was to chase your tail with dirt karts...

If the LR is moved back in tight, wouldn't it have more weight on it and not want to rotate allowing the kart to turn in?
 

paulkish

Premium User
"If the LR is moved back in tight, wouldn't it have more weight on it and not want to rotate allowing the kart to turn in?"

Either the fronts turn the thing and/or/or both normally it rotates around a LR which is pinned enough both on entry and exit to act like a rudder letting the RR either roll around it decelerating or out accelerate the LR.

If it's pushing either you have to make the fronts turn better of get the LR pinned/ruddered/acting like a brake enough to let the RR do it's thing.

... all just IMHO and ain't necessairly right anyway. ... :)
 

flattop1

Dawg 89
Honestly I always threw the kitchen sink at it.
The two main things you've changed are the tire and its location. At least that we know of . Same prep same air same gear , nothing else ?
Did track conditions change ?
 
We put a new LR tire on 2 races ago and ended up moving the LR out some. Other than that, nothing has changed. The track was a tad wetter this time than it has been. Looked like they really poured the water to it but nothing unusual for this place.

I did notice I had lost some stagger in the rear, hadn't paid the closest attention to it but realized last night that we're setting at 1" in the rear now, where as before we had 1-1/4- 1-3/8" That old worn out LR was in effect giving us more stagger. Odd thing is, on a track this size I wouldn't think you'd need much stagger.
 
Looking back, I think I know what happened... I moved the LR out and by using a new LR tire I lost some stagger. This is where my push came from. I plan to shrink the LR down to what the old one measured or Increase the size of the RR and move the LR back in some. That should get me back to square one....


Thanks for all the help fellas!
 
Looking back, I think I know what happened... I moved the LR out and by using a new LR tire I lost some stagger. This is where my push came from. I plan to shrink the LR down to what the old one measured or Increase the size of the RR and move the LR back in some. That should get me back to square one....


Thanks for all the help fellas!
Don't move it back in to close or you'll still be chasing it.
 
So just to update any of you that care- we raced again this past weekend and I did as I said I would do by adding more stagger to get us back to the 1.5" that we had prior to the new LR tire. It was better but still pushing bad on entry. I finally got out the old, worn out LR tire and put it back on. The kart came back to life! He managed a 2nd place finish out of 10 karts. The leader was hooked up! From what I could see, there was still a small push on entry though which caused him to turn too much going in and naturally making it a little loose center off.

I'm told by a few that these Prowlers liked a hard LR, one guy told me at least 10 points harder than the other 3 tires. I don't have a duro yet but I know our new LR Vega MCS is pretty soft even though I haven't put much prep at all on it (nothing inside).

Hey, I just noticed that I'm now a "New member" but I've been on here for almost 15 years! lol.....
 
Do you have any weight high up on the rear of seat. Sometimes that will help. Especially with light short driver.
Maybe move the left rear in a little. That is a band aid solution, but worth a try.
Try more air in left rear. and everything said above.
 
I do have some lead pucks up mid-way on his seat. Majority of it is lower left and right side. The one thing I haven't tried is more air in the LR... are you saying to run a reverse split (more air in the LR than in the RR?)
 
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