1/16 at the left front
left side percentages and cross relations
- Thread starter BANDIT 518
- Start date
1/16 at the left front
SKHMotorsports71
Member
Try it at an 1/8" Toe out and see how it does. I know I have a kart that is very very steering sensitive!! We tried all of it for 0-3/32" The kart just wanted to come around on entry. We changed only the toe from 1/16" to an 1/8" and it really helped stablize the entry a lot better. How is his driving line? Does he cut the corner short on entry making the kart snap loose or is it a nice fluid smooth entry?
racing promotor
Moderator
Have learned a lot since this post racing here in the NE and If I had to pick 1 cross number to set all the newer chassis to race anywhere in the NE it would be 64%.
alvin l nunley
Site Supporter
If the cross and left percentage are the same, the LF and the RF are equal. Increases in cross percentage make the RF heavier than the LF.
The more cross percentage, the bigger the difference between the RR and the LR.
The less front percentage, the closer together the RR and the LR become.
It amazes me how much you can learn with my corner weights spreadsheet.
The more cross percentage, the bigger the difference between the RR and the LR.
The less front percentage, the closer together the RR and the LR become.
It amazes me how much you can learn with my corner weights spreadsheet.
racing promotor
Moderator
Now your just going back to the same old Al stirring the pot " NO CRAP " never looked at your spreadsheet and even I can figure that out !!
alvin l nunley
Site Supporter
What about the newcomers? And yes, most experienced dirt Karter's can take 4 scales and a handheld calculator and make these calculations. All my spreadsheet is is a preprogrammed calculator, it does it a whole lot faster. Just put in the kart and driver weight, the percentages you want, "F" "L" "C", and instantly the weight for all 4 corners appears. Or, put in the corner weights that you just measured and all the percentages and kart & driver weight come up.
An email to to me will get you a free copy of all my spreadsheet utilities.
anunley@austin.rr.com
at last count I think there's 44 separate spreadsheets.
1fasttiller
Member
Glad I found this post! Good info for sure!
Kinda helps explain my sons Prowler over this first full racing season on low bite, sandy Florida tracks.... Every time I tried upping the cross to what Prowler or any others told us to it would immediately push. Granted this is a Jr2 kid that weighs 60lbs soaking wet. As long as I keep the cross down around 55-58% this kart works and is fast but as soon as we go up to 60-62% as always suggested we slow down.
Kinda helps explain my sons Prowler over this first full racing season on low bite, sandy Florida tracks.... Every time I tried upping the cross to what Prowler or any others told us to it would immediately push. Granted this is a Jr2 kid that weighs 60lbs soaking wet. As long as I keep the cross down around 55-58% this kart works and is fast but as soon as we go up to 60-62% as always suggested we slow down.
racing promotor
Moderator
Correct BUT keep in mind the more drive the LR has and the RF can handle the FASTER you'll be in the end, So if you get the RF to handle it by more Internal, more bite, camber or caster adjustment ( and there all maybes) you'll love that higher cross.
alvin l nunley
Site Supporter
Have you ever thought that that extra weight on the LR, and the resulting push, might indicate the rear stagger needs changin?
I find it hard to imagine the manufacturer of your kart not knowing how to set it up. I understand their recommendations are only starting points.
paulkish
old fart
I suspect the lower cross works for you because your light weight driver does not provide enough weight effort to operate at the higher cross. By definition lower cross will put more static weight up at the LF making it available to the RF for grip. If i'm thinking correctly on it with your light weight driver to go to suggested higher cross you will also need to raise your VCG(vertical center of gravity) to get weight higher up to better use it to operate your chassis. You can weight out exactly the same at all four corners with different VCG settings.
I have often seen young small drivers enter corners ok but then because their light weight down so low on the LR corner of the kart push like heck center off because they just can't get the low drivers weight to make the chassis work.
... and if I'm offering likely bad info I hope racingpromotor points it out and i'll learn along with you.
trying to net it out with high cross and a low VCG you just can't get weight on the LR tire off the LR tire and to the right side, after turn in.
1fasttiller
Member
"I have often seen young small drivers enter corners ok but then because their light weight down so low on the LR corner of the kart push like heck center off because they just can't get the low drivers weight to make the chassis work. "
Paul- I agree 100% with your post above and most certainly this statement above. This is what we fought many times over this past year. I don't think he transfers any weight being so light. He can drive extremely well but the kart (especially being a large tube adult chassis) doesn't flex enough with him. I'm highly considering switching to a Prowler Jr. Or Triton Jr....
Paul- I agree 100% with your post above and most certainly this statement above. This is what we fought many times over this past year. I don't think he transfers any weight being so light. He can drive extremely well but the kart (especially being a large tube adult chassis) doesn't flex enough with him. I'm highly considering switching to a Prowler Jr. Or Triton Jr....
1fasttiller
Member
Its Pretty high up on the seat now... and we did try the seat back way up for him (like 16" off the axle) but the kart handled terribly and thanks to JR Curtis and A few others on here we were able to determine that was a major cause of our handling battle and correct it.
racing promotor
Moderator
At the right time one would be amazed at what moving one 5 lb chunk up high on the back of the seat can enhance handling.
1fasttiller
Member
Care to elaborate on this "right time"? You've peaked my interest! I'm aSSuming it is when the track has Zero grip and the kart is suffering from a 4 wheel drift type situation?
racing promotor
Moderator
When adding lot's of weights always have some sides, front, and back of seat, have extra holes pre-drilled to move weight's if needed.
Bandit to answer your question, setup the chassis as manufacturer says, If those numbers happen to be say 45 nose, 58 left and 65 cross is "recommended", I would try to get those numbers dead on or within .2%. The manufacturer numbers are only a suggestion and what works for 80% of racers, 80% of the time, on 80% of the tracks. In order to find optimal speed you may have to step outside those numbers.
Msquared
Msquared
Now to address the falsehood remarks. In speaking about adding cross to a kart, keep in mind that I am not talking extremes here only a few percent, like 2-4%. Going to extremes on cross, say going from 58% to 72% is going to require a change to rear stagger and to your front-end. So, you have added say 2% cross. Now the LR/RF are heavier and the LF/RR are lighter. Lets break this down into what happens at each segment of the turn. First, cross is used to get the maximum weight distribution between the LR/RR on turn exit to allow the kart to drive as hard as possible off the turn without overpowering the RF.
At turn in, the front-end needs to have enough grip to not let the rear of the kart to over-power the front-end. It needs to do this in order to let the kart to rotate and allow the inertia to start the weight transfer process. This will allow the kart to “dive” down into the turn. So, adding cross pre-loaded the RF more and gives it (basically the front-end) more grip, sooner, and turn-in power while not allowing the added weight to the LR over-power the front. This is of course given the tires are right. Now we are still on turn entry but at the phase where the kart still needs to have good front grip in order to rotate properly at the apex. At this point weight is transferring forward and to the right helping to unload the LR which was pre-loaded more with the added cross. So, the LR is unloading and the RF is loading.
What is important here is the “balance of power” between the relationship of the RF/LR. As the kart gets closer to the apex this power begins to shift. At the apex you are at max weight transfer from left to right. A side note: I know when a track gets a lot of grip, karts running high cross, the LF is all the way off the tracks surface. Under certain conditions, when the RF is carrying all the load on the front-end, and you need the LF to do more work, adding cross is only taking away grip from the front-end.
Now for turn exit, this is where cross really struts its stuff! (False statement?) Here is where the LR drives the kart hard off the turn. (Another False statement?) There is a post out there where someone is asking about another karter really running off the corner (turn). Here is where you want maximum grip and have the least amount of rolling resistance which equals more straightaway speed. (Golly day! Another false statement!) The LR will dominate the RF but not so much as to cause a push coming off the turn. (OOOOPPPS, another False statement! I must have no idea!) Side note: the fastest karts I have ever driven pushed slightly coming off the turn for a lap or two and then stopped and took off like a rocket! The reason for all this LR dominance is because weight is now transferring back to the rear particularly the LR.
So, lets say you have a push somewhere on turn entry. So, if you add a little cross the added RF weight can help. Lets say you are loose coming off, adding cross can help by settling the rear of the kart by giving it more grip. Now if the kart is loose in or pushing coming off then do the opposite, reduce cross.
Today a lot of karts are running high cross (65% or more). If the kart has a push coming off here is what reducing cross can do. While lowering cross may make the push go away, what it does is hurts the kart (slowes it) coming off because of the added load put onto the RR. Basically the RR is overloaded dynamically. (True or False?) The load on the RF and the load on the RR is compressing the chassis and energy is being wasted because of the dynamic loads on the RF/RR.
The last thing is the chassis design itself. Some chassis are really stiff at the RF, some at the LR. Some have softer “waists”. Others have really still rears. This is why cross effects karts differently. (Guess I’m just nuts! Can’t quit making false statements!) One main point I make in my chassis manual is if you make a change and it does the opposite of what you expected, then do the opposite!
HOLY Jimmey Christmas! Now lets look at the RF and LR’s relationship to the CG of the kart. Move the RF out and it is less responsive to the cross adjustment because not only does the timing of weight transfer change but the amount of weight transfer also changes and with comes changes in the grip of the tire. With respect to the LR, moving it in will make it more responsive to the added cross. In other words it will reload faster coming off the turn giving more drive off. Guess that is false as well!
So, for a push on entry added cross can help because it adds grip to the RF, this is only if the tires are in the “ball-park”. For loose off, adding cross can settle the rear of the kart by giving it bite coming off. In these two scenarios adding cross either tightens the front or tightens the rear. Or, frees the rear and frees the front. However you want to look at it. But to say adding cross always, always, always tightens a kart I don’t know about that. It is all semantics.
I have read hundreds of posts on here when a guy say if I increase cross the kart pushes more, Then another guy says well I lower cross and it pushes more. Then when you see the setups you can clearly see why. They are in the “dead zone”, that is within 3% of their leftside. Just saw this exact example a few weeks ago.
I can post way more info here but this should be enough.
Msquared
At turn in, the front-end needs to have enough grip to not let the rear of the kart to over-power the front-end. It needs to do this in order to let the kart to rotate and allow the inertia to start the weight transfer process. This will allow the kart to “dive” down into the turn. So, adding cross pre-loaded the RF more and gives it (basically the front-end) more grip, sooner, and turn-in power while not allowing the added weight to the LR over-power the front. This is of course given the tires are right. Now we are still on turn entry but at the phase where the kart still needs to have good front grip in order to rotate properly at the apex. At this point weight is transferring forward and to the right helping to unload the LR which was pre-loaded more with the added cross. So, the LR is unloading and the RF is loading.
What is important here is the “balance of power” between the relationship of the RF/LR. As the kart gets closer to the apex this power begins to shift. At the apex you are at max weight transfer from left to right. A side note: I know when a track gets a lot of grip, karts running high cross, the LF is all the way off the tracks surface. Under certain conditions, when the RF is carrying all the load on the front-end, and you need the LF to do more work, adding cross is only taking away grip from the front-end.
Now for turn exit, this is where cross really struts its stuff! (False statement?) Here is where the LR drives the kart hard off the turn. (Another False statement?) There is a post out there where someone is asking about another karter really running off the corner (turn). Here is where you want maximum grip and have the least amount of rolling resistance which equals more straightaway speed. (Golly day! Another false statement!) The LR will dominate the RF but not so much as to cause a push coming off the turn. (OOOOPPPS, another False statement! I must have no idea!) Side note: the fastest karts I have ever driven pushed slightly coming off the turn for a lap or two and then stopped and took off like a rocket! The reason for all this LR dominance is because weight is now transferring back to the rear particularly the LR.
So, lets say you have a push somewhere on turn entry. So, if you add a little cross the added RF weight can help. Lets say you are loose coming off, adding cross can help by settling the rear of the kart by giving it more grip. Now if the kart is loose in or pushing coming off then do the opposite, reduce cross.
Today a lot of karts are running high cross (65% or more). If the kart has a push coming off here is what reducing cross can do. While lowering cross may make the push go away, what it does is hurts the kart (slowes it) coming off because of the added load put onto the RR. Basically the RR is overloaded dynamically. (True or False?) The load on the RF and the load on the RR is compressing the chassis and energy is being wasted because of the dynamic loads on the RF/RR.
The last thing is the chassis design itself. Some chassis are really stiff at the RF, some at the LR. Some have softer “waists”. Others have really still rears. This is why cross effects karts differently. (Guess I’m just nuts! Can’t quit making false statements!) One main point I make in my chassis manual is if you make a change and it does the opposite of what you expected, then do the opposite!
HOLY Jimmey Christmas! Now lets look at the RF and LR’s relationship to the CG of the kart. Move the RF out and it is less responsive to the cross adjustment because not only does the timing of weight transfer change but the amount of weight transfer also changes and with comes changes in the grip of the tire. With respect to the LR, moving it in will make it more responsive to the added cross. In other words it will reload faster coming off the turn giving more drive off. Guess that is false as well!
So, for a push on entry added cross can help because it adds grip to the RF, this is only if the tires are in the “ball-park”. For loose off, adding cross can settle the rear of the kart by giving it bite coming off. In these two scenarios adding cross either tightens the front or tightens the rear. Or, frees the rear and frees the front. However you want to look at it. But to say adding cross always, always, always tightens a kart I don’t know about that. It is all semantics.
I have read hundreds of posts on here when a guy say if I increase cross the kart pushes more, Then another guy says well I lower cross and it pushes more. Then when you see the setups you can clearly see why. They are in the “dead zone”, that is within 3% of their leftside. Just saw this exact example a few weeks ago.
I can post way more info here but this should be enough.
Msquared
bricklayer653
Member
Ok going to try and explain my question clearly but not sure how well I will do ...I will start by saying I know when cross is added by moving front end everything needs reset..camber ,toe
Numbers are just hypothetical percentages...let's say I have 65% cross and want more drive up out of the corner and decide I'm going to add cross and so wanting more drive off left rear would it be better to make a left rear pill change will that put slightly more weight on the left rear I know it will also put weight on the right front but will it add slightly more to left rear then right front because I moved the left rear down instead of moving right front down..
And if I have a push exiting the corner and decide I'm going to change cross would it be better to move right front up ...will it loose more weight on right front then on left rear because adjustment was done to front
Or is it just a wash and doesn't matter if you add 2% of cross the weight on right front and left rear gain the same regardless of which tire is moved down
And then does it matter because I've changed ride height at front or rear I'm sure it changes weight transfer on one end or the other
Hope it makes sense
Numbers are just hypothetical percentages...let's say I have 65% cross and want more drive up out of the corner and decide I'm going to add cross and so wanting more drive off left rear would it be better to make a left rear pill change will that put slightly more weight on the left rear I know it will also put weight on the right front but will it add slightly more to left rear then right front because I moved the left rear down instead of moving right front down..
And if I have a push exiting the corner and decide I'm going to change cross would it be better to move right front up ...will it loose more weight on right front then on left rear because adjustment was done to front
Or is it just a wash and doesn't matter if you add 2% of cross the weight on right front and left rear gain the same regardless of which tire is moved down
And then does it matter because I've changed ride height at front or rear I'm sure it changes weight transfer on one end or the other
Hope it makes sense