Jr2 Driver needing more weight xfer to RR?
- Thread starter 1fasttiller
- Start date
racing promotor
Moderator
Moved the LR hub out and the new LR tire, IS THAT ALL YOU CHANGED ? Where was the push on entry or exit ?
1fasttiller
Member
Yes, that was the only changes made. I had intended to ONLY slide the LR out to keep any variables out of the equation but the LR was basically shot. Had we been on a high bite, fast track I would still be running it but our local track is far from that 
My little guy stated the push was center off, I could not verify this time due to only being allowed to spectate from the bleachers on race night. He did appear to be pushing up on exit which is where he was almost passed...
My little guy stated the push was center off, I could not verify this time due to only being allowed to spectate from the bleachers on race night. He did appear to be pushing up on exit which is where he was almost passed...
1fasttiller
Member
My thought is the LR has been the cause for the loose condition all along. A fresh new LR tire gave us that needed LR "Bite" again and now we have a push. I'll continue to pull the LR out some and take some cross out until it goes away? I now need to unload that LR on exit, correct? Or get more weight on the front?
JPMKarting
Site Supporter
One thing to keep in mind, by putting a new LR tire on, not only did you add bite with a thicker tire, you also tightened the kart up via LR durometer. I'm sure that thin wore out tire was a fair bit harder then the new one. Especially as the race went on, and the LR started creating more and more bite.
I would be inclined to reduce the cross weight a bit. As for as sliding tires in or out, I have always liked to keep the tracking of all 4 tires the same to eliminate the variable of tires loading/unloading differently relative to their location.
I would be inclined to reduce the cross weight a bit. As for as sliding tires in or out, I have always liked to keep the tracking of all 4 tires the same to eliminate the variable of tires loading/unloading differently relative to their location.
racing promotor
Moderator
Yes If it's pushing on exit now It's to much grip on that new LR, I would NOT add any more nose weight your high now, I would NOT move the LR out anymore as J.P points out I don't like to use RTW as a go to adjustment either, ONLY reasons I suggested it was number 1 it was an easy way to prove your issue, and second you had both rear tires in to tight to start, since RR is still in tight IF you adjust any rear hub move the RR out a little, BUT your thinking correct lower cross will help it, If it needs more adjustment after cross I would just add a little more rear stagger, HOWEVER IF you have time and are able to re-scale it that's what I would be doing, Check the numbers now as it was raced, then use those numbers except lower cross, set RTW FIRST leave LR where it is now or out another 1/8" move RR out a little as well, then re-scale with same tires.
Good Luck !!
racing promotor
Moderator
[QUOTE=1fasttiller;755891 Your thought that the LR has been the cause for the loose condition all along.
That was part of it, HOWEVER with both rear tires in tight to the frame it was tight on entry causing added wheel input which was part of it as well.
That was part of it, HOWEVER with both rear tires in tight to the frame it was tight on entry causing added wheel input which was part of it as well.
1fasttiller
Member
racing promotor
Moderator
paulkish
old fart
I'm going back to the first post and thunk and write on clues with my regular bs(theory about how a staggered solid axle works and needs to be used) I see in 1fasttiller. ... now after being told something he did which worked
"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." Thunkin on that maybe you reduced air in the wrong tire/tires. More grip unless your out of hp and your ability to maintain momentum should always if increased in the right places reduce lap times. My first guess on why is you were thinking you had too much grip at the LR because you couldn't get weight off of it and you either reduced pressure evenly or not at the LR. Again guessing back if you would have just reduced air pressure at the LR you might have gotten faster or maintained your speed even with the worn out tire.
All above and below just IMHO and not necessairly right anyway. ... )
"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."
Hind sight I 'think' tells us the answer to your first question was yes. My general bs is that weight follows grip and grip is what can retain weight. With your worn out tire additional weight most likely would have worsened the problem because it would have reduced the time your LR tire was able to hold weight. You by adding grip increased the time your LR tire was able to hold weight. The other thing involved here is your changing the grip capability of the LR tire on a 'moving target'. If your problem is your LR loosing grip center off, which it appears it was, then if you cause the LR to hold it's grip longer you can end up on a place on the track where it no longer needs to laterally hold the back in.
... I need another cup of coffee real quick so I'm going to jump ahead in my thoughts. ...
... ok you got enough grip now at the LR and your moving on the track towards going straight but you are not yet going straight. Without reading the end of what's posted I think if i'm remembering correctly your next problem was a push. Well, what happened on your moving target to develop the push. You got a brand new tire on the LR and myself anyway will assume it's not because the LR went away.
????? if I'm thinking correctly and my bs reply is sort of ok, i'll ask all of ya why did the push start and what will be the fix.
LOL, I'm proly not remembering correctly about the push and i'm asking about something from my imagination. ... I'll get that coffee and fix my post later if needed. but maybe the question's ok anyway for brain hurt ????? ...
"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." Thunkin on that maybe you reduced air in the wrong tire/tires. More grip unless your out of hp and your ability to maintain momentum should always if increased in the right places reduce lap times. My first guess on why is you were thinking you had too much grip at the LR because you couldn't get weight off of it and you either reduced pressure evenly or not at the LR. Again guessing back if you would have just reduced air pressure at the LR you might have gotten faster or maintained your speed even with the worn out tire.
All above and below just IMHO and not necessairly right anyway. ... )
"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."
Hind sight I 'think' tells us the answer to your first question was yes. My general bs is that weight follows grip and grip is what can retain weight. With your worn out tire additional weight most likely would have worsened the problem because it would have reduced the time your LR tire was able to hold weight. You by adding grip increased the time your LR tire was able to hold weight. The other thing involved here is your changing the grip capability of the LR tire on a 'moving target'. If your problem is your LR loosing grip center off, which it appears it was, then if you cause the LR to hold it's grip longer you can end up on a place on the track where it no longer needs to laterally hold the back in.
... I need another cup of coffee real quick so I'm going to jump ahead in my thoughts. ...
... ok you got enough grip now at the LR and your moving on the track towards going straight but you are not yet going straight. Without reading the end of what's posted I think if i'm remembering correctly your next problem was a push. Well, what happened on your moving target to develop the push. You got a brand new tire on the LR and myself anyway will assume it's not because the LR went away.
????? if I'm thinking correctly and my bs reply is sort of ok, i'll ask all of ya why did the push start and what will be the fix.
LOL, I'm proly not remembering correctly about the push and i'm asking about something from my imagination. ... I'll get that coffee and fix my post later if needed. but maybe the question's ok anyway for brain hurt ????? ...
paulkish
old fart
... and because of that second cup of coffee i'm required to post more bull. ...
"Yes, that was the only changes made. I had intended to ONLY slide the LR out to keep any variables out of the equation but the LR was basically shot."
I already spoke to the additional grip you gained and now some regular bs(theory) on moving the LR out.
Not caring what it does to weight out numbers because of stagger when you move a LR out it lowers the LR corner of the kart. My experience with both karts and cars may go against the grain of what most will think but IMHO it also smooths out some the grip presented to the track by the LR tire. It puts the LR tire out on a longer lever which is pulled laterally against the track. It also aids in leveraging of the LR tire back into the track at the start of acceleration. If possible you always want to start your acceleration off of the smaller(low gear) LR tire.
As far as the developed push on exit before you worry about it you noted he also was in a 'racing' situation. The exit push may have developed for no reason other then he got on the gas or ended his maintaining of momentum too soon effectively creating the push because he was still turning more then before the push because of the racing situation. If that's the case and the LR is still able to hold in because it still has grip available your fix to gain during an exit racing situation may be to add some front end grip directly at the front tires(prep).
... or not because ya know this is all just IMHO and ain't necessairly right anyway. ...
... now who might want to talk about maybe getting rid of a very small loose off by changing "only", LR wheel offset?
"Yes, that was the only changes made. I had intended to ONLY slide the LR out to keep any variables out of the equation but the LR was basically shot."
I already spoke to the additional grip you gained and now some regular bs(theory) on moving the LR out.
Not caring what it does to weight out numbers because of stagger when you move a LR out it lowers the LR corner of the kart. My experience with both karts and cars may go against the grain of what most will think but IMHO it also smooths out some the grip presented to the track by the LR tire. It puts the LR tire out on a longer lever which is pulled laterally against the track. It also aids in leveraging of the LR tire back into the track at the start of acceleration. If possible you always want to start your acceleration off of the smaller(low gear) LR tire.
As far as the developed push on exit before you worry about it you noted he also was in a 'racing' situation. The exit push may have developed for no reason other then he got on the gas or ended his maintaining of momentum too soon effectively creating the push because he was still turning more then before the push because of the racing situation. If that's the case and the LR is still able to hold in because it still has grip available your fix to gain during an exit racing situation may be to add some front end grip directly at the front tires(prep).
... or not because ya know this is all just IMHO and ain't necessairly right anyway. ...
... now who might want to talk about maybe getting rid of a very small loose off by changing "only", LR wheel offset?
paulkish
old fart
Sorry I killed this great thread. ...
I'm still curious what you may try next if anything after reading the inputs on the why's of it and suggestions, to fix the push at the end of the race.
I hope I'm not out of line here or hijacking the thread with more of my thoughts and theories. When you apply weight to normally a right side tire or when left and rear tires are reloading after acceleration starts and turning lessens, IMHO there's to things to consider. The first is the amount of weight available to apply and how much, how fast it will be applied. The second is the direction the weight will come from which is normally IMHO the vcog(vertical center of gravity). If this interests you you may want to calculate via scaling the point on your kart or space of the actual location of the cog. It's not all that hard you do your weight outs with the kart level and then with the back raised up to find it. You'll find lots of references on the web to finding the vcog. If you do find it you can go to the left of the kart and sight down through to vcog to your RR bearing where the axle goes through it. IMHO the line I can visualize between the vcog, through the RR bearing inner race and to the ground is what weight rotates around when it projected to the right by lateral acceleration. I then think about how much turning is being done. If your turning more, more of the mass/forces of the vcog line through the RR bearing is being applied towards the rear. Less turning and the mass/forces acting on the line are being applied more towards the actual vcog. That's just my theory/thoughts on it and what I use to see forces applied. What's relative to this discussion(I think?) is how forces/mass rotating around the line apply force downward through the tire via your tire hub. I use what I just presented to be able to think about how moving a tire in or out effects how forces are applied to the tire via the tire hub. I wrote all this to help answer the question I posed above about wheel offset. I'm hoping now after reading through this you and others can visualize the differences which occur between > moving a tire in and out without changing offset and leaving the tire spaced where it is and changing offset.
To add a little in here just for my purposes I recently talked with a person on a high dollar sprint car team who told me they leave their tire spacing alone and make adjustments via wheel offset. I'm mentioning it hoping it will show a little understanding of the results of changing tire location in and out verses changing wheel offset. IMHO, there is no set thing to consider because it's about application of weight with many variables including available grip, available hp track banking and where on the track you intend to change performance of a particular tire. With a kart which this site is about we have argued till the cows come home about where front and rear roll centers are located. I think because of a general lack of suspension the end thoughts were the usable/viable rear roll center on a kart is either at in this example the RR bearing or the tire contact patch. I choose to use the RR bearing for a karts rear roll center and my thoughts on it revolve around it. pun intended In the case of a sprint car with it's suspension if you want to gain a mental understanding on rear weight application you need to include the sprint cars roll center at the intersecting point for the jacobs ladder bars. Being able to relate the intersection point to how weight and forces are going to be applied to the RR tire taking into consideration the vcog is then no different then on a kart. In the case of a sprint car it will also take away any magic you can't just seem to understand and put together in how when a rear sprint car chassis operates to both set the LR corner down and at the same time put it down in the angle you want be it flat or not. It's all about weight projection and how much force you have available to both apply weight and operate the chassis be it the operation of a complex chassis or the operation of a kart chassis around the RR bearing hanger. I have to add one thing in here because it concerns both karts and cars. The other thing which is involved in the actual application of weight to the RR tire is >tire diameter<. Tire diameter showed itself to me many years ago, probably 15 or more in the difference in performance between two local sprint car racers. One had a lock on one track and the other had a lock on winning at another local track. The "only" difference I came up with between the two was tire diameter because of one using Hoosiers and the other using McCreary's which were smaller in over all diameter. Even when they both used the same stagger because of track banking I calculated how the advantage changed tire application because of tire diameter.
Thanks for reading and I hope I'm not screwing up your thread with my bull. I hope I offered some insight into where forces come from to operate a tire and how they are actually applied to the tire contact patch. But as I like to say mainly because I ain't schooled on this formally it is all just IMHO and ain't necessairly right anyway. ...
... ok, where's that coffee?
I'm still curious what you may try next if anything after reading the inputs on the why's of it and suggestions, to fix the push at the end of the race.
I hope I'm not out of line here or hijacking the thread with more of my thoughts and theories. When you apply weight to normally a right side tire or when left and rear tires are reloading after acceleration starts and turning lessens, IMHO there's to things to consider. The first is the amount of weight available to apply and how much, how fast it will be applied. The second is the direction the weight will come from which is normally IMHO the vcog(vertical center of gravity). If this interests you you may want to calculate via scaling the point on your kart or space of the actual location of the cog. It's not all that hard you do your weight outs with the kart level and then with the back raised up to find it. You'll find lots of references on the web to finding the vcog. If you do find it you can go to the left of the kart and sight down through to vcog to your RR bearing where the axle goes through it. IMHO the line I can visualize between the vcog, through the RR bearing inner race and to the ground is what weight rotates around when it projected to the right by lateral acceleration. I then think about how much turning is being done. If your turning more, more of the mass/forces of the vcog line through the RR bearing is being applied towards the rear. Less turning and the mass/forces acting on the line are being applied more towards the actual vcog. That's just my theory/thoughts on it and what I use to see forces applied. What's relative to this discussion(I think?) is how forces/mass rotating around the line apply force downward through the tire via your tire hub. I use what I just presented to be able to think about how moving a tire in or out effects how forces are applied to the tire via the tire hub. I wrote all this to help answer the question I posed above about wheel offset. I'm hoping now after reading through this you and others can visualize the differences which occur between > moving a tire in and out without changing offset and leaving the tire spaced where it is and changing offset.
To add a little in here just for my purposes I recently talked with a person on a high dollar sprint car team who told me they leave their tire spacing alone and make adjustments via wheel offset. I'm mentioning it hoping it will show a little understanding of the results of changing tire location in and out verses changing wheel offset. IMHO, there is no set thing to consider because it's about application of weight with many variables including available grip, available hp track banking and where on the track you intend to change performance of a particular tire. With a kart which this site is about we have argued till the cows come home about where front and rear roll centers are located. I think because of a general lack of suspension the end thoughts were the usable/viable rear roll center on a kart is either at in this example the RR bearing or the tire contact patch. I choose to use the RR bearing for a karts rear roll center and my thoughts on it revolve around it. pun intended In the case of a sprint car with it's suspension if you want to gain a mental understanding on rear weight application you need to include the sprint cars roll center at the intersecting point for the jacobs ladder bars. Being able to relate the intersection point to how weight and forces are going to be applied to the RR tire taking into consideration the vcog is then no different then on a kart. In the case of a sprint car it will also take away any magic you can't just seem to understand and put together in how when a rear sprint car chassis operates to both set the LR corner down and at the same time put it down in the angle you want be it flat or not. It's all about weight projection and how much force you have available to both apply weight and operate the chassis be it the operation of a complex chassis or the operation of a kart chassis around the RR bearing hanger. I have to add one thing in here because it concerns both karts and cars. The other thing which is involved in the actual application of weight to the RR tire is >tire diameter<. Tire diameter showed itself to me many years ago, probably 15 or more in the difference in performance between two local sprint car racers. One had a lock on one track and the other had a lock on winning at another local track. The "only" difference I came up with between the two was tire diameter because of one using Hoosiers and the other using McCreary's which were smaller in over all diameter. Even when they both used the same stagger because of track banking I calculated how the advantage changed tire application because of tire diameter.
Thanks for reading and I hope I'm not screwing up your thread with my bull. I hope I offered some insight into where forces come from to operate a tire and how they are actually applied to the tire contact patch. But as I like to say mainly because I ain't schooled on this formally it is all just IMHO and ain't necessairly right anyway. ...
... ok, where's that coffee?
paulkish
old fart
What do you think you'll try next to fix the push late in the race?
edit: I sorry again if I'm screwing up your thread.
I'm going to add a question to all who might reply. What "1" thing would you do to try to fix the development of a late push off?
I already guessed at throw some grip to the front tires via prep.
... anyone else?
... Is my suggestion dumb?
edit: I sorry again if I'm screwing up your thread.
I'm going to add a question to all who might reply. What "1" thing would you do to try to fix the development of a late push off?
I already guessed at throw some grip to the front tires via prep.
... anyone else?
... Is my suggestion dumb?
1fasttiller
Member
Sorry Paul, been busy with travel for work and haven't been on. No worries about the thread, appreciate your input as well as all others.
We'll be racing again This Friday night, I plan to try some minor things first. My first shot was increasing the rear stagger some. I've added about 1/4" inch to see if that helps. I'm also taking out a couple washers of cross. If he gets too loose, I'll slowly add cross back to it.
We'll be racing again This Friday night, I plan to try some minor things first. My first shot was increasing the rear stagger some. I've added about 1/4" inch to see if that helps. I'm also taking out a couple washers of cross. If he gets too loose, I'll slowly add cross back to it.
paulkish
old fart
Thanks, It's tough for me to do but i've been waiting patiently for more words from you. ...
It's morning I think, the first cup of coffee and I feel like thunkin and writing. Hope you don't mind and don't take any of it for gospel.
My thoughts and theory about stagger. Though it's true more stagger in general will get you more rotation IMHO there's more to it then that. My bs on stagger is stagger works because of the difference in surface speed it creates between the two rear tires and your ability to apply weight to each tire at the right time all around the track. When you add stagger you increase the difference in surface speed between the two rear tires. Writing towards thoughts about the LR tire because it's generally easier to understand. The additional stagger and additional difference in surface speed between the two rear tires is either going to increase rotation or increase your ability to slip the LR tire depending on how your able to apply weight to the LR tire. Simply put you can't use the additional stagger unless you already have enough weight on the LR tire or you increase the amount of weight on the LR tire. In most cases when adding some stagger by reducing the size of the LR tire because of preload on the LR tire, you already have enough weight on the LR tire. So in most cases adding stagger does result in more rotation.
Here's where I'm going with this. You explained to us you added grip to the LR and it helped. I don't know but I'm thinking because of your over all setup you may be on the edge of using grip on the LR. Adding stagger may be the >right< thing to do and you'll find out. But there are two ways to add stagger. Either you reduce the size of the LR or you increase the size of your RR. In your case and because you also moved the LR out which helped, I'm thinking your addition of stagger should be by increasing the size of the RR tire. It will do two things. First it will effectively lower the LR corner in relationship to the RR corner gaining you some effective weight if you do need it because you really were on the edge of grip. Secondly it will direct forces from the vcog more inward towards the tire. If you don't need more applied weight to the LR to be able to use the additional stagger then it's a so what thing. But if he does get looser you may think adding stagger was not the way to go when it was not about the adding of stagger but how stagger was added.
If others think I'm right in my thinking that you should if at all possible do your adding of stagger by increasing the size of the RR, i'd sure like to hear it and I figure you would too. If that's not the way to go then input will help to because if you listen to me it will mess you up and that's why I'm never sure about any suggestion I make. Just throwing thoughts at you, your the one who has to try and see. In this case if my bs is ok though, the right fix of adding stagger may miss lead you with results because of how you added the stagger. By the way my thoughts about adding stagger with the RR are not about just throwing air to it. It would better relate to either a found bigger RR tire or growing the RR tire.
thanks for reading and I hope I didn't just confuse the issue ????/
paul
1fasttiller
Member
Yes, I will increase the size of the RR tire. A few hours in the hot box and 25psi will grow it quickly. Much simpler than shrinking the LR IMO.
1fasttiller
Member
Yes sir, we live 20 mins from Bubba Raceway and an hour from Volusia. The track we race at is actually only about 2 miles from Bubba's
XXX#40
2A supporter
Yes, that was the only changes made. I had intended to ONLY slide the LR out to keep any variables out of the equation but the LR was basically shot. Had we been on a high bite, fast track I would still be running it but our local track is far from that
My little guy stated the push was center off, I could not verify this time due to only being allowed to spectate from the bleachers on race night. He did appear to be pushing up on exit which is where he was almost passed...
when you moved the LR out you lessened the effect of stagger, with the new tire put your rear track back where it was
paulkish
old fart
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"."
_____________________
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.
In a turn isn't the LR tire the one which is most likely slipping if not always slipping? Isn't holding the LR tire under you about making it work and do what you need it to do for you as and anchor or rudder as long as possible? Isn't that because when it goes away too much you get loose because then the RR gets over worked and starts to give up? ... just askin?