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drewbagel423
2015.04.28, 10:24 PM
I'm getting some nasty traction roll at my local carpet track, coming off a long straightaway into a sharp 180 degree turn. Here's my setup:

98mm MM chassis
Soft tires in the front (glued), very soft in the rear
4.5mm 3Racing carbon T-plate
3Racing rolling damper with medium springs
PN V2 ball diff
PN V3 LCG motor mount

My next upgrades are the Reflex Racing St-St upper suspension arm pin and low profile front suspension set. Not sure if that will help.

Any thoughts?

DMALMAD
2015.04.28, 11:26 PM
What kind of front end do you have on? Also what type of tires (foam or rubber) If foam which brand? If you are running foam tires on carpet you should not be traction rolling. Make sure you are truing your tires to around 23.25mm or lower and ride height should not exceed 3mm. Usualy if you are flipping your sidewall is to soft. Generaly for foam carpet I recomend at least three coats of thin or medium ca. You want the ca to be very stiff but not go over onto the contact patch. This way you can have very aggresive steering without fear of traction roll. If you have checked your sidewalls and they are perfectly even, strong, and intact then lower your ride height and soften the front up a little bit. What DPS fluid are you running? Run a slightly thinner dps lube too. It is hard to tell exactly what your car needs you just have to remove steering whether through the tires or by setup changes until you can rely on the car.

Check out the X-power upper tower bar for your front end. Very simmilar to reflex except it gives one more aspect of tunability and the camber setting is easier to adjust in a rush. If you have the money go for the pn double a-arm but be ready to spend a decent amount of time setting it up and putting it on. Dbl a-arm is by far the easiest to work with once you have it installed but is a decent investment in time and money. If you are not looking to be competitive and win any a-mains in the near future I suggest maybe an atomic or pn lower arm in tandem with the x-power upper susp. mount

drewbagel423
2015.04.29, 08:39 AM
No front end, and PN is way out of my budget, hence my planned Reflex purchase. Foam tires, whatever Maj sells at the shop, I think 3Racing. Eddie glued my tires for me and the sidewalls feel pretty hard.

How can I lower ride height? Can I use the PN lower arm with the stock front end?

cowboysir
2015.04.29, 09:30 AM
Shims under the knuckle is a pretty easy way to lower ride height but you may have to compensate spring tension for the increased preload.

Are you sure it's front end roll.....have you examined how exactly the car flips in and at which part of the 180?

Kevinmueller
2015.04.29, 10:08 AM
If your tires are correctly secured to the rims than there are several other reasons why you would traction roll and a lot of different fixes you can do. Traction rolling at the very beginning of the turn is caused by too much front grip compared to the rear grip so the idea is to reduce front grip. Stiffing the front suspension to reduce weight transfer to the front of your car when off power will prevent weight being shifted forward, but will reduce front traction everywhere around the track. You can also use less negative camber and caster to reduce front grip. If those options don't work or can't be done then you would need to true your front tires down to a smaller diameter to reduce front grip or use a higher shore/degree front tire. It also I good idea to lower the CG of your car. Using light weight lexan windows in your body is a very good way to do this. PN also makes weights that you can secure to the bottom of your chassis as well. To increase rear grip on high speed turns the best thing to do is add a large wing to the rear of your body assuming you are already using the softest rear tires that is. Hope this helps

drewbagel423
2015.04.29, 11:09 AM
It's tough for me to tell exactly where the roll is because I'm so focused on try to run a good line that I'm having a hard time figuring out what the car is doing. I would say it's early-mid rolling, as the car ends up upside-down just past the apex.

I'm using the Aston Martin DBR9 body, which already comes with a pretty big wing, though I'm skeptical as to how much a wing will help at these speeds.

Kevinmueller
2015.04.29, 12:25 PM
The Aston Martin DBR9 looks like it has a long noise, I've never had one so I just looked on line. This means you will have faster weight transfer to the front of the car when you come off throttle, so going to a harder front spring/suspension setup will prevent the weight from shifting forward as quickly/ as much. The rear wing adds more weight to the back of the car which will also slow down/ prevent as much weight from shifting forward when off throttle. In mod classes rear wings make a huge difference in high speed turns. You can also lower the rear ride height or increase the front ride hight to get the same effect of less weight transfer to the front of the car.

DMALMAD
2015.04.29, 01:29 PM
If your tires are correctly secured to the rims than there are several other reasons why you would traction roll and a lot of different fixes you can do. Traction rolling at the very beginning of the turn is caused by too much front grip compared to the rear grip so the idea is to reduce front grip. Stiffing the front suspension to reduce weight transfer to the front of your car when off power will prevent weight being shifted forward, but will reduce front traction everywhere around the track. You can also use less negative camber and caster to reduce front grip. If those options don't work or can't be done then you would need to true your front tires down to a smaller diameter to reduce front grip or use a higher shore/degree front tire. It also I good idea to lower the CG of your car. Using light weight lexan windows in your body is a very good way to do this. PN also makes weights that you can secure to the bottom of your chassis as well. To increase rear grip on high speed turns the best thing to do is add a large wing to the rear of your body assuming you are already using the softest rear tires that is. Hope this helps

stiffining the front will NOT reduce traction roll. While a stiffer front may give slighty less steering it will not allow the car to roll thus instead of the outside of the chassis lowering and the inside side staying planted the car will want to actually tip. Giving more chassis roll reduces lateral grip and the more wheight transfer the more grip is lost and the lower the cg gets during cornering thus softening the front and lowering the rideheight will yeild a more stable car.

Also truing the front tires does not reduce grip it actually yeilds better performance and a lower cg so once again your principles are wrong.


The Aston Martin DBR9 looks like it has a long noise, I've never had one so I just looked on line. This means you will have faster weight transfer to the front of the car when you come off throttle, so going to a harder front spring/suspension setup will prevent the weight from shifting forward as quickly/ as much. The rear wing adds more weight to the back of the car which will also slow down/ prevent as much weight from shifting forward when off throttle. In mod classes rear wings make a huge difference in high speed turns. You can also lower the rear ride height or increase the front ride hight to get the same effect of less weight transfer to the front of the car.

And once again your are mistaken. More front weight = more rearward weight transfer so it would not make it flip actually having a long front end does the opposite. In regards to weight placement and transfer look at any modern 1/12th pan car; there are two chassis layouts, one with the battery transvers (more weight at the rear) and the longitudinal battery. In the chassis with the transverse battery with more weight at the back will provide more steering and be more aggresive than the transverse pack because weight cannot transfer to where it is already staying static. So when there is more weight in the front more weight is avialable to transfer to the rear and vice versa. Furthermore adding more weight to one direction of the car is not the right way to go about adjusting the car because the more weight that is removed from center the more the cg and the focal point of rotation changes. You can see this when some cars apear to rotate from the fron more or the rear. Ideally if anyweight shoud be added it should be at the lowest and center most portion of the car.

While getting less weight transfer to the front is the right idea you have proposed the wrong solutions. Also lowering the cg or rdide height in both the front and back will reduce traction rolling. You are thinking of weight transfer in the wrong sense. The more transfer the less total grip there is that is why stiffer suspension creates a much more responsive car because it allows less weight transfer and maintans an overall higher level of grip. Traction roll is caused by the sidewall of the outside tire gripping more than the inside side can transfer over thus the difference in grip and the lack of wieght transfer lead to the car wanting to flip. You have to think of it in the sense of the tires pulling or pushing the car and not the other way around. Then think about how the chassis reacts when it is being affected by the grip and the tires. Hopefully you can figure it out becuase your previous posts are complete nonsense despite your good intentions:)

Kevinmueller
2015.04.29, 02:00 PM
Unfortunately for you I'm not wrong and I can prove it by using your some of what you said. You said that the tires side walls are too soft and this is causing traction roll. So your solution was to put glue on the side wall, which in my opinion is just a band aid. You don't see real race cars driving around with glue on the side walls of their tires after all. By decreasing the tires diameter you decrease the amount the tire flexes. This is the same idea as gluing because your going to stiffen the side wall with a lower profiled tire. You also get the added benefit of having a more direct feel when turning. This is why all top racers use a tire truer and truer their tires down to 23- 22mm in the front. Secondly I know that when you decrease the diameter of the front tire you will decrease front ride height and that is why I said to increase the front ride height or lower the rear ride height both have the same effect but you should have the rear lower than the front. Maybe I didn't make that clear. As for the more weight in the front = more rear grip/ weight transfer to the rear you are going to have to explain that to me. Maybe just think about adding a 5gram weight to the front of your car and imaging how the car would handle. The nose would be heavy and therefore unload the rear tires while increasing weight on the front tires = more front grip and less rear grip. Maybe others can prove me wrong too about that.

cowboysir
2015.04.29, 02:23 PM
This discussion might be getting ahead of itself.....

I suggest that you might want to start with the obvious problems:

1. Tweak issues
2.front suspension binding
3. Grip balance

These issues correspond with front and middle traction rolls which are most likely.

I have had issues in the past with the DBR9 digging in (front splitter) on rcp but since you're on carpet that seems a bit unlikely.

DMALMAD
2015.04.29, 02:27 PM
Unfortunately for you I'm not wrong and I can prove it by using your some of what you said. You said that the tires side walls are too soft and this is causing traction roll. So your solution was to put glue on the side wall, which in my opinion is just a band aid. You don't see real race cars driving around with glue on the side walls of their tires after all. By decreasing the tires diameter you decrease the amount the tire flexes. This is the same idea as gluing because your going to stiffen the side wall with a lower profiled tire. You also get the added benefit of having a more direct feel when turning. This is why all top racers use a tire truer and truer their tires down to 23- 22mm in the front. Secondly I know that when you decrease the diameter of the front tire you will decrease front ride height and that is why I said to increase the front ride height or lower the rear ride height both have the same effect but you should have the rear lower than the front. Maybe I didn't make that clear. As for the more weight in the front = more rear grip/ weight transfer to the rear you are going to have to explain that to me. Maybe just think about adding a 5gram weight to the front of your car and imaging how the car would handle. The nose would be heavy and therefore unload the rear tires while increasing weight on the front tires = more front grip and less rear grip. Maybe others can prove me wrong too about that.

You are comparing apples to oranges because we are talking about carpet FOAM tire racing where no setup will work without a glued side walled. After running for nearly a full year with foam on carpet and trying nearly every copound avialable there is no way to race without a glued side wall. Also a stiff sidewall does not equal a stiff suspension. Side wall relate to grip created by the tire not by the suspensio so a harder sidewall decreases front girp as does a softer roll stifnessYou mentioned some wrong suspension and tuning theories and I clarified on those points. I am not trying to bash you but your understanding of weight transfer is wrong and you have no clue about foam tire racing. I run on the same track as the OP and understand what works and what does not so please save your advice for a different topic.

You also mentioned raising the front ride height to reduce tractio roll:eek: that would raise the front cg and cause even more flipping. Also what I have explained about weight transfer is valide verified information while your misconceptions are just that. I am not trying to argue with you but you are provideing false information that could be detrimental to the racign experience of others and yourself.

DMALMAD
2015.04.29, 02:29 PM
This discussion might be getting ahead of itself.....

I suggest that you might want to start with the obvious problems:

1. Tweak issues
2.front suspension binding
3. Grip balance

These issues correspond with front and middle traction rolls which are most likely.

I have had issues in the past with the DBR9 digging in (front splitter) on rcp but since you're on carpet that seems a bit unlikely.

I agree, on a stock car these are generally the first place to start. I just wanted to clarify on some other tuning and suspension topics.

Jshwaa
2015.04.29, 02:30 PM
If I may chime in here....

I've read the entirety of the thread and I'm not here to dispute a word, as I realize after reading some of DMALMAD's input on topics he's turned a lot of corners in his day and Kevin sounds like a well informed individual as well, but let's remember that these cars differ dramatically from actual race cars in almost every way except the 4 wheels. Real race cars have way more mass, independent suspension systems with springs AND dampers, and state of the art transmission and braking systems to handle every extreme the drive-train and steering system is encountering in real time. While mini-z's emulate much of what a race car is in it's own scale, it still deals with the same gravity, which brings it to a completely different domain of performance characteristics, for much the same reason a bug can survive a fall off of a 10 story building and a human cannot.

I love reading the long derivations of race car analysis though, as if one is competing for chief editor of Racers Digest, but let's be clear. There is nothing really verifiable here, without at least a little bit of diagram and math involved, or else it is all just hand waving and speculation. As much as you'd like to attribute any spectacular track performance to how well you tuned the front vs. rear weight response of your car, sooner or later you're going to have to admit that it was mostly because you know your car, you know the track, and you were lucky enough to have drivers in the race who didn't, regardless of whether or not real race cars use Elmer's, but on that note real race cars do use a composition of rubber that is so soft that at high speed turning it melts to a glue like substance to hug the corner, which is why the corners are so black and the tires need to be changed every so many laps, but.... Carry on... :)

DMALMAD
2015.04.29, 02:59 PM
I agree that Mini-z is different than larger scale cars but much of what I have stated comes from basic principles that are also applied on real racing cars. Also almost all the principles of mini-z can be applied to pan car 1/12th rc racing, especially when running foam tires on carpet. If you read in depth on rc-tech and other 1/12th information sites you will see that pro racers and sportsman club guys all have discovered and relayed the same principles. I am not trying to be an expert on the physics of suspension dynamics and cornering but I have provided a well informed explenation to some of the causes of traction roll and how that can be remedied, along with some basic and universal suspension principles. While what I have said may not work for everyone, I do know my local track extremely well and what works on it. So maybe not everything I said holds true on every racing surface on every type of tire but in generaly this is what works on the surface I race on.

Jshwaa
2015.04.29, 06:53 PM
I hear what you are saying. Across the board, there are principles that hold true for optimization purposes, such as low center of gravity, maximizing friction to the ground, etc. however much of what you do in the RC realm (ie. race on carpet with glue) is due to how unlike they are to real race cars, and so over time innovative enthusiasts such as yourself have found ways to stay on their throttle longer during a race regardless of the differences. Not taking credit away or saying that you don't know your stuff, but much of what say about controlling weight transfer exists in racing systems that have a front to back braking control, and with mini-z's we all know that they have integrated that function into to drag of the motor through the back tires alone. I don't know if you've ever driven a car with either the front or back brakes completely gone, but you would never catch a race car on a track without front brakes regardless of how much glue like traction the tires had to the ground. And don't get me wrong, I have my delusions of grandeur myself, such as the ever growing desire to get a real wheelie out of one of these little cars. I think I'll have to posi the rear end....

DMALMAD
2015.04.29, 07:19 PM
well put. some things with these cars make sense while other things do not. I think track time and testing is the only real answer.