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Tamiya mini cooper

Old 11-11-2015, 09:26 AM
  #26056  
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Originally Posted by KA2AEV
I'm guessing this is a carpet surface?
Do you sauce your tires, since you already did the ca on your front treads...
If you do, to what extent?
Yes, carpet as stated.

In this case, I sauced the rears about 3/4 - full width. The fronts, the first two inner treads.
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Old 11-11-2015, 06:30 PM
  #26057  
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Originally Posted by CSeils
Yes, carpet as stated.

In this case, I sauced the rears about 3/4 - full width. The fronts, the first two inner treads.
I'm guessing that you know about cleaning the tires too, so try full sauce
on the rear and if possible try hardening up that rear stablizer you got on there.
You could try removing it all together. Just make one move at a time incase
whatever you do makes the handling worse. You could go back one step
and try something else.
In addition. Try picking the brains of one of the top mini drivers at your track
Have him try driving your far to see maybe its something in the way your handling
Or maybe in your setup on your controller.
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Old 11-11-2015, 07:17 PM
  #26058  
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Originally Posted by CSeils
I am at full throttle on the straight which leads to a medium right hand high speed turn which leads into the sweeper. The rear end loses traction half way through the turn. I am usually able to correct it before going all of the way around.
Your picture doesn't agree with your description of the track.

That is not a sweeper (that track doesn't have one it seems), but a hair pin.

What you experience is liftoff oversteer (if you drive a FWD car you can experiment with this on a suitable road). This is a classic shortcoming of FWD cars and it is usually addressed with a lower ride height, placing more weight at the back, or anything that will help keep some load on the rear under deceleration. All of this will affect the balance of front vs rear grip. Another way to control this tendency is to accelerate mildly thus preventing rear end unloading. this requires a change in driving technique. You need to slow down on the short straight leading into the hair pin and start accelerating before you enter the hair pin. Again, this acceleration needs to be pharmaceutically adjusted to keep the car loaded just right. Keep in mind, you're not trying to gain speed, but to keep the car together around the hairpin.
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Old 11-11-2015, 10:57 PM
  #26059  
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Cseils already said that it spins on-power so it isn't a lift-off oversteer issue.

Mid-corner on-power spinning is often because of something mechanical happening at full roll. Something like the body catching on the ground or the front drivetrain binding up is a possibility. Very tight diffs can cause this too. If there is a large amount of droop as he mentions, it may also be worth trying to limit it, sometimes you can end up with too little load on the inside tyres and it gives up grip late in the corner. I would generally try stiffening a car up that is unstable at speed.
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Old 11-12-2015, 02:44 AM
  #26060  
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Originally Posted by niznai
What you experience is liftoff oversteer (if you drive a FWD car you can experiment with this on a suitable road).
It also applies to RWD and 4WD cars; anything that has a CG above ground.
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Old 11-12-2015, 05:47 AM
  #26061  
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Originally Posted by sosidge
Cseils already said that it spins on-power so it isn't a lift-off oversteer issue.

He did? All this time I thought his rear was loose off throttle.
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Old 11-12-2015, 06:20 AM
  #26062  
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As its a hairpin turn that's the issue, I am wondering if its the transition from braking, turning in then acceleration where the back end steps out. It could actually be a lack of front grip on entry and mid corner. I am wondering if Cseils is understeering to mid corner with a high amount of steering angle, and once he gets on the gas in the middle of the corner (with the steering still turned hard), the front end pulls hard and breaks traction in the rear?

Cseils, try to see if, just before you nail the throttle, if you start to reduce your steering, if the car stops this. That's the easy way to see if you actually don't have enough steering mid corner. If this is the case, then Id advise working on the front grip earlier in the corner, and reduce your end points on your steering. The fast guys always have enough grip through good setup, and minimal steering input.
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Old 11-12-2015, 06:38 AM
  #26063  
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Let me try to explain this again.

I am already at full throttle on the straight. I need to make a full speed right turn before the hairpin 180. The rear end will step out as I am making the full throttle right turn before the hairpin 180.

I can ease off the throttle at the end of the straight away before I turn to reduce the step out, but I lose a lot of speed before I get to the corner. I feel that I should be able to stay on throttle until I get to the hairpin. This is the only place it will do this.

You guys have given me some good ideas to try. I'm going to try the testing the droop setting first. From there I'll check the diff, sway bar and stiffening the rear up a bit.
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Old 11-12-2015, 08:08 AM
  #26064  
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I think you will also find that playing with the corner balance (raising the front and lowering the rear vs your current setting) and stiffer springs on the front might help too. I already posted this back a page or so ago if you haven't seen it.

Basically you have too much weight transfer to the front when you let off the throttle. Maybe play with your rear toe-in too.. give it another degree. GL!


Hey, Tamiya finally got a couple of parts I needed back like 6 months ago...
And any further comments on my servo question? Latency from D/A conversion vs actual motor speed.. Futaba's description of their S9551 is pretty skeptical about the processor speed being like half of something. Half of what, we will never know.
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Old 11-12-2015, 08:14 AM
  #26065  
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Originally Posted by sakadachi
Basically you have too much weight transfer to the front when you let off the throttle. Maybe play with your rear toe-in too.. give it another degree. GL!
he just said he is at full throttle.

Sounds like you have great front grip then. Sweepers like that are a F/R grip balance, and you have more front grip at that corner. How is the car in the rest of the track? I would be very cautious changing the car to loose front grip (to get the balance right), if the car is turning hard and fast in the slower infield area. If you go harder on the front springs etc, you may loose turning grip in the slower parts, and you will be slower.

I would try 2 deg rear camber first (3 deg is a little excessive, you may not be rolling onto the tread enough), then harder springs (and more preload) in the rear too. Maybe Tamiya white would work.
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Old 11-12-2015, 08:28 AM
  #26066  
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Originally Posted by axle182
he just said he is at full throttle.

Sounds like you have great front grip then. Sweepers like that are a F/R grip balance, and you have more front grip at that corner. How is the car in the rest of the track? I would be very cautious changing the car to loose front grip (to get the balance right), if the car is turning hard and fast in the slower infield area. If you go harder on the front springs etc, you may loose turning grip in the slower parts, and you will be slower.

I would try 2 deg rear camber first (3 deg is a little excessive, you may not be rolling onto the tread enough), then harder springs (and more preload) in the rear too. Maybe Tamiya white would work.
Okay, you're right. And I too think the front is gripping so much that the rear is just swinging around.

Maybe the diff is too stiff for the droop you have on the front and the inside front tire is lifting off the ground? Basically too much weight transfer to the outside front wheel. Adding camber to the rear sounds good, and give it a degree of toe in on the rear.
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Old 11-12-2015, 08:32 AM
  #26067  
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Originally Posted by axle182
Sounds like you have great front grip then. Sweepers like that are a F/R grip balance, and you have more front grip at that corner. How is the car in the rest of the track?
I can cut the rest of the track pretty tight. I don't usually have an issue in the infield.

I will try the change in droop first, then try Camber, then spring to see if I can settle it down to where I like it.
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Old 11-12-2015, 08:41 AM
  #26068  
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Originally Posted by CSeils
I can cut the rest of the track pretty tight. I don't usually have an issue in the infield.

I will try the change in droop first, then try Camber, then spring to see if I can settle it down to where I like it.
that's what I would do. Loosing any grip level on the front will mean you cant cut the rest as well. Id work solely on the rear, to settle it down in that one spot. Ill bet money the camber will help most. Droop shouldn't be affected, as you are still at full throttle, so no f/r weight change, only a left to right weight change. That's why I think Camber should be your first change. Adjust it by .5 deg each time till its great through that corner.
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Old 11-12-2015, 08:57 AM
  #26069  
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Originally Posted by sakadachi
Okay, you're right. And I too think the front is gripping so much that the rear is just swinging around.

Maybe the diff is too stiff for the droop you have on the front and the inside front tire is lifting off the ground? Basically too much weight transfer to the outside front wheel. Adding camber to the rear sounds good, and give it a degree of toe in on the rear.
Its the opposite. The situation has nothing to do with diff, its a f/r grip balance, at high speed. The front is not the issue, the rear is. I noticed on the initial setup, Cseils mentions he is running -3 deg rear camber, I feel this is way too much. Id be more around the 1.5-2 deg mark. I would bet that the tire is still running on the inside of the tread when its in the middle of the corner, and with it being a FWD car, with very little weight in the rear, the car doesn't have the rear weight to push into the outside tire, and push the tread over, to hit the full width of the tread onto the racing surface. Basically its skating over the surface with the inside of the tread, instead of rolling onto the full width of the tread.

This is why we start with neg camber. If you run your tires with 0 deg camber, the tire will roll off the tread onto the outside while corning fast. We start the tire with neg camber, to allow the full width of the tire to contact the surface (giving max grip) when the car has fully transfer weight to the outside, and the spring had compressed and the car is generating max grip in the middle of a corner.

When I say "the tire will roll" Ill explain what is happening here. Your car enters the corner, the outside tires are providing grip to enable you to change the direction (turn). What happens in a high speed sweeper, is the car requires the most grip in order to change direction (turn). As the car starts to turn, the tire grips, and now while the weight of the car wants to travel straight, the tires act against this travel, and the resulting force on the tire tread is what makes the tire roll. Now you can see from this explanation, that more weight is actually a good thing here to provide more tire roll. The more weight, the easier it is to roll the tire onto the tread. So a heaver car, you will use more camber, so u don't roll the tire too much, and off the tread. But this situation on the rear of a FWD mini, you don't have enough weight to make the tire roll onto the tread, when you start with -3 deg camber. Itll take a lot of force to make it roll that much, and the mini simply doesn't have enough weight to transfer into inertia, to make the tire roll from -3 deg to make the tread flat on the racing surface.

I've kept the explanation there purely to the static camber, the weight and the roll of the tire and tread. You can really really confuse the situation when you include things like side wall stiffness, camber gain, raising/lowering COG etc etc. Something I definitely wont do on here Hope that helps and kinda made sense lol
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Old 11-12-2015, 08:58 AM
  #26070  
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More info on why I feel its the camber, is also the choice of tire. The side walls on a S grip are quite stiff, meaning that the side walls are also not allowing the tire to flex down onto the full width of the tread, so the camber you start with is even more important. The type A tires are much softer and can be less finiky about the amount of camber, as the side wall will allow the tire to lie flat while cornering. But the same issue comes up, when the cornering forces become too much, it will easily ride off the tire tread. this is why on carpet, the S grip is a more preferred and way more consistent tire than the type A. It goes against what most of us racers would think. The type a is softer, and a slick! why doesn't it perform as well?! because the side walls are too soft.
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