How to cure grip roll?

[ghost2212]

Hi

I'm having some trouble with grip roll on my Scythe touring car on carpet. I have anti roll bars fitted though not sure if they are set up right.

Any help would be appreciated or just links to some guides.

Thanks

Brett

[sosidge]

Wish I could help but ever since the drop to 1350gm I've been struggling with grip roll myself! Still haven't found a solution, Scythe or Photon.

More testing needed...

[DCM]

what tyres?

[ghost2212]

I'm running Carpet dragons with nosram additive with a 13.5 motor. The track is relatively small and is at bracknell if any of you know.

How the anti roll bars work?

Thanks

Brett

[DCM]

you tried it without additive, as the dragons are pretty soft as it is?

[Big G]

nti-roll bars are like 'sideways springs', they only work laterally. Here's how they work: if one side of the suspension is compressed, one end of the bar is lifted. The other end will also go up, pulling the other side of the suspension up also, basically giving more resistance to chassis roll. How far and how strongly the other side will be pulled up depends on the stiffness and the thickness of the bar used: a thin bar will flex a lot, so it won't pull the other side up very far, letting the chassis roll deeply into its suspension travel. Note that the bar only works when one side of the suspension is extended further than the other, like when the car is cornering. When both sides are equally far compressed, like when the car is braking, the bar has no effect. So anti-roll bars only affect the lateral balance of the car, not the longitudinal balance.
Unfortunately, anti-roll bars aren't the only things affecting the car's roll stiffness; they work in conjunction with the springs and dampers. Suppose you add an anti-roll bar at the rear of your car without changing any of the other settings. When the car enters a turn, the chassis starts to roll. Normally, the suspension on the outside of the turn would compress, and the one on the inside would extend, making for a lot more pressure on the outside tire. With the anti-roll bar however, the suspension on the inside will be compressed, so the chassis will roll less, and the rear of the car will sit lower than normal. So the rear has more weight on it, and it's distributed more evenly over the two tires. This makes for a little more, and more consistent traction. Remember that this is in the beginning of the turn, the situation is different in the middle of the turn. Normally, without the anti-roll bar, the chassis would stop rolling when the roll torque is fully absorbed by the outsid e spring. But with the anti-roll bar, some of that torque is absorbed by the anti-roll bar, and used to compress the inside suspension. So the outside suspension won't be compressed as much as it normally would, making the rear of the chassis sit up higher than normal, so less weight is on the rear of the car, and more at on the front. It's as if suddenly the rear has become stiffer, making for more steering and a little less rear traction. Rear traction is more consistent however, because the weight is distributed more evenly over the rear tires, unless the track is really bumpy, that is; anti-roll bars can really mess up a car's rough track handling, so they're rarely used on bumpy tracks. Adding an anti-roll bar at the front of the car has a similar, but opposite effect: it decreases steering, but makes it much smoother and more consistent. It can stop the front from 'biting into' the surface too much, making the turning radius big and smooth. This can come in handy on large, wide tracks.
Math-wise, the torsion stiffness of the middle part of the bar goes up with the fourth power of the bar's diameter, and for the two side parts, torsion stiffness goes up with the square of the diameter. Keep this in mind while changing anti-roll bars.


taken from http://users.telenet.be/elvo/

[Mad-Wolfie]

Also make sure your ride height is set right.. about 5.5mm at the rear & 5mm at the front. if the car is too low it will roll as the chassis digs in to the floor & if's too high it will wallow about & topple over as you go into corners - as a rough guide if you haven't got a gauge, slide a wooden placemat or drinks coaster under your car's chassis, if it goes under it's probably OK, but if it won't the car is too low, if when you have slid the mat under the car you can pick up the mat & see daylight under it without the chassis actually lifting it's probably too high.

A trick i was told by some of the guys who run foams (but the trick is also useful but not as common to do with rubber) is to run a coating of superglue around the tyre walls this will stiffen up the tyres & essentially make them lower profile & stop any sideways motion in the wall of the tyre.

[ghost2212]

Thanks for all the help guys. I'll try and run sorex 28's next week and see how they do.

Thanks for the tip on the tyres mad wolfie. i did notice that the dragons have a lot of movement in the tire wall which the sorex's do not. I will post back here next week and tell you if i managed to cure it.

Thanks

Brett

[chris_dono]

Originally Posted by sosidge

Wish I could help but ever since the drop to 1350gm I've been struggling with grip roll myself! Still haven't found a solution, Scythe or Photon.

More testing needed...

Are you still running the same damping as you used to ?

[ghost2212]

Just had a thought that ive never balanced my car but i do not know how to. I currently run around the 1380g mark with a 2s 5000mah 20c lipo. Could someone please give me a link to a guide on balancing the car as i think it was only grip rolling when i turned right.

Thanks

Brett

[chris_dono]

easiest way is to put a piece of string through the middle of the shock towers and lift the car up, if one side is heavier then it'll fall on that side. It depends on which car you have though, as some have small holes on the bottom of the chassis

you can also use corner weight scales (just small scales really) on each wheel to see how much weight is on each wheel

[Donutt]

Here's an easy tip which you might not be aware of.

When you are trying to balance the car left-right, remember you can mount the battery further away from the centre line.

On the Scythe I think the battery is held in with tape - rather than putting the battery directly over the slots, move it away from the belts and closer to the side of the bodyshell - how much depends on the rest of the kit and the car.

Once you've decided on the best new location, get a couple of L brackets (Xray do some) and fix them to the chassis so you can place the battery in the right place every time. You only have to move the L brackets if you change any of the rest of the car.

Plus you can move the battery forward or backwards as well, but I've never found a need to do that.

I can't remember the ideal Front/Rear bias split for TC - maybe someone else can post that? I seem to remember that F/R (4WD) should be about 45%/55%?