When do you start playing with roll center
 

Hi guys when exactly do you start playing with roll center.

I am playing around my R4 and can't get enough front traction (off power steering) but i still didn't get to play with roll centers. I went to lighter front shock oil, harder springs in the rear, less rear toe in, less front caster but the rear is way to stuck to the ground.

Is it time to start altering roll centers?

Thanks

Try softer front springs...also what shore tires are you running with respect to the rears.....and can't forget about what front diff fluid you are running......it may be too stiff.....i use rc as a last resort....

What car ??

What springs

Sounds like it's time now. You can always go back.

You want more steering? Go narrower track in the front to start.

Where is your roll centers now ??

I see you mentioned that your rear-end is super planted. Do you ever traction roll? If so; I would raise the roll center of the rear. But I would do like some of the OP's said try changing. Too much rear traction takes away steering. Try harder tires in the rear. Find the point where your rear-end becomes too loose and then work from there.


Pass you soon...

You can also try giving the front about 1 degree of toe OUT. This helps turn in. You may also raise your rear ride height so that it is .5 - 1mm higher than the front. This puts more weight on the front tires and gives them more grip. I don't know what tires or inserts you're running but you can try running a bit softer insert in front. What are you running for a front diff? I have never tried a spool as with 17.5 classes that I race you don't need any brake so I run a front one-way. This will give you a TON of steering... Now I mentioned electric but I also ran a front one-way successfully in my Super Nitro RS4. I used brakes with it but you need to STAB at them. If you're radio doesn't have ABS capabilities, you'll need to pump the brakes manually with two or three very quick, very sharp pulses. Otherwise the car will spin under braking.

I would try to work on giving the front MORE traction rather than decreasing the rear's as this will allow you to maintain more corner speed.

Everything else mentioned here are possible fixes too. Just wanted to add the things I could think about which hadn't already been covered.

So if i run a lighter front diff it will give me better off power steering ?

Yes i am running softer front 37's and 40's in the rear.

Front is also narrower.

Springs i have the medium blue Kysoho springs up front and the have dark blue Kyosho springs in the rear.

Roll center is stock!

I thought of trying fronts 35

I really don't like running two steps in the shores because it always happens to me that the car becomes erratic after the tires warm up.

Obviously one-ways on Sedan are a thing of the past. And ABS just eats your throttle servo. Thinner oil will definitely help you with steering.

Try adding more shims to the rear upright. I have found this "loosens" up the rear.

I'd suggest posting pics of the track and your complete setup if you want the full help of everyone here. Just makes it easier. :nod:

If the back of your car is too stuck, just run the rear lower arm hinge pins on a higher position, this will make the car rotate more. To fine tune this setting add or remove shims from under the outside of the rear upper arm(the end that mounts to the knuckle). If you add shims it makes takes even more grip away(adds stering) and if you remove shims it makes it more stuck(less sterring).

You said you have no steering but not where...
I cant understand if you need more steering in the corner entry or in the middle of that.

because if you need steering in corner entry you can get harder front springs, or less caster angle, less rear toe-in, a stiffer rear antiroll bar... or decrease the rear downstop value

instead if you want it in the middle of a corner.. you need softer springs ...or maybe you have too less caster angle ..so the the car steers well in the first part of the corner but understeers in the second part.

Roll-centers affect a lot the setup when the car is on-power but not so much when you are off.
To have a more reactive car you can make the rear rollcenter higher but you will also loose traction in corner exit..and this you will feel expecially in the hairpins.
and in the front end you could make the rollcenter higher ( remember you have to slow down the pins..opposite to the rear setting). But this will take out steering on-power, expecially in the long fast corners.

Roll centers affect the car at all times, on power or off power. Be carefull when you say higher or lower roll center because people get confuse as to which way they have to go, lowering the hingepin does not equal lowering the RC, its the opposite.

Download the Xray set up book, it has all that information clearly explained.

Transfering loads... side to side - front to rear.
 

My understanding is that the geometry of your car (arms and suspension) form a triangular pair of vectors pointing upwards. The longer the triangle points upwards, the higher the roll center. I would have thought it to be a mid corner issue and I see it as a weight transfer from side to side.

What your car is indicating is there is not enough weight transfer from rear to front into a corner. This may be the rear up travel / droop that isnt transferring weight to the front wheels when u back off the power.

The others are correct in all their points too. I would also add the steering angle and rate, you may be "slipping" your front wheels into under-steer with too much angle/or/rate dialed on the chassis or TX.