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Tapir
2011.09.30, 04:57 PM
Hi.
First of all. What a nice forum!
Have been reading a lot here lately, but I still have a couple of questions about my MR-03.

Rear Roll center.
In front I understand that shimming the upper tower raises the roll center. But how about in the rear? If I raise the suspension mount on the motormount, do I raise the roll center? Also. What will this do to my setup? More/ less steering? More/ less traction rolls? (Tri damper)

Preload on the side dampers. Adjusting tweak.
If I have more steering to the left. What side do I add preload to get equal steering?

CG.
If I need to add weight to the car. Is it best to add it to the centre of the chassis, or to the sides?
Does it do any difference?

Thank you for all answers:)

EMU
2011.10.01, 11:31 AM
Welcome to the forums :)

Hi.
First of all. What a nice forum!
Have been reading a lot here lately, but I still have a couple of questions about my MR-03.

Rear Roll center.
In front I understand that shimming the upper tower raises the roll center. But how about in the rear? If I raise the suspension mount on the motormount, do I raise the roll center? Also. What will this do to my setup? More/ less steering? More/ less traction rolls? (Tri damper)
By raising or lowering the rear axle on the chassis, this changes the relation of the axle to the t-plate, and essentially changes the roll center with everything else held constant. Shimming the damper plate wont really do it, that will only increase the effect of the damper/suspension as the suspension will travel a greater distance with the same angle of movement from the motor pod.

Preload on the side dampers. Adjusting tweak.
If I have more steering to the left. What side do I add preload to get equal steering?
With a Tri-Damper System (TDS) in general if the car has more steering to the left, you reduce preload to the right side and increase preload to the left. That is the general rule of thumb... But it also depends how the TDS is designed. The TDS on my 90mm car is reversed compared to the 94-98mm TDS.
CG.
If I need to add weight to the car. Is it best to add it to the centre of the chassis, or to the sides?
Does it do any difference?

I think that this is relative to the track you are racing. Lower grip, and low CG bodies, you may want to increase CG... but other than that, it is usually best to put the mass as low to the center of the chassis as you can. Installing the mass on the front of the body will reduce the off throttle steering into the corner, but increase on throttle steering coming out. Mass placed in the rear of the body it will steer more coming into the corner but less out.

I try to install mass on the chassis itself. Most of my CG changes are done with the body choice, not with adding mass. With this scale, the body is about 20% of the mass of the car. So manipulating weight that is on the chassis already is more important than adding mass to balance out the car. You will see that many racers shave parts of the body to reduce weight. Especially in front of the front axles (front splitters) and behind the axles (diffusors), and remove the heavy plastic wings to replace them with lexan.

I hope my information was useful.

Tapir
2011.10.01, 01:01 PM
Wow!
Thanks EMU! Big thanks!
you are truly a big help around here:)

Regarding placement of weight I was thinking of adding it to the room in front of the switch.
Would it make a difference if I placed it in the "V" slots below the batteries instead?

Also. If I lower the car front with shims under the knuckle. I will lower the roll center right?
If I i.e. lower the car 0,5mm, I have to raise the roll center with 0,5mm to compensate?

color01
2011.10.02, 07:37 PM
It does make a difference where you put the weight. :) Adding it straight to the chassis center tunnel will make the CG low and the corner transitions fast, which is good for keep the load on the tires light. This is what you want to do on tight, high-grip tracks where agility and avoiding traction roll is key. If you add weight to the channel under the batteries, you will slow down the reflexes of the chassis a little bit, and load the tires more, which is useful on low-grip tracks to generate a little extra traction at the expense of agility. Hope that helps!

Tapir
2011.10.03, 04:30 AM
Thanks again Color01:)
Two of the experts answering me:o
I really appreciate it.

Anyone who can answer the front roll center question also?
If I lower the car with shims under the knuckles, the roll center will be lowered right?
Can I then compensate with shimming the upper bar to get the roll center the same again?

color01
2011.10.03, 07:35 AM
Can I then compensate with shimming the upper bar to get the roll center the same again?
Yes, that is exactly right, shimming the knuckles only will lower the roll center quite a bit. :) On the normal MR03 front suspension, you should shim the upper bar upwards the same amount as you shim the knuckles upward. Making the front roll center too low just makes the MR03 slow in my experience. I usually try to maintain the original Kyosho roll center, but sometimes even higher (using 1deg camber arms to maintain a slight negative camber).