lil-bump

iTrader: (89)

Well I double checked and I'm correct. I referenced the Hudy setup book.
I think you are confused with rolling and rotating. As you raise your roll center(ie make it closer to the COG) you will loose traction at that end of the car but when you loose traction at rear of your car it rotates better giving you the feeling of more traction. When you have too much rear traction it gives you a feeling that the car is understeering or pushing. It's not really pushing its just that the rear end is so planted that the rear of the car will not rotate.
If you get a second look at the Hudy set-up (Xray) and look at the roll center section it lays it out in plain english.
Hope this helps Race you later

quietstorm76

iTrader: (12)

I already referenced the Hudy book. I agree that as you raise the RC you lose traction at that end of the car. Therefor the car rotates more with the lack of traction. I fully understand roll center and the relation to CG, we disagree on which adjustment does what.

So you are saying that if you have your rear lower pins in the down position, your car has more rear traction than in the up position?

On a high bite track where do you run your lower pins?

lil-bump

iTrader: (89)

Okay so we agree on how moving the roll center changes how a car handles. If you also reference the chart under ADJUSTING ROLL CENTER (Rear) pivot ball suspension

It says to lower the rear roll center you

1. Raise the position of the inner upper camber link. (mugen part to-161)???
2. Lower the position of the outer upper camber link (remove spacers)
3. LOWER THE POSITION OF THE INNER PIVOT POINT OF THE LOWER ARM(THIS IS THE ADJUSTMENT WE ARE TALKING ABOUT)(I'm not sceaming just signifing this the point where we disagee)

If I'm on a high bite track. I run my pins in the highest position which raises the roll center, which gives lower traction, which prevents traction roll. I'm not worried about being too loose because I'm in high bite situation. My goal is to remove traction.

That's my understanding hope this helps

quietstorm76

iTrader: (12)

We have different experiences with the car. I run on a low bite track, and if I run the box setup it sucks. The rear steps out in every corner(massive over steer). I raise the pins to the middle and it plants the rear and gives good corner speed. If I go to WinterNats or Kissimmee and the traction is up, I lower the pins to loosen up the rear of the car and take away the understeer.

In my opinion and based on my experience, traction roll comes from the front having much more traction than the rear. Your traction roll stopped because you "lowered" the rear RC and increased rear traction. Ever notice that on the Mugen web page that all the setups for high bite tracks always run the pins in the lower position?

If I'm wrong it won't be the first time but these are my opinions based on my experiences with the car.

lil-bump

iTrader: (89)

To be honest I've never had to move my pins. The only track I run that has really high traction Is Toledo,Ohio home of the Great Lakes challenge. (guys would traction roll with 45 shore tires some guys ran 50's)The example I gave you was If I ever had to do such a thing but I can run with 42's all day. I base my point on written documentation not on car characteritics.
But If I did have that situation I would not adjust my lower pins I would work the upper camber link since it is a much easier adjustment. You are correct that most High bite set-ups have the pins in the lower position. But my take on this is that there are numerous other adjustment that can be made that can raise or lower the rear roll center. And most guys use those adjustments first rather going thru the trouble moving the lower pins( I believe the lower position is stock). Also adjusting the lower arms have a much bigger effect on roll center than the upper. I always use the smaller adjustment first. Been a pleasure talking with you maybe we can continue tommorrow anybody else want to add anything.

trebronpay

iTrader: (1)

I agree on both of you for the most part. Hudy and Serpent manual gave me a better understanding of roll center. Based on my experience, when I placed the lower arm of the rear closest to the chassis my car rotates more somewhat loose I can make it feel better by raising my shock to the fourth hole from the bottom. I know it is suppose to give me more traction when I put the lower arm closest to the chassis (Low Roll Center). I think because it is leaning to much thus, when I raised the shocks giving it a stiffer feel the car felt better. Raising the camber link to the very top of T0161 gives me more traction. It gives me more traction as well when I reduce the shim from the rear upright. Thus, I traction roll when the bite picks up. I hardly traction roll when I had 2mm shim on the rear upright and the camber link is on the middle of T0161. (Going Higher roll center).

asw7576

I'm talking about rear section only :

Ideally a very high traction surface needs higher RC ( increase the height of lower suspension hinge pins, increase the height of inside upper link, or decrease the height of the outer upper link ). Why ? the grip is already there, and you want the car not to body roll so much.

For poor traction surface, you want to lower RC ( ( decrease the height of lower suspension hinge pins, decrease the height of inside upper link, or increase the height of the outer upper link ). Why ? the grip is not there, and you want the car to have more body roll.

Shorter vs longer upper link determine the camber rise and reaction. Preferaby keep it short upper link.

On top of that, there are other factors to make your car drivable as you plan. Camber, Tires selection, Toe in / out, Differential Oil thickness, Springs, Oil Damper thickness, Ackerman, are among the other factors to determine racing drivability.

quietstorm76

iTrader: (12)

See at my home track we can't run 42's or we'd be drifting. You are so lucky. Hopefully someone got something out of this debate. It was fun.

lil-bump

iTrader: (89)

Yea that was a good conversation. I've never had to move my lower pins. but I guess it's all depends on how you like your car to feel. I personally like a car that has very little steering. I aboslutely hate a car that oversteers If my car over steers and is twitchy. I would not attempt to try to settle the rear; I would fix the oversteer first and then attack the loose rear end. But in most cases if you correct oversteer the rear will fix itself.
Toledo is a special track. In the middle of the summer during a long hot race the traction really goes thru the roof.
And the other thing is this track has close to no tire wear. If I drive smooth, I can use one pair of 42's and run 3 qualifiers and my tires will still be around 59-60mm. It's really a great track.


Race you later...

quietstorm76

iTrader: (12)

See I like lots of rotation in my car. Not twitchy but I don't have to turn the wheel very much to get the car around the corners. Recently I ran a 15 min main(it was getting dark). I started with 61s and ended with 55s. Yeah I know it sucks.

Roger

iTrader: (10)

6.0mm is alot of tire wear for a 15 minute main. The track surface your racing is very abrasive. What shores are your using ? 37's ?

quietstorm76

iTrader: (12)

40's..............that's about the worst I've seen at my home track. Usually it's about 6mm for a 20 min. main. Our track has never been sealed and we only spray grape soda and sugar water.

T-ROY22

iTrader: (2)

I got alot out of this "Debate"! Thanks guys!

Francis M.

iTrader: (2)

I try not to mess with the rear lower hinge pins and I hardly go to the highest settings since the car feels like it wants to jack up when the bite gets on the higher side.... When the bite comes up I usually try to dial out some steering through tires mostly of the settle the rear even more so I don't have to worry about traction rolling on turns or sometimes just having that inconsistent feal especially rear traction.....

CraigM

iTrader: (34)

I don't understand how any of this helps you not strip gears. Putting half a thrust bearing inside the clutch will make a huge gap and wont work on some engines e.g. my OS speed's crank isn't long enough to put shims inside the clutch

The kawahara carbon fibre mid brace is the best protection, combine it with the kawahara 1 piece engine mount and a 4mm chassis and you'll be laughing