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Author Topic:   tightening three link
Desert Mod
Dirt Full Roller

Total posts: 60
posted February 28, 2005 08:14 AM  
I'm looking to tighten corner exit on a three link with the springs on top of the rear end and long panard bar. The rear trailing arms are currently in the bottom holes of two-hole brackets. What advantage do I get if I move either or both arms to the top holes when the track goes dry slick? If I move one or both, should I readjust trailing arm lenghts?

Thanks.

wfoondirt
Dirt Forum Champ
Total posts: 505
posted February 28, 2005 08:28 AM  
quote:
The rear trailing arms are currently in the bottom holes of two-hole brackets

Are you talking about the mount on the rear end housing or the frame?

quote:
If I move one or both, should I readjust trailing arm lenghts?

Yes

quote:
springs on top of the rear end

Put your lr spring in front.


[This message has been edited by wfoondirt (edited February 28, 2005).]

Desert Mod
Dirt Full Roller

Total posts: 60
posted February 28, 2005 08:51 AM  
Sorry. I'm talking about the frame brackets. I'm trying to do this without moving springs. What advantage do I get when I raise the arms? I'm thinking it adds lead on acceleration. Also, any difference between lowering the arms on the rear end and raising them on the frame?

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted February 28, 2005 09:32 AM  
More up angle in the LR bar and flatten out the RR bar. Readjust lengths to keep rearend in the same place. Add new brackkets if you need to the chassis to get better angles. When looking from the back of the car angle the LR bar in at the front.

wfoondirt
Dirt Forum Champ
Total posts: 505
posted February 28, 2005 10:44 AM  
ditto what dirtbuster said

quote:
I'm thinking it adds lead on acceleration

Depends on your definition of lead. Raising the bars on the frame adds loose roll steer. The advatage of raising the left bar/lowering the right bar is that it creates a split in the amount of antisquat side to side which adds wedge on the gas.

quote:
Also, any difference between lowering the arms on the rear end and raising them on the frame?

Yes

Lowering the bar on the housing will reduce the amount of loose roll steer because the rear end will roll backwards more on the gas similar to a leaf car with lowering blocks. You also gain a slight bit of thrust antisquat.


Desert Mod
Dirt Full Roller

Total posts: 60
posted February 28, 2005 11:04 AM  
By lead, I'm thinking of leading the RR, as in making the right side wheelbase shorter than the left side. I guess I'm having trouble visualizing what the rear end does under excelleration when the bars are different from side to side. Maybe it's time to mock up a model to play with.

wfoondirt
Dirt Forum Champ
Total posts: 505
posted February 28, 2005 01:04 PM  
quote:
Maybe it's time to mock up a model to play with.

Good idea because it does exactly the opposite of what your picturing.

dluna
Dirt Freak

Total posts: 334
posted March 02, 2005 12:34 PM  
dirtbuster,

Can you explain why you toe-in the LR trailing arm up to the frame? If the rear end is trying to move left in the turn, doesn't this introduce some type of bind? The heims are only going to move so far. Just trying to picture what happens.

Thanks.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted March 02, 2005 12:52 PM  
Dont put so much toe in that it binds up either at ride height or at any time during rearend travel. I dont mean to go to an extreme, just put some angle in it.

The idea is that it moves the projected pickup point of the LR trailing arm furthur under the center of the car. It makes the LR bar act like its trying to pick up more of the cars weight instead of just the left side.

Now it will also induce a little loose roll steer because as the rearend moves left during roll it will pull the LR furthur forward or push RR back if it is toed in. Not much but it does.

drt mod rcr
Dirt Roller

Total posts: 10
posted March 03, 2005 09:28 PM  
something that might help. have the car sitting at ride height. take your floor jack and place it in front of the lr on the frame. have some body jack it up while you watch the rear end. it is better with the right side panels off. this would kind of simulate the car under accleration off the corner. you should be able to see the rear end move. change angles on the lr bar and you can see what that does to your rear end movement.

Desert Mod
Dirt Full Roller

Total posts: 60
posted March 26, 2005 08:24 PM  
Haven't run the car yet, but made the changes of adding a swing arm on the LR, longer bracket on frame and a lower hole on the housing. RR is still straight arm with a little angle at ride height.

I measured the wheel base as I raised the rear end evenly and the right side shortened a bunch (1/2 inch) and the left side stayed the same. When I raised the LR bar a hole and repeated the test, it did the same thing. So, what am I missing that increases the right side wheel base? Is there where the body roll comes in?

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