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Author Topic:   converting four bar to swing arm on dw8
dirtracr
Member
posted August 25, 2003 06:46 PM
I agree with Dustejr73. I too have a DW8 4 bar car, and this winter I'm planning on adding a rear z-link/swing arm mount on the RR. This should help deal with rougher tracks which tend to upset the chassis. Leaving the LR on the 4 link will promote roll steer and drive with the swing arm on the RR making the suspension more forgiving. You should try and determine what length of rear bar to run, especially if you will be keeping the DW8 12.5" lower link.


dirtracr
Member
posted August 26, 2003 12:58 PM
can you guys give more details on how to set this up??? also would like to try


dirtmod#2
Member
posted September 08, 2003 10:48 PM
can you guys give more details on how to set this up??? also would like to try


Chad
Member
posted September 09, 2003 10:26 AM
dirtracr- I was trying to explain a couple of options that you have. If you leave the spring attached to the birdcage and run the upper link to the rear, it's a Z-link, but if the track is very rough, you can mount the spring on the forward lower bar (but you need to increase the spring rate). What I'm trying to figure out is how long to make the rear bar. Some chassis' have a long bar with others running a short bar like a Rayburn latemodel. I know the shorter bar will induce more roll steer, but not sure what to use since the LR will be responsible for the rollsteer since it's a short 4 link.


dirtracr
Member
posted September 10, 2003 01:19 PM
In my opinion you would want the right side z-link to be at a zero roll steer, so however long the bottom bar is the top (backward) bar would need to be the same. On my DW8 it made the car feel looser. Better on the rough tracks,it would be the same as putting it on a wishbone on the RR, right? Any way that you can free the car up getting in and through the middle, then letting the LR take control off.

my 2 cents

STICK


Chad
Member
posted September 11, 2003 10:04 AM
Thanks for the input Stick01. That's what I thought, but I didn't know if running a 12.5" rear bar on the RR Z-link was the best thing to do. Seemed too short. That is the length of the bottom bar.


STICK01
Member
posted September 11, 2003 11:11 AM
I ran mine on a 4-bar / z-link most of the year or until the tracks got slick and black and then changed back to 4-bar on both sides... The z-link on the RR was fine but it never went as well as everyone elses seemed to. So, I gave up a little to not tear up my stuff and now we are really quick on the black slick tracks with the "long" 4-bar on the left and the "short" on the right.



Chad
Member
posted September 12, 2003 10:13 AM
When you say "long" 4 Bar on the left, what is the measurement of your links (Left and Right side)? What chassis are you running? I run a DW8 all 4 Bar with the links at 12.5" lower and 14.5" upper. Also, you said you felt the Z-link on the RR "never went as well as others" and you "gave up a little" with that configuration. Can you add some detail.

Thanks.


Dman
Member
posted September 12, 2003 12:50 PM
The RR links on a 4-bar car decrease angle as the car rolls. The RR gets stiffer due to spring indexing which compresses the RR spring from both sides at a faster rate. Assuming the springs are in front and on the birdcages, 4-bar both sides, the left rear will decompress from both sides. This will tighten the cars entry. When you flipped the top link to the rear, you probably ran less angle decreasing spring indexing on the RR and loosening the car on entry. Should have loosened you slightly on exit also because you had more net angle in the RR with throttle. If you want to soften the RR move the RR spring to a swingarm, increase rate, and do away with the RR spring indexing. You may have to lower your roll center to tighten entry. To figure out what spring to use go to the menu top left of page, the calculation is in the tool bax.


STICK01
Member
posted September 16, 2003 08:16 AM
MD,

Can you explain that a little bit better...That is the exact reason that I gave it up once the tracks weren't rough...But felt as if it did give up some on exit. In my car it always felt better on the RR with the top bar at a negative angle to the birdcage which I presumed decompressed the RR spring rate under body roll...was I on the right track, or on the wrong one....Where might I have went wrong???


MD
Member
posted September 17, 2003 01:40 AM
If you leave the spring on the birdcage (RR), the birdcage indexes in the same direction 4-link or z-link. More angle, more indexing. If you flip the top link and run the same angle down to the rear as you had up to the front your indexing would be about the same. However, with a 4-link on the RR the upward angle to the front decreases or even goes negetive(bottom) with roll. With a z-link your front arm is the same but the rear arm is increasing in negetive angle down to the rear and acting as a pull bar loading RR more with throttle comparatively. Don't forget about rollsteer, the only time it doesn't exist is with a Z-link with equal length arm at equal angles. If you're having trouble on a rough track get the RR spring off the birdcage.
I hope that made it more clear, or did things just get fuzzier...


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