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Author Topic:   swing arms that are short
Dirt Maniac

Total posts: 199
posted March 29, 2005 07:37 AM  
our dw8 was built as a four bar...i'm going to try the z link on the right with swing get the same length on the swing arm as i did the lower bar, i had to cut it, measures 12 3/4 center to center...i'm not as educated on the swing arms and a buddy said that was pretty short and suggested a softer rr spring, i was going to start the new season with a 250 on the arm..any thoughts on the spring rate with that short of an arm and am i fishin with the wrong pole..

Dirt Forum Racer

Total posts: 80
posted March 29, 2005 07:47 AM  
The effective spring rate on a swing arm is calculated by the following equation:
Wheel rate=spring rate*(spring to chassis length/overall arm length)^2

You might need a 400# spring to give you a 200 or 225 spring on the left rear, not uncommon.

Dirt Maniac

Total posts: 180
posted March 29, 2005 11:25 PM  
We used to run swingarm right side, and it was 13" center to center. We ran a 250 on the arm, it worked fine. Depending on where your mounting point for the slider is, it should get you to a 175/180# spring rate at the RR. Check the toobox for the formula, but a 400# spring sounds way too high...

Dirt Full Roller

Total posts: 69
posted March 31, 2005 08:53 PM  
you might try what David Murray uses (guy that won supernationals). he is running a 4bar/z-link, he has a 275 on LR and 225 on RR on tacky and changes to a 200RR when gets slick. thought this info might help.

Dirt Full Roller

Total posts: 53
posted April 01, 2005 07:29 AM  
What is the advantage of going from a straight z-link, with slider in front on birdcage, to a swing arm? What are the disadvantages?

Dirt Freak

Total posts: 338
posted April 01, 2005 07:37 AM  
we spent last season with our new dw8 trying to sort it out,
we run a 4 z setup and when we ran on the swingarm this was what we ran.

we ran a 225 on the rear of the bc 4 bar left and a 250 on the right on the swingarm, we ran a 20" swingarm and the spring may need to be stiffer for you on a shorter arm.

this year we are running with the rr spring on top at 200lbs and seeing if thats better.
we are also running a coilover clamped in the front on the left to see if that helps too. it was tight from the middle out last season.

[This message has been edited by rpm20 (edited April 01, 2005).]

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