lower link to rearend housing mounting postion thoughts!!

[scottm]

Scott what was the reason to cause your truck to have over 110% anti squat?

It had an unfinished 4-link when I bought it, with the lower link mount forward on the axle housing. I was not thinking about anti squat when I built a new axle and trailing arms with an under mount. I did not redo the frame mount on the lower link, so I had the exact situation shown by the dotted line in my sketch. The upward force vector actually lifted the back of the truck. This reduces traction by shifting weight forward, it fights the suspension stroke, and it makes the truck endo over jumps. Class 8 trucks are known for kicking over jumps, and I think excess anti squat is the real reason why.

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[atomicjoe23]

48" might be a little long (from what I have read). . . I have no idea what ratio upper:lower desert guys are running, but everything I have ever seen in writing regarding the design of a 4-link says to start somewhere around 75% (39" in your case) and work from there to get the geometry you want/need.

48" might be just fine. . .I don't know, you will have to see what all your numbers work out to be with your particular chassis.

[kdm73091]

Is there a calculation you can do? Its the giant motorsports link mounts so its almost the same pivot points

[kdm73091]

I did ended up doing them straight down. Came out nicely.

[kdm73091]

[Zambo]

I think I'd want more triangulation on those uppers.

[BRINGTHERUCKUS]

I think I'd want more triangulation on those uppers.

Yup... the narrow upper link spacing could be a problem... if all else fails link it.

[kdm73091]

Its not as narrow as it looks. The uppers are 48" long and lowers are 52". The back of the frames cut off so you cant get a refrence of how wide they are. There the giant link mounts so whatever the angle those put is what it is. And its directly to the frame so even if i wanted to make them wider i really couldnt.

[darinz]

No one has mentioned the spacing between the upper and lower mounts on the axle. If they don't have enough seperation then the forces on them will be massively increased. Rule of thumb is 1/4 of the tyre diameter should be the seperation eg 36" tyre means 9" of seperation.

I'm no expert on suspension design but you can't look at any one part of it in isolation. Link length needs to be calculated while taking into account link seperation, angle, pinion angle change etc etc. Also remember that link length is measured parallel to the chassis so the 75% rule is for that measurement and not the actual physical length. And upon saying that, to get the required AS and pinion change on my truck I've ended up with uppers that are about 80% of the lowers. Also the lower mounts on the axle are straight foward to aid in flatening the link due to have a high chassis height. (dual purpose truck so more like KOH than pure desert) To make up for this the axle mount seperation is about 9.5" and the truck will run from 35" to 37" tyres. (depending on type of race)

[Tech Tim]

@ kdm7 - Triaged designed up a cool little 4 link calculator, you can down load it by clicking here.


Play with it a little, it works well and will teach you quite a bit about link placement in regards to anti-squat, roll center etc.