Cycled my 4 link today.. Have a few questions

GearHead11

Well-Known Member
Joined
Jul 10, 2013
Location
Winston Salem
So I finally got to where I could cycle my front end today. Everything clears about as I expected it to. With both sides at full stuff, I get 4" of up with the diff hitting the frame being my limiting factor. If only one side stuffs and the other is at ride height or drooped it clears more than 4" of up. I could notch the frame to fix the diff clearance issue but my axle side uppers would then hit the rim of the oil pan and the only way around that would be to extend the wheelbase and all 4 links. I'm already at 106" on 37's with a 19" belly so I don't want to go longer so my question is.. do I set the shocks to have 4" of up to match the double stuff number or set it up with a little more so as not to limit the bump/droop scenario and set bump stops up to limit the double stuff scenario? This is my first time with links so I have/am still learning.

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IMO set the shocks to have slightly more than 4" of travel and mount your bump stops to limit it where you want so that the shock is almost bottomed out when the bump is. I am not a fan of shocks compressing to the point where the body of the lower eyelet contacts the body of the shock. Its an absolutely brutal feeling when it happens.
 
StretchASU said:
IMO set the shocks to have slightly more than 4" of travel and mount your bump stops to limit it where you want so that the shock is almost bottomed out when the bump is. I am not a fan of shocks compressing to the point where the body of the lower eyelet contacts the body of the shock. Its an absolutely brutal feeling when it happens.
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Oh I know... anytime I tried to rally the tacoma I was knocking teeth out
 
Stuntman Autoworks said:
I would move the upper links out enough to clear the oil pan and notch the frame to get a little more up travel than just 4".
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Since the lowers have almost no triangulation don't I need as much triangulation as I can get on the uppers to keep the axle centered?
 
You need 40 degrees total triangulation. Any combination of upper and lower to get that.

I agree with above about getting more uptravel.

Ideally shoot for having 1/2 the shock travel in uptravel.

4" uptravel is going to bring the suck on everything but Slow crawl rock gardens.
 
Mac5005 said:
You need 40 degrees total triangulation. Any combination of upper and lower to get that.

I agree with above about getting more uptravel.

Ideally shoot for having 1/2 the shock travel in uptravel.

4" uptravel is going to bring the suck on everything but Slow crawl rock gardens.
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I was under the impression that I needed 40* on one set of links. Good to know.

I've never had more than 3" of up so but I've also never done any go fast stuff either (mainly because I couldn't lol).
 
GearHead11 said:
I was under the impression that I needed 40* on one set of links. Good to know.

I've never had more than 3" of up so but I've also never done any go fast stuff either (mainly because I couldn't lol).
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Not even go fast stuff but also has a huge impact on non-crawl trails and ride quality.

When I had low uptravel it was much more tiring riding an entire day just from the poor ride quality.
 
Mac5005 said:
Not even go fast stuff but also has a huge impact on non-crawl trails and ride quality.

When I had low uptravel it was much more tiring riding an entire day just from the poor ride quality.
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A thought I've had on balanced up and down travel, is the chassis actually stays more level. Instead of having 3" of bump travel the axle actually goes up more instead of raising that corner of the chassis as much. Maybe it makes more sense thinking of it as having a central pivot like an tractor front axle. With more up travel it raises that pivot point higher. If I'm wrong tell me but this has kind of been my thoughts on it with playing with the travel bias on my jeep.
 
iwaxmyjimmy said:
A thought I've had on balanced up and down travel, is the chassis actually stays more level. Instead of having 3" of bump travel the axle actually goes up more instead of raising that corner of the chassis as much. Maybe it makes more sense thinking of it as having a central pivot like an tractor front axle. With more up travel it raises that pivot point higher. If I'm wrong tell me but this has kind of been my thoughts on it with playing with the travel bias on my jeep.
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Yes that's the right thoughts.

More uptravel equals more time to absorb bumps or articulate before changing the chassis position.

Any event that transmits that force from tire to chassis faster will usually result in a reduction of the ride quality.

Rock bouncers, and go fast rigs definitely have more uptravel yet comp crawlers are set up with minimal uptravel.

Both of those examples are built for specific reasons and driving styles. That's why I think it's a good plan to split the travel of the shock, if you can.
 
Is there an easy way to measure the angle of the lowers? I have a little tool I made to transfer tube bends that I can use to measure the uppers but the converge at a theoretical point too far back for me to do them the same way.
 
I know it's less than 10* because I have 10* axle mounts and they are still at an angle and not in line with the brackets.
 
Maybe some trig? Lol


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GearHead11 said:
Been out of school a while... If it can't be solved with a^2+b^2=c^2 then I'm lost haha
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You need Pythagorean Theorem to figure out your link lengths so you're off to a good start

C-your hypotenuse is your actual link length
A-is going to be the distance between your frame side mounts, minus the distance between your axle side mounts, divided by two.
B- creating a 90 degree angle from A all the way to your axle side mounting point.

Your upper links make two right triangles but since there is some distance between the axle side mounts there.

C^2 - A^2= B^2 is what you'll end up using which B^2 would have to be square rooted to get your actual length of that leg of the triangle.


As far as the Trig part to get the angles, I dunno which sin/cos/tan to use I'm learning that sort of now in college, lol.
 
Angle should be = 2 x arcsin(a/c)

Angle being total degrees between the two links, converging at the axle or frame. a referenced is half the difference of the link separations at axle and frame. c being link length.
 
So I jacked it back up to full bump and I don't have enough room on the truss to move the uppers out to clear the oil pan without significantly shortening the uppers. Right now I'm getting 5* pinon change on compressing and 7* on droop. How much is too much?

The other option would be to lengthen the lowers and uppers equally but I don't really wanna go longer on the wheelbase as I'm relatively low and only on 37's.
 
a_kelley said:
Lifting the motor could gain an inch or two...
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That may have to be round 2 of the build.. I'm trying to wheel this year. Thinking I'm just going to run with it as is for now and if I hate it I'll redo it next off season or something.
 
Post your link dimensions.

Horizontal distance from frame to chassis, as viewed in side.

Horizontal separation of lowers at frame and chassis.

Link length bolt to bolt. We can prob figure out your angles pretty quick.
 
Mac5005 said:
Post your link dimensions.

Horizontal distance from frame to chassis, as viewed in side.

Horizontal separation of lowers at frame and chassis.

Link length bolt to bolt. We can prob figure out your angles pretty quick.
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