Link material question

GearHead11

Well-Known Member
Joined
Jul 10, 2013
Location
Winston Salem
I'm linking my Sami buggy currently and am running 2" .250 lowers with 1.25" heims. On the uppers I have 7/8" heims with adapters for both 1" i.d. and 1.5" i.d. which leaves me with the option of 1.75" .120 or even 1.5" .250 so my question is, what's more important... Diameter or wall thickness?

Guessing the buggy should weigh in around 3200 lbs and it's a 4 link front that's up for discussion here.
 
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IMO .250" is a minimum thickness for lowers as they see impact. Uppers basically only see pulling forces on a properly set up triangulated 4 link, so thickness isn't as much of a concern. With that being said, I have always run .250" uppers as well but only because I keep .250" in stock. I'd have no issue running .120" uppers for a lighter weight or lower power rig.
 
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Kinda what I was thinking but I know there are people here way smarter than me so I wanted to confirm before I burn anything in. I guess I'm going to use the 1.5" .250 so that I can use the 1.75" .120 elsewhere
 
GearHead11 said:
I guess I'm going to use the 1.5" .250 so that I can use the 1.75" .120 elsewhere
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I don't do a ton of tube work here, so I'd (just for my own typical workload and use) use the .120" so I could use the .250" for steering needs. Tomato/ tomatoe

Paging @Fabrik8, @MarsFab, etc for real world data
 
I hear ya. That leads me into another question actually.. I'm going to run double ended full hydro, do the tie rods need to be .250 wall being that they are so short? I know .250 is a standard for full length tie rods but am not sure if the short length on a double ended setup can make up for thickness. Asking because my kit came with 1.5" .120 tube for the tie rods and I was expecting .250
 
Diameter makes larger difference to strength than wall thickness as the radius from center is greater to the od cross section.

This is for materials that want see a buckling load due to impact i.e.: uppers.

I would use 1.75 .120 wall for uppers. Also will help to cut some unsprung weight which is always good with a lightweight rig with heavier axles.

When unsprung mass starts to equal sprung mass some unfavorable suspension quirks start to show.
 
GearHead11 said:
I hear ya. That leads me into another question actually.. I'm going to run double ended full hydro, do the tie rods need to be .250 wall being that they are so short? I know .250 is a standard for full length tie rods but am not sure if the short length on a double ended setup can make up for thickness. Asking because my kit came with 1.5" .120 tube for the tie rods and I was expecting .250
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Toilet paper, birth control and steering are 3 places I don't skimp.
I'd make my own .250" links for any steering, let alone full hydro
 
Mac5005 said:
Diameter makes larger difference to strength than wall thickness as the radius from center is greater to the od cross section.

This is for materials that want see a buckling load due to impact i.e.: uppers.

I would use 1.75 .120 wall for uppers. Also will help to cut some unsprung weight which is always good with a lightweight rig with heavier axles.

When unsprung mass starts to equal sprung mass some unfavorable suspension quirks start to show.
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I guess I can see that.

Do you care to elaborate a little on your last point? My unsprung mass in the rear is a good bit more than sprung. Running waggy 44's on 37's and in the rear for spring weight it's a tubed backhalf, a fuel cell, and a little cooler and that's it.

Is there a particular anti squat figure to shoot for in the rear when there's no weight?
 
How long are your links? If the tube length is less than 20", chances of ever bending it are much less than if they were 30"+ just because of it's less impact area. The ones on my rig are pretty short. I also have a stick of 2.25 7075 aluminum if I ever do bend one. :D
 
XJsavage said:
How long are your links? If the tube length is less than 20", chances of ever bending it are much less than if they were 30"+ just because of it's less impact area. The ones on my rig are pretty short. I also have a stick of 2.25 7075 aluminum if I ever do bend one. :D
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Lowers are 31.75" and uppers are 24.25". Tube length on the uppers is like 17"
 
GearHead11 said:
I guess I can see that.

Do you care to elaborate a little on your last point? My unsprung mass in the rear is a good bit more than sprung. Running waggy 44's on 37's and in the rear for spring weight it's a tubed backhalf, a fuel cell, and a little cooler and that's it.

Is there a particular anti squat figure to shoot for in the rear when there's no weight?
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Shoot for less than 80% at full droop. That will help to avoid hop on steep climbs with decent traction.

The weight split has more to do with ride quality and suspension compliance.

Whichever has less mass will move sooner and farther that the item with more mass due to inertia.

If the vehicle is moving forward and you hit a bump, if sprung mass is less than unsprung, it can be tedious to get the suspension to absorb that event without just directly pushing the axle, suspension, and chassis upward.

To simply a lot, lower AS generally equates to a lower INstant center height, which generally directs more force through the suspension to chassis.

Steeper sloped links and higher IC transmit more force and faster through the links straight to the chassis.
 
Definitely makes sense. Also explains why when I back off the trailer nothing compresses and it's rough as shit.

I have air shocks all around so tuning is limited but I'm hoping I can get them feeling better with some time playing with oil volume.

Where does the calc show AS numbers during travel? I haven't stumbled on that yet.
 
Do what mac says i have 2 inch 250 lowers and 1.75 120 uppers lowers are beat to hell uppers look brand new

Sent from my SM-G930V using Tapatalk
 
GearHead11 said:
Definitely makes sense. Also explains why when I back off the trailer nothing compresses and it's rough as shit.

I have air shocks all around so tuning is limited but I'm hoping I can get them feeling better with some time playing with oil volume.

Where does the calc show AS numbers during travel? I haven't stumbled on that yet.
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Depends on what calculator you are running. Look for the newest download on pirate. It shows front and rear simultaneously.

Start with max oil volume -10cc and then set the air pressure to set ride height.

That's the trouble with air shocks, you cant separate spring preload from ride height.
 
Mac5005 said:
Depends on what calculator you are running. Look for the newest download on pirate. It shows front and rear simultaneously.

Start with max oil volume -10cc and then set the air pressure to set ride height.

That's the trouble with air shocks, you cant separate spring preload from ride height.
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Apparently I have the original calc installed. Downloading the one with the travel addition now
 
GearHead11 said:
Definitely makes sense. Also explains why when I back off the trailer nothing compresses and it's rough as shit.

I have air shocks all around so tuning is limited but I'm hoping I can get them feeling better with some time playing with oil volume.

Where does the calc show AS numbers during travel? I haven't stumbled on that yet.
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The third tab on yours tells you droop and bump geometry. It the one I showed you last weekend.
 
Chris_Keziah said:
The third tab on yours tells you droop and bump geometry. It the one I showed you last weekend.
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I downloaded a new calc that does bump/droop on the first worksheet with everything else.
 
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