School me on picking size and material for links

[Lil'John]

On the other board, there was a large debate about whether steel DOM or solid aluminum was the way to go for linked suspension.

I'll give my specific vehicle but would love to see any "generic" opinions.

My rig is ~4,000lbs; 472 big block cady, front kp d60, rear d60, full/half body(think s10 blazer cut down closer to truck). Rig will see mild technical wheeling on the Rubicon along with a bit of home snow plowing.

I'm doing front three link with "shorter" links(lowers ~33", upper is 28")

From what I've seen, aluminum and steel links end up getting close in price because of inserts... ~$100 or less difference.

I've got zero concern over weight.

Qs:
Which material would you choose?

How do you determine diameter of links? I'll steal this from Wide Open Design for aluminum:

Is this relevant for mild steel DOM?

Would you consider length of link in addition to weight of rig for diameter?

Where would you get your steel inserts from? I know RuffStuff has them.

Where would you get your aluminum links from?

 

[vikingsven]

AL is nice but gets scarred up pretty easily.

Another option I've seen, and what I'll be using in the future is a DOM steel tube slugged with solid aluminum. That way you get the benefits of AL with the wear resistance of steel on the outside. Just another thought for you to chew on.

 

[JohnnyJ]

The 4-link calc has a handy tab for showing bending strength based on material used, thickness, and length.

My neverending project is starting with 2x0.375 DOM lowers with all links < 36" long, but I expect to bend them and would like to go Aluminum at some point. Shooting for < 4000# buggy, and would like to get to around 3500#.

 

[Sterlingfire]

My rig will be over 6000 lbs. My links are about 40" long both front and rear upper and lower. Lowers are 2 1/2x.250 wall and uppers I'm going 2 1/4x.180 wall. I hope they're big enough lol
I found the info somewhere about what size i wanted n but can't remember where...

 

[rockdog57]

2” dom .250 wall. That way weld in threaded inserts will slide in. That way 1 1/4” heims or summit rebuildable joints are an option. I did this on my really heavy Toyota with v8 and tons. Over the years they have been bent from hammering on em. But never failed. Lowers are mega long too. My 2cents

 

[thedirtman]

Aluminum is nice but cost is more than double, weight is about the same. Aluminum is half the weight of steel but will be solid so that is thrown out the window. The 7075 has memory and will take hits without a permanent bend. I get inserts from Ruff stuff, Ballistic, and Barnes4x4. Barnes typically has the best pricing and their bungs do have a hex for a wrench which makes it way easier to get the jam nuts tight. I typically have them in stock in my shop in Reno if you need them. I also stock DOM in .75" to 2.5". Summit Machine will make your custom links in aluminum.

 

[Lil'John]

Thanks for the input so far... I've snipped stuff out of my quotes.

AL is nice but gets scarred up pretty easily.

Aside from looking ugly, what is the downside? My rig is starting life from a rusty hulk so I'm not worried about show rig.

The 4-link calc has a handy tab for showing bending strength based on material used, thickness, and length.

It sounds like I might have to plug my numbers into a more recent calculator

2” dom .250 wall. That way weld in threaded inserts will slide in. That way 1 1/4” heims or summit rebuildable joints are an option. I did this on my really heavy Toyota with v8 and tons. Over the years they have been bent from hammering on em. But never failed. Lowers are mega long too. My 2cents

I've seem 2" dom .250" wall mentioned a few times on the other board. I'm going with RE joints and spring bushings for now with 1 1/4" threaded stud; they were on my shelf so free ;) If they fail quickly, I'll probably end up with FK heims.

Aluminum is nice but cost is more than double, weight is about the same. Aluminum is half the weight of steel but will be solid so that is thrown out the window. The 7075 has memory and will take hits without a permanent bend. I get inserts from Ruff stuff, Ballistic, and Barnes4x4. Barnes typically has the best pricing and their bungs do have a hex for a wrench which makes it way easier to get the jam nuts tight. I typically have them in stock in my shop in Reno if you need them. I also stock DOM in .75" to 2.5". Summit Machine will make your custom links in aluminum.

My quick search between Ruffstuff dom/inserts and another company came up with ~$300 vs $400. The inserts add up quickly(6 at $16ea)

For weight, I'm finding ~4.67lbs per foot for 2" .250" wall DOM and 3.84lbs per foot for 2" solid 7075 aluminum. It is lighter but I don't care if I save 20-30 lbs.

In your opinion, who's insert had the best threads? I've heard of issues with thread issues in one case with a vendor.

 

[rockdog57]

Jillion , I think that’s her name??who owns and runs summit machine does the inserts with hex on em. I was up there the other day getting some new inserts to build new links on my buggy build. She’s a nice lady. She sold me a bunch right off the mill. They look so nice I hate to weld em. She said they are swamped trying to get all the orders out. Makes a nice rebuildable joint. I’ve never broke one. Have had one 9/16” grade 8 let go with a shitty outcome.

 

[Weasel]

https://www.bentfabaz.com/heat-treated-chromoly-link-120-p/bfhc-120.htm

Chromo Links

 

[YotaAtieToo]

2x250 bend the first real hit

Everytime I think aluminum links are the way to go, I see one fail. Bonus is you can't easily weld or repair it on the trail.

Heat treated chromo is definitely the way to go. Next best is 2.25x375 or 2.5x250

 

[Lil'John]

2x250 bend the first real hit

Everytime I think aluminum links are the way to go, I see one fail. Bonus is you can't easily weld or repair it on the trail.

Heat treated chromo is definitely the way to go. Next best is 2.25x375 or 2.5x250

I have to ask: what caused the failure of the 2x.250? Are you talking hold my beer and watch this?

Since you are going with old sizes like 2.25x.375 and 2.5x.250, where are you finding 1.25 threaded inserts for those?

 

[wvracer821]

2.25x0.375 would take a normal 1.5" insert. not sure about the larger 2.5x0.25. I looked into doing larger tubing like that for my truck or slugging steel links with aluminum but I ended up going with 2.5" solid aluminum from Wide Open Designs. my truck is going to be a big girl and my lower front links are 40" long. going solid aluminum was cheaper for me than ordering 2.25 or 2.5 DOM locally.

 

[YotaAtieToo]

I have to ask: what caused the failure of the 2x.250? Are you talking hold my beer and watch this?

Since you are going with old sizes like 2.25x.375 and 2.5x.250, where are you finding 1.25 threaded inserts for those?

I've never seen one fail, just seem to bend pretty easy.

Like it was already said, 2.25x375 is 1.5 ID

I'd be most places would make the larger inserts if you called and asked. HYDRODYNAMIC is using 2.5x250 on his build iirc.

 

[rockdog57]

In my opinion, bending 2” .250 wall is dependent on the length of your lowers in most cases. My lowers are close to 40. They are banana shaped now. When I built my sons rig I went way shorter and made the transition smooth off the frame. He has yet to bend them while slamming on the same obstacles.

 

[Lil'John]

Still curious what was going on before the 2x.250 dom bent.

FWIW, my link measurements of lowers ~33", upper is 28" include the joint.

Also, as noted, I'll be running RE joints with 1.25" thread welded on it:

Each of them has ~4" of 80k tensile thread at the end

 

['84 Bronco II]

The 7075 has memory and will take hits without a permanent bend.

I hate it when people say things like this. 7075-T6 doesn't have any magical "memory" that allows it to self heal. Any material will take a permanent set one the yield stress of the material has been exceeded. 7075-T6 however has a relatively high yield point when compared to mild steels (~70,000PSI vs ~50,000PSI for A513 DOM), which in combination with running solid 7075-T6 links makes them much harder to bend than a hollow link made of lower strength material. 7075-T6 has poor ductility compared to steel though and wont undergo nearly as much deformation before breaking. 7075-T6 is also softer than most steels and will tend to gouge worse and "stick" to rocks.

Heat treated 4130 or 4140 is really the best of all worlds. You can get yield strengths between 60,000PSI-100,000PSI depending on material and heat treatment process which is 20-100% stronger than A513 DOM and about equal or better than 7075-T6. It is harder than 7075-T6 aluminum and A513 DOM, stiffer than 7075-T6, and much more ductile than 7075-T6. The strength to weight ratio still isn't as good as 7075-T6, but since you don't need to run solid links with 4130 or 4140, and most of the link strength is derived from O.D. and not wall thickness, you can end up with stronger and lighter links than using 7075-T6.

For the OP, just make your life easy and run some thick wall DOM since you don't care about weight. 2.25" OD .375" wall would be pretty damn stout, and if you want complete over kill go 2.5" .5" wall for your lowers and just a size or two smaller for your uppers.

All you need to do to compare strength between the different materials and sizes is to calculate the buckling load (hitting something hard) and the maximum allowable bending moment (dragging on or hitting a rock). All you need is the modulus of elasticity and the yield stress for the material. You will also need to calculate moments of inertia for the geometry. Let me know if you want me to compare to specific material/geometry configurations if you need help. If I am bored later, I might put together a quick and dirty table.

 

[thedirtman]

Thanks for the input so far... I've snipped stuff out of my quotes.

Aside from looking ugly, what is the downside? My rig is starting life from a rusty hulk so I'm not worried about show rig.


It sounds like I might have to plug my numbers into a more recent calculator


I've seem 2" dom .250" wall mentioned a few times on the other board. I'm going with RE joints and spring bushings for now with 1 1/4" threaded stud; they were on my shelf so free ;) If they fail quickly, I'll probably end up with FK heims.



My quick search between Ruffstuff dom/inserts and another company came up with ~$300 vs $400. The inserts add up quickly(6 at $16ea)

For weight, I'm finding ~4.67lbs per foot for 2" .250" wall DOM and 3.84lbs per foot for 2" solid 7075 aluminum. It is lighter but I don't care if I save 20-30 lbs.

In your opinion, who's insert had the best threads? I've heard of issues with thread issues in one case with a vendor.

I have not had any issues with any of the vendors I use so far. I tend to go with Barnes because of the better pricing.

 

[Weasel]

I hate it when people say things like this. 7075-T6 doesn't have any magical "memory" that allows it to self heal.

lol same here just let it slide.

Unrelated, A buddy has some aluminum links that have grooves wore in them from his tires rubbing.

 

[HYDRODYNAMIC]

I searched through all the threads on lower link size and ended up choosing DOM 1020 2.5" x 1/4" wall.
For loading I figured the whole weight of the vehicle on one link, when most likely it will be half the weight of the vehicle on one link. But if your bouncing on it them it will probably be at 2G and then you are back to full weight on one link. Since the rear has a trailing arm, the coilover will be supporting some of the weight when high centered and the bump stops will be taking the bottoming out force off the link in the opposite direction when under compression. What this means is the front links will have a greater chance of bending from landing on them than the rears.

2" x 1/4" = Has a stress of 94,339 PSI with 5K on 40" link
everyone bends this

2" x 1/2" = Has a stress of 68,027 PSI with 5K LBS on 40" link
lasts for some

2.25" x 3/8" = Has a stress of 56,179 PSI with 5K LBS on 40" link
standard for a number of builders, good reports of lasting

2.5" x 1/4" = Has a stress of 55,555 PSI with 5K LBS on 40" link
What Im planning on running with TMR 2.5"OD x 2"ID tube adapters. Also happens that this is the heaviest wall the suppliers stock that has good pricing.

2.625" x 3/8" = Has a stress of 38,461 PSI with 5K LBS on 40" link
TMR trailing arm size

2.5" x 1/2" = Has a stress of 37,593 PSI with 5K LBS on 40" link
Go to for heavyweights, but still hear of rock bouncers bending these

Then there are the full aluminum or aluminum/DOM stuffed links variants and heat treated chromoly. None of which I was excited about using over DOM only.

For those interested in square or rectangle links vs round. Yes a straight edge of a square tube can hold more weight than an equal weight round tube when the load is aligned with the straight edge. When the load is applied at 45 degrees to the side and bottom of the square link. The square squeezes into a diamond shape and looses its strength and starts to bend. Round can be hit from any angle around the axis and have full strength. Square tube in A500 grade B is around 46,000 yield vs DOM A513 1020 which is around 55,000-70,000 yield. So the material is stronger before you even get into shape strength.

Surface hardness is important for wear and friction. Some have reported that soft aluminum will stick to rough rocks and not slide like steel tube. The friction is enough to not slide off the rocks and keep going. The soft aluminium when struck on one side can grab the rock and spin the link and if you are running left hand and right hand, the link will extend or retract and misalign the axle. Again steel is harder and will be less likely to happen. Heat treated steel will be even better at creating a hard an slick surface.

I want to remind people that my build is a family trail rig and not a race rig or rock bouncer. I can replace the links in the future if they do bend too much, but I do not want to go super overkill and add on a bunch of unneeded weight until it is proven that I need it based on my driving style.

The giant 2.5" to 1.25" tube adapters also help in welding as they offer more weld area. They also are more rigid than thin wall inserts, so thermal distortion will be lower.

 

[pennsylvaniaboy]

I have used 2x2 .25 wall square tube with 1.5" .120w DOM inside...They are strong but heavy. Uppers are 1.75" .120 DOM. I do a weld on JJ at one end, and 1.25 Heim on the other.

If I were to do it again, I would probable do the do it again, I would do double adjustable aluminum lowers. Purely for weight and ease of assembly.

 

[JohnnyJ]

It sounds like I might have to plug my numbers into a more recent calculator

I've seem 2" dom .250" wall mentioned a few times on the other board. I'm going with RE joints and spring bushings for now with 1 1/4" threaded stud; they were on my shelf so free ;) If they fail quickly, I'll probably end up with FK heims.

My quick search between Ruffstuff dom/inserts and another c
In your opinion, who's insert had the best threads? I've heard of issues with thread issues in one case with a vendor.

It's on the Materials tab. Not sure when 4link calc added it, checked on 3.1.1c from 2007!

Past experience was that 36" lowers from 2x0.25 DOM bowed pretty quickly under normal trail wheel use. Money saving tip: flip them every so often. :D

I use Barnes4wd, but I'm on the east coast and figured out it was when comparing part cost + shipping and quicker arrival than ruff stuff. Both seem equivalent.

 

[Bebop]

I have 2.5x0.250 lower links with a slug of 2" AL inside. They do weight a ton, but I'm not bending them. not now, not ever.

4500lbs buggy with a heavy right foot.

 

[rockyota83]

I have 2.5x0.250 lower links with a slug of 2" AL inside. They do weight a ton, but I'm not bending them. not now, not ever.

4500lbs buggy with a heavy right foot.

this

 

[Weasel]

I have 2.5x0.250 lower links with a slug of 2" AL inside. They do weight a ton, but I'm not bending them. not now, not ever.

4500lbs buggy with a heavy right foot.

this

Or you buy HT links and not have them weight a ton and won't be bending them either.

So your setup is around 30# per link. A HT link is either 7# (1.5) or 14# (2.0). Cost has to be similar?

 

[Bebop]

I don't know of a local heat treating company that would know what to do with link bars.

Other issue is trying to buy 1 single stick of 4340 heavy wall tubing, nobody carries it, nor wants to order it for you.

As for cost, no idea since getting chromo tubing here is bordeline impossible (see above).

Edit : To add some info, they are custom made trailing arms so no go on buying a complete, heat treated product from a company out in CA and shipping it to TN.

 

['84 Bronco II]

Or you buy HT links and not have them weight a ton and won't be bending them either.

So your setup is around 30# per link. A HT link is either 7# (1.5) or 14# (2.0). Cost has to be similar?

A 1.5" .120" wall 4130 won't even be close to the strength of his links, nor will the 2" .250" wall. Now, 2.5" .250" wall heat treated 4130 would be comparable strength and save him the weight of the aluminum slug.

I don't know of a local heat treating company that would know what to do with link bars.

Other issue is trying to buy 1 single stick of 4340 heavy wall tubing, nobody carries it, nor wants to order it for you.

As for cost, no idea since getting chromo tubing here is bordeline impossible (see above).

4130 and 4140 are much more common "Chromoly" grades for tubing. 4340 is stronger though.

 

[gt1guy]

Why all the worry about what the links weigh? I could understand considering the weight in a actual go fast race vehicle, because the extra weight is delt with by the shocks, which in turn will add heat to the shock oil. But in just about every other type of vehicle, that's not an issue. I guess if your engine makes 89hp, moving any weight is a problem.
Your links sit pretty low in the chassis, the LCA's are the lowest items short of the axles themselves. Weight that low isn't always a bad thing. Half of the link weight is sprung weight and the other half is unsprung weight. So half the weight of the links is factored into the height of your CG and it ain't moving it up.

I want links I can drop off a ledge and land on without them leaving me fucked. What they weigh, isn't a big concern. If I want to save weight, I'm starting at the roof and working my way down, cause that's the weight that matters.

 

[Weasel]

I don't know of a local heat treating company that would know what to do with link bars.

Other issue is trying to buy 1 single stick of 4340 heavy wall tubing, nobody carries it, nor wants to order it for you.

As for cost, no idea since getting chromo tubing here is borderline impossible (see above).

only if there wasn't a link posted somewhere of a vendor that will do that for you.

A 1.5" .120" wall 4130 won't even be close to the strength of his links, nor will the 2" .250" wall. Now, 2.5" .250" wall heat treated 4130 would be comparable strength and save him the weight of the aluminum slug.

You could run a solid steel link and claim the same thing, Why not do that? It would be way stronger then any of that. Who is breaking 2" HT link, let alone 1.5" links? Have seen some fail due to bad HT or poorly welded inserts.

Actually I'd bet that a set of 2 HT links would be stronger then the above setup.

Why all the worry about what the links weigh? I could understand considering the weight in a actual go fast race vehicle, because the extra weight is delt with by the shocks, which in turn will add heat to the shock oil. But in just about every other type of vehicle, that's not an issue. I guess if your engine makes 89hp, moving any weight is a problem.
Your links sit pretty low in the chassis, the LCA's are the lowest items short of the axles themselves. Weight that low isn't always a bad thing. Half of the link weight is sprung weight and the other half is unsprung weight. So half the weight of the links is factored into the height of your CG and it ain't moving it up.

I want links I can drop off a ledge and land on without them leaving me fucked. What they weigh, isn't a big concern. If I want to save weight, I'm starting at the roof and working my way down, cause that's the weight that matters.

Heavy sucks and breaks stuff. It's more weight your rig has to move. But yeah there is a point which it doesn't matter and things are light enough. I suppose everyone should run 1/2" plate skid plates, 3/4" axles tubes, 3/8" bumpers, water in the tires and steel wheels. Most all of that is down low weight. It would never break.

 

[Bebop]

only if there wasn't a link posted somewhere of a vendor that will do that for you.

My shocks and sway bar are mounted on the links, so I'd like to set up the mounts myself. Prior to HT.

I can TIG weld and wouldn't have any issues fabricating my own. Nor I'm arguing about the strength benefits of HT links.

My only problems are mentioned above and you're no help.

 

[Lil'John]

Well, I never knew there was a material in the calculator

So how do I use this: