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allthread in adjustable links???

1K views 3 replies 3 participants last post by  mudrover 
#1 ·
I'm vacillating over what diameter allthread (proper hardened allthread with rolled threads) to use in my adjustable links. I'm leaning towards 1" in the front uppers and 3/4" in the rear lowers. The front end will be a SG style 3-link setup but using a fixed length 1.75"/.250wall DOM center link for sheer strength. The uppers will be the same material although I've considered using 1.5"/.188wall DOM. The rear lowers will be the 1.5"/.188 wall with a stock A-frame upper link. I was wondering if anyone had viable input.
 
#2 ·
Don't know if I can offer much here, but I looked at all-thread once for a structural application. I would be concerned about buying just any all-thread as a lot are just some sort of mild steel, and their mechanical properties can vary quite a bit. If you get something like B7 all-thread, I think you can have more confidence in it's mechanical strength.

As far as sizes go, it's probably best to look at other similar components that have proven to work well. The actual loads in the 3-link may be difficult to calculate so empirical data may be the best way to go (my guess is you're on the right track in the sizes you indicated). My Rovertym adjustable rear links have 3/4" threads (probably just mild steel), and they seem to work fine (although these are relatively lightly loaded). I'd probably look at some fairly stressed applications to see what people are running (a 3-link failure could be disastrous). Also, ensuring that the links see pure tension/compression loads (no bending) will minimize loading on the threads (probably the weakest area) so joint design is important.
 
#3 ·
A quality allthread (hardened/rolled threads) will be used. I'm going to use a fixed center link of stout proportions because of strength issues. The links will see some sheer loads by their very application. It can't be avoided, but the loads should not be excessive or continuous. My idea is to sleeve DOM from a 1.75" OD down to a .812 Id and tap for the allthread. This sleeving will allow for 3" of insertion which should be strong enough. The allthread will be towards the chassis while the fixed bushing will be towards the axle. Overall length will be approximately 30" with this being divided roughly 24"/6". The 3/4" allthread would be easier to deal with but the 1" much stronger. I was posing the question in hopes that someone out there and setup adjustable multi-link frontends and could elaborate on strengths or weaknesses firsthand of both allthread and tubing size. Many heim jointed links seem to use 5/8" or 3/4" shafts with great success. I was applying the same principles to proper allthread. Lastly, many high hp racecars are using 3/4" allthread in rear four link setups. They see tremendous loads off the line without failure. If it weren't the frontend then I'd not be as concerned.
 
#4 ·
Why pay the prices for allthread and sleezing it when you can buy some beefy DOM and weld in some threaded inserts? Check out http://www.spidertrax.com/fabrication.htm for inserts. As for wall thickness I would use a minimum of .25 wall for all the links and larger (.375) for the lowers if they are going to hit any rocks. Use some quality 3/4 in. heim joints (not the cheap summit crap) or JJs at the frame end and just use standard bushings at the axle.
 
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