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Tubular Rear Arm Control Sheared

M

Mark T

CEG'er
Joined
Mar 24, 2003
Messages
77
Location
Over the pond in sunny England
As the title says really one of my tubular rear control arms has sheared at the rose jointed end link. I had a scary 5 minutes in it & it was just lucky I was only doing 20mph as if I was going faster it would have been a different story. Here's a few pics

Rearf wheel steer Mondeo, lol
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I went out yesterday & put the old arms back on now so I've just got to get the tracking redone & all should be OK again.

Looking at the where it's sheared the rose joint on the end has seized solid, so is the other side, so I think this is why the threaded bit, where the rose jointed end link goes into the arm, has sheared.
These were fitted last October & the car has done just under 8000 miles with them on. I don't drive the car that hard & I was greasing the arms up every 2000 or so miles so it looks like the good old British weather has taken it's toll on mine & they needed to be greased more often than that. Oh well doesn't matter as they are off now.

I'm going to look into getting a replacement end link for it & then decide to either sell the arms or put them back on & grease them more often but I expect I'll be selling them as I'm not sure I can be bothered to get out there & grease them all the time.

Sheared end link stuck in bar
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Sheared end link
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Has anyone else heard of this?
 
Whos arms were those? Ive seen rod ends sheer like that but only because they were too small for the application. I think your the first to do that on a Contour/Mondeo.
 
It looks like the heim is all rusted up. Or is it just the oil & grime?

I've had those toe arms on for close to 50k miles. I grease them every 8k miles, and clean them out with brake cleaner every other time.
 
qbcsvt said:
I paid for my TCA's like 4 months ago, I have yet to get them installed on the car! Holy Moly does that scare me!

- amyn
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If your worried, just get cromoly rod ends. They're strong enough to put your worries at ease.
 
i've had the same ones on my mondeo for a long time and alot of miles with no probs. but i'd better start greasing and cleaning them more!

sadly over here in the UK there is silly amounts of salt on the roads alot of the time.

what are cromoly rod ends?
 
That hiem joint size is pathetic for a suspension application... :nonono:

I'd see what you could do to get a larger joint on that arm - you can run a larger joint with reduction spacers if you need to, I wouldn't trust a joint of that size...

I'm probably bias though - I build 4x4 stuff and I'm used to running 1.25" joints with static load ratings ranging into the mid 70K LBS range...

That failure is not from road grime or lack of grease - the pivot point would fail before the joint would sheer like that - unless there was a defect in the manufacturing process.
 
KyleQ said:
That hiem joint size is pathetic for a suspension application... :nonono:

I'd see what you could do to get a larger joint on that arm - you can run a larger joint with reduction spacers if you need to, I wouldn't trust a joint of that size...
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would you care to suggest a minimum size for 2.5 and 3.0L with lowered and stiffened suspension which gets pushed hard on corners...thanks..G.
 
I'm using 5/8" made from mild steel on the rally car. It looks like the one in the picture is only 1/2". Mine will probabley never break. I think 3/4" is too heavy. 1/2" mild steel rod ends have a static load capacity of 8,338 lbs. 5/8" is 9,713 lbs. 1/2" 4130 cromoly is 15,500 lbs. The cromoly pieces also have Teflon in them. If anyone wants custom suspension pieces made up, let me know.
 
Those arms were designed and fabricated by me. Anyone who isn't a Ford suspension engineer offering an opinion on the size of the rod ends being used is supplying pure conjecture. What load is each individual suspension arm in the rear of our cars being exposed to? The main control arm handles the majority of the lateral loads, not the toe arms.

I have sold over 50 prs. of those arms and the second set of those arms are on my car and have been in continuous service since the Fall of 2003 with more than 40,000 miles on them. My car has seen track duty and is a daily driver in all 4 seasons here in the Great White North. The arms are exposed to a barrage of snow, salt and slush each winter. I have experienced no such failure BUT I maintain my 96 SE (over 200,000 kms) meticulously.

This particular failure was a result of corrosion-the ball was seized in the race. Why or what conditions caused them to corrode is the real question to be answered in this instance. This was not a design failure.
 
I agree fully that the reason the rod end breaking was not a result of any type if engineering failure. The only reason it broke was due to excessive corosion build up. I simply showed the different specs on the rod ends to show that cromoly rod ends are a good way to go. Yes they are very strong. But the mild steel ones are plenty strong enough for the rear toe link on a contour. The key benefit to the cromoly rod ends is that the sphere is coated in teflon. That teflon will eventually wear away, but it will allow for less servicing of the rod ends. If they are not serviced, they may eventually break too. I do not know if the toe link that broke had cromoly ends, nor do I know what size they were. I was just trying to be helpful. If I was spreading conjecture, that would imply that I do not know my stuff. I may not be a ford suspension engineer, but I know suspension fairly well. I am aware of of the design charactoristics of the contour's suspension, and I know how to tune it for control, response, feedback, feel, ect. In about one months time I should have enough evidence to prove it.
 
Bradness said:
Those arms were designed and fabricated by me. Anyone who isn't a Ford suspension engineer offering an opinion on the size of the rod ends being used is supplying pure conjecture. What load is each individual suspension arm in the rear of our cars being exposed to? The main control arm handles the majority of the lateral loads, not the toe arms.
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I'm not a suspension engineer, and never have specifically been one, but I've been involved in my fair share of OEM and racing chassis design . . . care if i comment? ;) You are correct, the toe links should not carry the bulk of the loading, but, this is a passive steer design, so removing the rubber deflection in the toe link will allow more load to be passed into the link, and if not allowed to pivot freely, it would result in bending loads as well; but more on that in a minute.
I've never seen your arms in person, but based on other's comments, I'm ASSuming they are 1/2" rod ends. This certainly seems to be adequate from the testing you have done, and from most other's cars that have been using them, and it probably calculates out that way as well. The only thing I will say here, is that I've picked up a rule of thumb of running at least a 5/8" rod end on any typical road car type suspension stuff. If I were designing those arms myself, I'd have probably used 5/8" based on that.

This particular failure was a result of corrosion-the ball was seized in the race. Why or what conditions caused them to corrode is the real question to be answered in this instance. This was not a design failure.
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Lack of maintenance, resulting in corrosion, and ultimately a siezed bearing, would allow the additional load put into the arm to translate into a bending moment on the arm, instead of pure tension or compression as its designed to handle. The bending load, reversing back and forth, will eventually fail the arm at its weakest point, which is in the threaded shank of the rod end. once the bearings siezes, the failure is inevitable. Rod ends on street car suspensions (or race car) need careful and regular maintenance. Even if Bradness had used a larger rod end like a mentioned above, it still would have eventually failed from lack of maintenance.

Goumba said:
I agree fully that the reason the rod end breaking was not a result of any type if engineering failure. The only reason it broke was due to excessive corosion build up. I simply showed the different specs on the rod ends to show that cromoly rod ends are a good way to go. Yes they are very strong. But the mild steel ones are plenty strong enough for the rear toe link on a contour. The key benefit to the cromoly rod ends is that the sphere is coated in teflon. That teflon will eventually wear away, but it will allow for less servicing of the rod ends. If they are not serviced, they may eventually break too. I do not know if the toe link that broke had cromoly ends, nor do I know what size they were. I was just trying to be helpful. If I was spreading conjecture, that would imply that I do not know my stuff. I may not be a ford suspension engineer, but I know suspension fairly well. I am aware of of the design charactoristics of the contour's suspension, and I know how to tune it for control, response, feedback, feel, ect. In about one months time I should have enough evidence to prove it.
Click to expand...

Chrome-moly will still break in this scenario as well. The only way to prevent it the failure after the pivot has siezed is if the rod end is grossly oversized so that the reversed bending load is much lower than the fatigue load limit. Which, if you're going to do that, you might as well make it a solid link without the rod end, as it would perform the same.

There are two things that users of these arms can do. The first is a must, and the second will just help.
1. Regular inspection. Ensure the rod ends are still in good shape, and are pivoting freely on a regular basis. Exactly how often will be determined by the type of usage and environment you subject them to.
2. Install seals or boots. Seals or even full rubber boots are available for virtually every standard size rod end. They will keep out a lot of the crap that leads to corrosion and siezing. But, the downside is they make proper inspection a lot more difficult.
 
As mentioned, an additional method to minimize (not prevent) corrosion at the ball/race interface exists. Aircraft suppliers sell a seal which fully encloses the ball on both sides with a flexible neoprene shell.

Also, the opposite end of my arms use a poly bushing which allows a small amount of deformation.

However, the key to avoiding failure is preventative maintenance.
 
Just thought I'd comment on this....I don't believe the failure was down to a design fault at all. I maintain my car very well as the car is an everyday car but is also a show car & has had a full feature in one of the UK Ford mags, Fast Ford, so you get the idea.
The car had done approx 8000 miles with them on & I greased them every 2000 miles so go figure???

I think this just comes down to one of those things & it wouldn't put me off putting them back on once I've got new rod ends (the price of getting the track set afterwards might though, lol)
 
Looks like there was an attempt to make it double sheer - these are designed for 4x4 applications, but you get the idea. 38 bucks a piece.

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The 2.63" Forged Chromoly Ballistic Joint is made to be the ultimate in durability and ease of use. 100% made in the USA, this joint was manufactured and designed for military use and quality, and meets all MIL-SPEC standards. Forged from solid 4140 steel, the forging is then quenched, tempered and then normalized in a dedicated heat treating facility, providing a yield strength of 208000 psi and a tensile strength of 238000 psi! Finish machining is performed after heat treat to ensure a perfect fit.

Using solid Nylatron GS races with nickel plated bearings, these joints are smooth, long lasting and quiet. The 2.63" Ballistic Joint uses no snap rings to retain the races, instead a retainer is forged into the housing. The opposite side uses a threaded spanner nut and set screw. Also, we've added a lot of material to the grease zerk / set screw area to add a much greater resistance to splitting. Any play that might develop over time can be removed by adjusting the spanner nut. All forged joints are clear "silver" zinc coated.

Otherwise, there is a chromoly joint like these
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These joints are simply the strongest and best available with superior load ratings and a self cleaning Kevlar/Teflon liner. Body is built from Chrome Moly alloy steel, heat treated and coated for protection. The race is self lubricating and self cleaning. The ball is 52100 hardened bearing steel, heat treated, hard chrome plated and precision ground. For top notch performance at a good price the XM series should be your choice. Static Load Rating: 40,572 lbs.

You can reduce the size of the bolt with spacers, they let the joint articulate more.
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Overbuilt? Probably, but you are creating non DOT certified parts and putting them on the road where people walk and drive - there is no excuse for anything less then overbuilt.

All this info was taken from www.ballisticfabrication.com
 
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