Broken sway bar

[Josh]

So I noticed the car pulling hard to the right when braking. Took a look and saw this. What would have caused this? Also is it worth fixing or just look for a new sway bar?


http://img.tapatalk.com/d/14/07/13/pupy6uha.jpg

[Tillsy]

That doesn't even look like a stock sway bar - was it not properly rated for the flexibility required there?

[D Knight]

The problem is the sway bar is also being asked to act as a radius arm. Installing the LCA brace kit or going with Dave's new arms will help to allow the bar to focus on controlling body roll.


-D Knight-

[NightFlyer]

So I noticed the car pulling hard to the right when braking. Took a look and saw this. What would have caused this? Also is it worth fixing or just look for a new sway bar?

Lot's of possibilities as to what could have caused that - everything from improper mounting geometry to hitting something that exceeded the bar's specs to defective metal in the manufacturing process. Hard to say for sure (probably impossible) exactly what caused your failure.

Personally, I don't think that repairing would yield acceptable results, thus IMHO, it's new bar time, unfortunately....

[Delorean Industries]

Without seeing it first hand in this case I have seen this once before. It was from a massive impact with a cinder block according to the owner. But there was no impact marks on the bar. Just sheered off where it necks down.

[Nicholas R]

Could be just the perspective but that sway bar looks bigger than stock to me.

[Josh]

lol, its a stock sway bar, just galvanized.

The LCAs are fine, these are DPIs SS units.

I have been driving on some rough roads lately. I think it is compounded by the fact I overtorqued the sway bar bolts. I also did this several times as I was working on suspension alot over the last month or so.

[Bitsyncmaster]

lol, its a stock sway bar, just galvanized.

I wonder if the heat from the galvanizing upset the sway bar heat treating. Looking at the photo it does not look like the sway bar has the correct geometry.

[Nicholas R]

I wonder if the heat from the galvanizing upset the sway bar heat treating. Looking at the photo it does not look like the sway bar has the correct geometry.

I wondered the same thing. I deal with the concern of distortion and residual stress from hot dip galvanizing a lot at work.

Either way, if you knowingly overtorqued it, that's likely the cause. The end of the sway bar is just mild steel that is threaded; it's no where near as strong as normal hardware. Most mild steels, (ie ASTM A36) have a tensile strength of ~60,000psi. That's not even as high as the minimum requirements for a bolt to be a certified grade 2 (sae) bolt.

I suppose there is a very slim chance that the bars may have been heat treated or case hardened from the factory since it's constantly loaded, but the heat treatment would likely be lost during the galvanization. Still, given where it broke, it looks like the bar was over torqued.

[Bitsyncmaster]

Hot dipped the temp bath of molten zinc at a temperature of around 860 °F (460 °C).

That would defiantly upset any heat treating. Now we need to find out if the bar is heat treated.

[Rich]

Hot dipped the temp bath of molten zinc at a temperature of around 860 °F (460 °C).

That would defiantly upset any heat treating. Now we need to find out if the bar is heat treated.

Normally a new/OE stabilizer/roll bar is heat-treated after it's formed into shape. Standard industry practice to strengthen it.

While your D is out of action be sure to check that you have the front recall kit in place and the crumple tube, the sway bar mount bracket and bushing are all OK. Whatever tore yours apart might have caused other damage.

[protodelorean]

I'm with Nick. I think it was overtorqued and/or possibly had stiffer (urethane?) bushings. Either, or the combination would've caused the bar to try to bend at the end and not pivot in the bushing.

[Josh]

I'm with Nick. I think it was overtorqued and/or possibly had stiffer (urethane?) bushings. Either, or the combination would've caused the bar to try to bend at the end and not pivot in the bushing.

I do have urethane bushings. Im thinking this was the case. I put in an order for a new sway bar, Toby helped me out in record time.

I welded the existing sway bar back together on sunday, seems good so far. Tightened to the good n tight spec, not with my torque wrench now. Im taking it easier on the bumps and turns in the meantime till the new bar comes.

[Rich]

Not sure how deeply your welding could have possibly gotten into the bar in order to get anywhere close to original strength but if I were you I wouldn't take the car above 20-25MPH and maybe not even that. I think I'd park it.

Remember that the bar is the main longitudinal and rotational-load link to the front hub. Besides taking it easy on bumps and curves you shouldn't expect the welded bar to hold the hub under braking. And full braking's the hardest thing to avoid since you never know when you'll need it.

Glad to hear a new bar is on the way. Good luck in the meantime.

[Gfrank]

Is it just me or is that bar in upside down?

[Bitsyncmaster]

Is it just me or is that bar in upside down?

That was the first thing I looked at when the OP posted. It looks correct but the photo looks like the bar is not angled correctly.

I don't think poly bushings are any stiffer than the old hard rubber bushings I removed when I did mine. The poly bushings I used the metal pipe inside them is a lot thicker than the OEM pipe also.

[D Knight]

It does look upside down.


-D Knight-

[Josh]

stumbled across this thread.

As stated I welded the sway bar back together and threw it back on the car.
I have put many miles on my car since, including autocross, brake torques, and driving like an idiot in general. I also have upgraded front brakes. All these things would put the sway bar through its paces.

The initial issue was over torquing the bar I suspect. I just tighten it by hand now, not torquing it to the spec.

[David T]

A broken sway bar (anti-roll bar) is a very rare occurrence. Because it is so rare, the reason yours broke is probably due to something unique to your bar and the way it was treated on your car. Typically you do not see the sway bars zinc coated (galvanized) because it can affect it metallurgical. Without actually seeing it, it is very likely overtorqueing it was the cause. I would not have recommended welding it but it would seem whoever did it knew what they were doing. I would still inspect it regularly, both sides. Best case would be to replace it, it is a very important part of the front suspension and if it fails, can cause a bad accident.