How bad/dangerous is this crack?

I finished installing my car lift in my garage today (Always wanted one and I am very excited!). Nothing like having a hoist... After I lifted my car for the first time, I noticed a crack in the lower front passenger side A-arm. It has probably been there for a while (maybe even since I bought it 2 1/2 years ago) and it will definitely be a winter project (together with some other projects).

My question is:How dangerous is this crack? I have driven my car about 5,500 miles since I got it and never noticed an issue. As I live in Michigan, and winter will be back in 3 months, would it hurt to still drive it around and make it a winter project, or is it a time bomb waiting to go off? I believe that I will be ok as long as I drive normal and don't push it. What do the "experts" here think? Thank you in advance for your contribution.
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Any crack in the suspension is dangerous in my book. I would replace it...tomorrow.

 

Risk assessment in a case like this is worrisome. You could be driving "normally" but a road hazard could take you out in a blink whereas with a correct A frame you may or may not survive. I am not a suspension expert but personally would consider myself given a gift of finding this out and getting it fixed before playing the odds game. Just sayin.

 

From what I can see it is not one of the common places to crack. To make that worse it is right at radius by both the shock/spring lower mount and the sway bar mount. Hard to imagine a more highly stressed part of the front suspension.

Park the car.

One lower arm and the time to install it just isn't that much of a bump in the road. Losing a wheel is.

 

The sound advice is park it, fix it. The metal is stressed, vibration and impact are going to destroy what is left in a short manner. If you don't do you own work have it towed. The car and money can be replaced but you can't.

 

It is toast. It is not just cracked ---- there is severe corrosion at the failure, and also appears to be some local buckling as well.

Just because you have put many miles on the car, does not mean the crack was present that whole time, either --- the crack itself could be much more recent, indicating that the arm may not be nearly as tolerant to this damage as that.

Few things are as potentially dangerous when driving a car as having a key suspension member fail ----- even worse than a brake failure or a tire blowout. Many a race car driver has been killed or seriously injured from suspension component failures.....at the very least, the cars often end up getting severely damaged from the uncontrollable accidents that can follow.

Replacing that arm is not too bad a job (good that it is a front and a lower, as opposed to a rear or an upper ), and you can likely find a good used one for under $300.

Please, please do NOT continue driving on it !

 

Listen to them! I've experienced a broken susp arm on the rear of my Pantera and I was driving slow in town and you have no idea what a car can do as unsuspected move. I was driving so slow I was Lucky enough that no damaged occur to anybody and the car had no damage at all but I couldn't move the car at all from where it broke. The 345 tire and Wheel were jammed in the wheelhouse. Imagine on the front driving just a bit faster.

Park the car and find a arm. Check all of them.

 

There's nothing a Duct tape can't fix.

 

I fixed mine with steel wire LOL!



But, Just to move it from where it was.

 

Thank you all for the good advise. I already bought a replacement A-arm on E-bay and will install it next week. I'm glad I actually got my lift, or I might not even have seen it until it would have been too late.....

 

Didn't you mention something along these lines in Forza?

I track my car a lot (as in for 17 years) and use different wheels with slicks. The grip is so much improved that my forearms are sore the next day when they used not to be with street tires.

Your article got me thinking and a little bit worried. I don't "think" I have a problem, but perhaps I need to get under there with a good light and start looking around.

 

Yea I did. It's easy for many of us to forget but these cars are getting old and some of them have been through a lot. Tires have improved so much that even with stock sizes we are stressing them more than ever intended. A tracked car really needs regular inspections of the arms, mounting forks and rear axles. They have all been known to break.

 

Park it and repair it, easier to fix now than after the accident.

Then check the other side with a big magnifying glass.

 

Tommy, Have you ever measured what lateral G force you are now pulling with modern R-comps?

I am curious as to how much lateral loads have increased over the years. When the 308 was new, Road and Track magazine measured 0.9 G in one of their performance tests. If modern tires up this to 1.0 G that would add 300 lbs additional lateral load.

I am not making this point to diminish the importance of frequent inspections but to express surprise at how small the lateral load increase seems and wonder if it is more the years of flogging that causes the failures.

It is remarkable how much tire technology has improved. I've got modern Bridgestone RE-11As on my car which undoubtably have more grip than R-Comps of yesteryear. I can't imagine getting much above 1.0 G though.

I am not a mechanical or tire expert, just a curious bystander.

 

Yikes!

Motivates me to crawl underneath and inspect everything.

 

Road and Track only got .81 out of a QV with far better tires than the original XWX's.
.9 out of a stock 308 in 1976 is pretty hard to imagine.
No one is suggesting it is the fault of modern tires. The point is at their advanced age and with hard or questionable histories some of these cars are being subjected to stress levels beyond that which was intended.

 

What you found shows why you must put our vintage car on a lift sometimes and inspect it:you did a great job with buying a lift.

My tip is to change it, as there is a big crack that could be very dangerous sooner or later even if it doesn't look to fail tomorrow: at least that is what i can understand looking at the picture.

So in my opinion it's a very intelligent winter project but i do not see the need to stop the car immediately, if you put just low miles on your car and do not stress it like on an handling race track and you don't drive at high speed on bumpy roads.

Please consider that just like an opinion based on a small low rez picture: my brain would say "change it immediately as it can affect your safety", while the engineer would say "it can go on a bit".


ciao

 

My real concern- were it my car- would be the apparent amount of corrosion that seems to be prevalant in the structural portions of the car, not just the a-arm. Again, were it mine, I'd start removing every bit of rust, road tar, and so on until I could see bare metal everywhere it counts. You can only do this by disassembling the suspension and so on. I would also consider pulling the engine , etc. This type of damage is extremely serious!

I assume the car's been driven where salt is used in the Winter...yes? Until you remove all corrosion and repair all corrosion damage, this car should not be trusted. Pretty much a major project but...

Cheers,
Rich

 

From the looks of your bushings, you may even want to consider doing all four corners. Yes, it's a lot more work and money, but...it might be a good time to replace that a-arm and refresh the suspension rubber, upper & lower ball joints, tie-rod ends, etc.

 

This man knows, call TRutlands or FerrParts and get one on the way!!!

I could loan you one, but you'd have to send it back..

The dent and the halo of corrosion tells me that was a road debris impact, knocking the OEM paint finish off, but you can also see the crack travelling vertically, since that initial event...IMO.

 

That's my read as well... and the way cracks work, they stay very small for a very long time, but once they propagate past a certain point they pick up speed very quickly. I wouldn't leave this till winter, even if the hypothetical impact happened long ago and the crack has been there a while.

The good news is that if it was started by impact damage, chances are it's a point problem and the rest of the suspension is good.

 

o.k., this is because of a broken fork -

but I would not take any risk with a crack no matter where in the suspension

.
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As I already ordered a new A-arm, I thought I'd try something with the old partially cracked one (just to experiment). I filled the crack with JB Weld and let it cure. Then I stressed the component by driving hard on rough roads, repetitively pushed the car through several hard corners, drove over rumble strips, slalomed the car and performed multiple emergency braking maneuvers (straight line full stop as well as emergency braking with sharp avoidance turns). I checked the part after this "abuse" to see if the crack had opened more and maybe grown further. I found that the JB weld in that area had fully held and nothing had happened to the crack it at all. I will leave the car parked now until I get the new arm, but I thought it was worth trying to see if I could make the crack grow. I am happy to report that I failed to affect it in any way.

 

Seriously?! That was one hell of a risky, high potential consequence experiment. I don't think you would find many mechanical engineers who would have supported that testing versus risk level... I would not recommend buying a lottery ticket any time soon, as you just used up all your luck for quite a while!

 

After all that, you're going to leave it parked?

If all that lunacy didn't concern you, why might a few hundred easy road miles worry you at all? Why be a woos now?

Ciao!

Hannibal