control arm failure at the track this weekend

[S197MustangGT]

wow I have learned a lot about front A arms.

 

[Vorshlag-Fair]

Even Ford's OE arms probably aren't 100.000% failure-proof under track driving conditions, taken over the entire population of arms produced. But I would expect Ford's analyses to have gone a bit deeper into evaluations of any potential failure modes if only because the cost of such analyses can be spread out over more cars/parts and/or because of a larger database of experience to draw from to begin with. ...

Norm

Yes, there are tremendous forces at play in certain suspension joints. Even Ford had a rash of front spindle failures on the S197. Remember the autocrossers popping spindles left and right back in ~2009? I believe they made spindle design changes prior to the big chassis updates done in 2010-11.

The OEM front LCA and bushings and spindles have all been revised on the S197 chassis, more than once - so nobody is perfect. This lower control arm can never be too strong, as you never want to see a failure here. The risks are just too high for the potential rewards, in some cases like this. Sure, in a dedicated race car you might go search for "ones of pounds" by using a tubular LCA, but only if the car is carefully cleaned/inspected after each race and only if you're looking for thousandths of a second in competition. For a street car? A baffling potential modification, to me. Normally these types of crack/weld issues are slow to happen and start with cracks that can usually be found with frequent race-car inspections before total failure - but who knows in this case?

I am not a fan of substituting "lightweight" control arms in critical load paths like the front lower arm on the S197. I've seen tubular front control arm and K-member failures time and time again, all the way from the Fox Mustang days to today. There just have to be better places to "save weight".

Conversely, we've been looking at the front LCA on the new Subaru/Toyota FT86 (above) and wondering - when will this flimsy stamped sheet metal piece bend or fail? Looks very weak in stock form, especially compared to the thick factory S197 piece, and I suspect there will be HEAVIER than stock replacements from the aftermarket at some point. These might work fine with 215mm wide Prius tires, but put big R compound tires on there and I suspect it would bend eventually. Who knows - might not be a concern once these are raced regularly.

Anyway, just always stay skeptical and inspect your critical suspension parts between track/autocross events.

 

[ArizonaGT]

I know ford changed the bolt to a finer thread on the spindle bolts to counteract that problem.

 

[Norm Peterson]

Fine thread bolts torqued to 166 ft-lbs (vs 148), and I think the knuckle itself was thickened slightly (0.020" comes to mind). The intent of both was to increase the actual clamp load.


Norm

 

[Vorshlag-Fair]

Fine thread bolts torqued to 166 ft-lbs (vs 148), and I think the knuckle itself was thickened slightly (0.020" comes to mind). The intent of both was to increase the actual clamp load.


Norm

We even noticed a difference between the 2011 and 2013 GT OEM spindle clamp bolts...

Factory Strut-to-Spindle bolt on oue 2013 Mustang GT

The picture above shows the front strut-to-spindle clamping bolt from my 2013 GT. These bolts have an enlarged "unthreaded" load bearing section that is SPLINED and fits inside the spindle holes TIGHTLY. Has to be tapped in lightly. Maybe this was in response to the loosening bolts on the earlier cars? My 2011 GT did not come with these splined bolts, FYI.

Just a weird thing we noticed.

 

[ArizonaGT]

Looks like I'll be ordering the 2013 bolts next time I need to replace em. Do you happen to have a PN on-hand?

 

[Sky Render]

I really wish a Ford suspension engineer would troll our CC section and chime in from time to time.

 

[sheizasosay]

I went to buy the new bolts for an install the other day and I got the new strut bolts with the old nuts.......sucked. So I reused my old ones unfortunately. I won't be putting slicks on the car. Most my car will see is an "extreme peformance summer" tire so, hopefully I won't run into an issue. I should probably swap those bolts out when I get new tires.

 

[Napoleon85]

Are there new part numbers for the nuts/bolts? I might pick these up too if I can be sure I'm getting the updated ones.

 

[sheizasosay]

If u have ur car on stands I'd take what u got down to the dealership and make sure and compare them. The thread pitch is different. My dealership couldn't get it right even when I informed them before hand. Part # would be good.


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[OkieSnuffBox]

Is there nothing similar to www.realoem.com or http://www.jimellismazdaparts.com/
for the S197 where you can pick your year and look at the diagrams with PN and all that?

 

[19COBRA93]

I can only come up with two part numbers for the bolts/nuts. It shows 05-07/22/2008 is one part number. Then from 07/22/2008 is another part number which shows the same all the way through 2014 model year. It's just not listing that new knurled bolt. I'll keep investigating.

 

[Sam Strano]

The knuckle breakage was from loose bolts, not a problem with the bolt. I think it's pretty funny that they are changing things so much when all they need a nut that stays tight. The stock one does fine when it's new, or you use loctite.... But once it's been off, it won't hold without loctite. If it isn't loose, the knuckle doesn't get banged around.

Raced an early S197 for 3 solid years with up to 3 other drivers.. no knuckle failures. In fact I only know of two total and in both cased the damned bolts were loose causing the knuckle to bang around and failing it.

As for wishing someone trolled. They do. But shockingly since we as a group can't seem to agree on a lot, neither do they with some of the guys here. Everyone has an opinion and the internet let's the world know it--right or wrong.

 

[zquez]

Well, I bent my stock 06 A-arm in my press trying to remove the bushings today. I ordered the Ford Racing Boss 302S arms with the extended ball joint to replace them. I guess I'll order some new hardware for the spindle while Im at it.

 

[sheizasosay]

You sure they will fit?


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[SoundGuyDave]

I think you'll find the ball joint stud diameter is a wee bit different between the early and late arms. You have an early car, and the 302S is a late model... You'll most likely wind up replacing the spindles as well to make the swap happen.

 

[Napoleon85]

I think you'll find the ball joint stud diameter is a wee bit different between the early and late arms. You have an early car, and the 302S is a late model... You'll most likely wind up replacing the spindles as well to make the swap happen.

Good info. That kinda sucks though... How much are the spindles?

 

[zquez]

Well ill be damned. Fuck. You guys think i could ream the holes to make em fit? Im not financially prepared to buy another 500 dollars worth of.parts i already have.

 

[SoundGuyDave]

Napoleon: Honestly, I don't know how much the spindles are... I replaced one after my wreck (prophylactic purposes), but I went the junkyard route. Was around $100, IIRC.

Zquez: I know there's a difference, but I don't know how much of one, so I would hesitate to recommend removing material from a structural member without knowing how much of a difference it really is. I'd hit the junkyards and look for one that has the rear end demolished. You'd have to check to be sure, but I think the change came in with the 2012 model.

 

[zquez]

New from Ford, they are $403 for the right and $366 for the left.

I know that there can't be more than a few MM difference. I'll verify when the arms get here this week. The knuckle that gets tightened onto the ball joint is pretty beefy so I don't see there being an issue with enlarging the hole slightly if it doesn't fit right off the bat. 730 bucks is a pretty big chunk of change to blow on a part if I can avoid it. I'll post here for those curious onlookers of my findings.

I'm already a little peeved that the steel bent before the bushing separated from the arm. Hopefully these $300 turned $900 bushings don't cost me anymore money.