Whichever word describes the motion, and I believe on this site it was first used years back by well known guru, on a archieved aftermarket K thread. I have a hard time imagining how of all the distortions the K might be subjected to, that this one is often likely in real world HP driving, short of having one front brake fail, or hit a stationary pole with one corner if the car. Bottom line, its not a very high concern on my list, yet.

However, 10? years ago, 245 was considered really wide front tire, 295 was recently considered a wide front tire, where as mentioned, 315 is current holy grail. Regardless, any structural improvement found thru the testing suggested, should likely show an improvement on any size tire, just some more then others.

I'll be honest, I've only seen a couple stock, factory suspension/k frames fail. One was an upper control arm ripping out of the mounts on a 73 duster, another was a lower control arm actually bending, though it's possible the driver hit the rumble strips on the interstate, which likely caused it. And the only other one i can recall was a drivers side engine mount ear ripping out of the k frame but the charger was pretty rough so likely the k frame was as well. but that's all i can recall having seen. Other than a few ball joints ripping out here and there as well, most of the time because the shop the owners used were idiots and pressed the ball joints in instead of screwing them in.

seems to be plenty of fast(er) 3500lb cars on way less than 315's...

Goody, I have a couple tons of bar stock and heavy flat stock at home. It wouldn't be hard to put together a rig like your model. That was what I had in mind.
Load testing for the engine weight could be done using an inverted stand. Simple hydraulics could apply the load measured using my proving ring. I have the general Dynamics calibration sheet on the ring that defines loads to 5500 lbs in 50 lb increments. The proper rig would allow testing deflection in heavy cornering due to engine weight as well.

My other gauges and instruments could measure deflection down to .0001" in multiple places.

In my opinion, some tests should demonstrate the strength of the K frame separate from the chassis. Any deflection would show additional load placed on the chassis.
The K should stand on it's own as much as possible and not rely on a relatively flexible chassis for support.

Thoughts?

K.I.S.S.

One thing to consider, looking at most, if not all, the aftermarket MII based K members out there is that the inner LCA pivots are not nearly as well braced as the factory K member. I suspect over time usage will spread those inner pivots outward.

That can be tested rather easily.

These tests would not be destructive in nature unless the frame is substantially under built and fragile.

I'm not interested in testing them to failure. That makes for good video but that's about it. Simple deflection tests would be sufficient. The assemblies should have the ability to deform slightly and return to their original state.

The fun part of these kinds of tests are when you use a long lever arm to apply a load (like Goody's example). The end of that arm can sweep a pretty wide arc.

Years ago, I was present for frame testing on light duty trucks. You could use the Toyota frame like a diving board.

Ya'll need to do this. And get it in a magazine. With as many K frames as you can get your hands on.

I would be looking at tires in the same size range as the new Mustang GT 350 if I was buying some for a car now, 295/35/19 front and 305/35/19 rear. on 10 and 11" rims.

*thread diversion*

I for one am not sold on wider always equals better. Data points:
- Corvette road racers on hoosiers - faster on some tracks with 275's square vs 315's square (275's faster on high speed tracks).
- Tom - faster on 275's square with a better compound vs 285/315.

My current line of belief:
-tire compound matters most
-tire temperature matters second
-tire size matters last

So sure, wider is better, but only if you get the first 2 right.

I also think R compound tires may 'buck the trend' a bit past a certain point. Whereas 200tw tires hold the rule a bit better.

Z28: 305/30/19 square
GT350: 295/35/19 front, 305/35/19 rear
GT350R: 305/30/19 front, 315/30/19 rear

305/30/19 is a good price in the RS3. Want.

Could you fit a 305 on the front?

I'm up for it if they are.

Probably. But could I turn? Who knows, haha. Started playing with fitment last night. I need to get my hands on a 1.0-1.5" wheel spacer to check fit. More than likely it'll be too much of a compromise to run it. We'll see though.

I've used stacks of washers on three lugs as temporary spacers to check fitment. Works better than buying a bunch of different spacers to test fit stuff.

I keep meaning to try the 285/35/19s off my Mustang an the front of my Valiant, might try in in a few months when I put the winter wheels on the Mustang. I would guess that that would be about as big as you could hope to fit without beating the front fenders out.

Studs aren't long enough for 1"+ of spacer. I tried! Ha

I based my tire suggestion mainly on whats available in a 200TW. A 305/30/19 is actually pushing it on an A-body already. BUT, those on an E or B body should be a breeze.

A picture is worth a 1000 words