They hold the stops so the seats won't go off the sliders.

John O

Yes, John is correct. It holds the limit on the primary slider keeping it from sliding too far.
Sorry, I would have answered earlier but I'm not receiving any notifications from CC.
Larry

Many thanks to both of you for clarifying this to me:)

Looks like a limiting stop, to limit for and aft travel.
Gary

tracks
 

Now a solution needs to be developed for preventing cracks in high horsepower cars at the rear of the lower track (the portion that bolts to the car) where has kind of a notch as it necks down to essentially a flat plate.

Sorry Mike, you're on your own for mods. We were trying to get as close as possible to original as they came from Chapman. Literally so exact that you couldn't tell the difference between an original and ours. It's what we shoot for with everything we've done.
Larry

I agree any effort to make new ones should be focused on originality, but there is probably some add-on pieces that may help the problem. For example, a stiffener of some sort under the tracks may help, ideally combined with some secure way of retaining the lower track onto the stiffener, as I suspect a lifting/vertical force toward the back during braking may be a factor.

Is this an issue happening often to tracks on 427 Cobras? We had a couple sets for reference, one from a Cobra 427 but they weren't cracked or deformed, just rust and pitting. One thing we did see was the metal strip holding the rollers was bent, keeping the rollers from rolling.

Larry

cracks
 

I've personally seen or aware of around a dozen instances; and I'm not even in the business. Most people probably don't even know theirs are cracked. I bet someone like McCluskey must have seen hundreds...

Interesting! I can see why at that spot as it's the weakest place. Without thinking about it much, a strap could be welded around the track to strengthen it I suppose. It would take away from the originality of course but would be on the bottom.
Personally, I think the way to deal with it would be to throw away the 50 year old tracks and buy a new set!:D

Larry

The OE tracks are made from period British Butter. If the lower track fasteners get loose, or were never tightened properly, movement will work harden.. then crack them. I suspect that’s 100% of the problem. If they are bolted down properly, nice and tight, no cracking.
It historically has been a PITA to properly tighten the lower tracks on both 289 & 427 cars. Many original owners half assed it. I have seen that in person.

weakness
 

I will add to the speculation with a general observation that the design at that area is so poor that I suspect it will be hard to completely eliminate the cracking for the more extreme usage applications. Think of it as a cantilever beam where the fixed end where it meets the center thick part of the track has a geometric discontinuity with reduced bending stiffness (look at how you even lose the inward wrapping flange there). Changing the outboard end constraint (more rigidly tightened bolt) or even material strength will only have a marginal effect. I assume these tracks are not heat treated after forming, so there probably isn't that much difference in the material properties for them to be formable without cracking. Also, you can only get the bolts so tight, as I recall you're going through the carpeting and the original square tubing there crushes easily. The best that can probably be hoped for is incremental improvements across multiple attributes described that may add up to enough improvement to keep the problem at bay. The ultimate solution may be something like a stiffening plate that bolts under the track with flanges that wrap up on each side to dramatically increase bending stiffness, combined with some way to capture the upper corners of the track on each side. This way it could be removed for when cars need to be aesthetically correct like going through the auction block.

I guarantee I can fix the issue with a material change alone. But you couldn’t afford them when done. Then the conundrum of a design change. Then, why have a Cobra? Go buy a new Ford GT. No seat tracks to deal with.