ALFAGTV6.COM

I think it's because Jim is trying to avoid major surgery so opening the chassis member is not an option.

Maybe he can partially strengthen the U by drilling at least 2 holes at then ends and weld a few strong stainless rods, the chassis member and U together. Minimum is 2 rods per U. The rods should be wide enough so that the pressure point isn't so concentrated

Not exactly ideal, but he can do this relatively quickly. I still think the U without a proper top to close the U is not so good, even with the rods.

Your solution is a lot better, but also requires a lot more effort.

I would definitely prefer to avoid surgery... Seeing how almost nobody else has had similar failures, I am more and more inclined to think its a fastener problem (saves me a bunch of trouble, too! ). Alfa bolts are M12x1.25, 120mm long. However, they cannot be used as ~13mm more total length is needed to accommodate the longer conical LCA bases (now 27.5mm long for increased camber), 5mm for the stiffener and ~3 for the large washer. So, no 1.25 thread commercially available in length >120mm. Now this is important: The Alfa all-metal self-locking 1.25mm pitch nut used has 10mm of useful thread, while the nylon 1.75mm pitch self-lockers I used have <8mm, the rest being plastic. Again, since this failure seems to be very rare among a crowd using (and abusing) their cars in a similar way, this nut thing may be the star of everything! Cheap solution: Use grade 10.9 bolts, tighten with one std nut followed with a proper all-metal self-locker on top of that -all to increase clamping length. No configuration change, same stiffener placement. Drive the pi$$ out of it in our December trackday and re-inspect carefully immediately after that to check for possible thread damage in stiffener area. All in all, a lazyman's fix! If it fails again... we'll get serious.
Titanium is a nice thought but I believe it's not stronger than steel when dimensions are the same -correct me if I'm wrong.
Jim K.

75,

Don't get too excited about using stainless on something like this. Welding stainless and carbon steel together can be done using the right electrode, but it isn't all that strong and takes a fair bit of heat to accomplish....difficult to do on stamped sheet metal.

JK,
If that "U" is welded all around over top of the frame rail it will act as a doubler and make that section of subframe much stiffer and give a good base for bolting in the cross piece. Drilling some holes in the "U" before installation and plug welding will help also.

That cross piece looks to be about as stiff as a wet noodle!

If I remember right, the stock arrangement had a lock washer under the nut.

Oh, almost forgot, use washers with the same strength rating as the bolts or they will deform under load.

hth,
Scott

All these talk about complex bracing, welding...in the end "hey I'll just buy new a new pair of nuts"

I think if the same bolts have been re-used with better nuts, that means it was the locking nuts that were defective. The threads stripped out.

A lot of talk/solutions.
But no feel for the real forces generated with your brake upgrade....

Let's see... Would a g-meter deceleration figure be good for you? I can hook up the G-Tech RR one of these days (after bolt/nut replacement) and do a few hard stops from ~160kph without tire lock.
Jim K.