Sub-frame connectors... Please build them correctly!

FISHBREATH said
For what it's worth. Not more than a few years ago, I saw a test done on the net somewhere. It was essentially a static load test to evaluate body torsion. If I remember correctly, the rear frame rails were anchored to the test bed at about the axle location. A fulcrum was built of steel and the K-frame rested on it. The apparatus was elevated such that the tires were not resting on the floor. The techs then began hanging weights from one corner of the front frame rails. They measured frame rail deviation between right and left sides with every weight that was applied.

They did the first test with a unibody car without frame rail connectors. The second test was with front-to-back frame rail connectors (welded). The third test was with connectors also welded to the floor sheet metal.

They graphed the results. The amount of twist in a normal unibody was ridiculous. (Twisting the body absorbs energy from the drive train.) Second best results came from the end-to-end connectors - the results were dramatic. The third test with the welded-to-floor connectors showed a further improvement.

I just wish I had the sense to save that test at the time.

Here is an interesting thread by some road racers:

http://www.pro-touring.com/threads/23278-What-do-sub-frame-connectors-really-do

I would love to see actual scientific evidence of one connector being better, since this thread really has nothing but opinions and wild *** guesses posted so far. Even if it's only a single type of test, which most should know wouldn't be definitive in all situations. I know XV did some testing awhile back when they were showing how much their products stiffened the Mopar uni-body chassis. I know they had some pretty fancy charts and graphs on the subject, but I don't recall them testing other types of connectors. And of course, they weren't exactly free from bias, since they were trying to sell their connectors, which I seem to remember were the weld to floor type.

Regardless, any frame connector is better than none. The idea that non-floor welded subframe's aren't good, or aren't the "right" way to do it is just completely asinine. I'm personally not convinced that the floor welded types are always stronger. I'm sure in some cases they are- the mopar performance "bolt in" connectors, even if welded in at the ends, are pretty small in cross sectional area and wall thickness. And even they're a big improvemnt over stock, there's plenty of people on this very site that are more than happy with the MP connectors. But most folks now are using 3x2" tube with a fairly thick wall. Not to mention other real world scenario's, like some people only stitch welding the weld-to-floor connectors because of poor fit, poor welding, or simply not wanting to do that much welding upside down under your car while eating welding slag for hours with your car up on jackstands if a lift or rotisserie is out of your budget.

The best way to install frame connectors is the way you can do it. If that means buying the little Mopar Performance bolt-in connectors, bolting them in at home and having them welded in at a muffler shop because that's your only option, then that's still a huge improvement over nothing. And its just as "correct" as any other way to add subframe connectors.