Hi all:

I posed this question a few months ago about subframe welding quality.

So I took in my car last weekend to a local fabricator that does subframe connectors and roll cages.

My subframe connectors originally had really lousy weld quality between the connector plates and the body of my car. basically just a bunch of lousy spot welds between the plates and undercarriage. The guy I went to re-did all the welds with decent looking seams.

The difference in the ride was dramatic. The ride quality seemed to improve moderately but mainly the handling has been a huge improvement after getting better welds done.

The car can accelerate through the tight turns a lot better now -- it feels so much more composed. Going through a long sweeper, the car feels so much more like one manueverable piece.

Under hard acceleration, definitely has a lot less squat effect with the better welding. Seems to have less brake dive too. Nothing else was adjusted on the suspension before and after the welding.

As far as body roll is concerned, the roll coupling seems more balanced now. Meaning that the front end seems to roll about the same as the rear, whereas before the front end seemed to roll noticeably more than the rear. So basically the front end seems to be rolling less than before.

All I have still are just the stage 1 connectors.
The fabricator guy might put on a few extra plates between the existing ones and will likely make me an X-brace as well.

So for any of you that can manage to get subframe connectors, make very sure that the weld quality is good on the install -- Bad quality welding will definitely sabotage a lot of the positive effect subframe connectors can have.

Once I get the interior reasonably well damped, I think the car can feel quite good, even over the rougher pavement.

Before last weekend, I was strongly considering buying a new car. But literally my car feels that much better now, I might pass up the idea of getting something new.

 

Glad you're enjoying it! get the x-bracing when you can, makes a big improvement. Let's see how creative your fabricator guy gets with the x-bracing dilemma.

Jae

 

I would have never settled for the spot welds.

Glad to see you got everything straightened out.

 

I didn't know I had spot welds until a few weeks after I got the car done the first time.

What my fabricator was suggesting was to cut off the part of the plate that overhangs the OEM frame rail (the part of the plate that has the holes drilled in it) and then have it welded on three sides instead of just the front and rear sides of the plates.

My fabricator suggested that the outer half of the plates have some flex while the inner half is secure since its welded to the rail.

So the fabricator suggested that the convenience of having a bolt-on X-brace means sacrificing some of the rigidity it could offer.

So the trick is to weld on some X-brace that doesn't interfere with exhaust system removal -- which may or may not be possible.

?? Maybe do an X-brace just between the front and middle plates and perhaps a lateral brace between the left-rear and right-rear plates. ?? Basically have to find a way to fish-out the B-pipe exhaust through the extra bracing. We'll see.

 

Hmm... I"m not following what your'e saying about the x-brace. Can you draw a simple diagram?
Jae

 

I'm confused. Your saying the SFC's improve roll, dive, and squat? I thought all they did was stiffen the under chassis and didn't connect to the suspension at all? Can somebody explain?

 

That's exactly what I thought, but now I think there might be some corelation. Here's how I can explains this: (just speculating, you tell me if is BS or not) When the chassis gets temporarily deformed (flexes) during the change in speed or direction, chassis center of mass physically moves in the direction of applied force (change in weight distribution,) which results in more roll, squat and dive.

 

A flexy chassis f$cks everything up, so it's plausible to me that good SFCs could improve all those things, at least subjectively. The real test would be track times, slalom, lateral Gs, etc.

 

As a theory I can def see how they help. But would the added weight not contribute to more dive, squat, and roll (at least somewhat)?

 

the added stregnth and stiffening probably out weighs the added weight and imporves overall handling

 

No, because the extra weight is at the lowest part of the car, meaning it lowers the center of mass which HELPS handling. SFCs are pretty much the best mod for our cars, period.