Public forum, want to chime in also:

Not a mechanical engineer but my good buddy is a mechanical engineer working for Mazda, he fully endorses the function of the Rigid Collar.

 

Any reason why?

 

The loading of the subframe and the bolts cannot be simplified to simple shear or bending. The front subframe supports the lower arms, the steering gearbox, the engine, and the body. Think about the dynamics under braking...then under cornering loads...then under engine braking...then all of these things at once. Think about hitting a bump with both wheels, then one wheel. Think about the grip provided by racing slicks and wider tires and the loading that puts on the subframe. If you put 255 wide tires on a car that was designed with 205 wide tires on the front, you've increased the loading through the subframe. If you've thrown bigger brakes on or used more aggressive pads, you've increased the loading through the subframe.

The gaps around the bolts are where the displacement under max loading takes place. When this displacement at the gaps occurs, the welds get stressed and distort. For the mechanical engineers in this thread, this would be a red area on an FE analysis and we are talking very small amounts at the corners. The difference in "feel" is the reduction in the displacement leading to a more instantaneous translation of movement, whether it's steering or damping.

Thepoi is correct that you can't strengthen the bolt with a collar, but that's not what's going on at that part of the car. Assuming the subframe is properly tightened to the body by the correct clamp load on the bolt (comparisons before and after install are pointless unless you've ensured the clamp load is correct. The change in clamp load alone would be enough to make you feel a difference if the bolts are loose or have lost tension to start with), the load path does go through the welded sheet metal - which is where the distortion comes from. Under braking, you have weight transfer forward from the body and momentum. At the same time, you have the tire-road interface applying force in the opposite direction. Now apply the vertical component of the force with brake dive as the chassis begins to slow down. The bolted joints are in tension in opposite directions and the sheet metal between is being placed in shear. The shear in the sheet metal causes displacement/stretching, the tension on the bolted joints from the vertical component allows for the distortion at the gap as the load alternates. This is the type of situation the collars are aiming to correct. If you remove that gap, the displacement can't take place at the joints and the subframe becomes stiffer as a structure. I realize this is long...I apologize if I lost anyone

 

Dang. I priced one out on Nengun they asked for something like $100 shipped. I must have had a bad night or something. I'll try again!

 

If you do not put your car under a high load then these have no use to you. These are developed for vehicles who take corners under a high G and cause subframe shift, or when going off track subframe shift.

If you are just driving your car to your local parking lot to talk to friends, or cruising the canyons then these are not beneficial to you.

Yes, they do help. Yes, there is a gap that these fill.

 

Actually it is quite the opposite. You feel it more during your everyday drive vs. the track. The track is reserved for quality damper setups which makes me question why people don't put enough emphasis on.

 

Completely agree.

 

what about these on ebay?

http://www.ebay.com/itm/Manzo-USA-Fr...6e6a9f&vxp=mtr

 

Ooooo, those make the car safer in an accident. And they're blue!

 

If the subframe were that loose, I would expect alignments to be all over the place. Not once have I noticed my alignment numbers shift grossly after my initial setting.