Subframe bushing?

[drop360]

I saw this on a Fiesta forum - http://www.stiffring.com/

Looks like they have a kit for the Demio/2. I was wondering if anyone had seen or used something like this (on their 2 or other car).

-Matt

 

[Racebrewer]

Hi,

Had anyone tried it on their Fiesta? Results should be pretty similar.

I believe someone else makes one for the M2. Perhaps Cusco?

It should make the handling a little more precise with an increase in noise and vibration. I think that it would be the last thing to do after all the strut bars.

John

 

[Mazdamatic]

if its like motor mounts expect better handling with lots more vibrations and noise. id be down to try these if they get good rep on other vehicles.

 

[Racebrewer]

This weekend I installed a front sway bar on the 2 and had to take the front subframe bolts out and lower the subframe. Basically there are no rubber bushings in the 2 (much to my surprise).

The two big bolts in the rear of the subframe bolt the subframe solidly to the body. As long as those bolts are tight, there is no subframe movement. I don't think those bushings will actually do anything.

Interestingly, the holes in the subframe are huge compared to the diameter of the bolts. If those bolts loosen or the subframe shifts, I can see the possibility of problems. Odd thunking noises and front end alignment issues.

John

 

[zoomerang2]

This weekend I installed a front sway bar on the 2 and had to take the front subframe bolts out and lower the subframe. Basically there are no rubber bushings in the 2 (much to my surprise).

The two big bolts in the rear of the subframe bolt the subframe solidly to the body. As long as those bolts are tight, there is no subframe movement. I don't think those bushings will actually do anything.

Interestingly, the holes in the subframe are huge compared to the diameter of the bolts. If those bolts loosen or the subframe shifts, I can see the possibility of problems. Odd thunking noises and front end alignment issues.

John

After looking over the info on the link, I think that is exactly what the "stiff ring" is actually made to address, it will center the bolt in the larger diameter hole of the sub frame.

Currently the situation that you described if the bolts loosen (even a small amount) is correct, the sub frame can shift relative to the body, which can affect the handling. This may actually happen to some extent even if the bolts are tight if there is enough load on the joint.

If these bushings are installed, then theoretically the sub-frame/body alignment will stay the same even under heavy loading such as hard cornering.

I am not sure how much effect they have on the 2, but if they were stateside I would probably look at buying them myself, depending on the cost of course...

 

[Racebrewer]

Correct and good points. "If" the bolts loosen. At 15,000 miles of uh,,,,,, enthusiatic driving, mine showed no signs of loosening. YMMV, of course. If they do loosen, a tire shop alignment may also be required since the subframe will move in relationship to the body and top shock mounts. That may account for the off center steering wheel in another thread.

Interestingly, my two big subframe bolts were not centered in the holes. One was centered and one was off center a fair amount. I think that Mazda is using the large holes to take up cumulative manufacturing tolerances in the body and subframe.

I may throw a piece of aluminum bar in my lathe and make up a tapered 'crush' washer and put that on the centered bolt. That and Loctite and 90 ft-lbs of torque should work.

Also, before I dropped the subframe, I put 'witness marks' (black Sharpie and white paint lines) on the subframe and body to make sure that it went back to where it was.

Might be a good place for structural adhesive (between the body and the subframe). Hhhhmmmmmmm..........

John

 

[zoomerang2]

I think that Mazda is using the large holes to take up cumulative manufacturing tolerances in the body and subframe.

That would make sense from a manufacturing standpoint, and may be a good reason to look into fixing this.

I may throw a piece of aluminum bar in my lathe and make up a tapered 'crush' washer and put that on the centered bolt. That and Loctite and 90 ft-lbs of torque should work.

Nice, that would be a quick solution if you have the capability. Theoretically it would only take the inner (between sub-frame and body) bushing to minimize any shifting of the sub-frame positioning

Might be a good place for structural adhesive (between the body and the subframe).

And that may be an even cheaper solution... (thumb)

 

[Racebrewer]

"Theoretically it would only take the “inner” (between sub-frame and body) bushing to minimize any shifting of the sub-frame positioning"

I may go with the "outer" instead. The bolts clamp the subframe to the body and I wouldn't want to mess up that 'sticktion' by putting anything in between.


Re structural adhesive: "And that may be an even cheaper solution... (thumb)[/QUOTE]"

Yah, but you'd never be able to get to the rack or front sway bar again<LOL> At least without a blowtorch and a big pry bar.......

John

 

[zoomerang2]

Theoretically it would only take the inner (between sub-frame and body) bushing to minimize any shifting of the sub-frame positions

I may go with the "outer" instead. The bolts clamp the subframe to the body and I wouldn't want to mess up that 'sticktion' by putting anything in between.

John

I understand what you mean, if your are concerned that the washer will reduce the surface area contact between the sub-frame and the body and reduce the overall clamping force from the stiction ...you could have a point.

However, I was thinking that if the bushing (between the body and subframe) protrudes into the body bolt hole AND into the sub frame bolt hole, taking up and slack in the gap between each hole and the bolt, it would be impossible for the sub frame to move relative to the body since all the play would be removed (assuming a perfect fit from the bushing)

Anyway, just a thought.

 

[Racebrewer]

Good points and a good idea. I can turn the necessary steps in an aluminum bushing without any issues. Probably every subframe is a little different though due to welds and assembly positioning. It may be a "one at a time" manufacturing process.

Installing the front sway bar was a 'Bear' and a knucklebuster, and I'm probably just cringing at the thought of dropping the subframe again.<LOL> IMHO, Racing Beat's instructions were a little optimistic in how far the subframe would have to be dropped.

I was surprised that the subframe wan't pinned in any way.

The next time I'm under there...............

John