How does IRS move?

[cop on my back]

Going from my 05 to the 15, I am wondering how the rear wheel moves when travelling up and down from hard cornering. The old straight axle was on an arc and wide tires would tuck up inside nicely. I am wondering how the IRS works and if the wheels travel straight up and down or if there is some negative camber introduced when the suspension is compressed.

A video showing the rear wheel would be great on track. Reason I ask is for putting spacers on while lowering the car. Yes lots of threads on whether or not certain combinations will rub or not, but I want to know how the wheel travels and have not seen anything on that.

That is my fairly ignorant way to try and explain what my brain is trying to understand.

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[Coaster]

Here is a graphic:

There will be a bit of negative camber under compression but it's mostly going to move straight up from what I've seen.

 

[cop on my back]

I've seen that, still doesn't tell me definitively. It does look like the wheel would travel straight up and down, but moving pictures speak volumes if you know what I mean. I am becoming intimately familiar with the IRS, as I am tearing mine all out of the car along with the entire rear cradle to replace the Diff bushings with BMR's set.

 

[Coaster]

Here is some video:

 

[jasonstang]

The H arm bushings are off set at an angle so the wheels don't move straight up and down. The rear wheels actually start to toe out as they go up to provide better handling.
The integral link is to stop the rear suspension from squatting when accelerating. And the upper camber and lower toe link is obviously to set static camber and toe.
The design of the rear suspension is almost a combination of double wishbone and semi-trailing arm combo. Double wishbone allows camber to stay the same while the wheels go up and semi trailing arm design allows the toe to change while the wheels go up.
For more information, look at this review.
http://www.edmunds.com/ford/mustang...15-ford-mustang-gt-suspension-walkaround.html

 

[cop on my back]

Thanks guys, I will check out that video when I get home, You Tube blocked at my work.

 

[cop on my back]

That doesn't show much. This what I am looking for as an example. This was my old 2005 on the track.

 

[Sharad]

Going from my 05 to the 15, I am wondering how the rear wheel moves when travelling up and down from hard cornering. The old straight axle was on an arc and wide tires would tuck up inside nicely. I am wondering how the IRS works and if the wheels travel straight up and down or if there is some negative camber introduced when the suspension is compressed.

A video showing the rear wheel would be great on track. Reason I ask is for putting spacers on while lowering the car. Yes lots of threads on whether or not certain combinations will rub or not, but I want to know how the wheel travels and have not seen anything on that.

That is my fairly ignorant way to try and explain what my brain is trying to understand.

In my opinion, you're WAY overthinking this. But the solution you're looking for is to look up a video of someone airing out their S550 on bags. You can easily see how the wheel moves when the suspension articulates.

 

[cop on my back]

Good idea. I just really like the look of a wheel flush or even a little proud of the fender but with my car destined for track use rubbing is a concern. I will look for bagged s550s

 

[Norm Peterson]

Here is a graphic:

There will be a bit of negative camber under compression but it's mostly going to move straight up from what I've seen.

Cliff's Notes version - for camber change under vertical wheel motion (aka "camber gain"), the shorter upper arm typically pulls the upper end of the hub carrier inward faster in 'bump' than the longer lower arm.

That description is most accurate when the lower and upper links are at least parallel to each other. Actual IRS front-view geometries differ, but the fact that the upper link arc is "faster" than the lower links' arc remains.


Norm

 

[Whiskey11]

Cliff's Notes version - for camber change under vertical wheel motion (aka "camber gain"), the shorter upper arm typically pulls the upper end of the hub carrier inward faster in 'bump' than the longer lower arm.

That description is most accurate when the lower and upper links are at least parallel to each other. Actual IRS front-view geometries differ, but the fact that the upper link arc is "faster" than the lower links' arc remains.


Norm

And to boil that down even further, the wheel/tire package will "tuck" in under the fenders on squatting. How much so is going to depend on far too many things and will require a healthy amount of testing with your individual car.

 

[Norm Peterson]

This site apparently doesn't allow .xls attachments, else I might try to post a spreadsheet animation.


Norm

 

[Sharad]

^^ around 1:05

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