Upgraded the IRS Cobra suspension with Poly and more

[z06killa]

as for the tech, I can't help but notice how much more convincing you are when you're not personally bashing another member... you've gone from " some troll" to "I hope he tells us more"......

so, was that video filmed with oem or poly bushings?
do you have any videos with the UHMW bushings?

That particular video was shot by a Full Tilt Boogie Racing customer that was going to do before and after videos for us. This video was shot with the OEM rubber bushings in the lower control arm. Similar deflection of the control arm would result with a poly bushings. This customer was also going to do an 'after' video for us as well but ran into some personal issues and ended up having to sell his car without installing the Delrin control arm bushings. We hope to some day shoot a video with the Delrin bushings in another car.

Control arm deflection is the axis of evil for drag racers, road racers and anyone that likes to corner carve with their car whether it be canyon roads or freeway cloverleaf on and off ramps.

SRA or IRS will have the same effect ...

CMC cars, even with a mere 260hp, are having issues with tearing up the factory torque boxes. Even with the reinforcement kits. There is a petition to allow the Mustang chassis the Wildrides Battle Box, but all the adjustability will probably keep it out of the rulebook. The factory rubber movement is not ideal in a race car, but there has to be a balance.

The problem is that when you add stiffer bushings to any suspension piece, its sister pieces/bushings end up taking more of the deflection. Eventually the damage will start to tear up pick up points, specially if you have no give in the suspension, like delrin or aluminum.

Unlike the thin layered sheet metal in a torque box, the IRS subframe is a significantly stronger assembly. You will NOT see control arm mounting point issues on an IRS subframe that you see in a chassis torque box for an SRA.

 

[white95]

z06killa

Does rotational force have any effect, in any capacity, on the irs subframe which would transmit to the torque boxes?

 

[z06killa]

z06killa

Does rotational force have any effect, in any capacity, on the irs subframe which would transmit to the torque boxes?

Unlike a SRA, where the forces are going directly from the driven axle to the torque boxes via the control arm, the IRS has the subframe to spread the load of the driven wheels to all four of it's mounting positions. The control arms on a SRA need to articulate to the chassis, not so with the IRS. With the IRS, the subframe is mounted rigidly and held in a fixed position in the chassis. Articulation is handled through the control arms to the subframe on an IRS and not directly to the chassis.

 

[white95]

Makes sense, thank you.

 

[cobraracer46]

Seeing you want tech MustangChris, let's take a closer look at control arm deflection from those crappy OEM rubber bushings that Ford installed in the Cobra IRS. This condition would also be manifested with some cheap assed aftermarket poly bushings in the same manner, I don't care who you get them from. This is what would happen to the poly bushings that the OP installed in his IRS.

Since Zo6 did not provide us with any numbers for the above untrue sales pitch for his bushings, I'll throw in some numbers to debunk it. As a review, recall that in this thread I listed a "Shore D" scale that rates a material's resistance to deflection. The shore D rating of the factory IRS rubber is below 40. Poly suspension bushings top out at 70. The shore D rating of Delrin is 83. Therefore, Zo6's notion that poly will "deflect the same amount as poly is simply untrue when the numbers show that poly is significantly stiffer than rubber and almost as stiff as delrin. Not what ZO6killa want's to hear, but it is what it is.

This is why our position is OEM rubber and aftermarket poly bushings have no place in a Cobra IRS. Anyone that actually puts poly in an IRS will eventually regret it.

Suspension optimization is paramount on a vehicle regarding handling, car control and cornering efficiency, particularly when suspension is as inefficient as an IRS. An IRS is twice an inefficient as a front suspension because it has twice as many control arms. It is WAY more important to 'fix' the IRS when compared to the front suspension of a Mustang.

Once again, where is your engineering data and numbers to back up the above sales pitch? You keep saying that the IRS is "twice as inefficient as the front suspension." How did you measure this so called inefficiency? What scale did you use to define it?

 

[MustangChris]

i didnt see a sales pitch in either of those posts....


i think it would be best for you two to take your egos and wiener-comparing-festival to PMs and stick to tech......


I have yet to see a sales pitch here.

 

[MustangChris]

Additionally, Z06's concept was that UHMW bushings have stronger rigidity as compared to rubber and many poly(s). Which is true. (I should know because I sell plastics and rubbers.)

Then you follow it up with "he's wrong" then regurgitate exactly what he said with a scale involved. .....






I dont understand you two. I dont understand if you two are the same person who just forgets to take his medication... I dont understand what each of you is trying to accomplish.... All I understand is how much I utterly cant stand you two. You're driving me nuts. I'm not one for pointing fingers at my members, but for the love of everything holy........

 

[cobraracer46]

i think it would be best for you two to take your egos and wiener-comparing-festival to PMs and stick to tech......

It would be fun to battle it out with Zo6killa in the road rage section, Mabye after all the dust settles from the road rage battle, he can see the light and switch over to poly. Since this my thread about IRS tech, I would like to keep this thread going so what else can I talk about? how about IRS brake upgrades?

I recently installed some Brembo components and I'm almost ready to to a complete how to on it, but for now, here is a quick preview on it.

For many years, my 2001 Cobra has benefitted from the ipmroved stopping power of a Brembo GT big brake kit on the front. The Brembo parts I installed in the rear wont work with the stock PBR Cobra front brakes. The Larger Brembo F50 4 piston caliper is a required in the front if a Brembo "lotus" caliper is going to be used in the rear.

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Meanwhile, the IRS still had the stock brakes.

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After many years of planning and collecting the nessary parts, the the rear brakes would finnaly be upgraded to a level that closely matched that of a super car rather than a mustang.


The parts I used to upgrade the rears


Brembo parking brake calipers.

Brembo 4 piston "lotus" type calipers commonly used on rear big brake kits.

328X28MM two peice rotors

From Maximum Motorsports, I sourced the mounting brackets for the custom brake lines that Technafit made for me.

Next, I fabricated my own mounting brackets for the calipers

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all of the Brembo parts mounted up

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Not much left to do other than to bleed the rear brakes and go out on a test drive.uttahere:

 

[white95]

Therefore, Zo6's notion that poly will "deflect the same amount as poly is simply untrue"

This is why we shake our heads reading through your posts... :deeplist:

 

[RichV]

Or battle it out on the race track.

 

[white95]

We all hope to win the lottery too lol

 

[z06killa]

Enjoy your forum guys.

 

[white95]

Damn, no good irs tech?

 

[ttocs]

I heard drilled rotors are more likely to crack?

 

[cobraracer46]

I heard drilled rotors are more likely to crack?

I installed drilled rotors on my car in 2007 and no cracks yet and I recommend them simply because they look nice.:grin:

 

[MustangChris]

at what point is bushing deflection a problem? I mean, most of our cars dont hit the track every day. ya know? how "bad" could they really be?

 

[MustangChris]

I heard drilled rotors are more likely to crack?

they are.

hairline cracks from hole-to-hole and hole-to-edge are not uncommon. The time to worry is when they get large enough they start to go through the rotor.

 

[cobraracer46]

at what point is bushing deflection a problem? I mean, most of our cars don't hit the track every day. ya know? how "bad" could they really be?

For the IRS, bushing deflection can become a problem with the differential support mounts in that under hard use, the OEM rubber diff mount bushings will allow the IRS pumpkin to move enough to break the diff cover.

The solution to this problem is to replace the the front and rear OEM rubber mounts with Maximum Motorsports Poly diff mount kit. The poly diff mounts are many times stiffer than the OEM rubber, but they will not transmit any gear noise or other clunk and slam noises into the passenger cabin like aluminum mounts would.

Running aluminum diff mounts on a street driven mustang cobra would be a huge mistake as a significant amount of gear noise will be transmitted inside the car when using aluminum diff mounts.

When replacing diff mounts, always run the same bushing material in the front and rear to avoid breaking the diff cover.

 

[MustangChris]

yes yes yes. we've all heard your MM pitch...

how often does this "IRS Explosion Fiasco" occur, i guess was my question. Obviously on a drag car there's cause to be worried, but what about a street-driven car that never sees the track

 

[cobraracer46]

they are.

hairline cracks from hole-to-hole and hole-to-edge are not uncommon. The time to worry is when they get large enough they start to go through the rotor.

Brembo Gran Turismo front brake kit I installed in my car in 2007 and even today, there the rotors have no cracks.

I'm a big fan of drilled rotors although scalloped rotors look good too.