Is an IRS swap SM legal (auto-x)? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 13 Old 12-13-2010, 02:00 PM Thread Starter
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Is an IRS swap SM legal (auto-x)?

Just like the title says, it is legal to drop a Cobra IRS into my 96 Cobra?


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post #2 of 13 Old 12-13-2010, 06:27 PM
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Rules say minor modifications can be made to facilitate allowed modifications, so I don't see why it wouldn't be legal.


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post #3 of 13 Old 12-13-2010, 08:55 PM
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I don't know if it's ever been resolved, but post 9 here highlights the potential problem area with the rules: https://forums.corral.net/forums/show....php?t=1246441
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post #4 of 13 Old 12-14-2010, 09:33 PM
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Quoted by MFE, praise from Caesar...

Quote:
Originally Posted by RollCamberCoef View Post
The potential problem with an IRS into a 94-98 is the rear IRS brackets. The rear frame does not have the blind nuts for the vertical bolts that the 99+ rear frame does. For a 94-98 car, one has to figure something out i.e. welding the bracket on or using extra long hardware and drill through the trunk floor. These problems exist for <94 cars but that swap would be 100% illegal in SP.

To my mind, SM and SP have different mindsets regarding what is legal. While I'm certainly not on any commitees, SP trends toward the rules as being black and white, IE you can only do what it says you can do. SM on the other hand is much more open to the gray, IE you can't do what the rules say you can't do, otherwise have fun with it. The linked post is intended only to point out the area of possible contention. I do not make any rulings either way.
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post #5 of 13 Old 12-14-2010, 09:52 PM Thread Starter
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Thanks for weighing in...I met Doug Gill at PRI last week and he said email me any class/build related questions...so, when he answers my email, I'll let everyone know.

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post #6 of 13 Old 12-15-2010, 12:31 AM
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well i have a 95 gt with a swapped 04 IRS. i run in ESP. as does my dad who has a 01 cobra. they said it was legal because you can update or backdate like models. so basically i could put a 4v in my car or a 351 with gt40 top end because the cobra r is also in ESP. so i dont see why it would be a problem in SM.

Got some stuff bolted on.. Some more stuff welded in.. Some rubber things that stick real good.. You know.. The norm
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post #7 of 13 Old 12-15-2010, 12:54 AM
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The problem comes from some type A, winning is everything even thought I only win a little sticker lawyer guy loses to an IRS's '95. Then he finds some minute, not really important detail to protest. The question isn't really if it is legal, instead it is would it stand up to a protest? While those should be the same thing, the bitch of it is that they are not.
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post #8 of 13 Old 12-17-2010, 10:06 AM Thread Starter
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It's Legal with stipulations...

We can swap an IRS from any Cobra (99-04) because the street prepared rules couple all SN95s together:

ESP
Mustang (SN95 chassis, NOC
including Cobra & Cobra R)
(1994-2004)

AND

15.1 AUTHORIZED MODIFICATIONS
C. Equipment and/or specifications may be exchanged between different years and models of a vehicle if (a) the item is standard on the
year/model from which it was taken, and (b) the years/ models are
listed on the same line of Appendix A (Street Prepared Classes). The
updated/backdated part or the part to which it is to be attached may
not be altered, modified, machined or otherwise changed to facilitate the updating/backdating allowance. Standard factory installation
methods, locations, and configurations are allowed.
The updating
and/or backdating of engines, transmissions, transaxles, and/or unibodies must be done as a unit; component parts of these units may
not be interchanged. Cars not listed in the Street Prepared sections
of Appendix A may not be updated/backdated until approved by the
SEB and published in the official SCCA publication.

Note the underlined statement, Doug said that this means that you may attach the IRS in the exact same manner as a 99 – 04 would have gotten from the factory, meaning bolt in, NOT WELDED. From what I remember, you have to drill a hole or something like that...

So, this is cool news. Yes, the IRS is somewhere in the neighborhood of 85 lbs. heavier (in the right place I might add) but a LOT less UNsprung weight. With the right bushings, bumpsteer set and some tuning, it would seem the IRS could be really fast.

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post #9 of 13 Old 12-19-2010, 12:26 PM
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It will be interesting to see how the swap works out, on the clock. Solo surfaces tend to be smooth, but the transient is pretty severe...hmmm, does the lower unsprung benefit outweigh (no pun) the increased total?? In any case, it will be nice to be able to put an alignment in the rear, without resorting to tweaking axle tubes...which I (personally) think is illegal, even though it appears to be done pretty often.
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post #10 of 13 Old 12-20-2010, 05:46 AM Thread Starter
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Quote:
Originally Posted by tigerdrvr View Post
It will be interesting to see how the swap works out, on the clock. Solo surfaces tend to be smooth, but the transient is pretty severe...hmmm, does the lower unsprung benefit outweigh (no pun) the increased total?? In any case, it will be nice to be able to put an alignment in the rear, without resorting to tweaking axle tubes...which I (personally) think is illegal, even though it appears to be done pretty often.
It is interesting. It seems that lots of people have done the swaps, but no one that is really 'competitive' has done any real testing. Not that I'm a pro, but I hope to get out there and doing some good testing with my friend's traqmate and then look for a good deal on a 01+ IRS. Once I get it, I can get the bushings and install it and hopefully have another round of testing with the traqmate.

I like the idea of having less unsprung weight and being able to dial in an alignment in the rear...


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post #11 of 13 Old 12-22-2010, 02:28 PM
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Quote:
Originally Posted by dpspeed View Post
We can swap an IRS from any Cobra (99-04) because the street prepared rules couple all SN95s together:

ESP
Mustang (SN95 chassis, NOC
including Cobra & Cobra R)
(1994-2004)

AND

15.1 AUTHORIZED MODIFICATIONS
C. Equipment and/or specifications may be exchanged between different years and models of a vehicle if (a) the item is standard on the
year/model from which it was taken, and (b) the years/ models are
listed on the same line of Appendix A (Street Prepared Classes). The
updated/backdated part or the part to which it is to be attached may
not be altered, modified, machined or otherwise changed to facilitate the updating/backdating allowance.
Standard factory installation
methods, locations, and configurations are allowed. The updating
and/or backdating of engines, transmissions, transaxles, and/or unibodies must be done as a unit; component parts of these units may
not be interchanged. Cars not listed in the Street Prepared sections
of Appendix A may not be updated/backdated until approved by the
SEB and published in the official SCCA publication.

Note the underlined statement, Doug said that this means that you may attach the IRS in the exact same manner as a 99 – 04 would have gotten from the factory, meaning bolt in, NOT WELDED. From what I remember, you have to drill a hole or something like that...

So, this is cool news. Yes, the IRS is somewhere in the neighborhood of 85 lbs. heavier (in the right place I might add) but a LOT less UNsprung weight. With the right bushings, bumpsteer set and some tuning, it would seem the IRS could be really fast.
Don't misunderstand my reply. I think it should fall into the update/backdate rule but if you change the text underlined in the rules you get a different outcome.

Don't you have to weld in the caged nuts to install it in a pre99 car?

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post #12 of 13 Old 12-22-2010, 02:35 PM Thread Starter
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Quote:
Originally Posted by Han Solo View Post
Don't misunderstand my reply. I think it should fall into the update/backdate rule but if you change the text underlined in the rules you get a different outcome.

Don't you have to weld in the caged nuts to install it in a pre99 car?
Good point, but aren't the nuts you weld basically so you can install it in the same manner as a 99+ Cobra would? This should fall under minor cutting, welding, drilling, etc based on my conversation with Doug at the SCCA.

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post #13 of 13 Old 12-24-2010, 05:55 PM
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Quote:
Originally Posted by dpspeed View Post
Good point, but aren't the nuts you weld basically so you can install it in the same manner as a 99+ Cobra would? This should fall under minor cutting, welding, drilling, etc based on my conversation with Doug at the SCCA.
It's just one of many times the rule book will contradict itself.

If you have an official email or letter from the SEB you should be good to go. If you decide to take the car to a National event I would have a copy of the email or letter with yoiu just in case a weener shows up.

If this is based on a casual conversation I would email [email protected] just to get the official reply. or is it .org?

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