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2012 & 2021 GT500 strippers
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I have them. I don't notice any NHV. I used the red bushings which are the lower durometer bushings. I would imagine the sets made out of aluminum would add NHV.
 

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2021 GT500 Iconic Silver
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You should also consider doing this as well

I looked at that kit because one of my buddies has it. We did some driving with a go pro watching the IRS and it didn’t seem to make that much of a difference so I held off on adding it.
It helps if you plan on dragging the car. Reduces subframe flex by 1/2”
I've seen that on a GT, but the Shelby cars use bushings of different durometers. Was that measured on a GT350 or GT500?
On 500 there is no issues and it takes up the slack of the IRS. On the 350 you can’t use all the bushing
I have them. I don't notice any NHV. I used the red bushings which are the lower durometer bushings. I would imagine the sets made out of aluminum would add NHV.
Hey guys, including @Goose17 and @HVCalTech and @Unclesams_svt , am looking for some input please. I don't drag race, I road course/track. I'm questioning the value of the bushing support system -- I haven't seen anything definitive that they help w/ tracking but maybe I've missed it.

I already have the Steeda jacking rails and will likely be purchasing the Steeda support braces on Labor Day sale this weekend.

Steeda 555 5754 Mustang Coupe Rear IRS Subframe Support Braces (15-22)

Beyond that, I'm considering two options:

1. Buy the Steeda alignment kit (center dowels) and bushing support system.

Steeda 555 4438 Mustang IRS Subframe Alignment Kit (15-22)
Steeda 555 4437 Mustang IRS Subframe Bushing Support System (15-22)

or

2. Buy the Keltrac posi-loc system -- which seems to achieve both centering and bushing support in one "solution".

S550 Mustang IRS Subframe "Posi-Loc" System (kelltrac.com)


Thoughts?
 

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2021 GT500
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401 Posts
Discussion Starter · #23 ·
Hands down I would recommend the alignment kit, it is the only thing on the market right now that actually centers the IRS subframe to the chassis, and if you ever need to drop the IRS for any reason you do not need to get another alignment because it will kit keeps the subframe in the same position.

The bushing kits I did not do as yet, as my car is a weekend cruiser right now, but if I start tracking it that maybe a different story.
 

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Moderator/Admin Dude!
2020 CFTP Red! 2011 Kona Blue
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Hey guys, including @Goose17 and @HVCalTech and @Unclesams_svt , am looking for some input please. I don't drag race, I road course/track. I'm questioning the value of the bushing support system -- I haven't seen anything definitive that they help w/ tracking but maybe I've missed it.

I already have the Steeda jacking rails and will likely be purchasing the Steeda support braces on Labor Day sale this weekend.

Steeda 555 5754 Mustang Coupe Rear IRS Subframe Support Braces (15-22)

Beyond that, I'm considering two options:

1. Buy the Steeda alignment kit (center dowels) and bushing support system.

Steeda 555 4438 Mustang IRS Subframe Alignment Kit (15-22)
Steeda 555 4437 Mustang IRS Subframe Bushing Support System (15-22)

or

2. Buy the Keltrac posi-loc system -- which seems to achieve both centering and bushing support in one "solution".

S550 Mustang IRS Subframe "Posi-Loc" System (kelltrac.com)


Thoughts?
I’ll be on the track next weekend for the first time with my Kelltrac mod.
 

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Hey guys, including @Goose17 and @HVCalTech and @Unclesams_svt , am looking for some input please. I don't drag race, I road course/track. I'm questioning the value of the bushing support system -- I haven't seen anything definitive that they help w/ tracking but maybe I've missed it.

I already have the Steeda jacking rails and will likely be purchasing the Steeda support braces on Labor Day sale this weekend.

Steeda 555 5754 Mustang Coupe Rear IRS Subframe Support Braces (15-22)

Beyond that, I'm considering two options:

1. Buy the Steeda alignment kit (center dowels) and bushing support system.

Steeda 555 4438 Mustang IRS Subframe Alignment Kit (15-22)
Steeda 555 4437 Mustang IRS Subframe Bushing Support System (15-22)

or

2. Buy the Keltrac posi-loc system -- which seems to achieve both centering and bushing support in one "solution".

S550 Mustang IRS Subframe "Posi-Loc" System (kelltrac.com)


Thoughts?
I have the Steeda alignment kit and didn’t go with the bushing support system. After talking with a bunch of folks even Steeda I came to the conclusion that their effects would be minimal because of the sleeves and IRS braces.
 

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Premium Member
2012 & 2021 GT500 strippers
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9,175 Posts
Both kits will do the same thing. I just think the Steeda system allows a bit more bushing movement which may contribute to a little less rigidity and therefore, a bit more ride quality. I don't know what possessed Ford to have so much clearance for the IRS cradle bolts. The alignment sleeves just make too much sense to me to keep the cradle centered. I've posted this before, but it's a good video of the type of motion you're fighting. I don't track my car, but I can't see that this lack of bushing control helps on a road course.


Stay in the video long enough to see the upper bushings. It begins with the deflection of the differential bushings. Steeda also has poly bushing inserts to help with that movement, and I have these as well in my car. Granted this test mule was a 2015 mustang GT and while the later mustangs and possibly the GT500 may have gotten an upgrade in durometer firmness, the bushing design remains the same. The car seems more controlled to me when the tires lose traction. These are pretty low buck, low install effort than can be easily reversed. You can always try them and see if your times improve.
 

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2018 GT350
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I have the Steeda alignment kit and didn’t go with the bushing support system. After talking with a bunch of folks even Steeda I came to the conclusion that their effects would be minimal because of the sleeves and IRS braces.
Same here. With the alignment inserts and the triangulation irs braces I haven't felt any movement in the rear that I would attribute to the bushings. If you were drag racing the diff bushing supports are probably handy, but the Shelby cars don't seem to suffer from extreme diff movement within the IRS cradle like the lower tier cars seem to.
 

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2021 GT 500
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1,042 Posts
Hey guys, including @Goose17 and @HVCalTech and @Unclesams_svt , am looking for some input please. I don't drag race, I road course/track. I'm questioning the value of the bushing support system -- I haven't seen anything definitive that they help w/ tracking but maybe I've missed it.

I already have the Steeda jacking rails and will likely be purchasing the Steeda support braces on Labor Day sale this weekend.

Steeda 555 5754 Mustang Coupe Rear IRS Subframe Support Braces (15-22)

Beyond that, I'm considering two options:

1. Buy the Steeda alignment kit (center dowels) and bushing support system.

Steeda 555 4438 Mustang IRS Subframe Alignment Kit (15-22)
Steeda 555 4437 Mustang IRS Subframe Bushing Support System (15-22)

or

2. Buy the Keltrac posi-loc system -- which seems to achieve both centering and bushing support in one "solution".

S550 Mustang IRS Subframe "Posi-Loc" System (kelltrac.com)


Thoughts?
I haven’t installed mine yet. I have to find somebody competent to align mine first. That’s not as easy as it sounds, either. There are plenty places with alignment racks, but finding a competent tech that I will let touch my car is not an easy task.
 

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2018 GT350
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I haven’t installed mine yet. I have to find somebody competent to align mine first. That’s not as easy as it sounds, either. There are plenty places with alignment racks, but finding a competent tech that I will let touch my car is not an easy task.
Seek out the local road race guys. They either know the good shops or know someone with a string setup that could do it for you for the right price.
 

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2021 GT 500
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Seek out the local road race guys. They either know the good shops or know someone with a string setup that could do it for you for the right price.
I’m going to reach out to a couple local guys tomorrow. One works at the Ford dealer and has a pretty substantially modified c7 z06. I’m hoping he might know a good tech at the dealer. The other guy has an 850 WHP S197 and has done a LOT of drag racing over the years. Hopefully one of them will have some suggestions.
 
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