Solid Axle vs IRS

[Jimmysidecarr]

but what is it that makes the Boss handle so well?
it can't be just a bare solid axle like it came stock on my GT...
I tried to find pics of the Boss rear suspension but no luck.

The front end design on the 05 and up Mustangs is significantly better than the fox and SN95 cars, it is VERY similar to what Porsche is still currently using.
Porsche Cayman/Boxster front end, similar but different. The control arms are two piece and they are not reversed.

Porsche 911 RSR reverse L lower control arm, Torsion bar and McPherson strut.

2012 BOSS L/S reverse "L" lower control arm, w/ coil over McPherson struts.

The 05 and up rear suspensions are a three link with a panhard bar.

That FAYS2 watts link is a truly awesome piece and could be substituted for a panhard on your car, and I am sure it would give superior results.

The Steeda 5 link is also a proven kit, but the MM 3 link torque arm kit appears to be preferred by many competitors.

The Griggs stuff is pretty much the Creme de la Creme of SN95 Mustang suspensions, but it is also the most money. Hopefully the Griggs re-org is going well and they will be back to normal levels of supplying parts.

I would love it if I could afford an Agent47 front end for my car.
If you have the budget for it, combined with someone's torque arm rear set up, you would be able to handle similar(close) to Carlos's 04 IRS/agent47 Cobra(racebronco2).

Assuming yours is set up right, corner weighted, bump steered, has the right coil over spring rates, shocks that match that rate and the sway bars are matched to actually work with the final set up.

That's why packages can be nice and sometimes actually are the right solution.:beer:

 

[98 Saleen Cobra]

You can still get Griggs parts you just gotta give Cortex Racing a call and all. :beer: Great feedback Jimmy.

 

[ac427cobra]

The new Boss has straight axle and performs well, nuff said.

There is absolutely no way an SN-95 SRA can be compared to an S-197 SRA. You're comparing a four-link-quadra-bind to a 3-link-PHB. Not to mention the chassis of these two vehicles and their suspension set-ups are direct polar opposites of each other! It's like comparing apples to strawberries.

Both SN-95 axles, SRA and IRS as delivered from the factory, are not very good in factory form. People have been putting band-aids like PHB's, Torque Arms, and Watts Links on SRA's to improve handling for decades. Those things do help, but you're never going to make an SRA handle OR ride like an IRS. If you could, cars like Ferraris, Lamborghinis, Bugatti Veyrons, Corvettes, GTRs, Vipers, Ford GTs, etc. etc. etc. would come with SRA's from the factory with all of these band-aids tacked onto them. The truth is NONE of these high performance, modern day sports cars comes from the factory with an SRA for a damn good reason. An SRA will never ride and handle like an IRS, no way, no how!

Now having said that, learning how to drive a lousy handling car will actually make you a better driver. It will teach you how to squeeze the maximum out of an ill handling car. So you may want to track a quadra-bind SN-95 SRA to improve your driving ability. Not sure though?

On the other hand, a properly prepared IRS will actually MAKE you faster and a better driver. It's more forgiving than an SRA. The 'window' between traction and loss of traction is much wider with an IRS compared to an SRA.

Some food for thought.

:thumbsup::coolman::beer:

 

[98 Saleen Cobra]

^^ I agree that a properly setup IRS will def out handle a SRA car.. But we are talking about Mustangs here.. Both the IRS and SRA are crappy lol. It's which one will be the best in the end on a Mustang.. IF FORD developed a car around a proper IRS and not the other way around the IRS hands down would kick ass but it's not the case. Just curious are you saying that a Ford IRS equiped with your entire package will out handle a properly setup SRA from say Griggs?? Just curious?

 

[TroyV]

Slightly off topic... Why is it when folks refer to Griggs stuff, they refer to it as "Full"? Not poking fun..just curious as to how this terminology came about.

 

[98 Saleen Cobra]

I refer to as full because there are different levels.. They have a panhard bar and stuff. Typically when I refer to griggs stuff I refer to a their watts-link, tq arm, coilovers, LCA's, subframes, etc.. But there are some people that don't have a full kit ya know?

 

[Jimmysidecarr]

Slightly off topic... Why is it when folks refer to Griggs stuff, they refer to it as "Full"? Not poking fun..just curious as to how this terminology came about.

I would like to know too!:shrug::dw:

When I hear that I assume that they have every part Griggs sells for that model including the long arm/short arm front suspension, and the brakes!

I wonder how often that actually is the case with "Full Griggs" claimers/users.:dw:
That is SERIOUS BIG MONEY!

 

[TroyV]

I see.

"Full" as in Fully depleted funds..

Sorry for the hijack..

 

[98 Saleen Cobra]

No not fully deplated funds.. We are talking about rear suspension so I think of the rear suspension.. When you talk the entire package there are still different levels.. Most of which is what you'd end up spending either way your went (IRS vs SRA)

 

[Jimmysidecarr]

Since the OP has a significant amount of Steeda stuff on the rear already, that might be a good enough reason to continue with the Steeda 5 link if the Steeda arms she is using are the same as that package.

Generally speaking though any application using a panhard bar can be upgraded to a watts link, I would think.

Any of you guys ever use both a torque arm and the 5 link both (not at the same time)to compare?
I have heard about the torque arm brake hop but I have not heard that much about the Steeda 5 link.

 

[ludbg]

IRS sure does feel better in the corners but don't forget the IRS is about 140lbs heavier than the SRA...

 

[ac427cobra]

IRS sure does feel better in the corners but don't forget the IRS is about 140lbs heavier than the SRA...

Without that IRS, a Terminator (other Cobras not so much so) is even more poorly balanced F-R than the 57/43 in the condition it was delivered from the factory! :read::idea:

Not the best thing to do if you're looking for performance and handling which was the OP's original question.

 

[99COBRA2881]

How much does an SRA with T/A and PHB weigh?

Yep the added weight of the IRS is on the right end of the car.

 

[TroyV]

I've not driven the Steeda 5 link, but one of the guys I run with did. The car was controlled, but He has broken the welds on the brackets where it connects to the axle more than a couple of times. Apprehensive about what to replace it with, he went with the majority of recommendations and got the MM TA/PHB set up and says that it is also quite controlled, and has the benefit of holding together for him. I drove the car in that state and thought it was quite nice, and with just a flick of the wheel you could get the car the change direction without the obligatory tank slapper the stock stick axle would bring.

 

[N/Angel]

Since the OP has a significant amount of Steeda stuff on the rear already, that might be a good enough reason to continue with the Steeda 5 link if the Steeda arms she is using are the same as that package.

Generally speaking though any application using a panhard bar can be upgraded to a watts link, I would think.

Any of you guys ever use both a torque arm and the 5 link both (not at the same time)to compare?
I have heard about the torque arm brake hop but I have not heard that much about the Steeda 5 link.

that is the reason for wanting to know more about the 5-link, actually also about the 5-link-2 since the second is the only kit that allows to use tailpipes according to Steeda. I just can't find much info on the Steeda parts because everybody is saying MM or Griggs, I don't really feel like changing out my entire suspension and I doubt mixing the different brands is a good idea.

IRS sure does feel better in the corners but don't forget the IRS is about 140lbs heavier than the SRA...

Without that IRS, a Terminator (other Cobras not so much so) is even more poorly balanced F-R than the 57/43 in the condition it was delivered from the factory! :read::idea:

Not the best thing to do if you're looking for performance and handling which was the OP's original question.

the weight distribution is a VERY good point, I did use an aluminum block for my Terminator engine build but still have the stock K-Member so the front is very heavy while the rear is way too light being completely gutted in combination with the solid axle


what scares me away of the IRS swap is the problem that I would need to buy a lot of extras additional to the IRS assembly.
to help me figure out what it would cost, can someone break down the IRS into parts so I know what all I need?
like control arms, diff housing, ?????

here's what I know I will need additional to the IRS:
-new KW Suspensions rear coilovers
-new differential/gears (or take out the T2-R/4.10 Combo of my SRA)
-complete bushing kit and everything else found on Full Tilt Boogie Racing
-rear brakes? (I have Bullit brackets and calipers now)
-rear swaybar?

if I would find a Terminator here locally who wants to swap to a SRA I would probably do it, but I doubt I'll find one, maybe I should make a post in the Europe section to see what happens :shrug:

 

[ac427cobra]

the weight distribution is a VERY good point, I did use an aluminum block for my Terminator engine build but still have the stock K-Member so the front is very heavy while the rear is way too light being completely gutted in combination with the solid axle

Mustangs in general and Cobras in particular have always been heavy. The aluminum block is an excellent weight reduction option.

what scares me away of the IRS swap is the problem that I would need to buy a lot of extras additional to the IRS assembly.
to help me figure out what it would cost, can someone break down the IRS into parts so I know what all I need?
like control arms, diff housing, ?????

Your best bet would be to find a hard core drag racer that wants a solid axle for his Cobra! There seems to be no shortage of these people! But that may be a challenge based on your locale.

here's what I know I will need additional to the IRS:
-new KW Suspensions rear coilovers
-new differential/gears (or take out the T2-R/4.10 Combo of my SRA)

Unless the T2-R goes with your axle that is an EXCELLENT diff and gear set for road racing or open track. I'd figure out a way to keep that even with a swap!

-complete bushing kit and everything else found on Full Tilt Boogie Racing

On our order page:

Full Tilt Boogie Racing Shopping Cart

you'll need:

FT 5000 Complete bushing kit with upgraded front subframe mounting bolts
FT 1800 Bumpsteer and upgraded toe link kit
FT 2100 OEM removal tool set
FT 1900 Adjustable sway bar end link kit (only if you're on coil-overs)

-rear brakes? (I have Bullit brackets and calipers now)

Depending on what you have for front brakes I would not necessarily upgrade the rear brakes unless the front brakes are upgraded. If you have upgraded the front brake to a larger diamater like a 14" you could look at our 13" rear IRS brake conversion kit FT 7000A.

-rear swaybar?

I would not mess with the rear sway bar. Tune the suspension with springs, fine tune with an adjustable FRONT sway bar.

Hope that helps.

:thumbsup::coolman::beer:

 

[wheelhopper]

I did not realize that the IRS was 140lbs more than a SA. I thought, from a MACA member, that stripped his car down as light as possible, and weighed everything he removed vs what he replaced it with, that the IRS was around 75lbs more.

It does put the weight in the right place. Here is the corner weights of my '90 GT with IRS. My car has factory style springs and has had no effort done to corner balance.

LF 929 891 RF
3259lbs
LR 746 693 RR

The car is actually a little lighter now. I have since removed the front fog lights, fog light mounting brackets, and light weight racing seats.

It was not that difficult to install. You also don't have to do a lot to them to get reasonably good performance. I am running about 2.5 seconds off of Summit Point Main TTD lap record with very little done to the IRS. I still have the factory differential and control arm bushings. Also no rear bump steer or even adjustable end links.

Definitely leave the rear sway bar alone. I had to install the Steeda HD sway bar on the front of my car. I had crazy oversteer until I installed it. It was the only sway bar I could find that was stiffer than the factory '90 GT sway bar.

 

[N/Angel]

okay, me again :rolling:

the car has been back on the road and got quite a few miles on the current setup.
my biggest mistake ever on this car were the 4.10 rear gears, those are coming out as soon as my 3.27s get here! driving on the German Autobahn cruising at 80+mph I'm already above 3000rpms in 6th gear, no fun...

the coilovers are set too stiff, need to change that around quite a bit to stop the hopping

and I just found an IRS in the market section I hope to get, haven't heard back from the guy since I said I want it but if everything goes well, the solid axle is history :rockon:

here's the for sale thread, will I be missing anything other then shocks, springs and catback? I'm already using an 03 Cobra driveshaft
http://www.svtperformance.com/forums/suspension-brakes-258/784246-f-s-03-cobra-irs-h-r-race-springs-tokico-d-specs-irs.html

here's what I was going to buy right away before the IRS goes into the car:
-FT 5000 Complete bushing kit with upgraded front subframe mounting bolts
definitely getting the rest of FTBR parts but I think the bushings are the most important ones, right?
anything else I need? a Billetflow diff brace is already installed.

I will have to find myself an IRS catback and buy a new set of KW V3 coilovers, the coilovers are going to be the most expensive part of the whole swap

 

[racebronco2]

Some how i missed this thread. My thought even though it's a little late. Irs and sra are almost equal on a smooth track. The steeda 4 link does have brake hop as does the tq arm. The irs will shine on a track like Nürburgring, looks like there are many sections that are a little bumpy. What rate coil-over did you get? What shocks do you have?

 

[N/Angel]

I have KW Variant 3 coilovers, adjustable rebound and compression, spring rate is 400lbs I believe