IRS to SRA guys, some questions

[phil a]

Considering the swap…

My car is basically a straight line street car, driven 500-1000mi per year
I make it to the track when I can but between work/kids it’s not as much as if mike
Still has IRS, FTBR bushings
Last time at the track was ~3600lb w me
Best 60’ of 1.51
28x10.5 slick with 4.10s
Right at 800rw

What appeals to me about the SRA is simplicity and weight savings
From what I’ve read, almost everyone cut a good amount of time off of their 60’ after the swap

I’ve talked with teamZ and a few other shops about control arms - everyone has suggested solid ends at both the upper and lower control arms

I don’t know anyone with a solid rear with solid rod ends to get a feel for noise/harshness/clunking - and that’s my dilemma

Car is loud as it is, it’s old with random rattles, and I’m not expecting a Cadillac. What I don’t want is something clunky and jarring that takes away from the enjoyment as a street car.

Any experience/input? Granted it’s subjective but hoping to hear pros v cons and yes v no whether you’d do it again or not.

Thankntoy

Phil

 

[5.0 Hatch]

Keep the IRS. I've had SRA on every mustang up until my 01. Between the ride and the look of the IRS exhaust, there's no way I would go back. Plus it'll knock the value of your cobra down quiet a bit or at least narrow down the pool of potential buyers. Just my opinion....

 

[01yellercobra]

No personal experience, but a friend of mine ran a drag set up on two of his fox bodies. All of the arms were heim jointed and he had an anti roll bar. He drove them all around town with no real complaints. Maybe add a couple pieces of sound deadener around the mounting areas to keep things quiet(er).

 

[BlckBox04]

if you're not an avid every weekend racer, keep the IRS. Now that I don't race my car much anymore I'm contemplating putting my irs back in.

the irs can work great if you use the right components and launch correctly. how many Supra's have gone deep into the 7's and 6's with stock irs'?

 

[Blkkbgt]

As a guy who went the opposite direction and ditched the SRA for and IRS you couldn't pay me to swap back.

The ONLY way it would be a consideration is if the car was weekend strip bruiser only and zero cruising.

Even with the stock GT springs and control arms the car rode terrible. Everything I added just made it noisier or harsher. I hade a PHB and it transmitted a ton of noise into the cabin.

 

[DCguy]

If you run spherical ends at all the control arm pickup points you will have a lot of NVH. You can quiet it down a bit by doing a hybrid setup.....spherical at the axle and poly at the chassis. That will help a bit.

If your thing is drag racing and street/strip stuff that will be ok. However, if you like to go corner carving, it is recommended you retain the factory rubber bushings in the upper control arms to keep the axle binding to a minimum.

I pulled my axle out and built it and while it was out also added upper/lower torque boxes, welded all the seems from the bottom of the car and added/welded a rear shock tower brace. Also welded axle tubes, added bracing, PHB, etc.

At the same time I added sound deadner throughout the entire car, firewall to tailights to try and minimize all the rattles and clunks in the cabin.

All that said, a well built solid rear axle car is pretty much bullet proof, but it does ride quite harsh, especially if you're running rear coilovers, spherical joints, etc. Its fine for a weekend blast, but don't expect to be driving around Mrs. Daisy in it. You do save about 100 pounds in weight and you gain quite a bit of clearance in the wheel wells to run a 12in wide wheels and 345s if you wish with the correct backspacing so there are some advantages to go along with the disadvantages of increased noise and NVH.

 

[03 Cobra DSG]

I swapped to a SRA with a TeamZ series 1 grip kit all spherical ends. Not that much more noise and it’s mainly a street strip car. It’s hard to hear anything over the turbo noises for me. If your going to track the car a lot than swap. If not just build the SRA.


Sent from my iPhone using svtperformance.com

 

[ITSTOCK]

Most people swap to the SRA the 1/4 mile, so you see people put in drag suspension parts; springs, shocks, ARB, etc. I can tell you that crusader shock to crusader shock valved the same, IRS to SRA, the driving is extremely similar on the road.

Solid ends are fine. You're going to feel the most with how you get the shocks valved and the spring weights.

I went 1.36 on the IRS, but that was breaking every other track trip (2 step and PD blowers are extremely hard on parts, not a surprise).

if you're not an avid every weekend racer, keep the IRS. Now that I don't race my car much anymore I'm contemplating putting my irs back in.

the irs can work great if you use the right components and launch correctly. how many Supra's have gone deep into the 7's and 6's with stock irs'?

With stock IRS? 0 that I know of. If there are any, they probably are the ones that ET the same as cars with 1/2 the power. The 6 and 7 second cars all either have $10k 8.8's or 9" rear conversion IRS, or they have 4 links.

 

[BlckBox04]

With stock IRS? 0 that I know of. If there are any, they probably are the ones that ET the same as cars with 1/2 the power. The 6 and 7 second cars all either have $10k 8.8's or 9" rear conversion IRS, or they have 4 links.

literally the first video to pop up on yt

 

[ITSTOCK]

literally the first video to pop up on yt

Literally not the stock IRS.

 

[BlckBox04]

Literally not the stock IRS.

Think our interpretation of stock is different

 

[ITSTOCK]

Think our interpretation of stock is different

Apparently so. The only thing stock about it is the suspension mounting points and that it is still IRS, other than that, the car had a 9" rear, which is what my post above said.

What exactly is your interpretation of stock? Surely it's not a 9" aftermarket cradle/center section conversion.

 

[BlckBox04]

Apparently so. The only thing stock about it is the suspension mounting points and that it is still IRS, other than that, the car had a 9" rear, which is what my post above said.

What exactly is your interpretation of stock? Surely it's not a 9" aftermarket cradle/center section conversion.

It’s still an irs, No? It just has upgraded components right?

 

[ITSTOCK]

It’s still an irs, No? It just has upgraded components right?

It is still "an" IRS, it is not a "stock" IRS. Nothing about it is stock.

Yes, I'm pretty sure if I built my current Cobra as a chassis car, had a 9" center section made/installed for the IRS, some very good coil overs, perfect weight distro, lots of track time, and an additional 1k horsepower, I could get this car to 1.teen 60'.

Or I could throw the 9" SRA in it (which it has now) and 1.teen 60' it this upcoming season in a full weight street car still with 1k horsepower less.

Hint: That supra that you posted was planning on switching over to an SRA. That car, with that power and money in to it, can easily knock a 1/10th off the 60 and get in to the 1.0's.

Either way, yea, we obviously have different definitions for stock.

 

[BlckBox04]

It is still "an" IRS, it is not a "stock" IRS. Nothing about it is stock.

Yes, I'm pretty sure if I built my current Cobra as a chassis car, had a 9" center section made/installed for the IRS, some very good coil overs, perfect weight distro, lots of track time, and an additional 1k horsepower, I could get this car to 1.teen 60'.

Or I could throw the 9" SRA in it (which it has now) and 1.teen 60' it this upcoming season in a full weight street car still with 1k horsepower less.

Hint: That supra that you posted was planning on switching over to an SRA. That car, with that power and money in to it, can easily knock a 1/10th off the 60 and get in to the 1.0's.

I agree switching to a 9” would be a huge upgrade but it still went 6’s with an IRS regardless if every component was upgraded, which is what my original post intended to convey

 

[robvas]

Kinda dumb to compare the cobra IRS to the Supra IRS or even the S550 IRS isn't it?

 

[phil a]

Thanks for letting ideas/input so far guys
Lots of real world experience here
I just wish I had the opportunity to ride in a SRA car with solid ends for comparison

I’ve talked with teamZ about the bushed/solid-ended control arms, kind of a compromise
But they’ve said - at least the guy I talked with - that the poly ends would likely be deformed/destroyed at the track

Yes, I would reinforce torque boxes, something I’ve looked into and decided it’s a must-do

I may build the solid axle and swap it in, run it for a while and see how it feels and how loud it is. Worst case scenario I can keep the IRS in the garage and change them out again if it’s too much noise/banging.

Thanks again - keep to coming!

Phil

 

[badcobra]

I've run solid everything and full time ARB for many many years. For a seldom driver, it's really just not a big deal at all. I have the Team Z double adjustable lowers, they are very nice pieces. I went with rear coilovers with double adjustable shocks as it really allows you to fine tune ride height and shock settings. You will most definitely 60' better with a solid axle, the car will be lighter, and as a result you'll be quicker/faster. Those are all wins in my book.

 

[LS WUT]

Well I don’t want to get too far ahead of myself. However I’ve found me a new cobra. It’s got an SRA, I’m not the biggest fan of that. Means it’s probably for more launches than nasa. However if that were to happen and I do pick this one up, you’re welcome to take it for a ride, and maybe even swap me your IRS for it

 

[hatchke]

I have a SRA in my car with all solid control arms, with coilovers on Viking double-adjustables. Honestly there's a really good bit of NVH, especially coming to this car from a mostly stock IRS in my old '03. It clunks, creaks and at highway speeds it generates a pretty good hum.

I didn't really care that it was SRA-swapped when I bought it, but the IRS rides SO much better. I wouldn't go through the effort of swapping an IRS back in now, but speaking honestly, it rides pretty terribly. I can't speak to the performance given how different my cars have been, but I will say that my SRA setup is quite predictable under load.