All in costs for the factory 5 IRS set up?

[natehall37]

Hey guys, Just trying to figure out budget for my future build. I am interested in the IRS and see that it is $2500, I am wondering what, if any, additional costs are associated with the IRS set up? Thanks.

[edwardb]

You need to add the center section and knuckles/hubs. New or zero mile takeouts (what I used) are in the $1200-$1400 range for the non-Torsen variety. Everything else for the suspension, including CV axles, is in the kit with the option added. The options for brakes are somewhat fewer than other rear suspensions. Choices are 2015/2016 Mustang or Wilwood today. Could be others in the future. But you'd have to buy rear brakes for the other suspensions as well. That should be nearly a wash. It's possible over time the center section and knuckles will be cheaper with actual used (salvage) parts available. But the price is already pretty reasonable for new IMO, so I'm not sure I'd try to save there. My build is still underway and some months before it's driveable. But early reports have been very positive. Good luck with your decision.

[ram_g]

Someone will chime in if this is incorrect, but I seem to recall that you also need to factor in 18" wheels as the Mustang brakes aren't cleared by 17". May not be so much a cost penalty as a looks penalty in these cars, IMHO.

[edwardb]

Someone will chime in if this is incorrect, but I seem to recall that you also need to factor in 18" wheels as the Mustang brakes aren't cleared by 17". May not be so much a cost penalty as a looks penalty in these cars, IMHO.

I don't think so. I'm pretty certain they will fit in the 17's. I have the Wilwood upgraded brakes in mine (similar rotor size) and the calipers clear the inner diameter of the 18 inch rim by at least 1 inch. 1/2 inch less clearance with the 17's should still fit. I would certainly confirm with FF, but I believe this is correct. I don't think you're locked into 18 inch wheels with the new IRS.

BTW, there's another builder (maybe more) that's installing 15 inch wheels with the 2015 IRS. Gordon Levy is apparently making the brackets, and I'm assuming they will be available for others. They've already confirmed the 15 inch wheels will clear the knuckles.

"Looks" penalty huh? I agree 18's are a different look than traditional 15's, but for me it's not a negative. I've got 17's and 18's sitting side-by-side in the garage. The difference is actually pretty subtle.

[CraigS]

EdwardB, when you bought the 2015 rear suspension from MPS(?) did the brakes come with it? If so that really helps the comparison.

[edwardb]

EdwardB, when you bought the 2015 rear suspension from MPS(?) did the brakes come with it? If so that really helps the comparison.

Nope. It was the complete IRS assembly including sub-frame, but no brakes or shocks.

[Duke]

Figure $2,500 from FFR, $1250 or so for IRS pumpkin & spindles (FFR offers it new from Ford racing but doesn't have it on their site), another $75 or so for the IRS breather & press in breather plug, and assume another $1,100 - 1,500 or so in brake parts. Add $225 for rear sway bar if you want to go that way too.

The 2015 IRS will fit 15" - 18" wheels. I'm the idiot who's building it with the 15's ;) Gordon is currently working on the bracket and parking brake setup for me and will offer it as a kit when completed.

[Lancaster Lad]

Mr Duke You will not be the only idiot as I am also going to go with 15" wheels and 2015 IRS. Plan on calling Mr Levy next
week to put in a order. If you go to the FFR order page the new ford racing diff spindles and hub are listed. That is how
ordered mine.

#8851 Lancaster, Ca

Cecil

[Kennyr]

As a newbie who is just starting the build planning process, I was under the impression that you couldn't have 15"s and IRS? Are you restricted on rear wheel width? Can you have pin drive wheels also?

[edwardb]

As a newbie who is just starting the build planning process, I was under the impression that you couldn't have 15"s and IRS? Are you restricted on rear wheel width? Can you have pin drive wheels also?

First, welcome to the forum. Maybe you know this already, but there are two flavors of IRS, and the answers are likely different for each. There is the 15+ year old T-Bird-based IRS, and the now 2015 Mustang based IRS. There's a lot of history with the older version, including use of 15 inch wheels, pin drive, etc. Officially, the new version is intended for 17 and 18 inch rims, and no pin drive supported. But as already mentioned in this thread, guys are working on fitting 15 inch wheels to the new IRS. I admit to being biased since it's what I'm building right now, but I would strongly encourage that you only consider the newer IRS in your build plan. It's the better choice for a number of reasons.

[Jeff Kleiner]

First, welcome to the forum. Maybe you know this already, but there are two flavors of IRS, and the answers are likely different for each. There is the 15+ year old T-Bird-based IRS, and the now 2015 Mustang based IRS...

The T-bird derived IRS is no longer offered.

Jeff

[edwardb]

The T-bird derived IRS is no longer offered.

Jeff

Hey Jeff. Thanks for the feedback. Didn't know that. I knew they were honoring existing orders (maybe all delivered by now) and promised ongoing support. But hadn't heard no new orders were being accepted. Makes sense. Don't see it on the order form. That makes the decision pretty straightforward.

[Courtnie Provencher]

Hey guys!

Through Factory Five the IRS option is $2499. You can then purchase your brand new center section, spindles and hubs with us for $1400. We offer two sets of brakes for the set up: Mustang brakes for $699 or Wilwoods for $1520. There is also the sway bar option for $221.

Just to clear the air with wheel sizes, the 17" and 18" rims will both work. While there are some customers who are using the 2015 IRS with the 15" wheels, please be advised that Factory Five does not recommend it.

[Mark Dougherty]

tbird Irs is still offered in the narrow width or pin drive width.

[David_Ingermann]

I have the new IRS with Wilwoods and the 17" wheels. clears just fine.

[Kennyr]

Thanks Edwardb. I've been digesting your amazing 20th Anniversary build thread, your patience and attention to detail are amazing, I hope I can do 1/4 of the job.

I am aiming for a largely period-correct build, with a FE and a toploader. 15"s and billboards are pretty important to me. I'll keep my eye on what other guys are doing to make the IRS work, but it seems that a 3 link is preferable to the Tbird IRS from a geometry point of view.

Ken

[rmiller64]

Keeping a close eye on this as I'd like to build a FIA with 2015 IRS and 15". Curious as to what Gordon Levy has cooking up

[edwardb]

Thanks Edwardb. I've been digesting your amazing 20th Anniversary build thread, your patience and attention to detail are amazing, I hope I can do 1/4 of the job.

I am aiming for a largely period-correct build, with a FE and a toploader. 15"s and billboards are pretty important to me. I'll keep my eye on what other guys are doing to make the IRS work, but it seems that a 3 link is preferable to the Tbird IRS from a geometry point of view.

Ken

Thanks for the shout out. Having fun with the build. I'm not sure exactly what you mean with the 3 link & Tbird IRS comment, but it's kind of a moot point if the Tbird IRS isn't available. I would call Factory Five and find out straight from them what's available and what isn't.