2nd Gen IRS

[jp455]

Hello all...followed project RePeeled closely and was waiting to hear some news on the Heidts bolt in IRS. Anyone have any experience bolting this on and/or driving in a car with it? The only drawback from looking at pictures are the the inboard brakes, but I guess some good cooling ducts could solve that, and the cheap looking shocks which of course can be changed. Another thing is, the geometry has to be compatible with the front end. Any thoughts?

[732ndgen]

d@z customs has that set up in his car.bumped into him at road america and that system was insane looking,their were more people looking under his car than looking under the hood. www.dandzcustoms.com (http://www.dandzcustoms.com)

[srh3trinity]

d@z customs has that set up in his car.bumped into him at road america and that system was insane looking,their were more people looking under his car than looking under the hood. www.dandzcustoms.com (http://www.dandzcustoms.com)

That is the project RePeeled that he was referring to. It looks like a cool setup, but I also was not a fan of the inboard brakes. It looks like they have a universal kit IRS on their website if you flip through their catalog.

[jp455]

Yeah those brakes look annoying. Mainly because if you get a front caliper that isn't compatible with the rear one and th master cyl. then you need to use a ton of bias valve on it. I'd rather be able to buy a caliper set and have a balanced setup with out one. Is this the only 2nd gen setup out there?

Any comments on how it drives/rides?

[MrQuick]

I think everyone gave up on the IRS deal since there are so many affordable link kits out there. I mean whos gonna pay $7K or higher for a non Jag based IRS kit?

Vince

[jp455]

I would think if you want the ultimate in handling you would go with the IRS. Is the difference not that noticeable? Although I must say that the whole thing about a solid rear being jumpy over bumps can also apply to cars with IRS. I had an S2000 that would step out a bit going around bumpy corners.

So if we stick to this ultimate ideal, which of the systems manufactured out there would be the best right now?

[MrQuick]

very true but it depends on fitment design that doesn't compromise the geometry.

I know a few leaf sprung cars that could keep up with a C5.

There would have to be a very large budget to engineer a system to fit a 2nd gen body properly. I am afraid more than the average hobbyist would be willing to pay. I can see a full frame job but not a unit using existing frame and floor.

Unless you have a machine shop with CNC equipment that would donate time, Heidts is the closest you will get to a bolt in IRS kit.

Straight axle....
With performance in mind I would go with an AME system since LD is now out of the loop. Also don't forget the system that Jake rod shop has going.

I believe there is a thread on the best available system.
Vince

[dipren443]

Had a long talk with Marcus at SC&C about this very subject once. New frame rails... That is what is needed for a proper IRS in a second gen. Narrower and higher up than the existing...

[MrQuick]

Fully fabricated system or C5/C6 based?

Vince

[srh3trinity]

The Cuda on Bullrun had a 350z IRS in it. Has anybody seen one of those outside of the car? Brakes might be an issue and I am unsure of the physical size.

[Bryce]

if we are throwing out ideas... what about a viper IRS?

[MrQuick]

Viper would be perfect but its big bucks for the parts. It would easily be a $7-8k job. Way too much to mass produce. Customers just aren't willing to pay that.

You could do it cheaper with C5 uprights and make your own arms.

We contemplated doing it to a 70 years ago but after all the parts, did the math and the budget would be insane, we just aren't there yet.
maybe if the economy gets better.

Vince

[jp455]

Vince I actually have been mulling this over for a while since I saw the Heidts system and then saw the full frame that Schwartz is doing. I thought maybe the rear of the frame could be changed to accomodate an IRS. That way you could install an actuall performance IRS and not one that was designed in the 60s. For production I would think the Viper system would be very expensive, but as a one off getting one from a wrecker shouldn't be too bad.

Although I have to say...the last scratch built car I worked on we did the uprights, A arms, etc etc...and it wasn't thaatt bad cost wise. Definitively not cheap but not as insane as one would think. We even had the A arms welded up by a place that does Indy car arms, they had the aerofoil shape and everything! Heres a pic of the full setup.

https://static1.pt-content.com/images/pt/2008/10/100_3991-1.jpg

https://static1.pt-content.com/images/pt/2008/10/100_3697-1.jpg

In any case...really wonder if the Schwartz frame/IRS combo is even possible. On a bit of a side note....nobody has riden in a 2nd gen with the Heidts system then?

[MrQuick]

Good stuff Manuel,

I think we talked about it 4 years ago?

I'd love to do it but had a hard time convincing a customer to take on the budget.

The Heidts system is new so I don't believe so. Have youy spoken to the guys that built Re-pealed?
Vince

[jp455]

You're right Vince, but it wasn't that long ahgo, more like 2 1/2 3 years ago. I haven't asked the repeeled guys directly, guess I wanted to see if there was a more general feel for the thing. Plus I also wanted to see what peoples opinion on installing IRs systems in the 2nd gen is since you rarely see it even though you see it on 1st gens. Maybe I'll look into designing something myself with a Corvette upright or something. I used to work at Mosler too, so the rear hub and all is there, even with center lock, would just need to figure out the frame to attach everything to.

[exwestracer]

The Cuda on Bullrun had a 350z IRS in it. Has anybody seen one of those outside of the car? Brakes might be an issue and I am unsure of the physical size.

We are putting a 350Z setup in a student's 78 Camaro right now. He's on this board, so maybe he'll throw some pics up here as we go. It does require some subframe mods to get the crossmember high enough in the car. Other than that it's an amazingly good fit... rotor to rotor width is 1 3/4" wider than the stock 10 bolt.

[silver69camaro]

The Viper suspensions are awful, I wouldn't bother with those. Solid axle cars can handle just as well as a IRS (presuming it's designed well) system, although they can't, in theory, ride as well due to a large amount of unprung weight. Typically IRS setups just aren't worth the extra cost.

[jp455]

Ray-Whats the guys name the 350Z system is going into? I really would like to see that!

Matt-I agree on a track both systems combined with our cars wouldn't be very different if at all. But driving on a bumpy road I bet the difference would be noticeable if the IRS is well tuned shock and spring wise. Plus its a great exercise to apply my skills in designing and building a system like this, even if it is a lot for that trick factor!:jump:

[mikedc]

IRS won't make a real difference on any decent track.


Windshield wipers won't help on the track either. But that doesn't necessarily make them a bad investment.


---

[exwestracer]

Ray-Whats the guys name the 350Z system is going into? I really would like to see that!

Matt-I agree on a track both systems combined with our cars wouldn't be very different if at all. But driving on a bumpy road I bet the difference would be noticeable if the IRS is well tuned shock and spring wise. Plus its a great exercise to apply my skills in designing and building a system like this, even if it is a lot for that trick factor!:jump:

I'd talked to him about this board and he knew all about it... I'll find out tonight if he's a member here. It will be a week or so before we're back in the shop and working on it again. He IS installing a full rect. tube chassis into the floor to lower the car, so the mounting points will all be on new metal; however, the Z subframe mounts line up exactly with the width of the stock rear subrails, just not high enough in the car...

[srh3trinity]

I'd talked to him about this board and he knew all about it... I'll find out tonight if he's a member here. It will be a week or so before we're back in the shop and working on it again. He IS installing a full rect. tube chassis into the floor to lower the car, so the mounting points will all be on new metal; however, the Z subframe mounts line up exactly with the width of the stock rear subrails, just not high enough in the car...

I would love to see it. I have searched ebay for a 350z and IRS and the prices are pretty cheap. I haven't emailed to see what parts that it comes with though. What is he doing for brakes? Re-drilling the 350Z rotors?

[jp455]

I think definitively need to fabricate a new subchassis/frame rails to take full advantage of an IRS.

[silver69camaro]

Matt-I agree on a track both systems combined with our cars wouldn't be very different if at all. But driving on a bumpy road I bet the difference would be noticeable if the IRS is well tuned shock and spring wise.

I agree.

[Macadoo355]

Ill be a full frame, full cage "mild" street car. No drags or any of that dumb stuff just the twistys. I have some basic pictures of the first stage of measurements and cuts ill post up later. I think it'll be a cool ride as long as I don't screw up to bad. Ill try to get them up once I'm home.

http://s14.photobucket.com/albums/a3...o-%20Take%202/

[exwestracer]

I would love to see it. I have searched ebay for a 350z and IRS and the prices are pretty cheap. I haven't emailed to see what parts that it comes with though. What is he doing for brakes? Re-drilling the 350Z rotors?

I talked to my student about it tonight. He is a member and agreed to post pics up as the build unfolds.

[jp455]

Definitively look forward to seeing it!

[Macadoo355]

Let me know if that link works out or I can try to post the image on here.

[jp455]

Link doesn't work...it just takes me to the photobucket home page.

[rednecknate]

I can tell you a rear end not to run.. second gen rx7... I did an irs set up in a 94 toyota pick up years ago and while the handling was unbelivable... And 4:88's and a posi was cool I was constantly breaking third member's and Mount's With a 245 wide tire and a built 4 cyl.. Around 200 ft pounds of torque maybe.. But man it was cool...
MarkV Supra rear ends should be a valid option also . lots of guys making 1000 plus horse outta those twin turbo monsters... Big brake option etc and realative cheap .....Much more support then probrobly any other import IRS.. My 2 cents...:enguard:

[jp455]

Yeah...I know many RX7 guys swap in a Mustang Cobra diff when they do the LS swaps. The thing with many of those IRS systems is that they are multi link arrangements with complex pick up points. A simple double A arm suspension I think would be easier to fab a subframe for.

[Macadoo355]

https://static1.pt-content.com/images/pt/2010/05/ryanshop009-1.jpg

https://static1.pt-content.com/images/pt/2010/05/ryanshop011-1.jpg

https://static1.pt-content.com/images/pt/2010/05/ryanshop013-1.jpg

https://static1.pt-content.com/images/pt/2010/05/ryanshop014-1.jpg

https://static1.pt-content.com/images/pt/2010/05/ryanshop017-1.jpg

https://static1.pt-content.com/images/pt/2010/05/ryanshop022-1.jpg

https://static1.pt-content.com/images/pt/2010/05/ryanshop020-1.jpg

https://static1.pt-content.com/images/pt/2010/05/ryanshop077-1.jpg

https://static1.pt-content.com/images/pt/2010/05/ryanshop078-1.jpg

Should be making progress mid next week? More pics then.

[jp455]

Lovin this mixin and matchin. Really curious how it turns out.

[BrianP]

Although I have to say...the last scratch built car I worked on we did the uprights, A arms, etc etc...and it wasn't thaatt bad cost wise.


https://static1.pt-content.com/images/pt/2008/10/100_3697-1.jpg


JP455,
What kind of spindle setup is this?

As far as the Heidts IRS: it's design looks pretty outdated. If you break a half shaft.... your crashing since the half shaft is used as a suspension member.

[jp455]

Thats a spindle we designed and CNCd from scratch for a supercar project I worked on. Theres more info in a thread I started called New Car. Its a cool piece cause only one model works for all corners of the car. It is a bit heavy, but its made for a road car where durability is key. Plus it had to stand the forces from the huge carbon brake discs. I forget the size right now, but they were either 14 or 15 inches but for reference thats a 20 inch wheel its in!

Yeah I know what you mean about the half shaft. That and the limited brake caliper applications.Thats why I mentioned that its outdated technology. But I'm still curious as to how it rides/handles since right now its the only bolt in system out there.

[BMR Tech]

Just something else to throw out there: The new GTO rears are not a double A-arm setup but they work really well, are very well packaged, and you can buy the whole setup brake-to-brake all day long for $250 on Ebay. You have very limited gear selection and posi units but they come with 3:45 gears and posi-traction from the factory designed to work in a 400 horse, 3800 lb. car so they do hold up fairly well. If you make more power we (and other companies) offer billet 300M CV shafts and stubs and there is even a company now making Ford 8.8" retrofit diff kits. For $250, you could buy a couple of spares!

[exwestracer]

Update on the 350Z rear install:
We put our heads together last night on how to best mount the Z subframe under the Camaro. Ryan (Macadoo355) made what I believe is the right decision in doing minimal cutting and using as much of the stock sheetmetal as possible. At this point the plan is to build a 2X3 "frame" from the front bumper all the way to the rear mounts for the Z suspension. This will be welded into the floor just as you would install subframe connectors, making a very strong unitized construction. At the rear, a crossmember will be installed between the stock subrails where the new frame ends. The new frame will incorporate mounts for Camaro type aftermarket front suspension and the geometry will be corrected along the way. Hopefully Ryan will keep posting pictures as the project progresses. He might move this build to the projects thread, but I'll make sure to post updates on the Z suspension installation here.

[jp455]

What I'm most curious about this install, and other that mix and match front and rear suspensions, is how much harmony the whole system will have when it works together.

[Stage4 Performance]

Very interesting stuff...
Subscribed!

[exwestracer]

What I'm most curious about this install, and other that mix and match front and rear suspensions, is how much harmony the whole system will have when it works together.

Actually it should work quite well with the changes we have planned at the front. We are trying to achieve a common roll center movement front and rear under roll compression. This should give the car a better "feel" for the driver, as both ends will be doing pretty much the same thing as the lateral forces go up.

Great theory, anyway...

The cutting is almost finished. Hopefully, we will be laying out the new rails tonight.

[jp455]

So does that mean you're going with a custom front end? It would be a huge coincidence if those geometries lines up with something that's already out there! I asked Detroit Speed for their front end geometry once to design an IRS, but they said no. Completely understandable, but it would have been cool to design something complimentary.

[exwestracer]

So does that mean you're going with a custom front end? It would be a huge coincidence if those geometries lines up with something that's already out there! I asked Detroit Speed for their front end geometry once to design an IRS, but they said no. Completely understandable, but it would have been cool to design something complimentary.

A little info on how I try to have the students approach a project like this...

We always start a project like this by establishing the lower control arm level in in both planes, then the upper arm mount is located to give the swing arm length to work with whatever tire is going on the project (lower profile= less camber gain). This is all done on the "concrete computer" - drawn out full size on the floor. We will also do the same for the 350Z rear and map out the swing arm length and R/C progression to compare that with the front.

Lastly we look at projected front/rear weight balance and C/G heights (admittedly this is usually an educated guess given engine type, fuel placement, etc.) to come up with an idea of front and rear roll moments and front anti-dive geometry. If we have time (and all the components), we'll weigh the car and do F/R tilt and side tilt weights just to verify our assumptions. Very rarely do we get that far given the time available and the emphasis on learning, not production.

This one is getting a 2X4 rectangular frame, Howe replacement lower control arms, coilovers, and SPC adjustable upper arms. We will be building all the mounts to fit the desired tire size, ride height and geometry.

[zamora7]

Just something else to throw out there: The new GTO rears are not a double A-arm setup but they work really well, are very well packaged, and you can buy the whole setup brake-to-brake all day long for $250 on Ebay. You have very limited gear selection and posi units but they come with 3:45 gears and posi-traction from the factory designed to work in a 400 horse, 3800 lb. car so they do hold up fairly well. If you make more power we (and other companies) offer billet 300M CV shafts and stubs and there is even a company now making Ford 8.8" retrofit diff kits. For $250, you could buy a couple of spares!

Damn! This is what first came to my mind when I saw the title of the thread, any idea how difficult would a set-up like this would be? I even thought of putting one of these into a :idea:4th gen fbody, but money is the only issue.:machine:

[exwestracer]

Damn! This is what first came to my mind when I saw the title of the thread, any idea how difficult would a set-up like this would be? I even thought of putting one of these into a :idea:4th gen fbody, but money is the only issue.:machine:

The GTO uses a semi-trailing arm suspension which is great for packaging (lots of rear seat room), but is always going to be a compromise when it comes to handling. The STA design has a very short swing arm length, and the angled mounts give caster, camber and toe change as the suspension travels. These things have been around for years in everything from Datsun 510s to BMW 850s (...so that's 340 cars...? lol). If you're going to go to the trouble of swapping one into another car, IMO the only reason to choose that design is for interior space reasons... There are much better packages out there.

[zamora7]

The GTO uses a semi-trailing arm suspension which is great for packaging (lots of rear seat room), but is always going to be a compromise when it comes to handling. The STA design has a very short swing arm length, and the angled mounts give caster, camber and toe change as the suspension travels. These things have been around for years in everything from Datsun 510s to BMW 850s (...so that's 340 cars...? lol). If you're going to go to the trouble of swapping one into another car, IMO the only reason to choose that design is for interior space reasons... There are much better packages out there.

Good to know this, thanks for the info.
340 cars lol.:lmao:

[exwestracer]

Well, we HAD photos...until Ryan's camera vanished out of the shop last week.:machine: GRRR...

The frame rails are laid out and tacked together, and the frame has been fitted into the floor. The guys are about 1/2 way through building the mounts to hang the IRS cradle. We are using heavy wall DOM tubing to make pins to go through the stock subframe mount bushings. Ryan can replace the bushings with solid later if he feels the need. The pins are welded into bosses off the frame, and internally threaded for cap screws to hold the cradle up. We may put some double shear plates on the front mounts just as a security blanket.

Once the rear cradle is in place, the next big job is to get the front arm mounts located and built. The Howe front LCAs are late (surprise!) getting here, so the front may get mocked up with the stock lowers (same geometry, he'll just need to use spacers for the Heim joints on the Howe arms).

Ryan was understandably PO'd about losing the camera, but he did take some cell pics Sat night, so he may post them. If not, I'll try to get a few before the frame goes in the car.

[exwestracer]

Some progress on the 350Z IRS installation. The Howe LCAs showed up today, and they're pretty disappointing... They advertise them as an OEM replacement, even specify the C/C length, and yet they're an inch shorter than the stock arms. Good thing we didn't have the front mounts on yet! The 2 arms aren't even the same as each other...but they'll work. The guys got the front crossmember placed tonight after I took these photos. We're using 2" X .120 DOM to build a "K" member that will pick up the LCA and motor mounts.

The rear cradle mounts are tacked in place, enough so it will hang on it's own bolts. The fronts will be boxed, and there will be some gussets added at all corners later. Hopefully, we'll get the front control arm mounts on and get this thing stuffed up under the body in the next couple of days.

[jp455]

Looking good! Whats the deal with the gigantic spring pocket though??

[exwestracer]

Looking good! Whats the deal with the gigantic spring pocket though??

Stock coil spring mount for the350Z. To save interior space, Nissan separated the spring and shock. You can just see the shock eye bosses on the top of the uprights. We had considered using those pockets...for about 10 seconds:bsjerk:... Since he won't need the spring perches, those bulky transverse links are going to be replaced with coilovers and straight tubes later.

[Macadoo355]

I have a bunch of pictures on my phone ill try to swap to the computer tonight, thanks guys

[jp455]

I figured they are the coil spring mount, they just look like the spring has a huge diameter! Good deal that you're getting rid of them, it looks like something a lot smaller and lighter can be substituted.

[exwestracer]

Well, a last update (from me anyway) on the 79 Camaro IRS project. The car is returning home and hopefully will be completed in good time.

Ryan has a few more detailed photos he may share.

The front K member was completed and we designed some innovative upper control arm mounts that mount to the large surface of the inside of the rail, rather than the top. There wasn't time to get the upper mounts for the coilovers built. The body was lowered onto the frame and everything fit together remarkably well. Getting the aluminum IRS cradle to fit for proper ride height required cutting about 1/2 of the rear seat bulkhead out, but the clearances were pretty close. If the cradle had been steel it would have been much easier for Ryan to modify it than cut more floor. Also, the decision to include a full frame welded into the floor probably took up a good week of our limited build time. I believe it was the correct way to go structurally, but the swap could be done much more easily by modifying the IRS cradle and stock rear subframe.

We ended up with a swing arm length of about 2X track width in front, which should be acceptable for the fairly low profile tires he is going to use. The rear is similar, and while we obviously did not get around to checking CG, I think the front and rear geometries will complement each other.

The car left rolling, which was a major accomplishment given that only 2 students did all the work. I hope Ryan will keep us all updated on progress and results.

[jp455]

Whatever happened to this project? Any pics of the end result? Would be awesome to see how it takes a curve!

[overZealous1]

attepting it in a 67 camaro next. will start another thread. these rear ends are getting plentiful and cheap!