Stephen

iTrader: (12)

Ah...OK

The GTO IRS is like that too. 4 bolts for the cradle.

iansane

iTrader: (1)

But the GTO/CTS/Solstice IRS is notoriously weak. The tbird/cobra stuff is the 8.8" I think?

GM just likes to use the smallest diffs available for some reason.

VAN454

The GTO rear end is plenty strong, and not related to any of the others you mention. There are plenty of guys running in the mid-low 10s over here with that rear end in a full size car. A 3rd gen is heaps lighter than a GTO, and if you want to go faster than 10s you wouldn't be looking at irs

iansane

iTrader: (1)

I think it's been established that IRS isn't the best choice for drag racing. There are other things in life than just punching the loud pedal. I like turning left and right myself.

ls six

Thats an idea but they use eavy cast steel LCA's but the Lincoln MKVIII uses aluminum pieces and there are several around the local yards.

The RX rear is a 4 point mounted rear also besides the shocks.
----------
I wonder if the Cattera diff is just as strong? It's an older version of the same car but only came with a 6.

VAN454

Me too, perhaps my point wasn't clear, I was just trying to point out that the GTO rear is more than strong enough for anyone who is setting the car up for cornering, since a drag launch is heaps harder on the diff and axles than circuit type racing. These rear ends are in all of the Commodores from '97-'06, and these are one of the most popular cars for racing of all sorts over here. However, this type of irs isn't the best kind, it's semi-trailing arm and you get a fair bit of toe in and camber change through the travel of the suspension. Still better than a beam rear end though.

ls six

Hey Porche (911) Nissan (Skyline GT-R) Mazda (FC RX-7) and lots of other great performance cars use trailing and simi trailing rears with success.

If it's good enough for them I think it'll be enough for a 3rd gen.

ryan91rs

iTrader: (1)

since when is the camaro a "good" straight line car? that's news to me

Guest

That is not all a bad thing. It actually is quite a good thing. Why?

That is not necessarily a toe in condition in body roll, it is roll induced understeer. It is only well utilized if the fabricator calculates in the ride height and articulation geometry so it maintains its correct posture when installed. This creates a more common slip angel front and rear for better contact patch balance in corners.

Solid rears can do this also- its all in how you set up the suspension geometry. I know a solid rear axle Camaro that eats C4 Corvettes for lunch in corners- ESPECIALLY if you also take into account and reduce the vettes tire size to 245/50/16's also, then its taking candy from a baby.

Its not all about what you have, but how you set it.

DirtyCanadian

first off do you think you really need suspension with your 305? i have an 83 Trans Am with 5spd, it has factory suspension with new shocks, and the car handles extremely well, i also have a pepped up 355 aswell, but even with my old 305 i could easily drift a corner or take nice curves at 180km+ I dont go that fast on highways anymore ive grown up since. You should build your car up to the amount of horsepower you feel is ideal, then choose suspension parts to suit your ride.. jus my opinion do what makes you happy thats all that matters.

VAN454

This is true, and I don't mean that these are a bad rear end, our family car is a Holden VZ Calais, which has the same rear end as the Monaro (GTO). But if you are going to go to the trouble of converting a car to IRS, I would sugest that you use something that is more common and is a more optimum set-up. The Corvette rear end is a better setup. Whether it is easier to fit is another story though. In my case I would probably use the Holden setup because it's easier to get for me than the Vette, but if I was able to get a vette rear end cheap, I'd rather use that.

83 Crossfire TA

iTrader: (2)

All of the IRS’s bolt to the body with a few location points. The really nice parts about using it that most of you are missing is that it was designed to bolt into a chassis that _was not_ originally designed with IRS and roughly the same size and weight range of an f-body. Add to that that it’s basically a strong (stronger than all the competitors mentioned here) 8.8” rear and there are tons of cheap parts out there for it and it has a lot of advantages.

The real question is why do it?

Even with the best IRS geometry you will not have a faster car around the road course than the stock torque arm rear (one of the “high performance driving schools” found that when you put late 90’s f-bodies up against similar vintage vettes they ran the same times but the drivers wore out faster in the vettes), and it definitely isn’t a faster setup in a straight line (and I would argue much less safe in a straight line) but you will have a car that will keep its composure over a bumpy road better. The problem with that is that the 3rd gen f-body front suspension is great and go-cart like if you limit it’s travel to a fairly short range, in other words, it doesn’t like a bumpy road better than the solid axle rear.

So the only reasonable answer that I can come up with for why someone would do an IRS in a 3rd gen is to prove that they could, which on the scale of things just isn’t that hard (vette and other IRS’s are swapped into things every day), or ‘cause it was there… so if you’re doing it because you think it would be cool… whatever turns you on, but if you’re doing it for performance reasons - you’re a fool.

VAN454

With all due respect, come on, IRS does give better handling in most real world (the road) situations. And even on a track if it is set up properly it is still better than a beam axle. I'm sure that you are well aware that the only race cars that use beam axles are the ones that have to due to regulations or drag cars. None of the road race catagories would use a beam unless they have to.

paul_huryk

Only on bumpy roads - IRS give enough deflection due to loads of components bending and bushings moving around on smooth roads to be a tie at best.

The only real advantage a Corvette would have would be the spring setup from the factory - either transverse leafs or coil overs depending on your year. Obviously coil overs in a Camaro (fronts) would give a decisive advantage over the spring on pockets.

Plus you can improve a third gen's handling by taking out front end weight - hard to do in a Corvette that already is fiberglass and has aluminum heads.

83 Crossfire TA

iTrader: (2)

Paul, you beat me to it.

Real world, IRS can feel better, but doesn’t result in better handling then a similarly properly setup live axle unless the road gets fairly bumpy, and in that situation I will stand by what I already said, you won’t make the 3rd gen front suspension work well enough in bumpy conditions to make it work adding the IRS in the back.

VAN454

If you are talking about ultimate development levels, IRS will still give better grip unless you are racing on glass. F1 and indycar don't use beam axles do they? And for ROAD use IRS is much more stable. I am not arguing whether it is or isn't worth doing the conversion, it depends on why you want it. Set up right you will get an improvement of the ride/handling compromise, are there easier/cheaper ways to get the same level of handling for road use? Of course. Are they as trick? No, and they won't ride as well for a given level of handling. Are you guys really sugesting that manufacturers build cars with IRS, which costs more, for marketing when you can't see it and most people don't know what it is?

83 Crossfire TA

iTrader: (2)

Of course it’s a marketing thing for the “sports car” market. Tons of times I’ve heard it debated, IRS vs live axle for the RWD, or independent vs beam axle being the FWD equivalent, usually by people that couldn’t even tell you if they’re looking at an IRS or live axle. When rack and pinions became prevalent for packaging reasons it was always mentioned in marketing even though a steering box/gear has better feel, stronger, more durable and adjustable. How about modified mcpherson strut suspensions, always marketed as superior but it’s only advantage is packaging, a more traditional SLA setup can be built with much better suspension geometry. How much crap did GM take for not going overhead cam when they designed the 3rd gen SBC (LSx engines), of course, no one really talks about how ford did go overhead cam and ended up with an engine as big and almost as heavy as their old school big block.

Just like the rest of these examples, yes, there is an advantage to an IRS setup, but it is not ultimate handling, and besides some coolness factor it’s a fairly lame thing to do to a “ponycar” which is all about a smallish, cheap setup with way more power than it really should have, since an IRS is never going to lay down that power as well.

And comparing a vette, GTO or t-bird IRS to an F1 IRS is like comparing their engines. Yes, they work on the same principals, but that’s about the end of the similarity. Nothing will interchange and even design goals are totally different since they are designed to operate in a totally different range. You might as well include a Saturn booster rocket in that engine comparison…

paul_huryk

That is mostly because the average person thinks that technology (like IRS) makes cars faster and better. That is why Porsche can charge close to $100K for a 911 when you can buy a base Vette for under 1/2.... Pure marketing.

F1 cars use IRS because of the tremendous spring rates they use to keep the suspension from bottoming out with all that downforce. The cars would bounce all over the place with solid axles....

Guest

I say there is no proof to anything till someone does it and comes race me. Its going to take you alot of work to get the balance and bugs out.

ls six

In that situation both cars are allowed to follow their ideal line with out interference. In an actual race the results will be different. Thats not to say the vett will win but in a race there are an entire field of cars vying for one line and one 1st place position.

[quote=83 Crossfire TA;3789884]Of course it’s a marketing thing for the “sports car” market. Tons of times I’ve heard it debated, IRS vs live axle for the RWD, or independent vs beam axle being the FWD equivalent, usually by people that couldn’t even tell you if they’re looking at an IRS or live axle. When rack and pinions became prevalent for packaging reasons it was always mentioned in marketing even though a steering box/gear has better feel, [quote]

That's ridiculous. It's true that cars are sold to the majority of customers by promoting attributes that they dont really understand but you cant tell me that a cavalier with a cheap twist beam will match my mazdas TTL rear.

You might be able to tune it to pull more lateral G's or ride smother or handle transitions better but it will never do all the above as well as a more advanced rear will. An independant rear WILL handle better than a solid rear with fewer compromises. I dont know if you have noticed but the 3rd gen F body isn't exactly cadillac smooth. At the very least an IRS rear significantly reduces unsprung weight. That means that one can use less severe damping and even softer springs and still have the same level of control.

When you hit a speed bump in any solid rear car the entire rear axle (100 + pounds) tries to go through the floor pan. It takes a lot more spring rate and stiffer dampers to control that much weight.

Theres no question at all that IRS is superior. Weather its worth it or not is some thing else.

About the steering box vs R&P... Remember there are many different types of box. Saying they are all superior is just wrong. I have never driven any box equipped car that matches the feel and accuracy of my mazdas, not even the T/A. Not even other mazdas like the 1st gen RX7 that incidentally also has a solid rear with a much more competent 4 link / Watts link setup that just cant match a good IRS. And I drive a lot of different vehicles in my line of work.

slow305

iTrader: (2)

That's it right there. Someone can put an IRS in a thirdgen but then they are going to have to tune it and get all the geometry correct.

IMO, the only reason people think about a Corvette suspesion or a front 4th gen suspension on their thirdgens is to have something cool for their signature blocks. If they have to ask if it can be done, they don't have the knowledge, fabrication or engineering skills to do it right.

Pat

1MeanZ

iTrader: (9)

figured I'd dig this thread back up for another angle on the debate.

I autocross my car quite a bit, and one thing I fight is severe brake hop, especially over uneven pavement. From frequenting the f-body road race forum, this is a common problem that many people have concocted solutions for, none of which are particularly impressive. Autocross courses are rarely smooth and flat, and road courses can have their imperfections as well, so throw your comments like "straight axles handle well on smooth pavement" out the window right now, because a smooth race surface is not common or likely in most situations.

The second problem I have is that I have a decent amount of power. Enough that my stock rear shouldn't be subjected to it with sticky tires.

I could swap in a 12bolt or a 9" to fix my durability problem, but this will just exacerbate my brake hop problem, as well as add quite a bit of unsprung weight which will hurt the car just about everywhere else.

The solution could be to swap in a Dana44 IRS. The swap would cost the same or less, and should solve my wheelhop issues. The problem with durability adds another reason to swap to this setup. Its not just for wheelhop, or just for strength, but for both.

BIG_MODS

iTrader: (9)

The biggest performance advantage I see to an IRS is the reduced unsprung weight which means that it will perform better over bumps. None of the road courses I drive on are even close to being smooth. As far as suspension geometry goes, there are goods and bads with and IRS.

My thoughts exactly.

What class is that going to put you in? I think you’ll be racing against yourself. Get some real shocks and some real springs. If you still need more, spend the money on a decouple TA or build one like I did.



To me, a beam axle is a fundamental part of a Camaro and an IRS is a fundamental part of a vette. I’m not talking performance or tech here, but just more philosophically or morally. If I saw an IRS in a third gen I might look at it just to see how they made it work, but overall my conclusion would be “why didn’t you just buy a vette?”. For the cost and time involved with making an IRS work in a 3rd gen, you could almost buy a C4. I'd compare it to putting a Ford motor in a Chevy, it is "wrong" to a certain, lesser degree.

1MeanZ

iTrader: (9)

I couldn't really care less about what class I'm in. I race the car because it's fun, not to compete in a class. I plan on building the car how I want, not how some class tells me I can build it. For the sake of conversation it will probably put me in e-mod. In my local region however, I could probably stay in street mod and no one would care unless I started kicking everyone's butt, which i suppose could happen eventually.

You do have a very valid point here. I haven't really given the solid axle a fair shot yet. The biggest problem i'm afraid is my jegster torque arm is too short. I have to run it to clear my exhaust, plus I wanted to get the torque arm mount off the trans. I had the jegster TA laying around for free, so I tried it. I have some control arm adjustments and shock/strut upgrades to make before I totally condemn the live axle.

The other problem is durability. I'm concerned about my rear axle being able to withstand the abuse. Obviously no amount of shocks, struts, or springs will make my rear axle hold up to the power. My huge problem with the 9" or 12 bolt is the weight. That has to be noticeable on the track not matter how good your dampers are....

I'm not a huge fan of corvettes, especially C4s. I dont hate them, but they just don't drive me crazy either. Hence, I really have no issue "cutting one up". So the bad karma associated with putting IRS in a Camaro doesn't really phase me. I feel confident that I could get it to work, plus be unique, plus it woudl be strong enough. I'm still excited about the idea, but I haven't bought the parts to do it yet either....

slow305

iTrader: (2)

Most of the issues I hear with brake hop are people with LS1 cars, and that has to do mostly with the crappy ABS. My old LS1 car had brake hop issues only once (on one corner on a really bumpy surface) and I ran the rebound on the rear Konis at full stiff. My '90 WS6 with Bilsteins never brake hopped. My '82 (built for ESP) has brake hopped on occasion, but I've found that higher rebound settings on the Konis make it go away (the rear pads might be too aggressive ... keep meaning to see what they are ). The rear suspension is super soft (150# springs, 18mm sway bar) so I can compromise with the shocks a bit.

In other words, before throwing $$$$ at the car, maybe tweak what you have? What do you have on the rear suspension?

Pat

VAN454

The point of this debate is really that set up properly, IRS is better. Whether it is worth the hassle and cost to swap it into a third-gen is up to the individual.

¡MR.AWESOME!

iTrader: (2)

Well, why put an LSx in a third gen? Why put a T56, or a Jerico in? Why not just buy a fourth gen? It would be easier, cheaper, and you know it will work how it's supposed to.

On another note, what kind of torque can a Corvette IRS handle?

VAN454

Well put, some of like to modify our cars to perform better than standard and to be a bit more "unique". Often that means we spend more money and time than if we bought a higher up model, but where's the fun in that?

88camaroluvr

I actually read about doing this in HotRod magazine July 2008. Zeus Performance did it to a fourth gen firebird. I contacted them about getting a copy of the lay out for the adapter brackets. They responded with this:

"We have only installed the IRS into one of our 4th gen Firebird so the templates are made for the 4th gen cars, but the 3rd gen would be the same. As of right now we cannot sell the templates until we get all of our paper work finalized with our lawyers so we cannot be held accountable for someone misinstallation of the IRS rear, i.e. not properly welded. If you are wanting to tackle this idea I would suggest finding a wrecked c4 with a good back half and the co-owner Jay may be able to walk you through some of it. As said, we cannot sell the templates yet, but we can do the install in house as an option. Sorry for the lack of details.

Ashley
Zeus Performance"

I just need to find a nice C4 rear to do it

Phishman92

My 92 was my first car and will always be the center of my garage. There is something about those third gen body lines that always looks fresh and new to me when i catch the reflection of it as i drive by a mirrored window or see my car from a distance in a parking lot. I certainly don't see anything "wrong" with adding whatever performance mods I see fit. Just because the car was built in 92 DOES NOT mean you can only use technology from that car, that year. Where's the fun in that?! I feel MORALLY and PHILOSOPHICALLY obligated to make my car the best it can be period. If some overconfident corvette owner happened to wrap his ride around a telephone pole (hopefully without major injury) and it ends up in a wreck lot with good engine/trans/suspension.....I would not hesitate for a second

and with that said, C5/C6 IRS & transaxle swap??!!! yeh's and neh's?

iansane

iTrader: (1)

Now that's what I've always wanted to do.

Phishman92

YES!! magically delicious 50/50 weight distribution


now the question is......which one of us will be be the first......

Stephen

iTrader: (12)

None of us....It's already been done.

iansane

iTrader: (1)

Pics? I've seen the c5/c6 transaxle done on first gens by ATS or something but not on a thirdgen, yet...

Stephen

iTrader: (12)

What a CROCK OF **** TGO IS!!!!!!!!!!!!!

I copy the damn URL & TGO can't recognize it's own URL & use it a link?

Screw this damn website...Page Not Found for one of ITS OWN PAGES!!!!!!!!!!!!!!!! There's the URL...I guess ya'll will hafta figure out how to get to it...TGO damn sure can't!


https://www.thirdgen.org/forums/ltx-...p-started.html

iansane

iTrader: (1)

...yeah.

I thought it was fairly obvious I and Phishman were refering to a c5/c6 transaxle when I said....c5/c6 transaxle. Guess not?

EDIT; Dude. It worked when you first posted it. A link to you posting three pictures of c4 axles under fbodies, right?

Stephen

iTrader: (12)

I missed the transaxle part.....

Phishman92

.... You'll get that sometimes at 1:30 AM

from reading other threads on here it seems the general consensus is that just plain IRS is "too much work", let alone adding a transaxle into the mix. So unless someone randomly posts pics of it I'm guessing it's never been done. Which is all the more reason to keep this thread alive til someone steps up to plate and gives it a shot!

There is a lot of debate as to what the gains would and would not be, but a third gen with a transaxle is an entirely different animal. I'm pretty damn excited about the prospect of seeing just what one could do on a track against thick german and italian accents.

Suaveat69

Has anyone ever converted to a front C4/5/6 style suspension or found a way to run a dual A arm set which eliminates the strut towers?

jaybdaboat

I give you life......




I'm bringing up an old thread to ask, would a frony corvette shock be a upgrade over oem front shocks for people on a budget. And it would it be a plug and play or what?

Z28ricer

iTrader: (2)

No you cannot use them.

jaybdaboat

Thanks for the quick response !
Can any be used or it will take work. Or only thirdgen shocks and springs

Flip 2

iTrader: (1)

For starters, 3rd gens have struts up front..... vettes don't.
Check what 1MeanZ did.... his posts were not just talk. Do a search and look at his build thread... lotta, lotta work. Lotta talent.

jaybdaboat

Thanks but I wasn't looking for a lot of work. I'll just get oem shocks

Z28ricer

iTrader: (2)

Get Bilsteins.

The only ones that will be quick and easy to find used would be 4th gen rears, theyll work in the rear of a thirdgen as well.

67FBird464

Awesome install! I know this is a very old thread - but if your brother still has the car or other pix, can you post any of how the dogbones/trailing arms and sway bar are mounted? Really trying to understand the geometry.
thanks!