IRS Camaros
 

I've seen several built or "under construction" Camaros with C5/C6 Corvette IRS's (like Tyler's 50/50 project). Does anyone have any reliable, real world performance comparisons between that configuration and a well prepared 3-link set-up. I'm looking for road course comparisons as well as braking performance. I am curious whether the lower rear roll center and the associated higher rear spring rates along with a further-aft center of gravity are making a significant difference in turning performance. Thanks.

Pappy

Looks like I need to narrow my question. Has anyone seen a first gen with C5/C6 independent rear suspension run on a track or autocross, and if so, what was your impression of the performance? Is anyone currently driving or building one of these cars with the intent of serious track time? Tyler?

I've got nothing to go on. You and I have been building our cars for a long time. I will say the reason I decided to do my chassis based on a C5 was because of the Mallett prepped 1999 Corvette that placed in the top 5 in the One Lap of America. I got to drive that car when it got traded in on a Porsche at the dealer I worked for.
That car was stupid fast, handled amazing, and was all I thought a race car should be.

That said, I'm going for an all out race car on my 50/50 project that I drive on the street. I hope that in time I can show cars like Bad Penny, Finch's yellow 70 Camaro, and Shipka's One Lap car some tail lights.

I don't know of any C5 based 1st gens running on the track that we could compare numbers on. There are at least 3 of them on the road though.

Tyler

Thanks Tyler. I'm getting closer -- built some longer LCAs for your ATS spindles and used a deeper offset front wheel -- that gave me a better scrub radius and allowed me to get a 315 on an 11 inch wheel up front with good turn radius. Also some interesting duct work for the oil cooler (inlet, diffuser, and air extractor/nozzle) and I'm finishing the underbody CF tunnels and belly pan. I'll get an update on my build thread soon. We need to get some of these IRS cars on the track, just for the sake of argument.

Pappy

hey Pap, you have any build threads of your camaro project, love to see it.

Vince

It's been said over and over that IRS cars typically only show a benefit over solid axles on bumpy surfaces, and ride quality is noticable on the street. IRS also allows you to adjust camber and toe, both of which are great things to have. But if you know what you are doing, you can do that on a solid axle as well. IRS setups typically wont have pad knockback issues either.

But, our cars just aren't packaged for IRS systems. If you want to chop the rear tin, go for it. Be prepared to run flat-faced wheels and narrow the IRS enough for the correct hub track.

If you want a all-out race car like Tyler, then I think IRS is worth considering. If it's a track day car, I wouldn't bother. But that's just my opinion.

I agree with Matt on this (and I'm a BIG fan of IRS). We did a 2nd gen Camaro here at the school awhile back. Full 2X3 frame recessed and welded into the floor, relocated upper control arms, and a complete Nissan 350 multilink IRS.

Track width wasn't really an issue with the Nissan setup, but getting the ride height down to 6" took a lot of cutting. Ditching the cradle might have helped, but would have meant a lot more setup and fabrication for all the mounts.

I've followed Teetoe's build, and they obviously started out with a gutted shell. Either way, it's not easy. Or cheap...

I have already completed the IRS in my car. I was just curious how any of the IRS PT cars were doing on track. I went with an IRS primarily to lower the rear roll center in an attempt to better "balance" the car with respect to front and rear roll angles under lateral g -- to make the rear of the car do more of the cornering work and to get better forward bite off a corner. Most of the new high performance stuff (Corvette, Viper, and even NASCAR) has taken this approach, using a lower roll center and stiffer rear springs and bars. You can also loosen or tighten the car at the track by changing the adjustable roll center. My car is not a Camaro -- it is an old previously straight axle Corvette, but the modifications are somewhat similar to what you have to do with a Camaro. I went with a highly modified C4 approach -- C4 bearing carriers with longer, adjustable forward four link (to minimize C4 roll steer characteristics and to make the instant center and anti-dive/anti-squat adjustable, something you can't do with a C5/C6 set-up without moving the control arm pick-up points); adjustable lower lateral link for both camber and roll center adjustment; a vertically adjustable toe link to fine tune bump steer; a bullet proof Tom's differential with "1000 horsepower" Drive Shaft Shop aluminum half shafts; etc. The body is widened six inches for bigger tires and to keep from having to narrow the suspension which creates too many angles during travel and affects camber gain. The rear tires are 345s on 13 inch wide X 18 inch HRE wheels. The front is equally as modified -- Woodward front steer rack, ATS spindles, custom roller bearing control arms, etc. As Tyler said, we have been working on our cars a long time with the hopes the effort will be worth while. Like Tyler, my car will be streetable, but with a bias toward the track.

Pappy

what has two thumbs and wants to see more pictures? this guy. http://www.pro-touring.com/forum/ima...es/icon996.gif

Here ya go you lazy bastards. It's a Corvette though, not a Camaro.

https://lateral-g.net/forums/showthread.php4?t=21031
https://lateral-g.net/forums/showthread.php4?t=20865

Tyler

Thanks Tyler. I'll have new pictures soon -- lots of new CF pieces, new duct work for the oil cooler, subtle modifications to the body (functional air extractors), aluminum firewall for the fuel cell (damn regulations), etc. By the way Tyler, did you know you don't really need an autoclave if your garage is at 134 degrees?

Hhahahahahah!! That's not making me miss Lost Wages at all. I have a few ideas for some new carbon items on my car to try and reduce weight as much as possible. Are you building one time use molds?

Tyler

Tyler,

Mostly, I build bucks (some are actually usable fiberglass parts, some are fiberglass over wood and/or foam), then I pull gelcoated fiberglass molds off of them. The molds are reusable, but mostly specific to my car. I have a few flat panel parts that I pulled straight off of aluminum sheet that served as more-or-less a one time mold. I have the wing, splitter, diffuser, trunk interior panels, lower splash pans behind the front tires, aero-farings for the back edge of the fenderwells, and I am finishing the molds for the underbody tunnels and the belly pan. I am going to build the aero-roof out of CF and will build a third rear deck lid with only the spoiler. Of the other two, one is clean (stock fiberglass) and the other has both the spoiler and the adjustable wing.

Pappy

Pappy - everytime you post, I get more impressed with your build and where you're taking it. You're like a one man wrecking machine! Props man...get that bad boy on the road...(you too Tyler!)

At the risk of being bombed for jacking the thread... I just want to ask a dumb question...

Putting the IRS (Kugel Champ quick change) under the rear of my '32 was not done for handling -- I chose it for looks only.... Will I notice any handling improvements at all?? Not that a hi boy is a handling machine. :rofl:

That's the problem with this whole PT boom and all the talk about what car or set up is faster. It's all about the DRIVER. This isn't the sprint cup series where it's less than a second from first to last. There are very few that are capable of setting there car up, wheeling it, and beating on it at the same time. I respect these high end IRS builds but having a functional car would be my first choice.

Gaetano, you talk a big game and may very well be the best road racer around these two sites. Practice makes perfect. Show up to RTTC next year and prove it. I seriously doubt you are 8 seconds faster than bad penny on a road course with an even playing field. That's a HUGE difference.

I have no problem with an ego, I've got a fairly large one myself. I just want to see you show up to one of these major events and back it up. I'll be the first to congratulate you. :cheers:

Thanks guys, I am enjoying the dialog. My primary focus regarding suspension configurations was to try to lower the rear roll center in a way that would force the rear of the car to do more work without making the car unusable on the street. NASCAR did it by putting the outboard panhard bar mount VERY low and close to the ground -- probably wouldn't work well on the street. With a Watts linkage, the moment center is at the pivot point of the link, so it is hard to move that down and keep reasonable geometry or to not get it too close to the ground. The roll (moment) center is very easy to control/change with an IRS. An "old style" set-up with a low front roll center and high rear, with stiffer roll resistance in front, can be set up well for specific dynamic conditions (lateral g, basically), but is not necessarily perfect for slinging the car back and forth in various turn radius turns at varying speeds (road course). There are lots of drawbacks to various IRS systems, and many can be outperformed by a well set-up 3-link; however, a properly designed, well sorted (not necessarily a bolt in deal) IRS should give the results I want (to answer Greg's question). Like most of you, I've had many early Chevy hot rods - 55-57s, Camaros, Chevelles - but as you know I'm also kind of a Corvette guy. I've had a couple of Vipers and I'm on my second C-6 Z-06 (a 2011 Z07 big brake car), and I see the geometry and tire changes they have made and the handling is beyond excellent. I am, by choice, stuck in the 60's, but I still want the cornering and braking ability of the new stuff. There is a lot of bantering about the IRS in a PT car, and its not for everybody, but I think you will find that a large percentage of the good handling first and second gen Camaros already have C5/C6 based front suspensions. Since I'm so slow at getting things finished (ackowledged,Todd), I am looking for IRS PT cars that are a little further down the road in making the handling improvements that I believe are possible.

Pappy

I'm no expert on suspension design but I think if you have the time and fabrication capabilities, IRS is the way to go. The arguments will likely never cease about which is better, stick or IRS, but I like seeing more and more builds with IRS. I'm doing Viper front and rear on my Dart so I'm definitely interested in results as you guys are finishing builds and getting them on the road and the track. Mine will be primarily a street car with occasional track time. I'm going for ride and handling and hoping to find the best balance with the IRS. This is a great discussion.

does anyone know the hub to hub dimension of the C5 IRS? within the past week i've basically changed my mind to go IRS. the full shi-bang like tyler, with the trans/diff. my car has escalated from mild bolt on parts to, F#%K it, its a streetable track car.

already started removing rear frame legs, i was already planning on replacing with some pre bent 2x3 parallel legs for my tubbs. i was planning on 3 linking, but im convinced this is the direction i wanna go.

in need of the hub to hub measurment to start layout. im checkin out my buddies dads Z06 this weekend to see whats up. i dont feel like flaring my fenders but im not against it. hoping my 19x12 c6 ZR1 +59mm offsets tuck.

From what I recall it was near 70 inches. That is wider than the fenders and rear 1/4 panels which is why I had to widebody and flare my sheetmetal on all 4 corners.

Good luck.

Tyler

Thanks for posting. So my plan was to replace my rear frame rails, adding a front crossmember to be able to move the legs inboard and to also mount subframe connectors. Im eliminating the dipdown in the trunk to do so, basically keeping stock sheet metal and clearancing where i need to. Do you know the diameter of the torque tubes, was yours shortend/lengthend, and if it would fit under the stock tunnel? Also wondering how far the transmission comes into the cabin

Do you think cutting (narrowing) the rear crossmember is a good idea? one of my friends is a welding wizard, just seems to me that there would be a lotta stress on the welds. Did you ever conside having a narrowed tubular crossmember made and copying all the suspension and diff mounting locations, to avoid flaring the fenders? definitly easier said then done. For the UCA's, did you copy the C5 specs for the mounting locations?

sorry for the rant, but im sure you have the most 1st hand experience with the C5 IRS swap.

http://youtu.be/jm8EvhX_2WM



here is a video of the finished product of the 68 with C-4 rear. Turned out pretty good!

Kyle,
Very cool product. I bet people would like to know the price...:thumbsup:

Kyle,

Can you list some benefits of the IRS vs the torque arm?

Anyone heard of Ame multilink?

http://www.artmorrison.com/2006cat/04.pdf

David Pozzi just installed one in Mary's car.... I believe he's also writing a magazine "how to" article -- her car is a second gen...

Thanks for the bump on this one... I liked re-reading the trash talk between Todd and Gaetano. :catfight:

:lol:

I don't see one post in here form Tracky :confused59:

Oh right. I can see things you can't. Gaetano wisely deleted his posts. I'll leave it at that. :lol:

Oh Jedi master....

STEP AWAY FROM THE

Cant wait to see how it performs. I am sure David and Mary will test it all the way when finished.

Matt Jones awsome 1gen had abs before, now it has irs and based on pictures ,there are place for speed sensors too. That could be hell of package on track.

Hey I'd post it back up but Gaetano knows where I live. :peepwall:

Dude...that was a double take. :headspin: :D

I'll start another thread on the Art Morrison IRS.
I have seen the future...

Here it is: https://lateral-g.net/forums/showthread.php4?t=45908

Really interested to see more on this!