New Art Morrison IRS

[Rod]

It goes in & out pretty easily with just 4 bolts.
We should have the car at Pleasanton Goodguys.

AWESOME!!! cant wait David see you there!!

[DJW32]

David,
Looks great!

Did you add any support to the stock frame rails?

[David Pozzi]

Yes, I plated inside the car on top of the frame rails with 10 ga cold rolled steel spaced 2" apart. I added support inside in the rear seat kick-up vertical area to compensate for cutting most of the rear frame rail away to clear the toe links. I also plated the remains of the frame rail kick-up in 10 ga steel.
David

[David Pozzi]

Baer made a kit to put 14" rotors & 6R calipers on the Camaro knuckles.
The rotor hat is like a Corvette, very shallow, so your wheel hub area needs to be made like Corvette wheels.

[chevelletiger]

david,is mary ditching the hotchkis 3 link and all the front set up...for sale?ha!ha!
phil

[Bowtie racing]

Thank you Matt for detaild information of this new irs. Much apreciated!

[David Pozzi]

The Hotchkis 3 link is going back to Hotchkis, they want to see how it's held up.
Did rear alignment yesterday, hope to drive it today! Old floor mats make great knee pads.

[andrewb70]

Looking forward to some driving impressions.

Andrew

[Nicks67GTO]

I just went through this thread for the first time and maybe I missed it but I have to assume this is much heavier than a traditional leaf spring/ solid axle rear....right? How much more does it weigh than the standard rear chassis that would be removed? Now for road racing/auto x, would that be a negative because the overall weight was increased? Or maybe positive because the cars weight bias be more evenly balanced?

[andrewb70]

I just went through this thread for the first time and maybe I missed it but I have to assume this is much heavier than a traditional leaf spring/ solid axle rear....right? How much more does it weigh than the standard rear chassis that would be removed? Now for road racing/auto x, would that be a negative because the overall weight was increased? Or maybe positive because the cars weight bias be more evenly balanced?

The main thing to consider is not only the total weight as compared to a live axle, but also the unsprung weight. An IRS system generally offers a significant reduction in unsprung weight, which simultaneously improves handling AND ride quality. This system uses a Strange diff housing which is cast from aluminum. I bet the increase in total weight is less than 50 pounds compared against an all iron and steel 12 bolt or 9", and I bet it is even less if compared to an iron Dana 60 (which this diff is based on). And as you pointed out, the extra increase in weight in the rear might be a good thing for weight distribution. I bet Mary's Camaro now is pretty close to 50/50, and I am sure that David will post some corner weights eventually (hint..hint...).

The other benefit to this system is a significant reduction in pad knock back and greater safety.


Andrew

[andrewb70]

David,

Can you clarify brake fitment a little more. I know the rear spindle is Gen 5 f-body, so I assume any Gen 5 caliper will bolt up. But since the hub is ZR1 does that change the rotor offset or will Gen 5 f-body rotors work as well?

Andrew

[David Pozzi]

I think 5th gen brakes will work, but I don't have any to try. They won't clear 18" wheels. Actually, it remains to be seen if 18" wheels will clear stock Camaro brakes. The Baer 5th gen rear brakes in 15" would have had 1/8" clearance which we didn't want to chance. It depends on the wheel shape.

I did have to open up the Baer rotor center hole to fit the Corvette hub. I'll give them feedback on it. Maybe the Camaro pilot is smaller?

I drove the car today. Driving on a familiar very bumpy road, the ride quality is excellent! The ride is better than any other Camaro I've driven there. Going from leaf springs to 3 link was a step forward, this is a leap forward! I'm very glad I ordered one for my 67 Camaro.

I didn't get to slide around any corners yet, but the car is very responsive, it changes direction with much less steering input, like it had a faster ratio rack installed. I gassed it in first & got wheel spin but no hint of wheel hop. There is no gear whine, no vibrations, the car runs down the road very smoothly!

[andrewb70]

Dave,

Thanks for the update. One thing that I would be interested in is the front and rear operating angle of the u-joints.

Andrew

[David Pozzi]

The first test drive went awesome! Super smooth ride compared to the old stuff. No gear noise or vibrations, the steering feels faster with the rear end helping. The rear feels very responsive, it doesn't GO anywhere but it feels like it wants to change direction, kinda "free" feeling that takes some getting used to, kinda like rear tire pressure is low. I have the rear steer amount set pretty high right now.

The car is SO much more comfortable, & responds quickly to small inputs. I didn't get to corner it very hard, but it felt pretty good. I used to hate driving it on the street, but now it's a car I would enjoy touring in.

I'll add up the weights, but I think we gained 50 to 80 lbs, but it's in the rear and low. We gained nearly 1%!rear weight! lost 1% front weight.
I can't wait to get mine running, I picked it up today with new frame rails.

[HellPhish89]

I think 5th gen brakes will work, but I don't have any to try. They won't clear 18" wheels. Actually, it remains to be seen if 18" wheels will clear stock Camaro brakes. The Baer 5th gen rear brakes in 15" would have had 1/8" clearance which we didn't want to chance. It depends on the wheel shape.

<snip>

18 should be fine, my C5 wheels clear. the 17" RT-S wheels will clear the camaro brembos safely as will the CTW's.

[silver69camaro]

David,

Can you clarify brake fitment a little more. I know the rear spindle is Gen 5 f-body, so I assume any Gen 5 caliper will bolt up. But since the hub is ZR1 does that change the rotor offset or will Gen 5 f-body rotors work as well?

Andrew

Brakes are fairly easy for this setup as, like you said, a 5th Gen knuckle is used. The C6/ZR1 hubs have a register diameter that is about .090" (or so) larger than the 5th Gen. My decision to use this hub was because of the wheel bolt pattern: Corvettes even to this day still use a 5x4.75 bolt pattern, while Gen 5 Camaros are 5x4.72. Rather than re-drill the bolt pattern, I'd rather have the rotor registers opened up slightly. I battled with this decision for a long time because each method has upsides and downsides. In the end, I ended up with this decision also because it lowered the overall cost to the customer by about $50 and gave the option of using a standard C6 hub, or the upgraded ZR1 hub which is so well proven.

[andrewb70]

Brakes are fairly easy for this setup as, like you said, a 5th Gen knuckle is used. The C6/ZR1 hubs have a register diameter that is about .090" (or so) larger than the 5th Gen. My decision to use this hub was because of the wheel bolt pattern: Corvettes even to this day still use a 5x4.75 bolt pattern, while Gen 5 Camaros are 5x4.72. Rather than re-drill the bolt pattern, I'd rather have the rotor registers opened up slightly. I battled with this decision for a long time because each method has upsides and downsides. In the end, I ended up with this decision also because it lowered the overall cost to the customer by about $50 and gave the option of using a standard C6 hub, or the upgraded ZR1 hub which is so well proven.

Matt,

Thank you for the clarification.

One thing that you guys want to consider is making some adapter brackets for C5/6 spindles in the front to accommodate Gen 5 Camaro breaks. If AM is going to offer this as an option for all of your chassis, I can see many customers opting to use the SS Brembo brakes that can be easily sources and seem to be well suited to heavy cars like A-bodies, considering Gen 5 Camaros are about the same weight. Food for thought.

Andrew

[silver69camaro]

I just went through this thread for the first time and maybe I missed it but I have to assume this is much heavier than a traditional leaf spring/ solid axle rear....right? How much more does it weigh than the standard rear chassis that would be removed? Now for road racing/auto x, would that be a negative because the overall weight was increased? Or maybe positive because the cars weight bias be more evenly balanced?

This is tough to answer because everybody has different axle weights. I had a 9" (iron center section, .188" tubes, 13" brakes, 3 link with watts) before, and this setup added about 50 lbs. Part of that was because now I have larger brakes (14.25") and I'm using the heavier Strange differential. You have the option of ordering this suspension with the OEM 5th Gen diff which is about 35lbs lighter. The advantage of adding a bit more rear weight (and it's down low) is usually a good thing for these cars. But like Andrew said the difference in unsprung weight is great, and you'll notice the difference immediately.

Anyway, on my first gen, it weighs 35xxlbs with 3/4" tank of fuel, 185lb driver, and a 50.7% front weight bias. I couldn't be much happier with that.

[jtwoods4]

The first test drive went awesome! Super smooth ride compared to the old stuff. No gear noise or vibrations, the steering feels faster with the rear end helping. The rear feels very responsive, it doesn't GO anywhere but it feels like it wants to change direction, kinda "free" feeling that takes some getting used to, kinda like rear tire pressure is low. I have the rear steer amount set pretty high right now.

The car is SO much more comfortable, & responds quickly to small inputs. I didn't get to corner it very hard, but it felt pretty good. I used to hate driving it on the street, but now it's a car I would enjoy touring in.

I'll add up the weights, but I think we gained 50 to 80 lbs, but it's in the rear and low. We gained nearly 1%!rear weight! lost 1% front weight.
I can't wait to get mine running, I picked it up today with new frame rails.

I am jealous

[silver69camaro]

Matt,

Thank you for the clarification.

One thing that you guys want to consider is making some adapter brackets for C5/6 spindles in the front to accommodate Gen 5 Camaro breaks. If AM is going to offer this as an option for all of your chassis, I can see many customers opting to use the SS Brembo brakes that can be easily sources and seem to be well suited to heavy cars like A-bodies, considering Gen 5 Camaros are about the same weight. Food for thought.

Andrew

That's a good idea. I'll check that out. I initially didn't want to offer the 5th Gen rear brakes because of the front mismatch, but a front adapter would solve that issue.