Sprung Vs Unsprung Weight / A Rear End Swap Observation

[GoDadGo]

Hey Gang,

The Project Car / My Son's 2000 Camaro:
1. I've been doing some work on my son's old car and did a complete rear end swap because the OE unit crapped out again.
2. The only change was the replacement of the 7.5" super light stock rear end to a rather beefy custom built Ford 9" rear from Quick Performance.
3. The springs, shocks and brakes remained the same but the stock control arms, torque arm and panhard bar were replaced with stronger tubular versions.
4. Wheel and tires are the same with 255/40-17's up front with 275/40-17's out back.
5. The rear ride height was increased by roughly 5/8" because of the spring mount locations.

In The Video Below You'll Find The Sheep In Wolf's Clothing:
https://youtu.be/jDd9F58WIEE

My Take Away From This Change:
1. The only change made was replacing the rear end so roughly 78-80 pounds was added to the car; however, all of that weight is unsprung.
2. Being OCD I scaled the car before and after the rear end change which helped balance the car go from 54%F / 46%R to 52%F / 48%R.
3. Driving the car before the swap felt more nimble but now it feels more sluggish with the heavier rear end.
4. The car does feel less tail happy when doing heavy corner carving and doesn't feel bad but does feel different.
5. Both rears had similar gear ratios 3.73 vs 3.70 and both have Eaton Style Tru-Trac differentials.
6. My biggest observation is unsprung weight really matters a lot more than I thought it would and the car feels better anchored but a bit more sluggish.

Anyway gang, what are your thoughts?

[JMD]

Great observations. I've always heard that unsprung weight is the devil. Performance drivers will go to great lengths to shave off a few pounds of unsprung weight, so I can imagine that adding 80lbs unsprung weight to one end of the car would make a very noticeable difference in handling. Sounds like your son's car is now less adept at corner carving but better set up for drag racing. ;)

I think this could also tee into the conversation about how much difference there is in handling between the IRS and solid axle roadsters and why. I don't have any experience with solid axles in these cars as mine is IRS and I've just started driving it, but would love to see if you observations carry over to this platform from those who have experienced both.

I had a 3.8L Camaro 25 years ago in high school as well, it was the older body style as a 1996. Did some minor performance bolt on upgrades to it. It was a wonderful car and the perfect amount of power for a high school age person who's into cars. I appreciate you're showing it some love and keeping it around. I can't believe we are now considered antiques...I mean, that those cars are considered antiques... ;)

[Mike.Bray]

Do you have a rear sway bar? I'm building a 68 Camaro and will be swapping out the 10 bolt for a 9" Quick Performance rear. A rear sway bar is in the plans, already have a big one in the front. I've also install gas shocks all around.

[PNWTim]

Do you have a rear sway bar? I'm building a 68 Camaro and will be swapping out the 10 bolt for a 9" Quick Performance rear. A rear sway bar is in the plans, already have a big one in the front. I've also install gas shocks all around.

Mike - not sure if you have picked out your rear sway bar but they are very difficult to fit to a Gen 1. There is a lot in the way (exhaust, fuel tank, frame rails, etc.) but perhaps with you 9" you are going to a 4 link or something else.

[GoDadGo]

Do you have a rear sway bar? I'm building a 68 Camaro and will be swapping out the 10 bolt for a 9" Quick Performance rear. A rear sway bar is in the plans, already have a big one in the front. I've also install gas shocks all around.

Yes, the old Camaro sports front and rear sway bars with urethane bushings.
Both were upgraded in size, but I don't recall the manufacturer.
I made sure that Q.P. added the sway bar mounts.

[gbranham]

How is this a Roadster thread? Maybe move to OT discussion.

[GoDadGo]

Great observations. I've always heard that unsprung weight is the devil. Performance drivers will go to great lengths to shave off a few pounds of unsprung weight, so I can imagine that adding 80lbs unsprung weight to one end of the car would make a very noticeable difference in handling. Sounds like your son's car is now less adept at corner carving but better set up for drag racing. ;)

I think this could also tee into the conversation about how much difference there is in handling between the IRS and solid axle roadsters and why. I don't have any experience with solid axles in these cars as mine is IRS and I've just started driving it, but would love to see if you observations carry over to this platform from those who have experienced both.

I had a 3.8L Camaro 25 years ago in high school as well, it was the older body style as a 1996. Did some minor performance bolt on upgrades to it. It was a wonderful car and the perfect amount of power for a high school age person who's into cars. I appreciate you're showing it some love and keeping it around. I can't believe we are now considered antiques...I mean, that those cars are considered antiques... ;)

I really appreciate your observations, especially since you owned a "Sheep In Wolf's Clothing" too. Your takeaway of the Solid Axle vs IRS is spot on as well.

As for me when I ordered my kit on 11/10/2014 the current IRS was not yet offered so I ordered the 3-Link rear. My buddy Donny ordered his kit (20th Anniversary MK-4) just before mine arrived and so he did get the New/Current IRS rear. The ride and cornering is superior compared to my MK-4; however, when we've played the stoplight game my car "Hooks & Books" a lot better even though we have similar power with similar rear gear ratios in spite of the fact he's running a larger well built 428 FE Ford while I'm running a smaller similarly well built smaller Dart 383 SBC. The other difference is I'm running the harder 200 TW NT-05's while he's got the stickier 100 TW NT-01's on his MK-4. The fact that my MK-4 out handled my beloved 1995 C4 Corvette in every way (See Video Below) is like comparing apples to oranges. That old Vette has a Gen-2 SBC, the same ZF 6-Speed and an IRS rear while the MK4 sports a solid axle.

My issue with my son's Catfish Camaro is that the car feels different, a lot different, than it did before the rear end swap.

Beloved C4 & 2000 Catfish Camaro:
https://youtu.be/svZX2BMSDEs

Having the solid axle in the Redbone Roadster probably gives my car superior straight line characteristics while still yields great handling, though not up to the IRS standard. In 2020 I sold my old beloved C4 which had 285,000 miles on it when I sold it but I must admit that I still miss that car that had for 25 years. The good news is I still see it around town and it is still going strong. Since I'm more of a drag racer than a corner carving fellow (See Video Below) I still enjoy playing the stoplight game while also going on back country runs with my Porsche Pals.

Cruising In Redbone & Giving It The Beans:
https://youtu.be/GpqvBPwIbzI

My recommendation to guys getting ready to pull the trigger is if you want superior handling, then get the IRS; however, if you want the best straight line performance that still produces great handling, then get the 3-link.

[CraigS]

I am surprised that you feel the car is sluggish. That extra 75-80# is like having a 10 year old kid as a passenger so your butt dyno must be very sensitive.

[GoDadGo]

I am surprised that you feel the car is sluggish. That extra 75-80# is like having a 10 year old kid as a passenger so your butt dyno must be very sensitive.

Craig,

I too am surprised and totally agree with you.

1. What has shocked me is because the car feels noticeably different than it did before the change.
2. Could it be more related to the fact that I replaced the control arms, torque arm and panhard bar?
3. Maybe it is just different and not sluggish because it does feel well planted when doing hard cornering.
4. The originals parts had rubber bushings but showed no cracks while the new parts have polyethene bushings.
5. Another observation, when comparing it to the Redbone Roadster, is it really is a lot of fun to drive a slow car fast.

The bottom line is I just don't know and that is okay because it is what it is.

Steve

[CraigS]

I agree w/ #5. There is something enjoyable about running a car to redline in 1st, 2nd, and maybe 3rd gear. Even when it is an 8 second 0-60 car. As we get faster cars there is less chance to do that because the mph just gets too unsafe on normal roads. I now have a 19 Stingray which does 80mph in 2nd. I sure don't get to do that very often.