JLMounce
01-20-2026, 08:02 AM
A couple months back I tore out a set of 12 year old Hotchkis 3" drop leafsprings and the 2" drop coils out of my 1969 Firebird. After adding a more powerful engine, the hotchkis leafs were exhibiting some handling characteristics that I wasn't keen on. While they still managed axle wrap under straight line conditions decently, on throttle corner exit started to get really hairy and unpredictable. Additionally, security under braking had gotten quite a bit worse. The rear end was no longer in the pavement.
I've long felt that the car has been a little too soft for the way I drive it, so I opted for some minor upgrades. However, because I've already got an SC&C stage 2+ kit on the sub-frame and a nice exhaust in the rear, I was pretty locked in to going with some sort of hybrid coil-over setup to get more spring rate in the front and keeping leaf springs in the rear. I opted for the QA1 Pro Coils in a 600 lb rate with their double adjustable shocks. For the rear I had Global West build me a set of their Cat5 leaf springs. Target rate on those was 180 lbs. I initially had a set of double adjustable QA1's in the rear as well, but ended up swapping those for a set of Verishock Quickset 2's. More on that in a second.
After the swap, handling characteristics were much better and over-all ride quality actually improved as well, especially in the front. The stiffer spring and slightly higher ride height is letting the progressive jounce bumpers do a better job, so there's less of a jarring nature to how the front end works over road imperfections. Rear ride is firmer, which was to be expected, but not harsh. The problem I'm running into is the back end won't stop bouncing.
Almost immediately it was apparent something was going on. I quickly surmised that the rear shocks lacked enough compression distance. The QA1 DA's have a modular design to the mount and it eats up a solid inch of your actual compression travel. I was just bottoming the shock as a result. I had Verishocks on this previously, so I went straight back to that shock, but in a double adjustable instead of the standard valved shock. This helped by a good amount, but didn't completely get rid of the bounce.
Next problem I discovered is that the top of the leaf springs were crashing in to the roof of my RideTech subframe connectors. I removed the rood section aft of the leaf eye centerline and made sure there was clearance everywhere to allow the leafs to pivot as intended. This also helped, but I'm still dealing with bouncing from the rear. All that I really have left in the toolbox at this point is changes to the shocks. The issue I'm running into is I can't get much compression in the shock before the car starts skipping. At 4 clicks from soft, the ride is starting to degrade. At 5 clicks from full soft, the rear end is skating over road imperfections. On the rebound side, I'm still lacking enough rebound authority to actively stop the oscillations. Even at settings nearing max hard. When I've got 12-14 clicks of rebound in the shocks, there's so much rebound damping, that the car once again develops quite a bit more oversteer than I am looking for. It's more controlled and not snappy like previous, but it's not ideal.
Because I'm at or near the limit of my ability to control rear oscillation, I've softened the front a bit as this is a tactic I've read may help improve porpoising. Here I can only go so far before the front ride gets floaty.
Apologies for the long post, but I'm hoping some experts around here may be able to poke some holes in what I'm doing here. I anticipated a stiff ride with this upgrade, I didn't anticipate so much bouncing that it kills the enjoyment of the vehicle.
Thanks in advance!
I've long felt that the car has been a little too soft for the way I drive it, so I opted for some minor upgrades. However, because I've already got an SC&C stage 2+ kit on the sub-frame and a nice exhaust in the rear, I was pretty locked in to going with some sort of hybrid coil-over setup to get more spring rate in the front and keeping leaf springs in the rear. I opted for the QA1 Pro Coils in a 600 lb rate with their double adjustable shocks. For the rear I had Global West build me a set of their Cat5 leaf springs. Target rate on those was 180 lbs. I initially had a set of double adjustable QA1's in the rear as well, but ended up swapping those for a set of Verishock Quickset 2's. More on that in a second.
After the swap, handling characteristics were much better and over-all ride quality actually improved as well, especially in the front. The stiffer spring and slightly higher ride height is letting the progressive jounce bumpers do a better job, so there's less of a jarring nature to how the front end works over road imperfections. Rear ride is firmer, which was to be expected, but not harsh. The problem I'm running into is the back end won't stop bouncing.
Almost immediately it was apparent something was going on. I quickly surmised that the rear shocks lacked enough compression distance. The QA1 DA's have a modular design to the mount and it eats up a solid inch of your actual compression travel. I was just bottoming the shock as a result. I had Verishocks on this previously, so I went straight back to that shock, but in a double adjustable instead of the standard valved shock. This helped by a good amount, but didn't completely get rid of the bounce.
Next problem I discovered is that the top of the leaf springs were crashing in to the roof of my RideTech subframe connectors. I removed the rood section aft of the leaf eye centerline and made sure there was clearance everywhere to allow the leafs to pivot as intended. This also helped, but I'm still dealing with bouncing from the rear. All that I really have left in the toolbox at this point is changes to the shocks. The issue I'm running into is I can't get much compression in the shock before the car starts skipping. At 4 clicks from soft, the ride is starting to degrade. At 5 clicks from full soft, the rear end is skating over road imperfections. On the rebound side, I'm still lacking enough rebound authority to actively stop the oscillations. Even at settings nearing max hard. When I've got 12-14 clicks of rebound in the shocks, there's so much rebound damping, that the car once again develops quite a bit more oversteer than I am looking for. It's more controlled and not snappy like previous, but it's not ideal.
Because I'm at or near the limit of my ability to control rear oscillation, I've softened the front a bit as this is a tactic I've read may help improve porpoising. Here I can only go so far before the front ride gets floaty.
Apologies for the long post, but I'm hoping some experts around here may be able to poke some holes in what I'm doing here. I anticipated a stiff ride with this upgrade, I didn't anticipate so much bouncing that it kills the enjoyment of the vehicle.
Thanks in advance!