Leaf Springs for 2nd gen T/A

[Henesian]

So, now that I have almost everything done and know how the car actually feels, it's time to start looking into aftermarket leafs. I have a pretty balanced set up running equal sized tires front and back. Currently 255/60/15s, but will be 275/40/17s all around in some unknown number of months or years.

Front Suspension
UCA - Pro-touring F-Body with tall balljoints
LCA - stock lowers with reasonably new polyurethane bushings, but old BJ(done by previous owner).
Steering links and system - stock, with unbelievably super god damn fast power steering unit.
Shocks - AFCO 1020 7/7 valve.
Springs -Third gen GM 700 lb/in 13.25" tall springs.
Sway bar - Stock T/A 1-1/4" solid with polyurethane links.
Brakes - Stock T/A with new discs and new 2.937" bore calipers.

Rear suspension
Springs - Stock T/A 4 leaf with polyurethane spring eye and hanger bushings.
Shocks - AFCO 1031(I think is correct part number) 6/6 valve.
Sway bar - ADCO 7/8 solid bar with 6" arms and their race downlinks(identical to the pro-touring f-body links) with polyurethane bushings all around.

Chassis
Subframe bushings - stock rubber
Subframe Connectors - N/A
Driveline/Powertrain - smog legal Pontiac 400 making about 275-300 horsepower mated to a TCI SuperStreetFighter TH350 with TCI Breakaway 10" 2400-2600 RPM stall torque converter to stock T/A driveshaft with 8.625" 10-bolt with stock axles and drums and 2.73 gears.( I can cruise on the highway at 2000 rpm at 60 and get 20mpg if going constantly.

After all these upgrades, it's super balanced. In the 50-90mph corners, I can go through the corner entry with the secondaries open, or even full throttle in some cases, and the car sticks like glue. I think this is mainly because I'm not putting down enough horsepower to the ground.

Could I gain some handling ability without losing that balance by using aftermarket leafs?

https://static1.pt-content.com/images/pt/2011/09/IMAG0191-1.jpg

Car's jacked up, thats why things are loosened up and the UCA is down.

https://static1.pt-content.com/images/pt/2011/10/IMAG0193-1.jpg

https://static1.pt-content.com/images/pt/2011/10/IMAG0090-1.jpg
Before the UCAs. Car looks the same, just with more camber.

[opnwide]

If its already balanced, then any change you make will make it handle WORSE! You could go with some performance springs in the 175lb (DSE, Hotchkis) or even higher, but you're balance will be off. With that said, you're running pretty strong front springs (700lb) so I would normally think a 200-220 (Afco) rear spring would be appropriate. You will need to remove that sway bar, though, as you will then have oversteer. I think the stock TA rear spring is 136inlbs or something like that.

Herb Adams believes you should only run enough spring to keep the car from bottoming out where you like to run (ie the track). Lowered cars generally need more spring rate. Is the rear suspension bottoming out? If so then def time to upgrade.

Lastly, are you sure your car is balanced? Have you taken it to a skid pad or a track? You should never drive 90-100% on the street.

[SLO_Z28]

If youre happy with it, then leave it alone! I would wait untill you get your final wheels/tires before you put any more work into it. It looks like you nailed it with the upgrades you made!

[Henesian]

If its already balanced, then any change you make will make it handle WORSE! You could go with some performance springs in the 175lb (DSE, Hotchkis) or even higher, but you're balance will be off. With that said, you're running pretty strong front springs (700lb) so I would normally think a 200-220 (Afco) rear spring would be appropriate. You will need to remove that sway bar, though, as you will then have oversteer. I think the stock TA rear spring is 136inlbs or something like that.

Herb Adams believes you should only run enough spring to keep the car from bottoming out where you like to run (ie the track). Lowered cars generally need more spring rate. Is the rear suspension bottoming out? If so then def time to upgrade.

Lastly, are you sure your car is balanced? Have you taken it to a skid pad or a track? You should never drive 90-100% on the street.
It doesn't even come close to bottoming out. The car barely moves one way or another up and down because of the 50/50 shock valving(I think). Yes. I'm sure the car is balanced. I do a lot of random weekend canyon driving where I've driven the car 90-100%. On the street, I've only really opened it up on a turn where I knew there was nobody, and it was like 10pm and I was coming home from school. There's a few turns that I know how fast the car can go and are low risk because the road is so wide. I know that on a slow 30-50 mph street turn, if I hit it hard too early the car will get a little out of wack and I'll look like Steve McQueen making the huge left turn with the in car camera view of him muscling the wheel, but I think that's just because of stupid Radial T/As.



And I definitely wanna keep the rear sway bar.

[exwestracer]

You could gain some rear grip (from springs) if you have travel to spare. Likely you are going to run up against the limits of those tires before you see any further improvement from suspension components. If you feel like the shocks are holding the car up in the low/medium speed stuff, you might make some gains by going to a digressive shock package.

Sounds like you're pretty happy with it. I'd enjoy the car as is until you change up the wheel/tire package; then you'll have a whole new can of worms to deal with...

And canyon driving IS the streets...

[Skip Fix]

A tire change will make more difference. When I went form 255-60-15 Eagl Wingfoots to 255-50-16 BFGs on my TA it was almost like swapping on road race slicks.

My car actually felt pretty neutral with the stock rear springs and stiffer front springs and Bilsteins from Guldstrand.

[Henesian]

You could gain some rear grip (from springs) if you have travel to spare. Likely you are going to run up against the limits of those tires before you see any further improvement from suspension components. If you feel like the shocks are holding the car up in the low/medium speed stuff, you might make some gains by going to a digressive shock package.

Sounds like you're pretty happy with it. I'd enjoy the car as is until you change up the wheel/tire package; then you'll have a whole new can of worms to deal with...

And canyon driving IS the streets...
Lol. I hear ya. And no it's not when it's the most well paved roads, super lawless(never patrolled), and no one ever on it besides me. haha.

[SLO_Z28]

I think you need to hit up the next autocross you can get into, and see how the car feels when driving on the limit when on a controlled course.

[Henesian]

I think you need to hit up the next autocross you can get into, and see how the car feels when driving on the limit when on a controlled course.
Don't I need an SCCA license first? Or is it just like the drag strip where for a street car, if you got the money and the car passes tech you're fine?

[SLO_Z28]

At any SCCA event you can just show up and buy "weekend membership" for $15, and that comes with a coupon to credit 100% of that to a full membership. I wouldn't worry about what class you're in, they'll help you with that, I would just focus on learning what an autocross is and having fun. The only thing you need is a safe street car(no major leaks, brake pedal doesnt drop to the floor, battery secure, trunk/interior free of debris that can roll around, and a helmet). If you dont have a helmet most clubs have loaners for you.

[badazz81z28]

The worst thing you can do to a suspension is mix and piece parts. I would recommend a kit like the Hotchkis TVS.

Once you are there...don't go cheap on shocks.

BTW, you need SFC! They are must

[SLO_Z28]

The worst thing you can do to a suspension is mix and piece parts.


I would argue not. I have mix and matched parts on my car, and it handles extremely well. I would also offer that the Hotchkis HPS shocks are the equivalent of what he ordered. Hotchkis springs are on the soft side for a autocrosser, but good for a driver.

[Henesian]

At any SCCA event you can just show up and buy "weekend membership" for $15, and that comes with a coupon to credit 100% of that to a full membership. I wouldn't worry about what class you're in, they'll help you with that, I would just focus on learning what an autocross is and having fun. The only thing you need is a safe street car(no major leaks, brake pedal doesnt drop to the floor, battery secure, trunk/interior free of debris that can roll around, and a helmet). If you dont have a helmet most clubs have loaners for you.
Lol, you wonder why my 2nd Drag Race helmet is a full face Bell Sport SA2005. So I could AutoX with it as well. well, the only debris I have rolling around is a box of spare quarts of fluids lol, obviously coming out.

[Henesian]

The worst thing you can do to a suspension is mix and piece parts. I would recommend a kit like the Hotchkis TVS.

Once you are there...don't go cheap on shocks.

BTW, you need SFC! They are mustWhy would I get the Hotchkis TVS when it my springs are 700 lb/in, theirs' are 600 lb/in. Just one example. Good choice. The AFCO shocks are not cheap shocks. Just because they're $64.99 a piece doesn't mean they're cheap. They're special shocks for Circle Track Street Stock classes that need stiff enough shocks for 1250 lb/in springs and banking, but in a stock configuration. Do I love them? Yes. They are amazing. Do I have equal rate side to side? Yes. Were they completely worth the $250 risk? Yes. Do they have drawbacks? Yes, 4" total stroke. Do I care? No. Not necessarily, I just take off the top when I jack the car up, five minutes of extra work.

[Henesian]

I would argue not. I have mix and matched parts on my car, and it handles extremely well. I would also offer that the Hotchkis HPS shocks are the equivalent of what he ordered. Hotchkis springs are on the soft side for a autocrosser, but good for a driver.

Lol, I call it "Old Man Asscheeks". Compromise between ride and handling because you're an old man with no ass lol.

[exwestracer]

Lol, I call it "Old Man Asscheeks". Compromise between ride and handling because you're an old man with no ass lol.

You may have a different opinion when you get those low-profile super tires on the car... Too stiff means you are shocking the sidewall on every turn-in or road irregularity. Those 60 series tires will put up with a lot.

[Henesian]

You may have a different opinion when you get those low-profile super tires on the car... Too stiff means you are shocking the sidewall on every turn-in or road irregularity. Those 60 series tires will put up with a lot.
Lol, This I know; first hand experience. My friend's Nissan 240sx with 8k/6k STANCE GR+ coilovers and 235/40/18s on 18x9.5s all around. The ride was so stiff and abrupt it made my manboobs jiggle every time lol.

[SLO_Z28]

You may have a different opinion when you get those low-profile super tires on the car... Too stiff means you are shocking the sidewall on every turn-in or road irregularity. Those 60 series tires will put up with a lot.

700 isnt stiff, you wont lose compliance with that spring rate.