AFCO and DSE vs Hotchkis TVS

[JLM]

I need to start picking out suspension components for my Firebird. I'd really like to get this right the first time. The car will be primarily a street car but it will see some open road style events and a few auto-x's here and there.

The car is pretty nose heavy. It has a pontiac 455 with iron heads and aluminum intake up front. Later on down the road and intercooler, turbo and piping will also be added. battery will at that point be moved tot he trunk.

Would you go with:

a) Hotchkis TVS with QA-1's
b) AFCO 700 or 750 lb springs, DSE rear leafs with QA-1's (stock front sway bar, no rear bar)

If you were to choose (b) would you go with the 2" or 3" rear leafs, and 700 or 750 lb front springs? How much springs would need to be cut up front?

I plan on doing slide-a-link in the rear as well. Any information and suggestions would be most helpful. Thanks in advance.

[wally8]

I can't help you with spring rates (I'm more of an A-body guy) but I could take some guesses if you can give more specs on the car (weight, and other things).

In any case, I'd recommend going with the AFCO's and some hidden weight jacks. Look up Dennis68's website if you want to see how they work. This will give you an in on cheaper springs and let you set your ride height any way you want without having to cut coils.

Here's a catalog link for the adjusters: http://www.speedwaymotors.com/xq/asp...qx/product.htm

As for shocks, I prefer bilstiens for a general, good quality shock. adjustables are over rated since you don't need to change them once you have them set (unless you run different tracks or something like that).

Sorry, can't help you on the rear except that AFCO makes leaf springs too (no recommendations though).


Wally

[dennis68]

I'll second the Bilsteins.

The AFCO hidden adjusters can be seen in the suspension page of my site (link below). You shouldn't need to cut any spring at all, that is what the adjusters are for. 750 might be a little stiff for an "F" body. I think Carl runs 650's and his Camaro sees much track time.

[chicane67]

b) AFCO 700 or 750 lb springs, DSE rear leafs with QA-1's (stock front sway bar, no rear bar)

If you were to choose (b) would you go with the 2" or 3" rear leafs, and 700 or 750 lb front springs? How much springs would need to be cut up front?

Well, you really need to find out what the rear leafs are rated at before you just throw out the 700 - 750 pound rate numbers. I would really need to know more about the chassis and other mods to even think about giving you a direction on rates. To run a 700 - 750ish front spring, you may just need a 300-320 pound rear. I myself run a 720 front with a 320 rear (with a small block) and I think its the ticket..... but that is for my specific chassis.

To really run a 700 front, you will need something in the 'hood of a 250 pound rear..... or so. You could probably get away with something as little as a 225.

I will also third the Bilstein recommendation, and if you do go that route, let me know and I can give you shock valving numbers for the spring rates you are looking at.

***OOPS***

I just re-read your post and an iron 455 will need more than a 700. Its more like a 750 to 800 with the weight you are talking about. Anywho, the offer still stands on the shock valving but you need to get more information on the rear spring rates available to you. If you dont find anything to your liking, I build F-body rear leafs for exactly what you are trying to do..... minus the slide-a-links. They are not necessary if the spring is designed correctly.

[JLM]

The DS&E units are 175 lbs I believe. So is 750 lb springs up front too soft then given the weight on the front end? So many choices. I'm glad you guys are here! I'm going to check out your sight now Dennis, thanks.

[chicane67]

No, the 750's are not too light...... but the rears are........

[dennis68]

I missed the part about the B/B too. That changes everything, especially a Poncho motor. 750's might even be a little soft.

[Ripper]

This might be a little off-topic, but one thing that suprises me is that american car builders tends to go with very soft springs. I ran 650 lbs/in on my Firebird -74 last season (app. 1.3 Hz, don't remember though..) and I thought it was way too soft, the car pitched too much during hard braking wich made it hard to control in the turns.

This year, I'm gonna try a pair of 1150 lbs/in springs and step down in sway bar diameter instead (together with 150 lbs less weight will that take me over 2.5 Hz).
My car is still a street car that will see some track days per year (5-8 I guess) and some AutoX.

I wonder if this is different filosofy, or if the tracks pavement are different?

I would say that 700 lbs/in is ok if you plan to ride with your car, but if you plan to drive it, you should go stiffer. ;)

[wally8]

I'll throw in my spring experience.

Softer is somewhat faster within given parameters. In a nutshell; if your suspension maintains decent geometry through a given range of motion, then softening the springs to the point where that range of motion is fully used will make the car faster in the end. You may think it rolls too much or you don't like the feel but the car will be faster if driven to the limit.

You need just enough spring to accept the weight transfer in the given travel that still maintains geometry. That's why picking springs involves a lot more than just knowing the weight of the car and the lateral g that you'd like to attain applied to the track width.


Wallly

[JLM]

Okay so here's where I'm at then 750+ lbs/in springs for the front, 250+ lbs/in spring rates in the rear.

It looks like acquiring the rear leafs will be the tricky part. Most of the off the shelf companies like DS&E and Hotchkis don't have the springs rates that I need.

Only question with the coil springs is what length do I need?

Question: The car will see on track events but primarily be a street car. I'd like to have at least "okay" ride comfort. would it be too much to assume that I could run a lower rate in the rear and add a small sta-bar to stiffen the back end up a little more to compensate for the front. Ultimately I would like the car to be as balanced as possible. If that means dealing with a harsh ride I'm okay with that, but it would be nice to have a somewhat smooth ride.

[dennis68]

That sounds OK, you can tune the rest with sta-bars from there.

Spring length??? You are running the AFCO style coils correct? There are only a few lengths, the most common is the 9.5" and offers the most selection of spring choices. Together with a 5.5" adjuster will put your total free length at 15". If at it's lowest adjustment you are not satisfied with the height you can pull the adjuster out at cut some off the top to give it a shorter starting point.

[JLM]

Okay here's my plan. Thanks for all the input on this, it's been much helpfull

-AFCO front springs 9.5" long with 5.5" adjusters (850 lbs/in)
-Custom built rear leafs de-arched to drop 2". 1" lowering blocks if needed (300 lbs/in)
-Bilstien shocks
-tune with sta-bars if needed.

[Mean 69]

Softer is somewhat faster within given parameters. In a nutshell; if your suspension maintains decent geometry through a given range of motion, then softening the springs to the point where that range of motion is fully used will make the car faster in the end. You may think it rolls too much or you don't like the feel but the car will be faster if driven to the limit.

Very well put, I agree completely. In general, folks/companies put really tight springs in cars to mask the geometry issues. Late model Mustang guys, with the Mc-strut are clear examples. Most run a really high wheel rate to overcome camber issues.

Just a general comment, don't forget the motion ratio! Comparing Firebirds to Camaros is fine, but I am not so certain the motion ratio for an A-body is the same as the F.

Mark