Suspension: Springs

[davbert]

Quote:

Originally Posted by George Willet So Davebert, you have a spring farm like I do??? Interesting thread, it is a good thing that some of go testing to find out what works and what doesn't work so that we can spend the winters doing the calcs, and wishing we were out on the track again.

[bryan]

Quote:

Originally Posted by davbert so does this mean 1:3 motion ratio and 1:9 force ratio? any insights on why the numbers are coming out so low?

[George Willet]

Davebert, I hate oneupmanship, so this is just to state a fact. I have NASCAR springs in MY farm.

They are more consistant in rating and are available in 100 lb increments, and are standard in height. Also a better grade of wire??

[davbert]

Quote:

Originally Posted by George Willet Davebert, I hate oneupmanship, so this is just to state a fact. I have NASCAR springs in MY farm. george They are more consistant in rating and are available in 100 lb increments, and are standard in height. Also a better grade of wire??

[vintage prep]

Most of that stock car stuff was available 10-15 years ago, but they were well kept secrets at the time

BTW, after reading the last 15 or so replies, I'll say that my race car engineering books, Milliken, Staniforth, Van Valkenburg and Adams all say spring rate at wheel center is different than at ball joint.

[105.31]

Quote:

BTW, after reading the last 15 or so replies, I'll say that my race car engineering books, Milliken, Staniforth, Van Valkenburg and Adams all say spring rate at wheel center is different than at ball joint.

[BlpltGTV]

Ok, after reading all 7 pages of this post, and understanding most of it, who has the best springs for autoX on a street driven 105? I'm thinking of the AR Ricambis, or perhaps calling Orion. My car needs a full suspension overhaul (its original to the car), and I'd really like to make it the cornering monster (without going way overboard) I don't mind somewhat harsh, but I don't want to recreate my Datsun that is hard, to the point of being painful on rough roads. I came to this conclusion this afternoon when I chased a brand new Porsche Turbo onto the freeway and could have thrown down a really sweet pass through the corner (had I wanted to be really stupid, the guy in the Porsche did that for me.)
That said, here are my thoughts, a set of Koni yellows with Poly bushings and ajustable upper upper control arms. I'd go with a set of Centerlines or IAPs but those seem to be more to lower the car for the sake of lowering it a little bit. I admit I'd like to bring my car down a little more than 1 inch, and I do understand that will send the roll center underground. I'm also thinking of running a set of 15" Panasports and hopefully loose some rotational weight while I'm at it (the stock steel wheels are so heavy and flexy.)
So what would be your recomendation? I like quick turn in and a car that is has a little bit of power-induced oversteer. The car most likely won't see the track, but should I want to, I'd like to have it set up to be surprisingly fast through a corner (a serious momentum car.)
I'm taking all thoughts into consideration before I buy anything. Think of it as trying to do my homework. I know traction is everything, so a too high of a spring rate isn't going to help, nor will the shocks be able to control the mega springrate. I think swaybar choice will be key as well (thinking 29mm up front). Yes I've read the Brits Vs Yanks post.

Thanks,
Will

[George Willet]

Will, the Centerline front springs are very good for the street and mild racing, and the rear springs for the 72-74 GTV in their catalog will give you a controlable oversteer without getting into dangerous territory. Just use stock shocks in the rear, or Koni red set on soft, (they are the same rate); and Koni yellow in the front set at soft to start with, follow the Koni web site on how to adjust them for your set-up and driving style. No rear antiroll bar.

Lower the car as much as you can for the terrain in your area so the oil pan doesn't drag. The lower the car, the less leverage in roll. Do it by eliminating the rubbers on the top or bottom of the front spring as needed to get the ride height you want. Make the rear the same as the front in ride height, even if you need to cut a bit off the open end of the rear spring. It will be a one to one ratio in the rear; cutting off one inch in static spring height will lower the rear one inch. It is about a 3 to 1 ratio in the front. Remove the rubber bump stops front and rear, they won't be needed with the stiffer springs, and can cause the car to spin if the car bottoms out on them.

Use stock bushings in the rear. The result you want is for the front to controll roll, and have the rear follow the front. Don't worry about roll centers, what we are trying to do is have matching roll couple: IE the rear rolls the same as the front in the middle of the corner, called neutral cornering

Use the Poly bushings for the caster rod in their (Centerline's) adjustable camber rods, and set the camber at one degree negitive (for the srteet), with caster set at minus 2 degrees; use slight toe out with radial tires, and slight toe in with bias ply tires.

Be sure that there is a Alfa Romeo lettering on the rear of your car, so the Porsche driver knows what blew past him. And have fun.

I've been using the above set up in cars I've built for years, with happy customers; and it is inexpensive to do. Hope this helps.

[60sRacer]

George is, of course, right on. One small subtilty you might choose: Swap your trailing arms for a pair from a 67. These have a smaller front bushing, which is a bit stiffer. Don't bother with the poly's here - they do little, squeek badly (even if installed well) eventually, and wear out way too fast. I think Paul Spruel makes an aluminum bushing reducer that adapts the smaller rubber from a 67 to the later trailing arms on your GTV.

Of course you then have to find a set of the early small bushings. Already premium priced, they are hard to find.

For a front sway bar, 29 mm is good. Be sure to reinforce the chassis where the bar mounts - the little straps are not storng enough for a vigorous work-out with the stiffer bar. poly bushings and link ends are available for these and give a little tighter control but only a small benefit for the $$$. If you can find one of the lever arm styles (the stock is just a bent bar) like the old Shankle one you again get a little more precision.

Depending on how you end up in the set-up, you might do with a rear sway bar. Do without as George recommends and you get neutral to slight understeer, which is the best overall set-up. Use your stock one for a little more oversteer - good on tight or slow corners to get a bit faster exit, but dangerous on straight and bumpy roads where the car can wander, or on fast exit ramps that tend to wind up tighter - oversteer and heavy braking as you approach the stop sign can spin the car unless you are very careful.

Shankle made a lever arm rear bar like the front one. It came with several different holes in the arms, and others can be drilled as well, to change the lever arm length; another way to tune the over/under steer. At the shortest, a different link will be needed to wrap around the axle on the front side, though this may be too much stiffness for a street car.

After the springs and shocks, the poly bushing on the rear end of the front caster arm (upper) makes the biggest difference in handling. [Except for spiders, where a chassis stiffener is even more important]. Be sure to get the alignment done carefully - caster and camber are very important.

Then get a great set of tires to go with the Panna's; Falkens are favored by many on the BB (or Hoosiers for the AX crowd).

And as always, reconsider track time. Join up with your local club for a great day of AX. Get one of the leaders to take you on a test run. The driving experience will do wonders for your ability to eat Porches. Nothing you can do to your car at all will beat what you can gain from seat time on a track or AX course, especially with good lessons. Besides, its really cool to drive in a helmet for a reason.

Robert

[jimcra]

Sunday morning, put Koni Sport yellows 80-1551 on the front of 74 GTV adjusted right in the middle. Have AR Ricambi red springs all around, Koni red in rear and 14" Panasports with Falken Azenis RT-615 195/60/14. Just my 2 cents, a little soft. Will turn it up a notch and add poly to front sway bar. Testing as I go...

[60sRacer]

Nothing wrong with feeling a little soft. Good handling is not from board stiff suspension - look at the BMW GT's - lots of spring travel makes bumpy roads smooth, which means more contact. It's tight control of sway and roll that matters on the stopwatch. It's hard to keep the Alfas from rollign more than you like, especially the Spiders. the front roll center is just too low, and you can't do much at the back to compenstate without BIG changes [sliding block, Watts link, Panhard rod, all of which mess with the emergency brake].

If you're testing one piece at a time, find a way to standardize your tests and measure the results. Seat-of-the-pants feel will mislead you, not make you faster. To prove this, just add a really stiff rear bar and drive a wildly oversteering car. Feels like you in a slot car track when on slow street corners, but can kill your stability on a long fast road.

Robert

[bryan]

Quote:

Originally Posted by jimcra Have AR Ricambi red springs all around,

[jimcra]

I'll measure and count the coils tonight. AR Ricambi is printed in script on the springs if that makes a difference. The Koni reds I removed were set on full stiff. It might be my imagination but they seemed stiffer than the yellows set at half? I do tend to like a stiffer ride, although 60'sRacer is correct in that set at half, the ride is very smooth and precise at 65-70MPH. I do appreciate the input from everyone...

[turbolarespider]

Quote:

Originally Posted by 60sRacer Nothing wrong with feeling a little soft. Good handling is not from board stiff suspension - look at the BMW GT's - lots of spring travel makes bumpy roads smooth, which means more contact. It's tight control of sway and roll that matters on the stopwatch. It's hard to keep the Alfas from rollign more than you like, especially the Spiders. the front roll center is just too low, and you can't do much at the back to compenstate without BIG changes [sliding block, Watts link, Panhard rod, all of which mess with the emergency brake]. ... Robert