Whatever you decide, one of the biggest improvements to the balance of the car is to get it corner weighed and corrected.

This will make the car balanced and thus brake real straight under pressure, etc. This is why race cars have adjustable spring platforms, so they can move weight around by jacking up a corner, etc.

With the front suspension design it is possible to lower the spring and thus move more weight forward (er, probably do not want to do this ... ) by simply adding spacers between the wishbone and spring plate.

Anyway the most important thing is to get the weight with the driver in the car even on both sides, ie. each front wheel carries the same weight and ditto for the rear. As explained above the front is easy to do ... but the rear (with the standard setup) is not.

Pete

 

Ride Heights

On a similar note...

By lowering a GTV or any other similar car by approx 1-2inches, how much is gained in terms of handling, and brake dive?

What is the weight distribution of a 105 gtv? does lowering a car tighten the roll significantly? or is all just aesthetics?

The way I'm imagining the whole thing is that the CoM is sitting a little lower inbetween the geometry of the chasis/suspension.

mmm....

 

My advice would be go with the setups developed by the people who've been doing this for a long time. Harvey Bailey (who used to race GTAs) in Europe and I think the Ward and Dean setup is similar.

I have copied the Harvey Bailey setup - 600 lb front springs, 30mm lower and 180 lb rear springs, 35mm lower - with a 27mm front anti roll bar and the handling is superb. Great on track and fine for the road. Ride suffers slightly but still quite acceptable for long drives.

Then you have to choose tyres.....

Oh, and throw away the rear anti roll bar.

 

Springs Rates

me again

From AlfaCentro:

My favorite spring set up for a competition GTV is a set that I had wound at 1150 front and 160 rear.

Thats amost double your 600lb rates? does this mean anything or have I misunderstood somthing? How come they are so different? This is for a 'competition' (track only?) GTV though so maybe it can be that hard. but that seems way too different!?


what are the stock rates? as these might put everything in perspective? Does anyone know?

 

My understanding (don't quote me) is that the standard spring rates are 400 lbs front and 90 lbs rear. I got the Harvey Bailey rates by talking to them myself so I'm pretty confident of those. 1150 lbs fronts does sound a lot but I'm not a spring expert.....

 

those spring rates djone 101 state sound a little to soft. Everyone I have spoken to have always suggested a spring rate between 1150 -1300 front ,150-190 rear.I know centerline rates there front as 1150 and rear as 160.International rate there front as 1300 and rear as 180.I am now a little confused can anyone shed some light on the subject.

 

1150 front, 160 rear spring rate sounds about right. 105 series alfa's have a 6:1 spring to wheel rate up front. So work this out with f/r weight distribution to figure out spring rates.

Example: 1150 spring rate front would be 191 wheel rate. With a rear rate of 160, this set up would probably work for a car with f/r weight distribution around 54/46%

 

Springs are an interesting topic. When I acquired my track car, it seemed very soft in the front when I first drove it. I didn’t know what springs it had, only that they were painted bright red. However, there is an equation for calculating spring rates. I’ve seen it in engineering texts, books on car setup and handling, and on several websites. I tend to believe it should produce a useful value. It says:

SR = (11.5x10^6 x WD^4) / (8 x NC x CD^3)

where SR is the spring rate in lb/in, WD is the wire diameter, NC is the number of active coils and CD is the coil diameter, all in inches. The constant is good for springs made from most any type of steel. The NC value is the number of coils or fractional coils that actually bend when force is applied. This means any coil or portion of a coil that is not in contact with another coil or that does not rest in a support saddle. Also, CD is the distance from the wire center on one side to the wire center on the opposite side.

Anyway, I grabbed every front spring I could find that I knew anything about and started measuring. Here are the rates I calculated:

Stock ’78 Spider 385 lb/in
Mystery red spring 485
Ward & Dean 878
IAP 898
Centerline 922

I haven’t seen a stock Alfa spring rate spec but I’ve seen AR Ricambi claim to have springs that are 19, 20, 40, 48 and 75% stiffer than stock depending on what document I look at. My mystery red spring is 26% stiffer than stock so I haven’t learned what it is. However, compared with the IAP springs I had on my last track car, I can see why the red ones felt soft. I don’t know why the W&D, IAP and Centerline springs have calculated rates that are so different from their claimed values. Maybe I count active coils differently than they do. However, I would have to be off by about a whole coil to account for the differences. I also have no idea what the batch-to-batch differences might be with any of these springs, especially if they come from different initial suppliers.

It would be very interesting to know whether of not anyone has actually compressed some of these springs with known weights to measure the rates.

 

Springs

Does anybody know what the red springs come from/
I have seen them on a lot of Alfas.
And what about the rocwell testing for them are that all the same as far as use?
PSB

 

Both IAP and AR Ricambi sell red springs and I would assume they are different.

FWIW, the Ricambi springs are the same as the old Shankle Engineering springs - they were silver when sold by John Shankle and red now but he same springs.

Joe

 

Red Ricambi springs.

Hello,

On my 73" GTV I have Red springs that I remember were purchased from Ricambi when they were still in Glendale, CA. I would like to find out more information about what they really are in terms of specs. If I remember correctly Ricambi sold several springs. Not sure if they were all red? Ours do not seem to lower the car too much (unless there are some spacers that would rise the car) but I don't think so.
Does anyone know the differen't springs and the colors of thsoe springs that were offerd by Ricambi?

Currently the car also has front and rear Ricambi anti-roll bars, red Koni's, and these mystery red Ricambi springs.

Any help would be appreciated.

Both IAP and AR Ricambi sell red springs and I would assume they are different.

FWIW, the Ricambi springs are the same as the old Shankle Engineering springs - they were silver when sold by John Shankle and red now but he same springs.

Joe

 

Hello, all. I'm relatively new here but I am learning a lot form this BB and think that it's top notch!
I am coming from a different discipline of vehicle (Ford Mustangs, oh no!) but the ideas about springs and their engineering is the same. I have mentioned in another post of two that I am in the midst of acquiring a 1972 GTV 2000 and I am trying to learn as much as possible about the chassis and suspensions on the Alfa's and what is available for them. First off, I have not seen anyone mention much about what shock they are using with their springs. That will make a difference, as I am sure most of you are aware. I will start out by saying that I am a HUGE proponent for Bilstein dampers. I have had several sets on my SN95 Mustang and have been pleased with their performance. I have ridden in a 1971 Buick Skylark convertible with Bilstein's and they made the car ride like a million bucks! I'm not saying I will want my Alfa to ride like a Cadillac or Mercedes, (becasue its a sports car ) , but I want to have some comfort. I have driven and ridden in several cars with Koni dampers and they have a much harder ride quality. Koni's are not bad by any means, but they have an inherent harder ride quality and in my opinion are great for track applications so the driver can fine-tune the rebound and compression qualities to their liking. These spring rates that have been mentioned in the 1100lb/in and 1300lb/in range is astonishing to me because of the weight of the cars. I used springs only slightly heavier on a car that was over 1000lbs. heavier! Anyway, I guess what I am after, is who is using what dampers on their cars and in what manner are you using the cars? I'm almost certain I will go with Bilstein, but I want to make sure they will match the spring rates I decide to go with for a high performance street car, as far as the handling is concerned. I’m not looking to make a rocket out of my car, just to enjoy weekend drives on the coast and through the country. Thank you for any input, have a great day.

 

Welcome aboard Matt, by using the search facility you'll see that spring rates and damper choices have been covered extensively and continue to be so. One thread is called something like "Brits vs Yankies in spring weights" or something like that, it makes for good reading.

I'd actually like to get some input from everyone about the original topic of this thread. Why don't I see progressive-wound springs on 105 cars, is it simply because the fronts seem too short anyway?

Alex.

 

Hi Matt-

Welcome. It's great to have new enthusiastic faces(?) around the place. There was a great thread about spring rates last summer. If you search for "British vs. Yankee spring weights" or something similar, you'll find it. I think the bottom line is that the Brits pay lots of attention to roll centers, which lets them run more reasonable spring rates. If you lower your Alfa in front without making geometry changes, the roll center dives fast. Then you need to run such stiff springs that the twisting of the car itself becomes a meaningful part of the suspension equation.

As for the 1100 lb springs, the Alfa geometry gives a 2:1-ish mechanical advantage, so the wheel would move an inch under a 550 lb load in this example.

Some folks consider Bilstein shocks too stiff for old Alfa. Search the forums some more for lots of discussion on this.

-df

 

So now we have read that the front suspension has a 2:1 rate and a 6:1 rate (and on another thread 4:1)... what the heck is the truth?! And please support your answer.

thanks

British v Yanks
http://www.alfabb.com/bb/forums/showthread.php?t=18169

 

Gentlemen,
I apologize, I should have spent more time trying to dig things up. I will search the "British vs. Yankee spring weights" thread, thank you!

It will be interesting to see what the rate of the mechanical advantage is...

 

Not to highjack the thread, I guess this may be off text a bit but...

I have heard some stories that too heavy spring/shock combo can cause stress fractures in the front end, is there any real world proof of this, or just guys talking. I am close to suspension overhaul on my GT, this is something of a concern to me. In a stock 35 year old car, metal fatigue could be a possibility, I know lots of track cars have shock mounts reinforced. As my car buddies would say, how does the metal know its 35 years old?

Again, not to change topic, but if this is the case, should I be concerned about getting the suspension to stiff. Any one experience this problem?

 

The motion ratio is probably closer to 3:1. A 1200 pound spring gives you a 400 pound(ish) wheel rate. In general, you don't need to worry about chassis cracks due to heavier spring rates. A monster sway bar could cause cracks around the mounts, but that is more a problem with the 750/101 cars.

Erik

 

Great! now we have 3:1! I'm not flaming your input genericwood, from everything else I have read of yours, you have a wealth of knowledge. It's just that for new guys like us, there are now 4 different statements about what the front suspension ratio is.

Mr. genericwood, can you provide us with info about why you believe that to be the case. Much thanks

 

Mr. genericwood, can you provide us with info about why you believe that to be the case. Much thanks

Well, two reasons. First, I've done the measurements based on the length of the lower a-arm, the position of the spring on the a-arm and the angle of the spring. But probably a more reliable reason is because I asked Jack Beck the other day when I saw him. He said it was about 3:1. Jack's Orion Motorsports is one of the most respected Alfa race shops in the country. Jack makes drop spindles, tubular sway bar set ups, panhard bars and lots of other cool Alfa stuff. He's also a multiple SCCA National Championship winner in an Alfa GTJunior. I have no idea what the motion ratio is on that car, however. It has a rocker-arm front suspension!

Erik

 

stress cracks

stress cracks are a common problem I've seen on many 105 series cars. Stiff springs don't help...... but most of the cars I've seen with this problem are street cars. The combination of unibody construction and 35 year-old cars...... The problem is easily solved by making re-enforcement plates and welding them to the front end. T.H.

 

Front Wheel rate vs Spring rate: 105 chassis

My caculations are based on measuring, remeasuring and then rechecking .

The distance from the inner arm pivot to the centerline of the ball joint is 12.75 inches, and the distance from the inner pivot to the spring centerline is 4.562 inches. So the motion ratio is .358:1.

Thus a 1200 pounds/inch spring has a wheel rate of 154 in/lbs.

Hope this helps.

 

Incidentally, since the spring pan is at different angles depending on the bump and droop of the car, the spring would have less installed height at the front of the pan if the car is lowered, so the rate would be slightly higher.

And if the coils bind, the rate goes higher. This is why it is only indicitive to use the formulas for spring rate, since you don't know for sure which or how many coils will be effective at an installed height, thus the invention of spring testers, and they start the spting at installed height, and then compress one inch to get the inch/pound rate of the spring.

 

Bruce

Thanks for the formula and the data. I'm not surprised there are diffferences in 'similar' sport springs. Even if the formula is off because of differences in counting numbers of 'active' coils, at least it gives a reference between different springs.

It would be really nice to take some of the springs sorted by the formula calculations to a spring tester. That'd help calibrate the coil counting technique.

Another issue to think about in choosing springs is the car on top of them. I have found a lot of the latest springs from IAP and CL to be a bit too stiff for my car. I've a 67 Duetto which weighs under 2000 lb - not a lot of insulation, carpeting and other goodies in the old simple cars. Springs that suit a sporty ride in a 2600 lb S4 spider are a bit too much for mine.

Fortunately I have a set of old Shankle springs that are just about right. I'll have to measure them to see hwere they fall in your list.

Anyway, thanks for the data!

Robert

 

Stress Fractures

Most of the respondents to this thread probably know a whole lot more about this topic than I do, but let me throw in a couple of points:

In response to "Sneds 67 GT":

Yes, the front suspension mountings of 105 cars CAN develop cracks. I am currently restoring a '65 Sprint GT, and when I got the suspension and accumulated grease off, I was apalled to see cracks in the welds that connect the front crossmember to the frame pressings. These were visible on both sides. While I do not know the history of my car in detail, it does not appear to have ever been a race car, nor have high mileage. It had the original Girling brakes on it when I got it, which shouldn't have put huge twisting loads on the crossmember. How does metal know it's 35 years old? Well, metal fatigue results from the # of cycles of stress imparted to the metal. So, I guess the issue would be miles, or more precisely, the number of times the brakes have been applied, not years. I just welded up the cracks, and hope it will last for another 42 years (by which time I will be 99 years old!).

"Genericwood" had written:

"The motion ratio is probably closer to 3:1. A 1200 pound spring gives you a 400 pound(ish) wheel rate."

Well no, not really. While the ratio is about 3:1 (or, 2.79 (= 1/3.58) as George Willet has calculated more precisely) keep in mind that this factor must be SQUARED to get the effective rate at the wheel. So with a 1,200 #/in spring, your rate at the wheel would be approx 1/9 that, or 133 #/in.

Someone else had posted the formula for this recently on another thread. Putting it verbally, the motion ratio comes into play twice (hence the squaring): Once because the spindle-A arm geometry puts more force on the spring than the wheel sees, and again because when the spring compresses 1/3 of an inch, the wheel will move 3 times as far, or one inch (I'm rounding the motion ratio to 3 for the sake of simplicity).

 

While the ratio is about 3:1 (or, 2.79 (= 1/3.58) as George Willet has calculated more precisely) keep in mind that this factor must be SQUARED to get the effective rate at the wheel. So with a 1,200 #/in spring, your rate at the wheel would be approx 1/9 that, or 133 #/in.

Putting it verbally, the motion ratio comes into play twice (hence the squaring): Once because the spindle-A arm geometry puts more force on the spring than the wheel sees, and again because when the spring compresses 1/3 of an inch, the wheel will move 3 times as far, or one inch (I'm rounding the motion ratio to 3 for the sake of simplicity).

OK, maybe i'm being dense here ( i studied EE, not ME ), but this makes NO sense at all to me.

we have an arm : lower a-arm
that arm is pivoted at one end
there is a weight in the middle of the arm : suspension spring
we are measuring force at the end of the arm : wheel

sounds like a classic simple lever to me.
http://www.engineersedge.com/calculators/levers/page_levers_3.htm

now, if the wheel rate was 1/9 of the spring rate :
stock front spring is approx 400lbs/inch, so the wheel rate would be 44.4lbs/inch.
i dare anyone here to lift their car up to extend the front suspension, and pull up on the tire with a measly 45 lbs using your arms, and see if the front wheel lifts one inch.

 

Good Sunday morning Robert. Some time ago I posted the spring rates for the popular suppliers when I had ready access to a spring checker. I'll get them out and repost them to this thread. They're in a binder in the shop, and it is 18 degreesF outside so I need a second cuppa coffee to brave the elements.