Alignments, Rear-End Work, More Driving Impressions

Last time, we had just finished installing the front end. The thing is, parts of the suspension are adjustable to make sure the wheels point in the right direction, and to have them sit at the right angle with respect to the road. To do this, I needed a specialized alignment shopt to do this - this could not be done at home.

In addition the rear end needed similar repairs as the front end: replace bushings, springs, dampers, clean things up, and check bearings. In addition, since the rear wheels are the ones driven by the engine, there is a differential back there to deal with. I figured I'd have the differential inspected and serviced as needed.

Before these repairs, the car seemed to float laterally over the actual suspension and wheels while turning and during transition. So rather than "pointing" in a fixed manner during a turn, the car pointed left and right of your intended target during turns. This made for scary-interesting driving, since every time you steer the car, you needed to wait to see what the rear end did, then correct your steering inputs, then see how these corrections affected the car, and so on.

Bushings are one of those things that tend to wear out over time on solid axle, trailing arm suspensions such as the ones found on the GTV. Replacing bushings and tightening up things would help minimize the lateral play on the suspension, making for crisper steering inputs with minimal need for mid-turn corrections and the such.

Given all these repairs, I figured I'd take the car to Group 2 and have them do all this work for me. They are my favorite car shop, and they happen to specialize in all things Alfa Romeo. The problem is that in mid-summer, every other AR owner in the region decides to also drive their cars (just like me.) Which requires lots of maintenance work, making for very busy times at Group 2.

So, I figured I'd just have the front end aligned, and do part of the rear end work: bushings, springs, dampers. I would wait until later in the year to do the differential work, as well as any bearing replacements and the such. That way, I could get the car back on the road and start chasing any of the numerous gremlins lurking in the car. And besides, it helps spread the cost over a longer timeframe, which is always a good thing.

Unlike the front end, the replacement rear end bushings were the polyurethane types from Centerline Alfa. The shop replaced the trunion arm-to-differential bushings, as well as the bushings in the trailing/radius arms, and the bushings holding the rear sway bar in place. Polyurethane ("poly", for short) tends to be stiffer than rubber, and hence, helps keeps uncontrolled supsension motions to a minimum, but at the possible cost of a bit harsher ride. However, this upgrade is a very popular one in the Alfa community, and worth trying out.

The shop also installed the AR Ricambi springs I had purchased earlier in the year (which matched the already installled front springs), as well as Koni Sport dampers (again, matching the front end Konis I had installed already.)

The service was very much worth it. The car now rides in a much truer fashion. During turns, the car feels predictable and easy to point within the turn. There was still a bit of tail-end lateral slide, which can be tuned down by using these poly washers where the trunion arm connects to the chassis.

Regarding the rear springs, the car rides a bit higher in the rear than I would like (about half an inch.) The ride is not harsh, however, so from a spring rate perspective, I am very happy with them. Correcting the ride height involved cutting down springs, so I asked the shop not to do this for now, and see how the car rode before going drastic on the springs (one thing at a time...)
At first, the adjustable shock absorbers were set a bit too stiff (which was my bad - I had set them myself), which made the ride jarring and shakey - even over smaller bumps. After softening the fronts to almost full-soft, the car's ride became much less jarring while still keeping the car motions under control.

(I will be posting my spring rates, shock absorber settings, and other technical numbers in a future post.)

One thing that started worrying me were the brakes; they felt soft and spongy, with what seemed to me as too much pedal travel. This kept me from driving as I normally do - in traffic, I had to leave extra space between cars, brake earlier, and the such. This is something that needed to be addressed quickly.

But even with the soft brakes, I had a bit more confidence in opening up the car and seeing how it ran. And run it did - the car accelerated quickly and pulled strongly (for a 2.0 liter four-banger, of course!) Throttle response was quick and sharp. Steering inputs were much sharper and predictable. The transmission was loud, and shifting required very long throws and patient double clutching during downshifts (especially 3rd-to-2nd downshifts.) The clutch felt nice, though, engaging smoothly, linearly, and strongly. The sounds emanating from the engine compartment were nice - lots of fan noise at slow speeds, changing to loud engine intake noise, manifold growls, and a shade of valve clatter. Very good sounds indeed.

Highway driving was loud - lots of wind noise, road noise, engine noise, car noise. All this noise could be confused with music for Alfa addicts such as myself, however, and I was happy to put up with it during my short test drives.

Overall, the car drove very nicely, for a 34 year-old car.

I still needed to service the rear differential, and address the soft brakes. And I still need to chase all of them gremlins lurking out there...

Springs, Part 5 - New Toys.

So, in the last post, I mentioned my adventures with hubs and wheel bearings, and how Group 2 helped me with this. During my visit, I figured I'd ask Joe English, Group 2 proprietor, about springs.

Remember the springs? I removed them quite a few posts ago. Replacing them was one of the main reasons for working on the suspension, remember? I must admit, I have not kept up with springs recently. That ends today.

So, as you may recall from a previous posting, when buying new springs, the two main issues are:
- spring rate
- spring free length.

The main equation that ties all this together is:

k = Fs/(Lf-Lc)

Where:
k = spring rate
Fs = load at spring
Lf = free length of spring
Lc = compressed length

At normal ride height, we measured and figured out:
Fs = 1879 lb
Lc = 8.0315" (204mm)


During my visit to Group 2, I mentioned to Joe that I was looking for a set of springs that would keep the front end from bottoming out during heavy braking (which tends to require stiffer springs) while keeping the road ride quality reasonable (which tends to require softer springs.)

Well, Joe thought that was a good plan, and suggested a set of AR Ricambi Super Sport springs. He felt these springs are a great compromise for the road (not too stiff, not too soft), keep the car much more stable than the stock springs, and helps with the bottoming out issues. He also indicated ride height issues can be fine-tuned by adding shims to the springs; this is something they do all the time at the shop. Joe also indicated they had this spring set in stock.

So, I was curious: what were the spring rates for the AR Ricambi springs? I'd been looking for something in the 600-800 lb/in range. After a bit of digging through his records, he found the front springs are rated at 580 lb/in. These rates are close to the bottom end of my "pulled-from-thin-air" range, so this was very encouraging.

A decision needed to be made: do I go with the AR Ricambi springs, which have been used and tested by countless, more experienced Alfisti before me? Or do I keep spending/wasting time digging for springs shops on the web, hoping to find someone that could custom make springs for my very special needs, pay tons of money, hoping that I alone know better than fellow, more experienced Alfa experts?

So, I went ahead and bought the AR Ricambi springs. Admittedly, this is very out of character for me ("you mean, there are folks out there that know more about this stuff than I do?") Besides, Joe and the folks at Group 2 have never let me down before, and I had no reason to start doubting them now.

I must admit, I was curious to see how the springs fit with the numbers and computations I've shown so far. So, I measured the front springs' free length, and punched in the numbers.

Free Length (Lf) = 11 5/16" = 11.3125"

Rearranging terms from the above equation:

Lc = Lf - Fs/k
= 11.3125" - (1879lb / 580lb/in)
= 8.073 inches
= 205 mm

This is very close to the measured spring compressed length of 204mm - almost a dead-on match. This tends to support the analysis and measurements done so far.

At the end of the day, though, these numbers don't mean anything until the car is back on its wheels, and we can measure and test the end result. Once this is done, I'll re-measure everything, and summarize all of this analysis. I guess I should start putting the car together sometime soon...

(Next up: parts get cleaned and painted. Stay tuned.)

Springs, Part 4: Finally, some work gets done.

So, I've been away from the keyboard for a while. But things have been a bit busy at the House of Speed. It's time to catch up on things online.


If you remember, I was wondering about spring sizes and the such. The two important things to figure out are:

- spring rate
- spring free length.

Once we decide on spring rate, we can compute the required spring free length using the math I've discussed in previous posts.

Online, there are two main schools of though regarding springs:

a) Go with stiff rates, and keep the stock sway bars
b) Go with medium stiffness rates, and make your sway bars heavier.

(I'll explain sway bars in a future post.)

The problem I run into is that most folks seem to favor a racy, stiff, ready-for-racetrack setup. In all honesty, I do not want to race the Alfa; I just want to drive the car around during the weekends, and hopefully not have to work too much on it (once the thing is ready to run, of course.)

So I am of the school of though of "go with springs as soft as possible, as long as the front of the car does not bottom out too badly, and the handling is not too numb". The current springs allow the car to scrape with the ground under heavy breaking, so any replacement springs should probably be stiffer (to prevent nose dive) while keeping a similar ride height (lowered cars tend to scrape on the ground more than non-lowered counterparts.)

So, what what kind of springs do I have in the car, currently? Well, the best way to find out is to remove them and see what I've got!

At first, this sounds a bit scary, since you have to deal with fairly stiff springs (450+ lb/inch; for comparison, my Miata's front springs are 375 lb/in.) And compressed springs are dangerous - if they break loose while you are undoing things, they can get launched like a projectile and hit stuff and people. Dangerous stuff.

Fortunately, there is a cheap and fairly safe way of dealing with this, as explained here: http://www.centerlinealfa.com/tips/images/installation/spring_install.pdf

Basically, this method involves using two 12" threaded rods to replace two of the bolts that hold the spring pan in place, removing the other two bolts that hold the spring pan in place, and slowly lowering the spring pan with the remaining threaded rods until the spring comes free. I used this method, with two variations:

- I used three rods.
- I greased the rods once the upper double nuts were tightened, to prevent any wear on the threaded rod (and potential binding or jamming up.)

The extra third rod was a bit redundant, but it did make me feel a bit safer. It does add to the total time it takes to undo each spring, since you have to do 50% more work (3 rods vs 2 rods.) I also highly recommend adding some grease, as jackscrews will wear quite rapidly and either jam or break the thread (airplanes have crashed due to poorly greased jackscrews - no kidding!)

The whole process took about 1.5 hours per side. I was taking it easy at first, learning the process and all. I suspect once you learn the ropes, you can bring this down to about an hour (with three rods - probably less if you use two rods.)

I did make a mistake: I forgot to loosen the antisway bar at first. That added a about 30 minutes worth of agravation, but I lowered the opposite side enough to loosen up the sway bar and removed it. After that, everything was cake.

Once you are done undoing the springs, you are left with a lower spring pan (which is secured to the lower A-Arm of the suspension,) a spring, and upper and lower rubber isolator pads (two per side.) These rubber pads prevent metal-to-metal contact between the spring, the chassis, and the spring pan. This helps prevent squeaks, and makes the ride a bit more comfortable.

Well, both spring pans were very dirty, and a bit rusty. Plus, the paint and undercoating overspray made things look nasty. On the passenger side, the lower pan had about 1" worth of dirt, and you could barely see the rubber isolator buried in all that dirt! On the driver side, however, the rubber isolators were completely missing (both of them!) Hmmmm...

The spring themselves were dirty and a bit rusty, too. All the overspray covered any present marking (e.g. spring type, part no., etc.) So, I went ahead and measured the length of springs, and they came out to about 12.5 inches. This matches the length of the stock springs. I am starting to think the springs are definetely stock. Go figure.

So, assuming these are stock springs (about 450 lb/in), we know a medium-rate spring (600-800 lb/in) would help with the bottoming-out issues. This is a bit reassuring - I was concerned the already-mounted springs were of the 1100lb/in variety, and any decrease in rates would make the car more likely to bottom out.

Next up - the front suspension comes apart.

Springs - Part 3

On my last post, I mentioned the next step would involve measuring the compressed length of the springs at the stock ride height. How does one do this, you ask?

Well, in theory, it's not too hard: one just needs to set up the suspension to the stock ride height, and measure the distance between the top spring perch and the bottom spring perch.

The problem is that when the car is sitting on the ground, it is hard to get under the car. But if you lift the car and rest it on jack stands, the wheels come off the ground and the suspension droops towards the ground.

So, the best way (given my tools/resources) is to lift the car onto the jack stands, and remove the springs. One can then raise the suspension up/down with a hydraulic jack until one gets the proper suspension ride height. Once this is done, you can use a string and a measuring tape to get a read on the perch-to-perch length.

The stock ride height is determined by measuring the distance from the lower A-arm pivot to the ground (measurement A) , and the distance from the lower ball joint to the ground (measurement B). The difference between A and B should be 34mm +/- a few mm. (I'll have to post a link to a diagram illustrating this -- stay tuned.)

So, by raising the suspension up/down with the hydraulic jack, one can zero-in on the proper ride height and measure the compressed spring length.

(I'll detail the removal of the springs on my next post.)

The compressed length came out to 204mm, or 8.0315".

This is very close to the 200mm test load used in specifying the spring rates (see my previous post.) At this stock ride height, the distance b/w the center of the hub to the fender lip came out to 14 5/8" (371mm.) Furthermore, compressing the suspension 1 1/8" (18/16") caused a compression at the spring perch of 7/16", giving a 18:7 (2.57:1) ratio in travel b/w the outside of the hub and the spring perch.

Why is this useful? Well, these numbers can be used to compute the amount of force with which the spring is compressed at the stock ride height. Assuming the following spring rate and free length (from my previous post):

Front: spring rate = 7.797 kg/mm, free length = 313.5mm

With a compressed lenght of 204mm, then the spring is compressed a total 109.5mm with respect to the stock ride height. The amount of force on the spring is computed with the spring equation:

Fs = Spring Rate * (Free Length - Compressed Length)
= 7.8 kg/mm * 109.5mm = 854.1 kg = 1879.02 lb (aprox.)

This can be used to compute the required free length for springs with different spring rates. Recall:

k = f/(Lf - Lc)

Where:
k = spring rate
f = load at spring
Lf = free lenght of spring
Lc = compressed length

Clearing out Lf, we get:

Lf = (f/k) + Lc

For example, take an 800lb spring (and rounding out a few terms):

Lf = (1879lb / 800lb/in) + 8.0315 = 10.38025"

So, in theory, obtaing a spring with a rate of 800 lb/in and with a free length of 10.38" will yield a ride height very close to stock ride height. This is a big piece of the puzzle - I can now pick my rate, and by plugging in numbers into these equations, I can compute the free length required for the spring. Wee!

(A caveat: the springs are installed with rubber isolators on the top and bottom of the spring. This effectively decreases the actual compressed length somewhat. I wll have to measure these and correct the compressed length before doing computations "for the record". I will do this in my next post.)

A new problem arises when one asks: "What if I want to lower the ride height by X inches?" Well, we have a numbers for that.

Recall that the ratio between the hub-to-fender length and the compressed length is 2.57:1. We can then assume that a 25.7 mm (about 1") decreased ride height implies a 10mm decrease in spring compressed length. We further assume that the force on the compressed spring remains the same (big assumption - probably off by a bit.) We can then punch the numbers into our previous example:
(Note: 10mm = 0.3937")

Lf = f/k + (Lc-10mm)
= (1879lb / 800lb/in) + (8.0315" - 0.39") = 9.99"

Pretty cool, eh?

So, in summary, the numbers to remember are:

f = 1879lb = 854.1 kg
Lc = 8.0315in = 204 mm
Motion at hub:Motion at spring = 2.57:1

And the key equation:
Lf = f/k + (Lc - (correction))

The "correction" term refers to any adjustments in ride height we may want to do, as described above.

The bigger moral of the story: algebra and high school-level physics are actually useful in real life!
:-)


Next up: Back in the garage, removing parts from the suspension.

Springs - Part 2

In my last post, I mentioned I would be discussing:

1. Figure out the stock spring rates and free lengths.
2. Figure out the compressed length of the springs with the car riding at stock ride height (as described in the owner's manual.)

I'll do part 1 first; I need to get under my car to be able to do part 2.

The information to figure out the stock spring rates and free lengths can be found in one of of the books I purchased last month at Books4Cars.com, The Alfa Romeo Technical Characteristics and Principal Inspection Specifications Manual for the 2000 Berlina, 2000 GT Veloce, and 2000 Spider Veloce. This manual is very nifty, as it provides (as the name suggests) a lot of specs numbers regarding a bunch of aspects of my car. Among these, we can find (guess what): spring free lengths, and compressed lengths for given test loads.

First, free lengths:

The front spring's free length is listed as 313.5mm; the rear spring's free length is listed at 445mm.

Next, spring rates:

The spring rates are not listed directly. However, the manual shows values of length under test loads(i.e. compressed length) for various test loads depending on the kind of stock springs installed on the car. It seems the GTV had five varieties of front springs and three varieties of rear springs installed at the factory (one assumes lucky customers would end up with slightly stiffer springs than less-fortunate brethren.)

For the front springs, the "Length under test load" (i.e. test compressed length) is 200mm. The test loads for the various stock springs are:

- 858.5kg - 868kg (Spring ID no. 43)
- 869kg - 879kg (Spring ID no. 44)
- 880kg - 890kg (Spring ID no. 45)
- 891kg - 901kg (Spring ID no. 46)
- 902kg - 911.5kg (Spring ID no. 47)

For the rear springs, the "Length under test load" is 252mm. The various test loads are:

- 280kg - 285kg (ID no. 18)
- 286kg - 292kg (ID no. 48)
- 293kg - 298kg (ID no. 49)

I suspect these ranges exist due to the variation in tolerances allowed during the manufacture of the springs used in GTVs. The factory probably winds a few hundred spring coils, tests them, and depending on the resulting rates, it stamps a different ID number on them.

How is this useful?

Well, these numbers indicate how much the springs are compressed under a standard load. This information can be used to determine the spring rates values for the stock springs.

First, the front springs.

Difference in length = Lf - Lc
(Lf = Free Length, Lc = Compressed Length for a given load)

Lf - Lc = 313.5mm - 200mm = 113.5mm

From my previous post, the spring constant (k) is defined as:

k = load/Lf-Lc

For the various springs listed above, I'll use the midpoint values for computing the spring rate (k)

Spring ID no. 43, k = 863kg/113.5mm = 7.604 kg/mm = 425.778 lb/in
Spring ID no. 44, k = 874kg/113.5mm = 7.700 kg/mm = 431.205 lb/in
Spring ID no. 45, k = 885kg/113.5mm = 7.797 kg/mm = 436.632 lb/in
Spring ID no. 46, k = 896kg/113.5mm = 7.894 kg/mm = 442.059 lb/in
Spring ID no. 47, k = 907kg/113.5mm = 7.991 kg/mm = 447.486 lb/in


For the rear springs:

Lf - Lc = 445mm - 252mm = 193mm

For the various rear springs listed above:

Spring ID no. 18, k = 282.5kg/193mm = 1.464 kg/mm = 81.965 lb/in
Spring ID no. 48, k = 289kg/193mm = 1.497 kg/mm = 83.851 lb/in
Spring ID no. 49, k = 295.5kg/193mm = 1.531 kg/mm = 85.737 lb/in


So, to summarize, here are the specs for stock springs (using mid-point values):

Front: spring rate = 436.632 lb/in, free length = 12.343 in
Rear: spring rate = 83.851 lb/in, free length = 17.512 in

In metric:

Front: spring rate = 7.797 kg/mm, free length = 313.5mm
Rear: spring rate = 1.497 kg/mm, free length = 445.0mm


An observation: I suspect the folks at Alfa Romeo probably sourced springs with rates of 7.8kg/mm and 1.5kg/mm for the front and rear ends, respectively. If so, we can use these values whenever we talk about stock spring rates. This converts to about 437 lb/in and 84 lb/in for the front and rear springs, respectively. I'll settle on these values when refering to "stock spring rates."

One thing down. Next, we need to figure out the compressed length of the springs when the car is riding at the stock ride height. How is this done? Stay tuned...

Springs - Part 1

So, the car remains half torn apart as I wait for parts to arrive - a new water pump, suspension bushings, ball joints, and adjustable control arms. I figured while I wait, I might as well read some of the books I've bought, and see if I can learn something useful.

Well, I think I have.

As you may recall, I've been a bit worried about the current springs installed in the Alfa. For starters, under heavy braking, the sump guard scrapes against the pavement. So I suspect the current springs might be too soft and/or too short. (I also suspect the shocks are worn out, but that's another story.) So, I am trying to find out what to do about springs.

(What follows is a newbie's interpretation on coil springs as used on cars. I am not 100% sure this is accurate, but here it goes.)

You see, springs affect how the car rides (the stiffer the spring, the harsher the ride, kinda), how it handles (stiffer springs can improve handling capability, and keep the car from leaning away from curves and the such), and how high the car rides (longer springs make the car ride higher; shorter springs make the car ride lower.) So, getting the proper stiffness and length of a spring is pretty important in determining how happy the owner feels about the way a car rides and handles.

So, I need to determine which spring stiffness and free lengths to specify for any new springs I install on the car.

What do these things mean, you ask? Well, let's start with stiffness:

Spring stiffness is basically the resistance of a spring to be compressed (or stretched) under a give load or force. Spring stiffness is specified by measuring how much force it takes to compress (or extend) a spring by a certain length. This value is known as the spring constant. For example, if it takes 100lbs to compress a spring by 1 inch, this spring would be said to have a spring constant value of 100 lbs/in. To figure out the spring constant, the following equation suffices:

spring constant (k) = force / difference in length

Or:
k = f/lf - lc

Where:
k - spring constant
f - force
lf - free length with no load
lc - compressed length of spring under the force f.

(This assumes a linear spring, where the spring constant for the spring actually remains constant throughout the range of available compression. Note also that the range of compression is limited - as you compress the spring, the individual coils get closer and closer, until they eventually make contact. Once this happens, the spring is not a spring anymore - it's more of a column of metal which does not behave as a spring would.)

Note that suspension springs do most of their work while being compressed. So most of my discussion will only address springs under compression only.


How about length?

Well, length is just that - the length of the spring. However, you can measure length when the spring is unloaded, or when a certain force is applied to it. The unloaded length of a spring is its free length, while length measured under a give force f can be referred to as compressed length.

Once you know the spring constant (k) and the spring's free length (lf) you can compute the length of the spring for any force using the spring equation shown above. For example, assume:

k=500 lb/in
lf= 10 in

Then, under 1000lbs of force, the spring's compressed length will be:

500 lb/in = 1000 lb / (10inch - lc)

Moving things around:

lc = 10 inch - 1000lb/500(lb/inch) = 8 inches.

Also: once you know a given spring rate (k) and a given free length (lf), you can use these values to order springs from vendor and/or manufacturers. (In short, these two values serve as the initial "size" for specifying and obtaining automotive springs.)

Why does all this matter?

Well, using these relationships and measuring a few things in the car, I can determine which spring rates and spring free lengths I need to use for a given car ride height. In other words, given:

a) The ride height I want to have on my car
b) The spring rates I would like to have on my springs
Then I can determine:
c) the free length of the springs.

Once I figure (B) and (C), I can order springs and be all happy.

Now, my goals with respect to springs is to:
a) Keep my ride height as close to stock as possible--within half an inch lower than stock, but not any higher.
b) Install springs that are stiffer than stock - this will help keep the car from bottoming out during heavy braking, and will help the car handle better
c) Make sure the springs are not so stiff - this would make the ride quality harsher.

So, my approach to deciding on springs will be as follows:

1. Figure out the stock spring rates and free lengths.
2. Figure out the compressed length of the springs with the car riding at stock ride height (as described in the owner's manual.)
3. Survey the various spring kits available for my car, as well as comments posted on various BBs and the such, and figure out what folks think
4. Based on (3), decide (guess, really) which spring rates I want to use
5. Once I decide on spring rates, figure out the free length required for my chosen spring rates.,
6. Order the springs from someone.
7. Install the springs, cross my fingers, and hope this all works.

That's enough babble for now. I will babble more regarding items 1-3 on my next post.