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.)
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