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» Northern California Ford Owners     » Automotive   » Tech Talk   » Specific Vs Progressive Rate Springs

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Author Topic: Specific Vs Progressive Rate Springs
BlackDrop50
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Which is better?

Right now I have specific rate springs and while the car handles good for basically stock, the ride is ROUGH, and I've almost gotten to the point where I want to change my springs.

I've heard that progressive springs ride better, but don't handle as good? Any truth to that, or is it all in the shocks+struts?

Is it worth it to switch to progressive springs?

(coil-overs out of my price range)

Posts: 1379 | From: 510 East Bay | Registered: Aug 2002  |  :
rr_mustang
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ref:

A constant rate spring will give you the same amount of resistance to compression, all the way until it is fully compressed. So, if the spring is soft, you will have a comfortable ride, but it may not hold as much weight, or handle as well. And, if the spring is too stiff, the ride may be harsh, and handling may suffer as well, due to lack of suspension travel, but you will be able to carry a heavy payload. So, you may have to find a happy middle ground, and compromise some ride for payload or handling characteristics.

A variable or progressive rate spring is the spring designers compromise between a soft comfort spring, and a stiff payload spring. It works like this, one portion of the spring has the windings spaced farther apart, and they get closer together, as you near the other end of the spring. This way, when the spring initially starts to compress, it is easy, and "soft", but as the compression continues, the spring gets stiffer. With a progressive spring, you *should* get comfort, handling, and payload capabilities.

More info

Depending on what you want to do with the car, don't waste the money going to progressive, although you can probably pickup a used set for $50. If you are leaning towards RR, Auto-X or even OT, save up for the coilovers.

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Dart 408 w/ AFR 205's

Posts: 473 | From: San Jose, CA | Registered: Feb 2002  |  :
flatacid
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im in the same boat as you right now. i have specific's on my car, and im seriously considering going to h&r's.

what kinda specifics do you have? im running 620/260 maiers racing.

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89 mustang gt w/ t5

Posts: 573 | From: nowhere | Registered: Feb 2002  |  :
BlackDrop50
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BBK 1.5" drop specific rate springs
Posts: 1379 | From: 510 East Bay | Registered: Aug 2002  |  :
Bill/APEX Motorsports
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The specific rate springs I've seen are way too short, the manufacturers being of the mindset that "lower and stiffer is better." Far from the truth! Most Mustang specific rate springs are _very_ short in height, causing the car to bottom out over even the smallest bumps. Making matters worse, we see many lowered Mustangs come in with the stock bump stops/pinion snubbers.
The trick is to use the proper rate and the proper height springs. We only use specific rate springs, because it's impossible to tune your suspension (i.e. with adjustable shocks/struts) if the rate is always changing with progressive rate springs. The setting that might be good at, say, 500lb. will be too soft at 600lb. No real race car uses progressive rate springs. Not to say that we all drive race cars, but the ride can be very pleasant and controlled with specific rate springs.
It's also imperative to use a shock that's capable of controlling a stiffer/lower spring. The only ones I recommend are Tokico Illuminas and Koni Yellows (single adjustable or double adjustable). Bilsteins are good, but we don't use them because they're not adjustable. (Our thought is that even if you never adjust the Tokicos or Konis after the first day, you can at least set them where _you_ want to set them, rather than where the manufacturer thinks you want them set (i.e. non-adjustables).)
(As an aside, not all adjustables are created equal. Like I said, the Tokicos and Konis are the only ones we've found that work well enough for our suspension setups. KYB AGXs have a limited range of adjustment, and dampen very badly.)
When customers say, "I don't want specific rate springs. I want progressive rate. I don't want the car to ride like a dump truck," my first question is, "Have you ever driven a car with proper specific rate springs?" "Ummm....no." Basically, Eibach has done a great job of making people think that progressive is the best thing going.
Our "basic" suspension consists of 350lb. front coil-overs and standard 300lb. rear springs. However, the height of the springs is such that the suspension won't bottom out unless the bump is _really_ big. In six years, we've only had two people want softer springs, and both were over 60 years old. The only change we ended up doing was 300lb. front springs, and they were very satisfied.
So, it's all a matter of taste, but with the amount of conversions we do from progressive rate springs to our setup, it's apparent that people really do enjoy our end product with specific rate springs.

[ December 29, 2002, 09:45 PM: Message edited by: Bill/APEX Motorsports ]

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Bill Kaiser
APEX Motorsports
Santa Clara
www.apexmotorsports.com
408-562-1000
bill@apexmotorsports.com

Posts: 488 | From: Santa Clara, CA | Registered: Dec 2001  |  :
BlackDrop50
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Thanks for the info and the advice.

I'm going to be saving up for some good shocks and struts, then try to adjust them til it rides better.

Posts: 1379 | From: 510 East Bay | Registered: Aug 2002  |  :


 
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