Visual difference between stock and Progressive springs?

fellfrosch7

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I picked up a used set of these and they look exactly like the stock springs. Are there any markings on them that I can use to verify that they are in fact the progressive ones?

Sorry if this is a noob question...
 
Do you mean "Progressive" brand springs or just any progressively wound springs?
If you have a stock spring to compare with, and a pair of vernier calipers it is easy to determine if these springs are stiffer than stock, or not.
Just measure the wire diameter of the spring, spring diameter and count number of windings. Also just compare free length.
Thicker wire, or smaller spring diameter , and/or fewer windings means the spring is stiffer. Longer free length just gives more spring preload (not stiffer as in lbs/in)
 
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The best way to know would be to buy new springs that have the brand name on the box. Depending on who you get them from they may not lie to you.
If they fit in your forks, test ride and see if they are better. If not try again.
Leo
 
A progressive springs gets stiffer as it compresses, right.
So on little bumps it is soft. On bigger bumps They get stiffer. Shouldn't it be the other way around.
Leo
 
I guess that's why RaceTech recommend linear springs to be used with their "Gold Valve Emulator" compression damping valves.
I agree with that firm springs/damping on small bumps, and more compliant action on bigger bumps is desirable. It is, however, difficult to make a degressive (gradually softer) spring.
 
The original springs (for the 35mm forks anyway) are dual rate and progressive but are usually sacked and too soft by the time we get them. I usually find the free length about right but they're still too soft. Free length is about 472mm for the '77 springs and 482mm for the '78-on ones. I think you'll find the free length of aftermarket springs to be longer so that would be one way to tell if they're originals or not.
 
I used a set of springs that fit an older Harley FX , XL and XLCH. that used a Showa 35 mm fork. The springs are A bit longerthe wire they are wound of heavier. I have the specs some where.
Being longer and thicker wire they are much stronger.
With the adjustable caps, in the softest setting, on the later forks I get about 25 mm sag. The stock springs were closer to 40 mm.
On the second setting it's about 12 mm sag.
I got them from J&P, item # 230-584, $49.99 a set when I bought them, last I checked they are $49.99.
With the Minton Mods on the dampers and about 7.5 ounces of ATF they work very well.
Leo
 
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