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Dual Spring Rate?

FR4life.

FR4life.

Monkey
Nov 2, 2004
606
0
The Bay
I know it's probably not necessary for bikes, but nowadays I see more and more dirtbikes/quads with dual spring rate suspension. Why not on mountain bikes? It seems to me like it would be helpful for bottom-out resistance on those hard hits and such... Thoughts?

 
binary visions

binary visions

The voice of reason
Jun 13, 2002
22,213
1,413
NC
I figure it's partly because most MTB shocks now are tunable to avoid bottoming out, and because you suddenly have an exponentially larger number of springs.

Each mountain bike suspension is different, each rider is different, and as it is you have to have a million different spring lengths and rates. Imagine if you now had to stock every spring length, every initial spring rate, and then a variety of secondary rates for each initial rate and each length...

Same reason E.13 avoided colored bashguards for a while until they stopped producing 5-bolt bashguards. You had large 5-bolt, compact 5-bolt, 4-bolt, each available in 32, 36, 38, 40, 42 & 44t size, and then if you took all those variations and multiplied it by multiple colors...

For the record, there were several manufacturers producing progressive springs for a while, Stratos being one of them, but now with tunable air chambers, independently adjustable high/low compression, more carefully designed shim stacks and more advanced bicycle suspensions, there are a lot of ways to prevent bottom-out. Aren't most MX bikes single-pivot? A single pivot is nearly always a straight or a regressive rate, requiring much more progressive shock/spring designs to keep it from blowing through travel.
 
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jonKranked

jonKranked

Detective Dookie
Nov 10, 2005
89,626
27,823
media blackout
Curnutt shocks (Foes) have dual rate springs as an option. Extremely pricey though... and only work on Curnutt shocks... which subsequently work only on Foes bikes.

Also, I think it may have something to do with the fact that a mountain bike vs quads/dirtbikes/cars you have a substantially smaller mass that you have to dampen.
 
T

Trekrules

Turbo Monkey
Apr 12, 2007
1,226
148
The foes curnutt shocks have indeed the dual spring rate as a upgrade option.On Interbike 2005 they have explaint what that does.A dual spring rate has 2 seprated springs a lower and a higher spring rate.But there are also triple spring rate but those are most common into the ATV and Truck world.

Multi-Rate Springs, Dual-Rate (DRS) or Triple-Rate Springs (TRS), allow the optimum spring rate for each application. These multi-rate springs are soft at the beginning to soak up the small bumps, but transitions (crosses over) to the stiff part of the rate to resist bottoming on jumps and other big "hits."


Dual-Rate Springs (DRS) have two linear (straight) rate springs: a short spring with a "stiff" linear (straight) rate and a longer second spring with a "soft" linear (straight) rate. As both springs compress they result in a soft, or initial rate. The spring set will retain this initial rate until the short spring stops compressing. At that point, the spring rate "crosses over", (transitions), to the stiffer, or final, rate. On Works Performance shocks, this "crossover" point is set by means of crossover spacers, or with an ARS option. By adding or removing "crossover spacers", the rate can get stiffer sooner, or stay softer longer. The ARS option allows the rider to select the "crossover" point with a lever. The application of Single-, Dual- or Triple-Rate Springs is based on the overall length of the shocks, the shaft travel, and the available spring rates

http://www.worksperformance.com/html/multirate_desc.html
 
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