The mono-tube vs twin tube arguement - Nissan 350Z Forum, Nissan 370Z Tech Forums
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post #1 of 5 (permalink) Old 08-29-2008, 05:52 AM Thread Starter
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Alright, theres been some discussion (here and elsewhere) of why exactly a monotube is better than twin tube coilovers / shocks... First the facts.

Twin tube shocks.
- They have been around since the mid 20th century, a testament to the design.
- Utilize a a 2 chamber design, an inner tube where most of the work takes place, and an outer tube which acts as a fluid resevoir.
- In the outer tube a low pressure gas charge is used as a back stop and for extra dampening.
- Due to the design and the fact that all energy is converted into heat, means that as the fluid heats up it starts mixing with the nitrogen causing shock fade.
- Cheaper to produce
- Smaller piston surface area
- Produces a very linear dampening force across all piston velocities.
- Exterior tube provides for more protection from dent damage

Mono tube shocks
-Utilizes a single tube with dual pistons. the first piston is attached at the end of the piston rod. The second piston is a free floating piston that seperates the nitrogen charge from the main fluid resevoir.
-Design inherently reduces the chance of heated fluid mixing with the nitrgen charge reducing suseptability to shock fade.
-Larger piston surface area increasing initial dampening
-Difficult and more expensive to design due to the longer tube requirement.
-During low speeds the dampening force is non linear causing commonly causing it to "bounce"
-less protection from dent damage as any damage to the tube effects the pistons path.
-can provide for dampening rates that are near twice the rate of twin tube designs.

Now as for Comfort... well thats all in the eye of the beholder. While one person may not mind the low speed bounce so much(think grandmas old cadillac(exagerating)) some may find the the linear performance of a twin tube is a must. For race applications where tremendous heat is generated, mono tube is a must. For those that just do the occasional spirited driving or the 3 to 6, 45 second runs at the autocross track you will probably never come close to reaching shock fade in a twin tube. Ultimately, its your money, buy as you see fit.

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post #2 of 5 (permalink) Old 08-29-2008, 09:40 AM
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post #3 of 5 (permalink) Old 08-29-2008, 10:30 AM Thread Starter
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sweet! Theres a bit more to it but off the top of my head it contains the most critical and common factors.
Cheers!

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post #4 of 5 (permalink) Old 09-04-2008, 05:23 AM Thread Starter
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Heres some pictures so people can better understand how each works.



Above are cutaways of the most common monotube shocks. they are very simplified.
D=divider chamber type.
P=piggyback type, where the divider chamber is piggybacked onto the main shock body
H=external reservoir type. The nitrogen reservoir is connected to the main shock body via a stainless braided line.
** ignore E due to the fact its a monotube design that you wont see for our application, known as an emulsion type.

Next here are 2 examples of twin tube, one simplified and one detailed.






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post #5 of 5 (permalink) Old 10-17-2008, 07:18 PM
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