ADVrider

Go Back   ADVrider > Riding > The perfect line and other riding myths
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 04-30-2014, 06:26 PM   #1
SloMo228 OP
World Class Cheapass
 
Joined: Sep 2012
Location: SE Michigan
Oddometer: 1,578
Twin shocks vs. monoshocks?

Maybe this is the wrong forum, but I'm interested in hearing people's thoughts on the differences between an old-school twin shock and a modern monoshock rear suspension. Assuming you could somehow have two otherwise identical chassis, one with a monoshock swingarm, and the other with twin shocks, and the shocks/springs themselves are of equal quality and appropriately set up for the rider, what are the inherent advantages/disadvantages of each?

Are there any handling (or other) advantages to a twin shock swingarm, or are bikes which have them simply designed that way for aesthetic or perhaps economic purposes?

I'd like to hear some people's ideas about this.
__________________
--------------------------- Steve----------------------------------------
'93 GL1500 frankenbike basketcase in progress
'96 DR350SE
SloMo228 is offline   Reply With Quote
Old 04-30-2014, 07:06 PM   #2
NJ-Brett
Brett
 
Joined: Sep 2010
Location: Southern New Jersey
Oddometer: 6,257
Dirt bikes or street bikes?
Its hard to get 12 inches of travel out of the dual shock setup.
On the street, twin shocks make it easy to adjust for added load, and the shocks keep bags out of the rear wheel, otherwise the single shock setup likely has some performance advantages but uses up space.
NJ-Brett is offline   Reply With Quote
Old 04-30-2014, 08:04 PM   #3
Moronic
Beastly Adventurer
 
Moronic's Avatar
 
Joined: May 2006
Location: Perth, Australia
Oddometer: 1,513
Consider how it would work if you replaced the monoshock on a "modern" rear end with twin shocks mounted in the same place.

What difference would that make? 1: More parts. 2: Probably more static friction (stiction) from using two small seals on two small diameter shafts rather than one big seal on one big shaft.

But probably, looking only at performance, not much difference at all.

So, looking purely at the choice of one or two shocks, the main advantages of the single shock seem to be space efficiency, cost efficiency and serviceability.

Okay, but twin shocks on a monoshock chassis wouldn't be an old-school twin-shock suspension. So let's look at the question from the opposite end.

How would it work if you replaced the twin shocks on a traditional twin-shock bike with a bigger single shock just on one side?

In fact plenty of bikes these days are built like this, and some makers (e.g. BMW) were doing it in the '80s. The advantages of the single-shock set-up will be exactly the same as in the former case: space efficiency, cost efficiency, serviceability.

However ... in order to use the shock just on one side, the swingarm and its pivot on the frame have to be stiff enough to carry the significant torsional loads generated by having the load on the tyre resisted by a single component that is offset several inches to one side of the tyre.

On a twin-shock bike, that torsional loading is balanced by the torsional loading from the shock on the opposite side. So ... one manufacturing advantage of the twin-shock set-up is that you can get away with a less robust swingarm.

As suggested above, there are also design and serviceability advantages to running the shocks either side of the wheel (or on one side) rather than in front of the wheel: it frees up space between the tyre and the engine, and shocks placed there can be (much!) easier to remove and adjust.

IMO that just about sums up the theory. What about the practice?

In practice, the main advantages of the single shock chassis tend to be improved stiffness and a better shock (as it is cheaper to build one big shock than two little ones). The cost of upgrading the single shock will be lower also, to similar performance levels.

A secondary advantage is that some chassis designs run the single shock through a progressive linkage, which allows a single-rate spring to act like a progressive-rate spring - at the cost of placing a bunch of small bearings in some of the grittiest spots on the bike.
__________________
Sorting out the S4Rs Ohlins shock: click here.
Moronic is offline   Reply With Quote
Old 04-30-2014, 09:25 PM   #4
scootrboi
Beastly Adventurer
 
scootrboi's Avatar
 
Joined: Jan 2011
Location: Vermont
Oddometer: 1,295
kind of an old idea

The rear wheel comes off like a car wheel. That is what I like.
__________________
42 years on a Heinkel Tourist
scootrboi is offline   Reply With Quote
Old 04-30-2014, 10:35 PM   #5
Moronic
Beastly Adventurer
 
Moronic's Avatar
 
Joined: May 2006
Location: Perth, Australia
Oddometer: 1,513
Quote:
Originally Posted by scootrboi View Post
The rear wheel comes off like a car wheel. That is what I like.
Nice one. You can't do that with trad twin shocks.
__________________
Sorting out the S4Rs Ohlins shock: click here.
Moronic is offline   Reply With Quote
Old 05-01-2014, 06:01 AM   #6
scootrboi
Beastly Adventurer
 
scootrboi's Avatar
 
Joined: Jan 2011
Location: Vermont
Oddometer: 1,295
chain in oil bath

]
Quote:
Originally Posted by Moronic View Post
Nice one. You can't do that with trad twin shocks.
The chain drive monoshock swingarm design is from 1951 and was used on all Heinkel scooters and minicars. Changing wheels on the back takes a few minutes, and a spare is mounted under the luggage rack.
__________________
42 years on a Heinkel Tourist
scootrboi is offline   Reply With Quote
Old 05-01-2014, 07:31 AM   #7
DAKEZ
Beastly Adventurer
 
DAKEZ's Avatar
 
Joined: Mar 2007
Location: OR
Oddometer: 19,522
Quote:
Originally Posted by NJ-Brett View Post
Its hard to get 12 inches of travel out of the dual shock setup.
THIS ^^^^ [burp]
__________________
“Watch out for everything bigger than you, they have the "right of weight"
Bib
DAKEZ is offline   Reply With Quote
Old 05-07-2014, 07:37 PM   #8
daviethebiker
Adventurer
 
Joined: Dec 2012
Location: Watsonville, CA
Oddometer: 39
Quote:
Originally Posted by NJ-Brett View Post
Dirt bikes or street bikes?
Its hard to get 12 inches of travel out of the dual shock setup.
On the street, twin shocks make it easy to adjust for added load, and the shocks keep bags out of the rear wheel, otherwise the single shock setup likely has some performance advantages but uses up space.
I have a 1984 Husqvarna 500xc that uses two shocks in the rear. The bike is stock and has 13.8 inches of rear wheel travel.
daviethebiker is online now   Reply With Quote
Old 04-30-2014, 10:19 PM   #9
RFVC600R
SAND EATER!
 
RFVC600R's Avatar
 
Joined: Dec 2011
Location: SAND LAND
Oddometer: 2,180
Sorry to go off topic, but is that the bike you spent 42 years on?? Good job man, I hope to have my XL half as long as that.
__________________
'83 Honda XL600R 618cc 11:1 Wiseco, XR's Only Exhaust, big tube header, 6 Sigma stage 3 carb mods

Quote:
Originally Posted by Carter Pewterschmidt View Post
He's the XL600 Jesus, his bike dies for our sins.
RFVC600R is online now   Reply With Quote
Old 05-01-2014, 12:19 AM   #10
JohnCW
Studly Adventurer
 
Joined: Dec 2013
Location: Sydney, Australia
Oddometer: 930
Quote:
Originally Posted by SloMo228 View Post
Maybe this is the wrong forum, but I'm interested in hearing people's thoughts on the differences between an old-school twin shock and a modern monoshock rear suspension.
A monoshock has the significant advantage of allowing a longer rear suspension travel.

JohnCW screwed with this post 05-01-2014 at 12:33 AM
JohnCW is offline   Reply With Quote
Old 05-01-2014, 01:20 AM   #11
Moronic
Beastly Adventurer
 
Moronic's Avatar
 
Joined: May 2006
Location: Perth, Australia
Oddometer: 1,513
Quote:
Originally Posted by JohnCW View Post
A monoshock has the significant advantage of allowing a longer rear suspension travel.
Perhaps ...

__________________
Sorting out the S4Rs Ohlins shock: click here.
Moronic is offline   Reply With Quote
Old 05-01-2014, 03:06 AM   #12
Rucksta
Chronic Noob
 
Rucksta's Avatar
 
Joined: Oct 2008
Location: Gold Coast
Oddometer: 2,583
Some may find this article interesting

http://www.carbibles.com/suspension_bible_bikes.html


Look for
Motorbike suspension - back end.

about 1/3 down
__________________
My bike is slow but the earth is patient.
Rucksta is online now   Reply With Quote
Old 05-01-2014, 08:37 AM   #13
SloMo228 OP
World Class Cheapass
 
Joined: Sep 2012
Location: SE Michigan
Oddometer: 1,578
What's been posted pretty much sums up what I expected, though I never thought there would be a difference in suspension travel. Makes sense, though. The single shock is usually mounted far forward of where dual shocks would be, so the shock doesn't require a full 12" stroke to get 12" of suspension travel due to the lever effect of the swingarm.

One plus of dual shocks that I liked on the ZRX I owned was that not having the single shock allowed for a pretty big storage area under the seat. It was very handy when using the bike as a commuter.
__________________
--------------------------- Steve----------------------------------------
'93 GL1500 frankenbike basketcase in progress
'96 DR350SE
SloMo228 is offline   Reply With Quote
Old 05-01-2014, 09:57 AM   #14
NJ-Brett
Brett
 
Joined: Sep 2010
Location: Southern New Jersey
Oddometer: 6,257
Yes, there are also two setups for single shock, a small shock with a linkage in front of the rear wheel, and the early setup like my xt200 has, a giant shock under the seat and gas tank.
That takes up all the space on a bike, the battery was put in a small box mounted behind the motor and in front of the rear wheel.

Twin shocks gives lots of room under the seat.
NJ-Brett is offline   Reply With Quote
Old 05-02-2014, 08:02 AM   #15
markk53
jack of all trades...
 
markk53's Avatar
 
Joined: Dec 2007
Location: Delaware Ohio
Oddometer: 7,695
Didn't read it all, but key points for a single shock set up were:

  • less mechanical parts to make a rising rate suspension system.
  • hard to bend a single shock in the center of the bike when you crash on a log or such.
  • One shock to adjust.
  • If hung on the one side with a single side swing arm makes the rear wheel accessible quite easily for road bikes.
As far as travel, there were 12" travel twin shock bikes in the late 70s, so that really isn't the reason.

The thing that is hard for me to comprehend is why it is so much more expensive for a quality single shock over a similar quality twin shock replacement set for a road going bike.
__________________
Ever get lost? You know, that good kind of lost - come to a dirt road intersection and you have no idea where you are or which way to turn? I like when that happens!

Mark - klx678
95 KLX650C w/Vulcan piston bigbore, Now an 09 KLX250S, selling my 90 Zephyr 550
markk53 is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


Times are GMT -7.   It's 07:50 PM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014