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double shock absorbers? why?
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idratherbesurfing
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Joined: 06 Nov 2008
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Location: In my garage with a cup of tea and the heating on


1985 Land Rover Defender

PostPosted: Thu Oct 08, 2009 7:34 pm    Post subject: double shock absorbers? why? Reply with quote

why do some people have double shock absorbers on the back axles of their trucks?? (like two shocks on each side, so a total of four for the back axle - does that make sense?? Confused )

what do you gain from it?

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dodewalker
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PostPosted: Thu Oct 08, 2009 8:00 pm    Post subject: Reply with quote

On an offroad vehicle for speed events you can reduce the heat created when racing, fine tune your rebound etc.
You can have remote reserve shocks to have more oil (less heat in the shock)
"A problem shared is a problem halved."

Then you get overland vehicles,possibly heavily loaded using the twin shocks to help reduce the wear & tear being inflicted on them.
Fine tune the suspension, you can use softer springs x 2, & appropriate dampers. (back up in event of failure, thats not really so, but often stated.)

This is a simplifications, but just to give an idea.
Here are 3 different vehicles set up from this years Hill Rally (Perthshire.)
& a link to the 00 car from the event & its twin shocker set up.
www.4allfours.co.uk/supercharged.htm

EDIT, WHY DO MAY PICTURES POSTED ON HERE ONLY APPEAR WHEN LOGGED IN?
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teamidris
Mud Obsessed


Joined: 24 Feb 2008
Odometer: 3369
Location: Staffordshire UK



PostPosted: Fri Oct 09, 2009 6:56 am    Post subject: Reply with quote

Cost Very Happy You can find cheap standard rangy ones about the place and get the damping of an expensive set.
Definately surface area for cooling. One bloke had lorry ones on. They were very low rating for their size, and could easily disipate the heat! Now I come to think of it, it seems odd that high spec shocks don't come with fins on the outside Confused
Why not redundancy? My ordinary rears are rangy, the other two 110. If If I pull the end off the rangy shock, there is still the longer one to save the brake lines Cool

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dodewalker
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PostPosted: Fri Oct 09, 2009 7:43 am    Post subject: Reply with quote

Do you mean like 'Ribbed for pleasure!' ?

'Shock' porn pictures below. (possibly only when logged in.
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andyb66
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Joined: 18 Jun 2004
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Location: Ferndown, near Bournemouth



PostPosted: Fri Oct 09, 2009 9:39 am    Post subject: Reply with quote

teamidris wrote:
Now I come to think of it, it seems odd that high spec shocks don't come with fins on the outside Confused


Cos in off-road usage they will clog with mud and worst than no fins.

(regarding the original question) As has been said it is often for disappating heat. Altho as had been shown a single shock with a remote reservoir is a favour solution so that you don't had to add additional mounting points to the axle casing and often there isn't the room for another shock but the reservoir can be mounted on the cage or shock hoop as shown.

Someone said it is for tuning you rebound....this cannot be done by fitting twin shocks alone. They need to be shocks that can be revalved for both bump and rebound independantly not just adjustable shocks.

The pictures above are a mixture of twin normal shocks, remote reservoir shocks and coil overs.

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http://www.challengemotorsport.com

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dodewalker
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PostPosted: Fri Oct 09, 2009 4:08 pm    Post subject: Reply with quote

Somebody that said it was for rebound, (me) also said
"this is a simplification"
& it was only one example of use in some applications.

I didnt go into details of which shocks (dampers) etc you might be using to achieve a sophistocated or unsophisticated setup.

But over the years i have managed to get good results with mixed paired shocks that were inexpensive & not too fancy in their adjustability,
'bump' & 'rebound'.
just a known quantity used in a compatably pairing. (not revalvable)
But results acheived by trial & error and a knowledge of the standard dampers properties.

This can achieve a pretty unsophistocated & cheap reliable set up that works quite well.
That may not be easily achieved using a 'single' cheap/unadjustable damper.

i didnt want to go more into a subject & bore him more than was necessary.
george
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idratherbesurfing
Just got MTs


Joined: 06 Nov 2008
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Location: In my garage with a cup of tea and the heating on


1985 Land Rover Defender

PostPosted: Fri Oct 09, 2009 4:38 pm    Post subject: Reply with quote

Quote:
i didnt want to go more into a subject & bore him more than was necessary.
george


hey!! bore away!! Wink im all up for some more learning!!

The reason I ask was in this months TOR theres a write up of that disco build, thats owned by that fella on Bonkas4x4. I saw that its got two shocks on the back, and wondered why it might need two.

The disco in question was built as a rock crawler, so my first thought was that there was two on there, in case one snapped or something!

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dodewalker
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PostPosted: Fri Oct 09, 2009 5:15 pm    Post subject: Reply with quote

So much variety in what you can do. springs provide spring and the vehicles sprung weight sits held up by the springs.
And 'shock absorbers' are actually 'dampers'.
A vehicle fitted only with sprimgs would bong up and down.
Possibly uncontrolably.
Sometimes you can do this, fit soft/long springs to a slow trial car and just
use this to get unrestricted articulation..(usually on a pretty light vehicle.)

But as designed a 'shock absorber/dampers' slows you down from bonging along a road.
& get tuned to suit what the vehicle requires.

Leaking shocks may just compress but not rebound very well, leaving you back with a bongy feeling.
Hense people giving the car a press down and seeing if the shockers have gone.

You can fit a shock absorber that will do whats required to make the vehicle drivable, then fit a second 'Air Shock' or Hydrolic shock' etc and use this to raise lower your vehicle etc.in rock crawling situations.
A modern Range Rover & Discovery 3 kimd of does all this for you without much input from the driver.
choose the setting & let a micro proccessor get on with it.

This could equally be an air bag fitted to do the raising or lowering, & still have a shock absorber.

Or as in the challenge suzuki built by Rob at Offroad Armory,fitted with Air Shocks & no springs. Giving him total control of the articulation etc.
www.offroad-armory.com
george
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andyb66
Just got MTs


Joined: 18 Jun 2004
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Location: Ferndown, near Bournemouth



PostPosted: Sun Oct 11, 2009 10:08 am    Post subject: Reply with quote

dodewalker wrote:
Somebody that said it was for rebound, (me) also said
"this is a simplification"
& it was only one example of use in some applications.


Apologies, I thought the "simplification" related to overland vehicles.

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http://www.challengemotorsport.com

Read more about Challenge Motorsport here
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gawxo
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PostPosted: Sun Oct 11, 2009 10:42 am    Post subject: Reply with quote

Why stop at 2 , just like engines 1 or 2 or more cylinders , each has different charachteristics , and fine tuning is easier ,

Often though , 1 Bigun is enough ,!!!!! JP.
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dodewalker
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PostPosted: Mon Oct 12, 2009 4:01 pm    Post subject: Reply with quote

There is a lot to be said for one big one.
But then two big ones might be better.
george

(there is a picture here, but i think it only shows when logged in.)
PLEASE SOMEBODY, WHAT AM I DOING WRONG WHEN DOWN LOADING PICTURES?
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waveydave
Mud Obsessed


Joined: 10 Jan 2006
Odometer: 2740
Location: waveyvillie oop norf


1994 Land Rover Discovery

PostPosted: Tue Oct 13, 2009 7:27 pm    Post subject: Reply with quote

I used to have twin shox on the disco cos it was the cheepest way of getting the damping i needed,

I was a very very heavy car and on single shoxs it bounced about when crawling over stuff (like big water falls !) causing me to either loose balance and roll, or make it bounce and loose traction, ohh and the worst thing was it had a habit if bouncing and smashing windows.

Having a better damped car ment it was all under control so i was able to do rather silly things and make it look easy Wink

So your answer is its a cheep way to get a better set up.

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idratherbesurfing
Just got MTs


Joined: 06 Nov 2008
Odometer: 434
Location: In my garage with a cup of tea and the heating on


1985 Land Rover Defender

PostPosted: Tue Oct 13, 2009 9:08 pm    Post subject: Reply with quote

so would my weekend warrior pajero benefit from double shocks? or would it just be overkill?

Laughing

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tacr2man
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Joined: 02 Sep 2007
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PostPosted: Sat Oct 17, 2009 7:58 pm    Post subject: Reply with quote

Have a look at a Stalwart, 3 axles first two 4 shocks each ,
I found twin shocks helps when working hard , eg corrugations on outback roads , helps keep het build up down . Shocks have to work much harder on coil sprung vehicles, old leaf sprung landies , you didnt notice if you had any or not after a few years with the springs rusting up Smile

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1986 110 CSW 3.9i
1992 90 300tdi auto
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w3526602
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Joined: 10 Jun 2002
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PostPosted: Sun Oct 18, 2009 5:11 am    Post subject: Reply with quote

Hi,

I once saw a DAF/Sherpa chassis-cab, brand new. One rear shocker was in front of the axle, the other was behind. Was this a mistake, or some clever way of controlling axle tramp?

602

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peeprox1991
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PostPosted: Sun Oct 18, 2009 9:02 am    Post subject: Reply with quote

w3526602 wrote:
Hi,

I once saw a DAF/Sherpa chassis-cab, brand new. One rear shocker was in front of the axle, the other was behind. Was this a mistake, or some clever way of controlling axle tramp?

602


The very first/proto Range Rovers had one in front and one behind; it got dropped for production though for some reason.

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Nathaniel
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Location: North, North Yorkshire


1979 Suzuki LJ

PostPosted: Sun Oct 18, 2009 4:54 pm    Post subject: Reply with quote

w3526602 wrote:
Hi,

I once saw a DAF/Sherpa chassis-cab, brand new. One rear shocker was in front of the axle, the other was behind. Was this a mistake, or some clever way of controlling axle tramp?

602



I've seen another commercial vehicle like this too - I wanna say escort van but I'm not so sure.

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If You Open Your Mind Too Much Your Brain Will Fall Out
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THE DIGGER
Just got MTs


Joined: 12 Nov 2008
Odometer: 186
Location: Co wicklow, Ireland



PostPosted: Sun Oct 18, 2009 7:28 pm    Post subject: Reply with quote

w3526602 wrote:
Hi,

I once saw a DAF/Sherpa chassis-cab, brand new. One rear shocker was in front of the axle, the other was behind. Was this a mistake, or some clever way of controlling axle tramp?

602


do surfs, l200"s etc not do the same??
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(pete)
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PostPosted: Sun Oct 18, 2009 10:05 pm    Post subject: Reply with quote

hilux pick ups run the shocks one in front and one behind

i kinda remember its something to do with load carrying on the bigger 4x4 pickups and could be the same for the big trucks and vans too

so im just getting my head round this twin dampers thing if i run twin but identical dampers will it not stiffen the ride up

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w3526602
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Joined: 10 Jun 2002
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PostPosted: Mon Oct 19, 2009 6:45 am    Post subject: Reply with quote

Hi,

Somebody once told me that shox mounted at an angle ie. lying across the truck at 45*, would damp out any sideways bouncing. ???? The only vehicle I can remember seeing which had a front axle that could float sideways was an Austin 7. Transverse front spring with swinging shackles at each end. First mod is to weld up one end.

602

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J.
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PostPosted: Mon Oct 19, 2009 7:52 am    Post subject: Reply with quote

Early MK1 escorts had the back like that 602 it supposedly takes out some of the body roll. But of course you've got to increase the damping because of the geometry of it all.
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Roger
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Location: Redditch Worcestershire



PostPosted: Mon Oct 19, 2009 9:39 am    Post subject: Reply with quote

(pete) wrote:


so im just getting my head round this twin dampers thing if i run twin but identical dampers will it not stiffen the ride up


Yes.

Roger
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Roger
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PostPosted: Mon Oct 19, 2009 9:47 am    Post subject: Reply with quote

w3526602 wrote:
Hi,

Somebody once told me that shox mounted at an angle ie. lying across the truck at 45*, would damp out any sideways bouncing. ???? The only vehicle I can remember seeing which had a front axle that could float sideways was an Austin 7. Transverse front spring with swinging shackles at each end. First mod is to weld up one end.

602


It is listed under "Wandering Steering" in "The Book of the Austin".

I quote:-

"One of the most common of these faults, in the case of the Seven, is due to the "U" bolts which hold the front spring coming loose, owing to the wood block between the spring and the chassis bedding down. This, of course, only happens after considerable service. The cure for this trouble is simply to tighten down the nuts on the "U" bolts, and make sure that they are tight."

Roger
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GED
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PostPosted: Mon Oct 19, 2009 11:19 am    Post subject: Reply with quote

XJ has the rears set at an angle and one in front, one behind.
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w3526602
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PostPosted: Tue Oct 20, 2009 4:39 am    Post subject: Reply with quote

Hi,

Has anyone ever fitted the Jag IRS onto a Land Rover? To remind you, the diff is bolted under the chassis. The hub carrier is held laterally by the fixed length half shaft, and a top wishbone. There is no bottom wishbone, and I believe some people do way with the fore'n-aft tie bars. Shocked

Cleeeen, man!

602

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Roger
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PostPosted: Tue Oct 20, 2009 8:11 am    Post subject: Reply with quote

w3526602 wrote:
Hi,

Has anyone ever fitted the Jag IRS onto a Land Rover? To remind you, the diff is bolted under the chassis. The hub carrier is held laterally by the fixed length half shaft, and a top wishbone. There is no bottom wishbone, and I believe some people do way with the fore'n-aft tie bars. Shocked

Cleeeen, man!

602


Personally, I would consider that to be a pointless exercise. What would be the benefit?

Roger
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w3526602
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PostPosted: Tue Oct 20, 2009 2:54 pm    Post subject: Reply with quote

Hi Roger,

Well, if you are going to be pernickity ............

It should be able to take the power of any engine that you are likely to stick in a Landy. V12 Jag on tarmac?

It wouldn't be too difficult to do, and if nobody has done it yet .........

And, if the mood takes you, you can paint it pretty colours, and mount spot lamps to show everyone what you have done.

Now, if you could find a way of using the same diff at the front, there might be some purpose to the exersise. It should be easier to keep mud out of the calipers if they are mounted inboard.

Very Happy Very Happy Very Happy

602

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clbarclay
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1987 Land Rover Range Rover

PostPosted: Tue Oct 20, 2009 3:05 pm    Post subject: Reply with quote

w3526602 wrote:
Hi,

Has anyone ever fitted the Jag IRS onto a Land Rover? To remind you, the diff is bolted under the chassis. The hub carrier is held laterally by the fixed length half shaft, and a top wishbone. There is no bottom wishbone, and I believe some people do way with the fore'n-aft tie bars. Shocked

Cleeeen, man!

602


About a quarter of the way down this page for an example of a jag axle based 4x4.

http://forum.difflock.com/viewtopic.php?t=14499&postdays=0&postorder=asc&start=120



peeprox1991 wrote:
w3526602 wrote:
Hi,

I once saw a DAF/Sherpa chassis-cab, brand new. One rear shocker was in front of the axle, the other was behind. Was this a mistake, or some clever way of controlling axle tramp?

602


The very first/proto Range Rovers had one in front and one behind; it got dropped for production though for some reason.


They actually had one damper behind the rear axle for ~15 years of production. I don't now the dates of all the changes, but it was around 1985/86 that the RRC recived a lot of design updates. My 1986 has both in front and a friends 1984 has one behind.

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and the Lord help them caught helping there selves.
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Roger
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PostPosted: Tue Oct 20, 2009 4:51 pm    Post subject: Reply with quote

w3526602 wrote:
Hi Roger,

Well, if you are going to be pernickity ............

It should be able to take the power of any engine that you are likely to stick in a Landy. V12 Jag on tarmac?

It wouldn't be too difficult to do, and if nobody has done it yet .........

And, if the mood takes you, you can paint it pretty colours, and mount spot lamps to show everyone what you have done.

Now, if you could find a way of using the same diff at the front, there might be some purpose to the exersise. It should be easier to keep mud out of the calipers if they are mounted inboard.

Very Happy Very Happy Very Happy

602


Solid axles with coil springs are the accepted way to build a standard 4x4.

It has been proven to be the best if you want "off-road" ability.

Independent suspension, either up front or all round, will improve ride at the expense of this ability.

Inboard mounted brake discs will plough through the central mound on a lane and rapidly destroy the whole system.

I like the idea of pretty colours for a Landy, pink perhaps?

Roger Wink Wink
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Terranosaurus
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Joined: 26 Apr 2007
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PostPosted: Tue Oct 20, 2009 5:13 pm    Post subject: Reply with quote

Roger wrote:
w3526602 wrote:
Hi Roger,

Well, if you are going to be pernickity ............

It should be able to take the power of any engine that you are likely to stick in a Landy. V12 Jag on tarmac?

It wouldn't be too difficult to do, and if nobody has done it yet .........

And, if the mood takes you, you can paint it pretty colours, and mount spot lamps to show everyone what you have done.

Now, if you could find a way of using the same diff at the front, there might be some purpose to the exersise. It should be easier to keep mud out of the calipers if they are mounted inboard.

Very Happy Very Happy Very Happy

602


Solid axles with coil springs are the accepted way to build a standard 4x4.

It has been proven to be the best if you want "off-road" ability.

Independent suspension, either up front or all round, will improve ride at the expense of this ability.

Inboard mounted brake discs will plough through the central mound on a lane and rapidly destroy the whole system.

I like the idea of pretty colours for a Landy, pink perhaps?

Roger Wink Wink


For a production car I'd agree on your independent comments but Hummer seem to disagree as do a lot of cross country racers. Purpose built independent can have the best of both worlds.

As for the inboard discs they so much higher up tat a live axled vehice would ave een sat on its diff long before inboard discs would touch and properly skidded who cares, te suspension can still partly droop and gain some tracion in those conditions.


On the double shock front whilst there are times and machines on which the are warranted there are also a number of vehicles out there upon which they are nothing more than a fashion accessory or fitted on the basis that if 1 pair is good 2 pairs must be better, when in reality they could well be worse.
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