Jump to content


Boxed trailing arms, what is the purpose?


  • Please log in to reply
26 replies to this topic

#1 _Big T_

_Big T_
  • Guests

Posted 04 June 2007 - 01:51 PM

Howdy,

I discovered on the weekend that my UC has boxed trailing arms so I told Mrs Big T. She says "thats nice dear, what do they do?" The blank look on my face and my response "dunno, something good but" suggests I need a proper explaination for why boxed trailing arms are a good thing. My assumption is that they strengthen the trailing arms for stability? :huh:

Cheers,

Mr Big T

#2 _rocket_

_rocket_
  • Guests

Posted 04 June 2007 - 02:00 PM

Tell Mrs Big T, they make it safer to drag with.

#3 _Big T_

_Big T_
  • Guests

Posted 04 June 2007 - 02:03 PM

HAHAHAHA, great minds think alike Rod. Thats EXACTLY what I told her !!! I said it means the car will straighter on the strip because it reduces twist in the rear !?!?!?! She bought it, sort of...... :D

#4 _rocket_

_rocket_
  • Guests

Posted 04 June 2007 - 02:07 PM

No matter what the topic, tell em what they want to hear.

#5 GML-31

GML-31

    Oh My, Don't you post alot

  • Members
  • PipPipPipPipPipPipPip
  • 5,239 posts
  • Name:Kev
  • Location:Highland Park
  • Car:too many
  • Joined: 08-November 05

Posted 04 June 2007 - 02:46 PM

big horsepower and they will bend otherwise

#6 _Big T_

_Big T_
  • Guests

Posted 04 June 2007 - 04:40 PM

So not really required for my little 308 then Kev? Ah well, looks like Ive got it set up for the twin turbo 454 I'll drop in her one day..........dreaming.

#7 _ingles_

_ingles_
  • Guests

Posted 14 June 2007 - 03:51 PM

If you really want to baffle her with bullshit;the boxing of the arms stops them deflecting when you put your foot down-this wastes horsepower(energy) and results in higher et.Therefore not wasting this energy ,rather using it to propel the car forward and hence lower et.SO ,your original answer was correct.

#8 Litre8

Litre8

    Thrillseeker

  • Administrators
  • PipPipPipPipPip
  • 2,399 posts
  • Name:Howard
  • Location:Melbourne, Victoria
  • Car:1976 LX SLR8000
  • Joined: 05-February 07

Posted 14 June 2007 - 04:01 PM

When you nail the throttle the lower trailing arms come under compression as the diff housing tries to rotate in the opposite direction to the wheels. Boxing them adds strength and helps prevent them bending or kinking.

#9 marko1au

marko1au

    Forum Member

  • Members
  • PipPipPip
  • 207 posts
  • Location:Elizabeth S.A.
  • Car:LX sadan
  • Joined: 05-April 07

Posted 03 January 2008 - 08:33 PM

good found one of the posts i've been looking for. can anybody explain to me how this is done as in what is required and the correct way to do it.. oh and pictures speak a thousand words. hint hint thanking you's mark

#10 rodomo

rodomo

    To advertise here, call 13TORANA

  • Members
  • PipPipPipPipPipPipPip
  • 17,997 posts
  • Name:R - O - B Dammit!
  • Location:Way out west of Melbourne Awstraylya
  • Joined: 10-December 05

Posted 03 January 2008 - 09:00 PM

There is another thread about rear end movement that you might get some info from. Plenty of pics too.

http://www.gmh-toran...showtopic=23896

#11 _Big T_

_Big T_
  • Guests

Posted 03 January 2008 - 09:49 PM

Geeze, I cant remember if I saw the replies to my original post or not but I'm glad this came up agian. Just explained this to Miss Big T (as she prefers to be refered to these days, until she does in fact become a Mrs) and she was happy that others have confirmed what I initially thought.

Anyway I digress.....

Attached are some photos as requested Mark. I just went down to the shed and snapped off a couple to give you an idea of what they look like. PM me if you want a few more and I can jack the car up on the weekend and take some measurements if you wish.

Cheers,

T

Posted Image

Posted Image

Posted Image

#12 _Herne_

_Herne_
  • Guests

Posted 03 January 2008 - 10:27 PM

Thanks for bringing this up Big T. It has reminded me that its something else I need to get done.
I always knew about the trailing arms but quite frankly I had forgotten all about them.

Cheers
Herne

#13 marko1au

marko1au

    Forum Member

  • Members
  • PipPipPip
  • 207 posts
  • Location:Elizabeth S.A.
  • Car:LX sadan
  • Joined: 05-April 07

Posted 04 January 2008 - 06:42 PM

thankyou big T as i said a picture speaks a thousand words now that i have seen it i fully understand what needs doing, no need to take any measurements but what gauge do you think the steel is......1/8th maybee a touch thicker thank's again mark

#14 _Bomber Watson_

_Bomber Watson_
  • Guests

Posted 04 January 2008 - 07:05 PM

I would go atleast 3mm mate, or around 1/8th.

And remember if you have a LC/LJ you need to cut a hole so you can do up your spring...LH/LX dont have this drama.

Cheers.

#15 mag5000

mag5000

    Forum Member

  • Members
  • PipPipPip
  • 156 posts
  • Joined: 08-January 06

Posted 04 January 2008 - 08:47 PM

you can also change (lower) by drilling ? the top diff control arm bolt holes on the body to help even further.

#16 boblhslr

boblhslr

    Forum Member

  • Members
  • PipPipPip
  • 199 posts
  • Joined: 11-April 07

Posted 04 January 2008 - 09:10 PM

you can also change (lower) by drilling ? the top diff control arm bolt holes on the body to help even further



Mag5000 What do you mean by this.

#17 mag5000

mag5000

    Forum Member

  • Members
  • PipPipPip
  • 156 posts
  • Joined: 08-January 06

Posted 05 January 2008 - 02:37 PM

"Trick tips for torana rears"

Posted Image

artical from old mag - Building a Tougher Torana No1 - A Technical Guide , page50

#18 mag5000

mag5000

    Forum Member

  • Members
  • PipPipPip
  • 156 posts
  • Joined: 08-January 06

Posted 05 January 2008 - 02:51 PM

Posted Image

this is page part of another mag - Torana Power - No3 page 41

theres a sentance that starts (By simply) that tells of whats what.ive tried both boxing and lowering diff arms all work well and no big budget required

#19 _Brewster_

_Brewster_
  • Guests

Posted 11 January 2008 - 08:07 PM

I remember reading in another thread somewhere that using the Nolathane bushes in the rear trailing arms wasn't good for comedy. If you stregthen the arms and don't stregthen the mounts and use Nolathane, you'll push your arms up through the floor. Is my memory correct? Is this true? If you strengthen the mounts on the body side, and then use Nolathane, it should work better that way...perhaps? Can anyone shed a bit of light on this? Cheers :D

#20 TerrA LX

TerrA LX

    Fulcrum Fixture

  • Members
  • PipPipPipPipPipPipPip
  • 14,241 posts
  • Location:Sid 'n' knee
  • Joined: 31-May 06

Posted 12 January 2008 - 10:01 PM

I have never seen a Tory arm bend or a mount rip out but Commys are notorious for it.
What is happening is when you plant the right foot the shock of the tyres rotating is transfered to the diff which tries to rotate in the opposite direction, so you either bend the arms or rip the top mount off the body.

#21 Toranamat69

Toranamat69

    Forum R&D Officer

  • Members
  • PipPipPipPipPip
  • 2,117 posts
  • Location:Brisbane
  • Joined: 07-November 05

Posted 12 January 2008 - 10:43 PM

I've seen a few LX's rip the lower control arm brackets off the floor.

Big slicks and an 11 sec pass and you are getting into the danger zone.

I wouldn't be using poly bushes in the top arms or boxing them.

Both the arms and the bushes are designed to flex for a reason.

Don't make me post a pic of my boxed upper arms with the failed polyurethane bushes again. I had only done about 10,000k's when they failed and they were the softest grade available. Clearly a result of not being able to flex as a bushing needs to be able to do with this style of rear end.

Don't worry, when I was young and silly, I wouldn't be told when it came to these types of things but guess what - some of those guys were actually right.

The top arms won't bend under accelleration because they are under tension.

Making everything mega stiff is fine for the drags but if you want to go round corners, it will make the car go round corners on 3 wheels which it will do slower than it will on 4 wheels.

Oh btw, if running a panhard, rubber upper control arm bushes are a must.
You will have a very shite setup for cornering if you use stiff bushes.

A converging arm 4 link already has a roll centre defined. Installing a panhard defines a second centre much lower and guess what? The rear end can only pivot about 1 centre, not 2 so unless you have some compliance somewhere in some rubber bushes, you will either break something or you will make the weight transfer worse than the original shite setup.

I think you will find all the old touring cars that used panhards also had rubber bushes - they knew the converging arms sucked but were stuck with them - they did the best you can really do without removing everything and changing the whole fundamental design.


Two things those magazine articles fails to mention about lowering the front mount of the top control arms is

1. It will make your rear end more prone to tramping under really hard braking.
2. It raises an already discustingly high rear roll centre even higher which will make your car handle worse around corners - one of those articels even bullshits and says it helps in all forms of racing. Typical low level bullshit that comes out in those types of mags.

That lowering the front mount of the top control arm is only a drag racing modification.

M@

Edited by Toranamat69, 12 January 2008 - 10:47 PM.


#22 _Brewster_

_Brewster_
  • Guests

Posted 15 January 2008 - 08:54 PM

Thanks very much for that M@, as always, you have very valuable information at your disposal to share with us novices. You are the man! :D

#23 Tiny

Tiny

    Oh My, Don't you post alot

  • Administrators
  • PipPipPipPipPipPipPip
  • 10,018 posts
  • Name:Tiny
  • Location:Sydney
  • Joined: 04-February 07

Posted 24 January 2008 - 07:05 PM

Very Interesting topic guys! And thanks M@ for the great info.

It's funny... but in the HQ which is the same setup as an LX torana... Koni adjustable shocks, Whiteline springs ( 1.5" lower than std), boxed lower arms and nolathane bushes with rubber uppers seem to work fine for what i do with the car (Street/strip). Oh.. ive got swaybas front and rear too!

No 90/10s, nothing else trick, and running a pretty easy 11.9 on drag radials... Interesting to see tricks like this spoken about but i dont think i personally would bother!?

Cheers!

#24 _rorym_

_rorym_
  • Guests

Posted 25 January 2008 - 04:22 AM

I have a spare set of top arms I will now fit with rubber bushes and slip in because I am fitting the panhard rod. As usual.M@ explains things clearly again. 1 more tick in his box! :clap:
R

#25 StephenSLR

StephenSLR

    Oh My, Don't you post alot

  • Members
  • PipPipPipPipPipPipPip
  • 6,707 posts
  • Name:Stephen
  • Location:Sydney
  • Car:1976 LX SL/R
  • Joined: 12-November 05

Posted 26 March 2008 - 09:26 PM

Don't expect miracles.

I read it can quicken your 1/4 mile time by up to 0.1 second.

They give you better throttle response.

s




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users