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Rear trailing arms "Cranked"


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#1 natas

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Posted 30 May 2012 - 08:23 PM

can someone explain how/why these work better than stock on a stock height vehicle?
sorry I am clueless..............

http://www.gwynlewis....uk/page17.html



I am changing all the shocks and springs but staying at stock height.
The front will be to accomodate the extra weight of a winch bumper and winch.
All Gwyn Lewis challenge.

Thanks.

#2 Retroanaconda

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Posted 30 May 2012 - 08:31 PM

They don't.

I'm sure they're well made, Gwyn is known for his stuff being of good quality (better than his spelling anyhow :P), but there would be little or no advantage to installing those ones over the stock arms if you're staying at standard height.

#3 Bowie69

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Posted 30 May 2012 - 09:14 PM

As above, stock height, no need for cranked arms, you'll just overload the chassis bushes permanently otherwise.
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#4 ajh

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Posted 30 May 2012 - 10:54 PM

The basic thing to look at is the angle of the trailing arm vs the bushing mounting bracket surface. If it is parallel then you don't need any cranking, if it is under tension then you want as much 'crank' as returns the arm to parallel. My gut feeling is that the stock height arms could do with some cranking but cost means they're straight as this is the strongest configuration with the least weight.

Now for 'need' it is more and more needed as you lift since the pressure on the bushing in one direction while sitting at static resting height puts strain and causes extra wear. The 'correct' fix is to have something like X-Arms or Rose-jointed arms which eliminate the bushing pre-load by their design.
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#5 Team Idris

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Posted 31 May 2012 - 07:24 AM

Above sounds bob-on from what I see. Especially about standard needing a slight crank.
But it depends where in the standard axel movement you run. My 'coiler' runs quite high, so my bushes are stretched all the time.
I run standard soft rubber bushes to get flex. Which also reduce shock loadings.

Cranked will help the axel drop fully at one end, as long as the other side isnt bound-up by the chassis bush, which has to flex more on full compression. Do you even reach the bumpstop now when cross axeled?

Still a good product if you are going to stand the truck on them over a log, or drive like a crazy person :)

#6 moose

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Posted 31 May 2012 - 10:51 AM

some of the original stock arms are like tooth picks esp. early range rovers ones and bend surprisingly easily.

you would be hard push to bend these arms.

just a thought....
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#7 offshore1987

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Posted 31 May 2012 - 11:57 AM

Stick with the stock ones if you ever wanna do trails with most clubs they dont allow cranked arms

Daniel

#8 Disco-Ron

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Posted 31 May 2012 - 12:19 PM

its pretty much only alrc affiliated clubs that 'shouldn't' allow cranked arms . In standard class anyway. . . I have cranked arms for strength, however, as they are made for lifted trucks they tend to be a tad longer than stock, to retain diff angle. . . So my trailing arm bushes are in front of the chassis to get that right! . .

#9 offshore1987

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Posted 31 May 2012 - 12:58 PM

Hants and berks dont allow cranked arms, neither do a few other clubs. In the "alrc" as you have said, but we did a friendly trail a month or two back and run are trucks with so many no nos lol I think i failed on something like 6 things

B.9.6. Any radius arms that have been welded to, drilled or cut into, deliberately notched or bent up/down/sideways are prohibited. Plus C.5.5.

The only club that i know of that allows arms and so on is AWDC which has millions of class's but they seem to run under there own book

Just worth a thought if you ever wish to try trailing propley, that some places might not like the cranked arms

Daniel

#10 natas

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Posted 31 May 2012 - 08:36 PM

No clubs in The Bahamas. I just want to make her as bush worthy as possible.
I was told that with +2 shocks and relocators the cranked trailing arms would help with articulation.
kinda makes sence.

#11 offshore1987

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Posted 31 May 2012 - 08:40 PM

It just tips the axel/diff, back to where it was, which helps road handling, iv got them fitted to mine and its lush on the road with the med spings, my dad dosnt have them and its god awful to drive on the road

Daniel

#12 Disco-Ron

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Posted 31 May 2012 - 09:11 PM

standard springs and plus two shocks will almost certainly dis locate!




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