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Front Suspension 
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On the Road

Joined: Mon Jul 13, 2015 6:32 pm
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GTM: Libra
Post Re: Front Suspension
I always thought that stainless was more brittle than regular 8.8 and 10.9 so avoided it in suspension components because of the potential shock loads but must admit that I had only formed that opinion on something someone once told me.


Tue Nov 06, 2018 9:27 pm
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Joined: Wed Aug 11, 2010 9:27 am
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Location: Sheffield
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Post Re: Front Suspension
Not true unless the metal has been too heavily work hardened.

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Tue Nov 06, 2018 10:22 pm
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Part built GTM

Joined: Wed Apr 15, 2015 4:52 pm
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Location: Devon
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Post Re: Front Suspension
Thin wall stainless tube for a wishbone for instance, particularly if holds spring partway along it's length, so subject to bending loads could work harden.
The 12mm bolt has no bending loads and is massively strong.
Stainless is used throughout yachts - the mast on mine is held by a 10mm diameter triangle
This holds 4 tonnes when sailed to lift a hull plus of course the shock and snatch from the boat heaving around on the water.
In a boat there are 2 areas where stainless is particularly checked
1. Pocket corrosion where the stainless is hidden and away from oxygen
2. Rigging where the wire is changed at 10years.
Partly unseen pocket corrosion inside the multi strand wire.
Partly the bending mentioned earlier which work hardens the metal.


Wed Nov 14, 2018 5:04 pm
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GTM Nirvana
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Joined: Sun Oct 19, 2014 10:10 pm
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Location: Bristol
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Post Re: Front Suspension
I agree with the above and that the top wishbone is normally only ever in tension/compression loading so very little scope for fatigue. One thing about your set up though is having the ARB coming onto the top wishbone. I've not seen it onto the top 'bone before so I'm guessing that is part of your modifications. The shorter drop link certainly makes sense but not sure how it impacts on the movement ratio? By using a more compliant linkage you've taken some of the shock out of the ARB link but having it there will add a degree of bending force into the 'bone so may have an impact over time. I agree that the cross sectional area of the M12 bar is much greater than the tube and for straight push/pull that is what matters but with any bend or twist the geometry of the tube with the metal that there is being further from the centre line makes the metal in the tube wall count for more than the metal in a smaller diameter solid rod (can't remember the calculation but there is some squaring of radii involved, for torsion it might even be a square times a square?). I reckon you'll be fine but having seen early fatigue failures that weren't expected I'd keep an eye on things to make sure!


Wed Nov 14, 2018 7:23 pm
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Joined: Mon Jul 13, 2015 6:32 pm
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Post Re: Front Suspension
Blimey, some great technical knowledge on display here chaps :D


Wed Nov 14, 2018 10:03 pm
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On the Road

Joined: Wed Aug 11, 2010 9:27 am
Posts: 619
Location: Sheffield
GTM: Libra
Post Re: Front Suspension
Generally work hardening only occurs if the bending loads are above the elastic limit of the material. Bear in mind that carbon steel works the same way in terms of elastic/plastic deformation and work hardening, it's just the values (tensile strength etc) that differ depending upon the material that govern how each metal acts/is affected.

Main reason(s) such parts are not made in SS is cost - of material and processing/machining etc.

I would quite happily replace all my suspension components with SS, it's just a case of cost and the time to make up jigs copy the originals etc...

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Thu Nov 15, 2018 12:15 pm
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