Ian
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Registered: 28th Aug 99
Location: Liverpool
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Four bolts go through the rear beam, through the spacer and in to a thread in the drum.
If I know the spec of the OE bolt, is there a way of working out what would be required if the spacer gets bigger?
As I understanding it the shear loading will increase as the spacer gets larger so if the OE is M12x55 10.9 at what point would you need to go higher tensile?
Also is there a limit to what the thread in the drum can sustain?
[Edited on 13-03-2012 by Ian]
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alan-g-w
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Registered: 9th Nov 07
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No sort of calculations or anything needed here tbh Ian, if the OE bolts are 12x55 and the spacer's 20mm thick simply stick in 12x75s. No need for higher tensile bolts or anything, the FOS will mean you'd probably be able to use 3 bolts and not notice a difference
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Ian
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Registered: 28th Aug 99
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Its for going even bigger, there's a guy making 30mm and 40mm spacers and I wondered at what point they would exceed the current tensile spec.
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Steve
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Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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i dont think its safe tbh, think of the twisting force it also transfers to the beam mounting
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Steve
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Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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30mm probs ok, but 40mm+ can see it being dodgy
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craig-dodd
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cap head bolts are 12.9 grade if you wish to have stronger bolts
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alan-g-w
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quote:
Originally posted by Steve
i dont think its safe tbh, think of the twisting force it also transfers to the beam mounting
The bit they attach to is stationary at all times, no twisting forces exerted. Plus it's not a driven wherl so there would be no twisting forces on the hub at all, even when the car's moving, because that's what the bearing is for.
Edit to say, apologies, you might get twisting foces exerted on the hub when you're braking but with four 12mm bolts holding it on they'd be negligible.
To give you an idea of what an M12 thread can withstand Ian, we have M12 stainless eyebolts in the work. They're probably about 3/8" thick on the ring with about a 30mm thread sticking out - screwed in fully, one eyebolt can lift something like 300kg. We've got forged ones that are stronger but basically it demonstrates the actual strength in what looks like a small bolt.
Definetely wouldn't hurt to change them to cap heads as suggested as long as it doesn't pose any sort of clearance issues
[Edited on 13-03-2012 by alan-g-w]
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Ian
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Registered: 28th Aug 99
Location: Liverpool
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What's the advantage with cap head? Just that they're 12.9 not 10.9?
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Steve
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Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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i mean vertical leverage type twisting force
|-D will apply less vertical leverage than |---D
[Edited on 13-03-2012 by Steve]
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Tiger
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Registered: 12th Jun 01
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It looks like a PAT test 'pass' sticker on that shock 
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alan-g-w
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Location: Glasgow
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Ian, I'm not entirely certain on the ins and outs of it but my understanding is that the higher the number, the better the quality of material - you can torque them tighter than you would with normal bolts, they'll take more force to fail and in general are a good idea - but you've got to remember that they're only as good as the material they're going into.
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alan-g-w
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quote:
Originally posted by Steve
i mean vertical leverage type twisting force
|-D will apply less vertical leverage than |---D
[Edited on 13-03-2012 by Steve]
I'd say that's more of a bending force
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Steve
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Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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yeah bending is probably a better choice of words
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Gary
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Registered: 22nd Nov 06
Location: West Yorkshire
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Will be fine. As alan said, the FOS will be pretty high so no need to worry.
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