Thinking about it
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| posted on 31/8/10 at 08:38 PM |
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crush tube bolt sizes
I have some of the Rally Design Poly bushes and crush tubes. I was of the understanding that these took a M12 bolt. I have bought some M12 bolts and
they are a loose fit in the bush.
Are they 1/2 inch?
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Minicooper
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| posted on 31/8/10 at 08:51 PM |
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Yes and the crush tube is 2mm wider than most aswell
Cheers
David
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Macbeast
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| posted on 1/9/10 at 07:36 AM |
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Surely the bolts are not supposed to be a tight fit in the tube ? I thought their function was to tighten the ears of the bracket down on to the crush
tube which is then held in position by the pressure.
I'm addicted to brake fluid, but I can stop anytime.
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tony-devon
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| posted on 1/9/10 at 08:34 AM |
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hmm I know this feeling, bought a M12 bolt kit, fitment was like a prick in a shirt sleeve, all heaved into the odds and sods bucket, 1/2" bolt
set in place now
I have also got to take down the ends of my crush tubes by a smidge, and my bushes need reaming out as well as the ends taking down by a tiny bit
once the bushes were in the wishbones, it was a large vice/hydraulic press job to try and get the crush tubes into the bushes
damned annoying when you buy it all together and expect things to actually fit
oh well was an excuse to play on the lathe 
heavy is good, heavy is reliable, and if it breaks, hit them with it
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Minicooper
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| posted on 1/9/10 at 09:49 AM |
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quote:
Originally posted by Macbeast
Surely the bolts are not supposed to be a tight fit in the tube ? I thought their function was to tighten the ears of the bracket down on to the crush
tube which is then held in position by the pressure.
I didn't guess I asked Rally Design, the hole through the crush tube is 13mm, so even a 1/2 bolt has some side to side movement
Cheers
David
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procomp
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| posted on 1/9/10 at 12:18 PM |
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Hi
This whole saga of 12mm bolts being supplied by the kit manufacturers and by some bush suppliers is ridiculous.
The basic facts such as the crush tube needing to be 10 tho wider than the finished measurement of the bush when finally fitted into the wishbones is
the first problem that is never addressed. In the majority of cases the wishbone end eyes are never machined to any accuracies. They are simply cut
off in a chop saw and quickly linished round. This inaccuracy when combined with the tolerance of the bushes leads to the crush tubes having to be
machined to fit each individual bush.
Secondly the brackets fitted to the majority of chassis have a large tolerance on the internal width. This again means that its every bush requiring
an individual fit. If you just tighten up the bolts till you have locked the crush tube in place you'll find that the inner bracket faces are
not square. This causes binding of the bushes on either the inner or outer edge of the bracket.
Combine all these inaccuracies with 12mm bolts fitted through 1/2" bore tubes and your on a hiding to nothing. Every individual bush needs to be
sorted if you are to have compliant and accurate suspension movement. The trouble i that the majority of the kits and parts sold are not to an
acceptable tolerance. Check every one of the bushes bolts tubes and brackets.
Cheers Matt
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