Hugh Jarce
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 posted on 18/10/04 at 04:21 AM |
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Suspension Bolts - from the Horse's Mouth!
I was just looking at the "Mojo" thread and followed a link to the Sylva web site. After a bit of poking around, I found this interesting
little excerpt:
"A bolt is a clamping device. It is not a pivot. A suspension mounting bolt’s primary function is to clamp the chassis mounting bracket against
the bush pivot (crush) tube. The suspension does not pivot about its mounting bolt. 0.5" (12.7mm) holes are drilled in the suspension mounting
brackets and 12mm bolts are supplied in the bolt pack. This results in a 0.7mm clearance. This is by design. Just to reiterate, the bolt is just a
clamping device, not a pivot. If the 12mm bolts are correctly torqued, there will be no slop or play in the suspension.
Tightening Torque
All 12mm suspension bolts, 65 - 75 foot pounds."
I believe Sylva have been building cars for some time, so I presume they know what they're talking about. 
The pay isn't very good , but the work's hard.
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JoelP
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| posted on 18/10/04 at 07:20 AM |
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on every thread regarding bushes that i have read, this has been universally agreed upon. the point of contention is whether the crush tube is longer
or shorter than the bush, ie whether the bush is slightly free or slightly compressed.
Beware! Bourettes is binfectious.
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Hugh Jarce
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| posted on 18/10/04 at 07:35 AM |
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I seem to remember someone was adamant that a bolt was OK to use as a pivot.
I think it's fairly universally accepted the length of the crush tube has to be the same as the internal width of the bracket and then, if using
PU bushes, they should be around 0.5mm longer overall (when assembled as a pair) than the crush tube.
Obviously solid plastics such as acetal and Nylon would need to be the same length as the crush tube.....but bush length was not what this thread was
about.
The pay isn't very good , but the work's hard.
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James
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| posted on 18/10/04 at 08:15 AM |
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As the bowl of petunias said:
"Oh no, not again"
James
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mackie
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| posted on 18/10/04 at 08:29 AM |
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Is there a rule of thumb for what bolt diameter to use with what crush tube ID?
We are using Nissan Bluebird trailing arms with the std bushes and the ID of the crush tube is bigger than the rest of our suspension (GTS poly bush
kit). I'm not sure exactly how big but i'd estimate maybe 14mm.
Also, is the idea to get the crush tube to fit as precisely as possible in the bracket so when tightened it doesn't bend inwards at all?
I'd guess it is so would you just use washers to space it out suitably.
Nice little nugget about what torque to do em up to, that's a lot higher than I'd have thought!
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MikeRJ
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| posted on 18/10/04 at 08:45 AM |
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quote:
Originally posted by mackie
Is there a rule of thumb for what bolt diameter to use with what crush tube ID?
We are using Nissan Bluebird trailing arms with the std bushes and the ID of the crush tube is bigger than the rest of our suspension (GTS poly bush
kit). I'm not sure exactly how big but i'd estimate maybe 14mm.
Also, is the idea to get the crush tube to fit as precisely as possible in the bracket so when tightened it doesn't bend inwards at all?
I'd guess it is so would you just use washers to space it out suitably.
Nice little nugget about what torque to do em up to, that's a lot higher than I'd have thought!
Amazingly I have seen an "engineer" insist that the bolts were designed as the pivot and had thoroughly greased them up and fitted nylocs
so the nut would saty put whilst loose enough to allow the cruch tube to rotate!
The GTS crush tubes are most likely designed to take an M12 bolt, the Luego ones are as well. Others use M10, either is more than adequate in terms
of shear strength for this job.
The ID of the crush tube and the holes in the brackets should be such to give a minimal "clearance fit" to the shank of the bolt IMO
(12.5mm for a M12). Excessive clearance in this application would wreck any chance of getting repeatable suspension geometry.
Idealy the crush tube should be a sliding fit in the bracket to ensure that both sides of the bracket are parallel when the bolt is torqued up.
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stephen_gusterson
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| posted on 18/10/04 at 08:50 AM |
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all I can add is that whenever ive worked on car suspensions using rubber bushes, the suspension arms didnt flop down when diss-assembled, so the
rubber stops that happenning. IE, the rubber 'twists' not the inner tube....
atb
steve
[Edited on 18/10/04 by stephen_gusterson]
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blueshift
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| posted on 18/10/04 at 12:03 PM |
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quote:
Originally posted by Hugh Jarce
I seem to remember someone was adamant that a bolt was OK to use as a pivot.
Yep, it was Syd Bridge. And only Syd. Everyone else took the course of sanity.
Enough said, I think?
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ned
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| posted on 18/10/04 at 12:05 PM |
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James,
You must stop taking those drugs!! 
Ned.
quote:
Originally posted by James
As the bowl of petunias said:
"Oh no, not again"
James
[Edited on 18/10/04 by ned]
beware, I've got yellow skin
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DaveFJ
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| posted on 18/10/04 at 01:56 PM |
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OH God - please no........
Not the great bush/crush tube deabte again??? life really is too short 
Dave
"In Support of Help the Heroes" - Always
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andkilde
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| posted on 18/10/04 at 03:20 PM |
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I hear the Americans are doing away with bushes altogether in the upcoming election...
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mackie
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| posted on 18/10/04 at 03:32 PM |
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Here we go again...
Syd,
What's the problem with this?
Is it still a bone of contention what Hugh said about the bushes being a fraction wider than the crush tube? It all seems perfectly sensible to me,
you've even said on here that there's nothing wrong with the PU bush/crushtube arrangement where the bush pivots on the rigid crush
tube.
A bit of clamping force on each side of the bush will stop if from slopping side to side will it not?
I don't really want to open a can of worms but reading your previous comments on this subject, I can't see what the problem is.
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indykid
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| posted on 18/10/04 at 03:33 PM |
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LOL andkilde
[Edited on 18/10/04 by indykid]
[Edited on 18/10/04 by indykid]
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Northy
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| posted on 18/10/04 at 05:22 PM |
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Rescued attachment can_o_worms.jpg
Graham
Website under construction. Help greatfully received as I don't really know what I'm doing!
"If a man says something in the woods and there are no women there, is he still wrong?"
Built 2L 8 Valve Vx Powered Avon
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mackie
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| posted on 18/10/04 at 05:27 PM |
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quote:
Originally posted by Northy
It wasn't me!
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stephen_gusterson
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| posted on 18/10/04 at 05:40 PM |
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you had to edit that twice!!!!
quote:
Originally posted by indykid
LOL andkilde
[Edited on 18/10/04 by indykid]
[Edited on 18/10/04 by indykid]
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stephen_gusterson
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| posted on 18/10/04 at 05:41 PM |
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about the bush thing....
someone said on the radio today that in Iraq
'shock and awe'
has not turned into
'aaaawwwww shucks!'
atb
steve
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Cita
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| posted on 18/10/04 at 07:47 PM |
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indykid
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| posted on 18/10/04 at 08:07 PM |
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quote:
Originally posted by stephen_gusterson
you had to edit that twice!!!!
as i replied, mackie beat me to it, so i added a name(1 edit) then spelt that name right(next edit)
should've just deleted it really
tom
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ned
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| posted on 19/10/04 at 09:36 AM |
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for your info, the second time you edit a post you can delete the first bit that says 'edited by' etc so you only ever need show one
'edited by' line.
Ned.
beware, I've got yellow skin
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indykid
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| posted on 19/10/04 at 10:09 AM |
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ah touche
cheers
tom
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