ned
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| posted on 26/11/03 at 09:42 AM |
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blueshift,
I doubt rally design would sell the bolts separately as they're longer than standard for the spacer to fit the capri vented discs. maybe worth
asking anyway, afterall what do i know!
Ned.
beware, I've got yellow skin
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JAG
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| posted on 26/11/03 at 12:42 PM |
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OK. I have looked up the spec of the bolts - but it's not good news.
Seems that the guys designed their own bolts specifically for this purpose. No grade is specified just a material - which is useless for judging the
final strength of the finished part. Only other bit of info I have is that the threads are rolled rather than cut - for obvious reasons.
Last bit of info; I didn't notice originally but in the four bolts per caliper there are two different sizes.
The largest (7/16 x 20UNF - 2A) should be 95/75 Nm.
The smaller (3/8 x 24UNF - 2A) should be 68/54 Nm.
Hope that helps.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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timf
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| posted on 26/11/03 at 01:10 PM |
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ARP do these sizes maybe worth a call to the uk importers as they are rated to 170,000 psi
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blueshift
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| posted on 26/11/03 at 02:43 PM |
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Thanks JAG. sigh.
I'll go and take some stress out on our sierra calipers, de-rust them - again. That's what I get for leaving them in the garage for a week
after de-rusting, apparently. I think the bores have rusted slightly too.
bollocks.
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locoboy
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| posted on 26/11/03 at 03:22 PM |
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Well lockwire and check regularly, this will provide a visual check which will be quick and easy, if anything looks out of place then re torque to
specified torque.
Or using a scribe or a permanent marker mark the head and the calliper to again provide a quick and effective checking method.
I guess the moral here is CHECK REGULARLY
(im a guilty party, i have split my callipers about 3 times and never renewed the bolts and to be honest never torqued them to the correct spec either
and have done many '000 miles on them without problems)
[Edited on 26/11/03 by colmaccoll]
ATB
Locoboy
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mackie
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| posted on 26/11/03 at 03:57 PM |
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As have many others I think. It's not a difficult job and I guess using some for of thread locking goo will help too.
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craig1410
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| posted on 26/11/03 at 08:05 PM |
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Hi,
What about using Aerotight (or Stiff Nuts if you prefer). I remember Mark Evans using those on A Plane is Born or A Chopper is Born. Use those with
loctite and locking wire and I think that should cover it... 
This blackart stuff is a bit much and I tend to agree with you Syd that common sense is work ten times its weight in blackart!
Here's a quote from this (http://www.modelfixings.co.uk/special_nuts.htm) website regarding Aerotight nuts:
"They are an all steel construction and so are suitable for high temperature applications such as engine manifolds etc. These nuts give
excellent resistance to loosening and are effective in even the highest vibration application. Although more costly than Nylocs, an important feature
of Aerotight nuts is that they are re-useable many times over."
Cheers,
Craig.
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blueshift
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| posted on 26/11/03 at 11:18 PM |
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If aerotight are nuts only, not bolts, that wouldn't help.. cortina caliper bolts screw into threads in the calipers themselves.
I am in two minds about this situation.. on the one hand I can't imagine the calipers coming apart or leaking catastrophically if we torque them
up properly with high temp locking compound..
.. but on the other hand, it's the front brakes, really not somewhere we should be making guesses and hoping for the best 
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craig1410
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| posted on 26/11/03 at 11:26 PM |
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Well spotted Blueshift...Doh!
I just assumed that the bolts went all the way through and had nuts on them...
Yes I agree with you that it is not an area to mess with. However, who's to say that the previous owner(s) of the calipers that we currently own
used the correct bolts or for that matter the correct o-ring seal?
My feeling is that I'd rather buy some high quality 12.9ton socket cap bolts of my own and fit them with some high temp locking compound and
wire them to the calipers.
Cheers,
Craig.
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Browser
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| posted on 27/11/03 at 02:30 AM |
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This whole thread kinda makes me glad i've got Sierra claw type single piston calipers, no splitting involved
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JAG
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| posted on 27/11/03 at 09:12 AM |
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I think that you should all be 'OK' if you replace with 12.9 cap head bolts, torqued up properley with thread lock - use locking wire if
you want to be doubly sure.
Most of all keep an eye on them and check at each MOT/Service or whatever.
I doubt you will have any trouble.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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mackie
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| posted on 27/11/03 at 10:09 AM |
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timf, do you know who the uk dealers for ARP bolts are?
Or anyone for that matter. I take it if I specified the details that JAG posted above they'd know what I was talking about...
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ned
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| posted on 27/11/03 at 10:54 AM |
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mackie,
i'm sure rally design (raldes.co.uk) stock arp bolts, maybe worth a call...
Ned.
beware, I've got yellow skin
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JAG
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| posted on 27/11/03 at 11:18 AM |
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Guys,
Please don't think this is a strength issue.
It's more about fatigue (due to pressure cycling) and vibration. Vibration alone can kill just about anything.
Hence my comment about checking the caliper/bolt integrity on a regular basis.
Justin
Who is this super hero? Sarge? ...No.
Rosemary, the telephone operator? ...No.
Penry, the mild-mannered janitor? ...Could be!
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blueshift
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| posted on 27/11/03 at 02:08 PM |
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thanks guys, just to clarify on torque (syd? jag?) if we torque the bolts to their stated limits, if that's higher than specified for the
caliper bolts might we risk overstressing / damaging / ripping the threads out of the caliper?
Alternatively if we only torque them to the spec (as JAG posted before) might the bolts not be in their elastic range and thus suffer from vibration
loosening / fatigue?
I'm inclined to torque to the bolt limit and doubt it will harm the caliper.. but just wanted to check.
thanks guys.. I don't know what we'd do without this forum. probably either give up, spend a lot more money or die from failed brakes 
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