 | Home > Technical > Bolt specification?...Stainless?.or not? |
 
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20334  
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Yes, but I can't remember what exactly now.  IIRC it's stamped on the head of the bolts. I too would be interested to know what could be used safely and legally.
 But I'd also like to know if a spreader plate is really required required or not too  ⭐️⭐️God Bless the USA 🇬🇧🇺🇸 ⭐️⭐️ |
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3rd Mar 2013 10:22pm |
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| x-isle Member Since: 26 May 2011 Location: Midlands Posts: 1327  
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I think a min of 8.8 will do you. Craig Rogers
2007 Puma 110 XS 2011 Evoque Coupe Dynamic Lux www.craigrogers.photography |
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3rd Mar 2013 10:40pm |
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| smb Member Since: 15 Jan 2013 Location: Cheshire Posts: 1232
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Always make sure they are graded 8.8. There will be a lot of Dynamic forces applied to the system(nut, bolt & thread) whether you are accelerating, decelerating, bumps, etc... and that is just in normal driving. You then need to consider the forces applied in an emergency. 8.8 is not that much more expensive as long as you don't go to Landrover, Halfords, etc... |
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3rd Mar 2013 10:40pm |
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| custom90 Member Since: 21 Jan 2010 Location: South West, England. Posts: 20334
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That's the spec I was trying to think of. I think that's what mine have on at the moment. ⭐️⭐️God Bless the USA 🇬🇧🇺🇸 ⭐️⭐️ |
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3rd Mar 2013 10:48pm |
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| Clemmo Member Since: 03 Aug 2012 Location: Mile Oak Posts: 1217  
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So is that the number stamped on the head of the bolt?
Clemmo Make today a little better than yesterday but not so good as tomorrow.... Defender 90 HT............Pangea Green BMW X3 Msport............Carbon Black Mini Electric................Grey. (wow!) MGB Roadster……..........Vermillion 17k miles Honda Benly CD200....Maroon --------McLouis Fusio........7.4m of fun |
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3rd Mar 2013 10:52pm |
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| Laurie Member Since: 22 Feb 2008 Location: Sussex, England Posts: 2897 
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Stainless steel bolts fatigue more easily than HTS bolts.
Better to stick with HTS.  |
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3rd Mar 2013 11:02pm |
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| leeds Member Since: 28 Dec 2009 Location: West Yorkshire Posts: 8580
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Yes.
Some details here http://www.hi-tensilebolt.com.au/Head%20Markings.html Please note in general terms stainless bolts do not have the same tensile strength as high tensile bolts, they are weaker. General rule of thumb you do not use stainless in importan high strength areas so not on tow ball. Common available stainless bolts are A2 70 (700 MPa) whereas standard high tensile bolts are 8.8 or 800 MPa. Brendan |
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3rd Mar 2013 11:08pm |
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| XS Pete Member Since: 13 Jan 2011 Location: Suffolk Posts: 632 
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As per Brendan's link, you can get A4-80 (800MPa) which is broadly similar in strength to 8.8 high tensile if you want to go stainless, and these were what I used for some of the more 'cosmetic' fixings for my NAS step.
For everything which is subject to shock or is more heavily loaded, as x-isle said go for a minimum of 8.8 high tensile and not stainless, such as the tow ball. I used 12.9 for all of mine including the ball just for peace of mind, and they weren't much more expensive than 8.8 either. You then just need to make sure that you torque them up (preload) them properly, and the job's a good un. Pete |
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4th Mar 2013 8:37am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17363 
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If your vehicle is "M" series Euro-type approved (ie not commercial) then the the towing system must also be type approved and this will include fasteners. Replacing any fasteners other than with like-for-like will therefore technically be illegal.
Personally I don't see any point in not using grade 8.8 BZP or ZPP fasteners; these will match the original and will both strong and durable. There are several issues apart from strength which can affect stainless fasteners (ask anyone who's tried to dismantle a Patriot rack after a few years)! A normal off-the-shelf "high tensile" fastener will (unless you specifically order/ask for something else) be grade 8.8 unless is it a socket-head capscrew or bolt (hex, spline, or Torx socket) in which case by default it will be grade 12.9, which is in effect the next grade up from 8.8. |
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4th Mar 2013 10:03am |
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| Clemmo Member Since: 03 Aug 2012 Location: Mile Oak Posts: 1217
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Can you please explain? Cheers Clemmo Make today a little better than yesterday but not so good as tomorrow.... Defender 90 HT............Pangea Green BMW X3 Msport............Carbon Black Mini Electric................Grey. (wow!) MGB Roadster……..........Vermillion 17k miles Honda Benly CD200....Maroon --------McLouis Fusio........7.4m of fun |
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4th Mar 2013 10:22am |
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| leeds Member Since: 28 Dec 2009 Location: West Yorkshire Posts: 8580
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A2 stainless is rust resistant in fresh water and is most commonly available stainless bolt.
A4 stainless is rust resistant in salt water marine and more chemical environments. Note have said rust resistant rather then rust proof. For specialised environments yes it is possible to get special exotic grades of stainless bolts but not relevant here. It is possible for stainless to cold weld itself to a bolt IF you have not used some paste. If it cold welds itself then you may well shear the bolt before undoing the nut. OK I do not fully understand the process of cold welding
Have a read HERE This is one of the reason Nakatanenga/Entreq has a tube of paste with their stainless kits. Brendan |
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4th Mar 2013 10:32am |
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| Go Beyond Member Since: 30 Jan 2012 Location: Headcorn, Kent Posts: 6678
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I don't understand cold welding either but I've managed to do it
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4th Mar 2013 10:34am |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17363
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Exactly as Brendan has said! Throw in a large number of countersunk hex-socket-head capscrews and just about every fastener will end up being destroyed if you have to dismantle the rack.
You will probably have gathered that I am not personally a fan of stainless fasteners for everyday use, although in the right environment and circumstances and used correctly they are great. |
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4th Mar 2013 10:35am |
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| BigMike Member Since: 13 Jul 2010 Location: Lancashire Posts: 2253
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Just replace them like for like then spray them with acf50 and every 6 months. job done.
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4th Mar 2013 11:25am |
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