Stainless steel bumper bolts for front wings

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  • redmonty
    club member
    Club Member
    • Jun 2024
    • 29

    #1

    Stainless steel bumper bolts for front wings

    I have been bugged for many years by the old rusty chrome front wing bolts on my 1985 Marlin LWB roadster. Why I have never changed them I never know, so now before I start doing major mechanical work to get it back on the road, I thought I would do a nice easy cosmetic job to replace the front wing bolts with something that will never rust again (the area around the bolt head has sunk in slightly into the wings now, making a nice water trap to encourage more rust). I have been looking at various listings on Ebay and none of them give the thread diameter, square size under the head or the domed head diameter!

    These are the dimensions of the existing chrome bumper bolts I have:
    The threaded bolt diameter is just over 6mm (probably 1/4"), the square bit at the top is fractionally over 6mm wide and the head is 14mm and their length is about 3/4" in total including top of head. So are these bolts Escort M1/MK2? If they are fractionally longer that isn't a problem, but the bolt threaded diameter and square bit at the top is important.

    Has anyone else used polished stainless bumper bolts from ebay?
  • A_Hogg
    club member
    Club Member
    • Nov 2016
    • 315

    #2
    Take a look at Westfield Fasteners website under the coach bolt section - you'll find all the relevant information you're after for the various bolt sizes. Just replaced those on son's Roadster with 8mm stainless button heads. And good luck getting the nuts undone as there is nothing to prevent the bolt spinning so in all likely hood you'll need to cut nuts with a dremel or similar.

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    • redmonty
      club member
      Club Member
      • Jun 2024
      • 29

      #3
      Originally posted by A_Hogg View Post
      Take a look at Westfield Fasteners website under the coach bolt section - you'll find all the relevant information you're after for the various bolt sizes. Just replaced those on son's Roadster with 8mm stainless button heads. And good luck getting the nuts undone as there is nothing to prevent the bolt spinning so in all likely hood you'll need to cut nuts with a dremel or similar.
      Thanks for the info... I looked and found something that was a close match, but they don't seem to be highly polished. What was the finish like?

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      • A_Hogg
        club member
        Club Member
        • Nov 2016
        • 315

        #4
        Button heads finish I considered good , but maybe more of a satin than what you would get with Chrome.

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        • redmonty
          club member
          Club Member
          • Jun 2024
          • 29

          #5
          Originally posted by A_Hogg View Post
          Button heads finish I considered good , but maybe more of a satin than what you would get with Chrome.
          Thanks for letting me know. I think I'll get some and then polish them to see if I can get them to look like they are chromed. Cheers!

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          • dave_kitson
            club member
            Club Member
            • Nov 2011
            • 269

            #6
            If you are still looking -
            For my Cabrio build I used quite a lot of stainless fittings. My favourite supplier was Dave Middleton, ultra quick despatch, fine machined finish on bolt heads, sensible prices. I just checked the website stainlessmiddleton.co.uk and there were 19 different coach bolts, surely one to meet your needs!

            One word of warning with coach bolts. I used them on the bumpers, and put nyloc nuts on them, but when I wanted to undo them they would not move, and had to resort to a nut splitter. They now have plain nuts with a spring washer.

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            • A_Hogg
              club member
              Club Member
              • Nov 2016
              • 315

              #7
              I wonder how many kit builders have taken the trouble to file a square hole to take a coach bolt. Most I suspect just bore it out big enough!

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              • Ye Ol Ripper
                club member
                Club Member
                • May 2016
                • 294

                #8
                My Roadster was built with square holes to take chrome headed bolts on the front wings. The wing sits on a rubber washer, possibly a tap washer. The chrome bolts with a square were probably off a 1960-70's car that had chrome bumpers. Ford, BMC and laterly Leyland cars used them.
                Last edited by Ye Ol Ripper; 16-09-25, 09:50 PM.

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                • dave_kitson
                  club member
                  Club Member
                  • Nov 2011
                  • 269

                  #9
                  Thinking a bit more about this, I don't like the idea of using coach bolts in fibreglass. Any resistance on the thread, and you will not only destroy the square hole, but also possibly the wing! What about using caphead bolts with an allen key hexagonal hole in them? Maybe not quite as neat, but much safer and only need round holes. When building my Cabrio I went for further neatness, by devising a means of securing the wing without any visible bolt heads - not really an option if you already have holes in the wings, but worth considering on a new build. Dave

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                  • andyf
                    club member
                    Club Member
                    • Sep 2014
                    • 928

                    #10
                    I used cap head bolts and they look ok. I am considering switching to hidden fixings though when I get the wings resprayed
                    Mk2 SWB Marina Roadster with a 2.0L Pinto built in 1986

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                    • Ye Ol Ripper
                      club member
                      Club Member
                      • May 2016
                      • 294

                      #11
                      1) If the threads of the bolts after the nut has been fitted are painted and then additional clear waxoyl applied. Then the nut will never sieze and then tear the square hole.
                      2)Alternatively you can use white plumbers ptfe tape on the threads to seal out moisture.
                      They will then always undo easily.
                      Because those 2 tips aren't in the Haynes manual, people are largely unaware of both of those methods of siezure prevention of nut and bolt threaded applications.

                      The wing bolts only need to be nipped up , as the spring washer and rubber tap washer idea is supposed to absorb vibration.

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                      • redmonty
                        club member
                        Club Member
                        • Jun 2024
                        • 29

                        #12
                        Originally posted by dave_kitson View Post
                        If you are still looking -
                        For my Cabrio build I used quite a lot of stainless fittings. My favourite supplier was Dave Middleton, ultra quick despatch, fine machined finish on bolt heads, sensible prices. I just checked the website stainlessmiddleton.co.uk and there were 19 different coach bolts, surely one to meet your needs!

                        One word of warning with coach bolts. I used them on the bumpers, and put nyloc nuts on them, but when I wanted to undo them they would not move, and had to resort to a nut splitter. They now have plain nuts with a spring washer.
                        Thanks Dave, I wanted SS bolts for 2 reasons... no rust on the polished bolt head to worry about and also if using SS nyloc nuts, no seized nuts/bolts. So were the bumper bolts you used SS with SS nyloc nuts? And are the SS coach bolt heads polished as standard from Dave Middleton or do you have to do it yourself?

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                        • dave_kitson
                          club member
                          Club Member
                          • Nov 2011
                          • 269

                          #13
                          Bumper bolts were stainless with stainless nylocs, so why they were stuck I can't say. Nearly all bolt heads from DM have a fine machined finish, but not polished. Only exceptions are some small bolts which still have raised lettering. DM does some starter packs which offer quite a saving and include common sizes (not coach bolts) - you soon find a use for them! At least you could assess the finish on them for yourself. Another thought - on painted surfaces, it is worth putting a nylon washer under the bolt head - also available from DM. I should be on commission!!

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                          • redmonty
                            club member
                            Club Member
                            • Jun 2024
                            • 29

                            #14
                            Oh that is interesting Dave. I have now looked it up and this is why SS bolts and nuts seize...
                            "Yes, stainless steel bolts and nuts are prone to getting stuck due to a phenomenon called galling or cold welding, where the threads fuse together due to friction, heat, and the breakdown of protective oxide layers. This is especially common with austenitic stainless steel and can happen during tightening or even disassembly. To prevent galling, use an anti-seize lubricant, install fasteners slowly to reduce friction, ensure threads are clean and undamaged, and avoid using "pulling" forces to draw joints together".

                            This is a new one on me, never thought in a million years that SS nuts and bolts could become stuck as I'm about to replace all the wing bolts with SS when I get the leaking petrol tank sealed. I thought the salt from the road may cause some slight longer term corrosion to the bolts inside the wheel arches due to road spray, but never thought that galling was a thing! My front wing bumper bolts being SS I thought would also prevent the issue there too. Looks like I'm going to have to invest in some anti-seize lubricant on each bolt wherever I use them.

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                            • dave_kitson
                              club member
                              Club Member
                              • Nov 2011
                              • 269

                              #15
                              Wowee! That prompted some frantic googling! Austenitic stainless (eg grades 303 and 304) is commonly used for nuts and bolts, though it is possible to get them in other grades which are not so prone to galling. I wonder what grade DM uses - or indeed any of the other suppliers I've come across - likely one of these. I wonder why I haven't noticed the problem in any other place where I used stainless - possibly not enough heat generated when tightening, maybe cutting through the nylon contributed on the bumper bolts. Every day a school day!

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