Fastener specs

[madbilly]

Hi all,

I was getting together new fasteners for my damper/spring replacement and I used the very helpful parts listings on Deroure.com. On suspension parts there's also dapinky's very helpful parts listing viewtopic.php?f=80&t=22764.

However, I discovered I don't know how Dave found out what the specs are, particularly the tensile strength (very important for suspension, amongst other things).

So, on the one hand I'm sharing a tip here, and on the other hand asking for help.

Tip: To find out if the fastener you need has a fine thread (as opposed to the normal spec thread), take the part number from the part diagram on deroure.com, then put it back into the search, find the entry for "Lotus Price Table" and then it should tell you the thread pitch, e.g.:

https://www.bellandcolvill.co.uk/deroure?qs=1&preview=1&make=1&model=23&groupid=2223
https://www.bellandcolvill.co.uk/produc ... PBID=63079
https://www.bellandcolvill.co.uk/derour ... rchparts=1
https://www.bellandcolvill.co.uk/produc ... ID=1452738

However, what about tensile strength? For example, dapinky somehow worked out that A082W7053F https://www.bellandcolvill.co.uk/produc ... PBID=63055 should be 12.9. In that case I think he used his judgement rather than finding it in reference material. I know the strength should be stamped on the fastener, but if the one on the car is rusty and impossible to read then where do we find it out? The Lotus Price Table does say the tensile strength sometimes https://www.bellandcolvill.co.uk/derour ... rchparts=1 but is this 100% reliable?

The fall-back is to buy the specific part and not try and source the fasteners via another route. However, that's 1) boring!, 2) means we can't get stainless alternatives, 3) potentially more expensive (but less time consuming).

Why am I thinking about this right now? I'd like stainless A082W7053F, and I did source them but then later thought about tensile strength.

Cheers

[Tuga2112]

one thing to be very aware of (because i got burned by that) is that the books are not in sync with fasteners around the suspension.

i ordered 80 quid worth of stainless fasteners for the suspension and only £6 worth of it actually matched the book. (possibly because i look at the S2 book and my car is a 91SE but i am assuming the documentatnio is not very reliable)
ideally you remove the bolts 1 by 1 and take measurements before orderting the whole shebang.

i wil be installing updated coils in the winter, and will be taking notes then. but untill then, you wont get any practical help from me.

[dapinky]

To try and assure you of my complete and utter comprehension of the whole matter - I basically guessed!

Okay, that's not entirely fair or true - I did a bit of metallurgy and material science back when Jesus was an apprentice to Joseph - but the actual theoretical and physical properties hasn't changed,

I worked on the principle that all suspension bolts should be a minimum of 8.8 grade HT steel - and then used the fact that 8.8 grade mild steel has the same tensile strength as -80 grade stainless..... and the easiest bolts to find in that grade (in the UK, anyway) are all A4 marine resistant material.... but not ALL A4 bolts have this strength, some are -70 rated.....

.... so my 'basic' starting point was to find a bolt of suitable size in A4-80 grade (Westfield Fasteners are my supplier of choice for larger orders of smaller quantities of each size).

Industry standards dictate that a rating of 8.8 will have a Hex-head on a metric bolt (or setscrew). (obviously this doesn't apply to special orders etc)

Likewise, a recessed allen-headed bolt will (generally) be either 10.9 or 12.9 grade.

So, where the parts book (or my observation of the car) shows these style bolts, I knew that getting them replaced with stainless wasn't going to happen (unless I spent an absolute fortune on them - even Titanium bolts were cheaper!).

In that case, I just used a higher grade steel bolt - it is only really in the heavy shock areas that you find them - ie, shock absorber to yoke, shock to bottom wishbone and top wishbone to balljoint....
.... my selection of 12.9 for the one application was purely overkill on my part - I'm fairly sure that 10.9 would be enough, but for a very small price increase, it gives me peace of mind.

As you say, if a smaller pitch is stipulated, it allows for a higher torque figure to do it up correctly - and 8.8/10.9 have lower permissible torque figures than 12.9.

So it was a combination of factors which got me to the final selections - based on a belief that Lotus know what they are doing, but they are doing it to a cost - I am prepared to spend a bit more for future convenience, but want it to remain as 'strong' as designed.

Where a smaller pitch is used (eg, the track rod ends, ball joints etc I use an M12x1.5 nut made from mild steel, NOT stainless - again, on the 12.9 bolt, I use a mild steel nut, not stainless - if you try to do a stainless nut up to the same torque as a mild steel one you risk deforming the threads in the nut, as the material isn't as strong.

And remember, a stainless bolt will stretch more than a mild steel bolt, so they need torquing to a 24% lower number than published in the manual.