pros and cons of new stainless steel fasteners throughout

[Oakmaster]

What are pros and cons of new stainless steel fasteners throughout when re-building onto a new Galv Chassis ?

cheers

[Frax]

There are good and bad points, the stainless will not rust but it does cause corrosion around the nut/bolt unless it is insulated from the other parts.

I did use them on my rebuild and put them in well greased and have no problems as yet after 3 years.

[miketomcat]

Don't use them for anything structural as they are nowhere near as strong as steel bolts.

Mike

[Team Idris]

If you over tighten them they grab each other and then they are worse than rusted bolts to undo. But you can use SS bolts and ordinary nylock nuts. Maybe they'll still corrode solid, but drill the nut, chisel it and the bolt isn't stuck in. So far mixing 8.8 and SS has worked for me.

I suspect that if you use A2 for one and A4 for the other they don't lock up? I had wondered about brass nuts?

[Retroanaconda]

You can get thread lubricants to stop the stainless locking into itself.

Used in the right places they're not a bad idea. But not for structural fixings as above, unless you want to go for the very expensive high grade stainless which I am told is as strong as 8.8. But some suspension bolts are 10.99 or even 12.9 so use original stuff for them.

[mike4444244]

As above cold welding of the nuts and bolts can be a huge problem, I use a lot of stainless screws and plates at work and it can be a huge pain getting them undone!

[FridgeFreezer]

http://en.wikipedia.org/wiki/Galvanic_corrosion

And as Miketomcat says, random SS fasteners are not as strong as random steel ones so shouldn't be used to take any sort of loading / stress unless you know what you're doing and what rating your fasteners are.

Stainless is harder but can be very brittle, not good news, and when a stainless nut & bolt "bind" it's pure evil - plus of course being harder material it's a proper pain to drill out.

[robertspark]

http://forums.lr4x4.com/index.php?showtopic=91429&view=&hl=&fromsearch=1

Previous discussion may be worth consideration

[Tanuki]

SS fasteners fitted into other SS fasteners [or, any other situation where two SS components are in intimate, stressed contact] are subject to "Galling" - essentially they grow together and become very difficult to separate.

The effect also happens when initially torquing SS fasteners against each-other: you may hit the specified torque well before the desired level of fastener clamping-force required has been achieved. There are ways round this - my late father developed one - chemically etch the sliding surfaces and then use several-hundred atmospheres of pressure to force microparticles of PTFE into the etched surface.

I invariably think of SS fasteners as blingy: the aviation industry uses Titanium for some of its 'serious' stuff but it always looks matt and dull and so loses you bling-points.

[qwakers]

i use stainless everywhere i can on my landy. just one less thing that will be a pita to get undone later....

[miketomcat]

Use anti bloc fett to stop firing up. Copper slip works but I'm not sure of the long term effects of adding another metal to the equation.

Mike

[Litch]

Answered this one on here before.

I rebuilt my 90 using SS fixings throughout (apart from suspension, brakes etc) and used Copperslip and / or Waxoyl on assembly and I have not had a single problem with corrosion, seizing, shaking loose or any other such issue. This doesn't just include nuts / bolts & washers but even items such as the self-tappers that hold the floor-plates down, head-light bezels etc, even all the small fiddly fixings behind the dash. Many of the the fixings in the under bonnet area, exhaust plus larger items such as swing-away spare wheel carrier, front & rear bumpers etc, all of these are SS.

When necessary, all fixings have come apart with ease and I can't see a single reason why not to do it.

The timescale? I did this 14-years ago so I think you can look at it as a long term test.

Best place to buy is from a fixings supplier, far cheaper than the likes of DIY stores, Screwfix, Ebay etc. Kits are ok but if you want to put a bit of effort into it you can buy a lot more for your money. In that time I have also rebuilt a couple of motorcycles and once again used SS throughout. By buying in relative bulk and saving money, I always have a ready supply of fixings to hand whenever I want to do a bit of work.

[supaimpy]

use milk of magnesia on the threads, used to use it on power stations so should be no issues on LR's

never use S/S on suspension as although tightened they act in shear

[SOA 93]

I'm obviously missing something about this strength issue with bolts, if the bolts tensile strength is the same then surely the bolts are as strong as each other?

An 8.8 grade bolt has a tensile strength of 800N/mm2

An A2/80 Stainless bolt has a tensile strength of 800/mm2

An A2/70 Stainless bolt has a tensile strength of 700/mm2, even that is hardly a weak bolt, these are what Scewfix stock.

If you used the next size up in bolts then it would more than compensate for the tensile strength, surely, so if you used an M12 A2/70 instead of an M10/8.8 the stainless bolt would be stronger.

I thought the whole 'Stainless steel is Harder' was a misconception arising from people trying to cut or drill it in the same manner as carbon steel, whereas it is in fact softer and requires different speed/techniques.

I'll ask 'The' question: Why shouldn't I use a A2/80 M16 bolt in the radius arm mounts of my Discovery? Assuming the standard bolts are 8.8, I cannot see the reason you would need stronger than 8.8 it's M16 after all.

What do they use in the North sea? A4/80 I would of thought.

[western]

I used this body to chassis kit during my chassis change. http://www.a2stainless.co.uk/Land-Rover-Defender-110-Chassis-Bolt-Kit_AJ5PM.aspx?nh=1

I only buy my SS fixings from them.

[SOA 93]

I see they do towing kits in stainless and even a Nato hitch kit, Spawn of Satan obviously.

The Nato hitch kit does come with a safety note mind. I assume the bolts are A2/70.

[Anderzander]

SOA

My understanding was that the tensile strengths are not the issue - it's in shear that stainless is weaker.

I think someone already mentioned that the load on a lot of suspension bolts is in shear - as it is with your radius arm example.

Certainly tensile is not the only way to measure bolt strength or quality.

Seems difficult to find quoted shear strengths for a given standard though.

[Quagmire]

Stainless seems to yield less (if at all) before it goes ping? Its usually good to have some warning.

I use steel bolts and copper grease.

*edit - although using any kind of grease on a bolted connection throws up a whole load of questions as to what torque it should then be tightened to in relation to stated manufacturer figures.

[SOA 93]

I understand what you mean by the bolt being in shear in the radius arms, only as I understand it, it is the clamping force of the bolt on the bush sleeve that is keeping everything in place, and if the bolt is tight enough then it should see no sheer force on the bolt, the sheer force should be resisted by the bush sleeve being clamped by the axle mountings.

Regarding the shear strength of bolts, well as above, not really certain they should be used in a shear situation, they should be using their clamping force to resist shear.

Think of a ring gear in a axle you are not relying on the shear strength of the bolts to resist spinning on the diff centre but the clamping force and the friction/resistance between them, which can be demonstrated when the bolts come loose and do indeed shear off.

Bolts are also listed as having an elongation measurement, I'll admit I don't understand most of these measurements which is why I posed the question about the radius arms, I never stop learning, so I'm happy to be educated/proved wrong, it's all good stuff, it's just when I read comments like:

" Don't use them for anything structural as they are nowhere near as strong as steel bolts."

From someone as respected as Miketomcat, no offence Mike, then what little I know about fasteners is called into question.

Going by Litch's comment they sound like a great idea, I have been replacing bolts on my disco with SS, I used M12 on my custom damper mounts, if there is a 'structural integrity' question mark about these bolts then I'd like to be educated.

I should point out that some of my comments are also referring to the linked previous post on the subject.

It would be nice to get a reasoned answer on this subject, and put it to bed once and for all.

[western]

some charts for comparing SS A2-70 & normal steel 8.8 bolts in http://home.jtan.com/~joe/KIAT/kiat_2.htm

[miketomcat]

No offense taken my comment is based on two things firstly information given to me by people I respect.

Secondly I use stainless bolts all day long at work (i'm a boat builder) would I use them structurally, no, I can shear the head off a stainless bolts easier than I can a steel bolt. They fire up for a past time normally just before they go tight.

I do use them for non structural. I don't doubt if you up the size the strength is similar but most of the time you can't up the size. Lastly land rover spent a lot of money and time spec'ing bolts for a job.

Mike

[tacr2man]

i used stainless in my 90 build, not in all situations tho, where I used stainless against the ali , I insulated with nylon washers, and squirted rtv in before tightening .

Slightly off topic but relevant , what was the coating land rover used to use on the old series bolts that were green, as I have found that they undo easily after 50 plus years of assembly ?

[SOA 93]

Thanks for clarifying Mike I was full aware of your background which is why your comment carried so much weight. What grade bolts are you using at work?

I use SS wood screws occasionally, I don't have a clue what grade they are but they are softer, the heads chew much more easily, trouble is with cordless drills and impact drivers we forget just how much torque we are applying.

Sorry Mike, could you redo that one sentence, "They fire up for a past time normally just before they go tight." I've tried to understand what you mean and looked at my keyboard to try and fathom if there was a miss typed key or something, to no avail, it looked like it should be an important comment.

As for Rover specification, I would think cost would be far too much to even consider Stainless steel.

Many people on this Forum spare no expense on Land Rover modifications and Rebuilds, so the expense of SS fasteners is not the question in this case.

On paper at least, there are Stainless bolts that are comparable to 8.8 steel bolts in strength.

Galling is a known issue with stainless as has been stated already, however when I put all new suspension on my Disco in the Summer I'd say 75% of the bolts on my Disco had to be undone with a 240v 115mm adjustable.

How many of us have had a 5 minute job turn into a marathon ordeal because of a rusted bolt.

The lower bolt on the panhard drop arm had rusted into the arm, nut came off ok, but I ended up snapping the head of trying to get it free, things like that are why I'd like to use SS if its up to it.

[SOA 93]

Yrm are selling radius arm bolts as a kit A4/80 grade, 4 bolts and nuts for £20, making them 3-4 times more expensive than normal 8.8s.

[miketomcat]

I use A2 70 and A4 70 & 80 job dependant.

A4 80's are used in high load areas (i should point out they are designed and spec'ed for the specific job) but quality does seem to vary and they are pricey.

Sorry I didn't word the sentence very well I meant that stainless has a bad habit of firing up (galling) solid just before it pinches up on the job making it very difficult to cut off.

Just to clarify Galling is caused by friction creating heat and effectively welding the two together it can happen both tightening and undoing, without and with lubrication (less so with) A2 and cheap A4 are especially bad for it.

I guess the bottom line is I wouldn't use them for structural but that is my opinion based on what I've been told/experienced.

Mike