lorenzo Posted June 24, 2009 Report Share Posted June 24, 2009 OK, I pulled my brake discs off the other day so i could get the wheels powder coated. The old bolts were a little gnarly on some of them and didn't reallt want to come off too easily, despite me using the impact driver thing on them. I'd like to replace them with something that's not normal steel and won't rust to buggery and get chewed up so easily; what's the verdict on stainless disc bolts? One half of me says that they can't be lethal death traps, or they'd not sell them would they. The other half of me says that stainless is much less ductile than plain steel, and they'll suffer much more with fatigue than the originals, causing potential shitting of trousers followed by decapitation. And before somebody says so, I can't afford 10 bloody titanium bolts, they're worth more than the bike. Link to comment Share on other sites More sharing options...
Hendo Posted June 24, 2009 Report Share Posted June 24, 2009 I had this issue when I put new ones in my R6. I sent an email to pro-bolt asking them what the crack was with stainless bolts, as Id heard rumours that they werent strong enough. They replied saying they use a different grade of stainless steel and they are more than up for the job (it was worded better than that though!). Anyway I bought them. They were very well made and seemed spot on. I never had any grief with them, I did sell the bike about a month later mind. Sorry I cant be more scientific about it all. Send pro-bolt an email with your query. Hendo Link to comment Share on other sites More sharing options...
TriGGer Posted June 24, 2009 Report Share Posted June 24, 2009 Good quality Stainless Bolts are easily strong enough for the application. The problem stems from lubrication, ie, you shouldn't use it on disk bolts, you should use you favoured retainer. This however normally leads to corrosion being a problem, because once metals start to react with one another, you'll need either heat or a miracle to shift them without snapping. Let's put it this way, I've drilled out more stainless disc bolts than I've fitted. Link to comment Share on other sites More sharing options...
tootall Posted June 25, 2009 Report Share Posted June 25, 2009 Interesting. So use original equipment bolts and risk having to drill the feckers out due to heads made of cheese, or use SS bolts and risk having to drill them out dur to snapping. Hmmm. What's your (metalurgical, not financial) opinion on titanium for disc bolts? Link to comment Share on other sites More sharing options...
gurninman Posted June 25, 2009 Report Share Posted June 25, 2009 I've seen a lot of hysteria on the information superhighway about using stainless or titanium disc fasteners, but have yet to hear of any stainless disc bolts actually failing ! Granted, the tensile strength of A2/A4 stainless isn't as high as Gr8.8, let alone proper HT fasteners, but you have to remember the load on the disc bolts isn't all that huge - they are screwing into aluminium, FFS. I'd happily use stainless or Ti for disc bolts - they are usually pretty well made. I've got Ti screws holding my calipers on (I took them off a GSXR400 that was going for scrap), and they have been fine for the last 2 years. Link to comment Share on other sites More sharing options...
deviant Posted June 25, 2009 Report Share Posted June 25, 2009 Torque up to the reccomended torque and then and keep an eye on them. Good attempt at making 'draw a line on them in permanent marker' sound technical Link to comment Share on other sites More sharing options...
lorenzo Posted June 25, 2009 Author Report Share Posted June 25, 2009 OE bolts ordered then to replace the mullered ones and I'll just never swap the discs again. It's simple that way. Thanks for the advice. Link to comment Share on other sites More sharing options...
Mark/Foggy Posted June 25, 2009 Report Share Posted June 25, 2009 FFS!!!! SHUT UP! How on earth can you break the sacred circle of engineersand give away out hallowed secrets? You'll be drummed out and have your cerimonial scientific calculator broken across the great heigensheidt alter... Woo Get You. Ten smacks across the palm with a Slide Rule Link to comment Share on other sites More sharing options...
alexp5 Posted June 26, 2009 Report Share Posted June 26, 2009 Quality Ti fasteners have rolled threads, and the price will reflect this. Average ones will have cut threads and if screwing them into alloy, will most likely gall the alloy thread. I've never heard of stainless disc bolts, whatever grade, fail. Personally, I don't use Copper Ease or suchlike. Just clean the male and female thread, dab of Loctite blue, and mark the heads. Link to comment Share on other sites More sharing options...
David W Posted June 26, 2009 Report Share Posted June 26, 2009 Let's put it this way, I've drilled out more stainless disc bolts than I've fitted. You're gonna have to explain to me why stainless bolts suffer electrolytic corrosion in alloy worse than standard Hi-Tensile plated Steel ones? Isn't stainless supposed to lack the vital valent electrons needed for it to happen? Link to comment Share on other sites More sharing options...
alexp5 Posted June 26, 2009 Report Share Posted June 26, 2009 You're gonna have to explain to me why stainless bolts suffer electrolytic corrosion in alloy worse than standard Hi-Tensile plated Steel ones? Isn't stainless supposed to lack the vital valent electrons needed for it to happen? Electrolytic corrosion is corrosion between two dissimilar metals, but caused by a different process to Galvanic corrosion which is what we are dealing with between stainless / alloy. Galvanic corrosion occurs when two dissimilar metals form a battery when immersed in an elecrolyte, e.g. salty water. The best fasteners for this environment would be A4-70 grade (marine) stainless. This has a similar grade and hardness to 8.8 tensile steel, and is what I use to replace bike fasteners (I have contacts!). Any thread lubricant should be nickel-free as apparently this speeds up the cold welding process. I may have dreamt all this. Link to comment Share on other sites More sharing options...
David W Posted June 27, 2009 Report Share Posted June 27, 2009 The best fasteners for this environment would be A4-70 grade (marine) stainless. This has a similar grade and hardness to 8.8 tensile steel, and is what I use to replace bike fasteners (I have contacts!). That's pretty much what I thought (It's nearly 20 years since I did my Materials Technology theory and I've actively avoided the subject ever since ). I guess like most things there is stainless steel, and there is stainless steel depending how deep your pockets are. Link to comment Share on other sites More sharing options...
gurninman Posted June 30, 2009 Report Share Posted June 30, 2009 That's pretty much what I thought (It's nearly 20 years since I did my Materials Technology theory and I've actively avoided the subject ever since ). I guess like most things there is stainless steel, and there is stainless steel depending how deep your pockets are. Wonder how much it would cost to have a full set of fasteners for the bike made from something like Duplex 2304 ? Link to comment Share on other sites More sharing options...
monty_zac Posted June 30, 2009 Report Share Posted June 30, 2009 I have been looking at this thread worrying as I needed to swap over discs from two nc30 wheels and a 16" Blade one. Low and behold bolts seized on half of them, after much stressing about it I decided to spray a big blob if ACF50 on them and go and get drunk for the evening. Next morning they just cracked and undid easy as that, what happens there then? Does the ACF50 (or WD40 whatever) run around the thread or get between the head and the disc? Link to comment Share on other sites More sharing options...
alexp5 Posted June 30, 2009 Report Share Posted June 30, 2009 I have been looking at this thread worrying as I needed to swap over discs from two nc30 wheels and a 16" Blade one. Low and behold bolts seized on half of them, after much stressing about it I decided to spray a big blob if ACF50 on them and go and get drunk for the evening. Next morning they just cracked and undid easy as that, what happens there then? Does the ACF50 (or WD40 whatever) run around the thread or gt between the head and the disc? In a word... yes. Sometimes all it takes is a smack with a deadblow hammer and pin punch in the allen key recess, or very slightly tighten the bolts before undoing, usually enough to crack the gunk thats holding it tight. BTW, if using lubricant on the threads, this will alter the torque value of the fastener, so be warned. As I said, on disc bolts I just use loctite blue, no lube. Apparently WD40 can alter the torque value by 20% or more, grease could alter it by upto 50%. I may also have dreamt this too . Link to comment Share on other sites More sharing options...
lorenzo Posted June 30, 2009 Author Report Share Posted June 30, 2009 Monty it's because you have some sort of intermittant muscle wasting disease. Yesterday you were weak, today your are big and strong. I get it whenever my Mrs asks me to do the cleaning, I can barely lift a mop. Link to comment Share on other sites More sharing options...
gurninman Posted June 30, 2009 Report Share Posted June 30, 2009 I have been looking at this thread worrying as I needed to swap over discs from two nc30 wheels and a 16" Blade one. Low and behold bolts seized on half of them, after much stressing about it I decided to spray a big blob if ACF50 on them and go and get drunk for the evening. Next morning they just cracked and undid easy as that, what happens there then? Does the ACF50 (or WD40 whatever) run around the thread or get between the head and the disc? ACF50 has a strong capillary action, so would have crept into the threads. Quality stuff, but I'd clean it all out before fitting the new fasteners. Link to comment Share on other sites More sharing options...
monty_zac Posted June 30, 2009 Report Share Posted June 30, 2009 Umm, yeah well its also on the disc... Geepee, fancy doing a shake down test..? Link to comment Share on other sites More sharing options...
monty_zac Posted June 30, 2009 Report Share Posted June 30, 2009 Give it a clean with brake cleaner? Whats wrong with getting geepee to do it? Brake cleaner is harmful to the trees. Link to comment Share on other sites More sharing options...
Mark/Foggy Posted June 30, 2009 Report Share Posted June 30, 2009 And why can't we clean GP with brake cleaner Application of a cigarette at the optimum momentys might save many fine motorcycles from cruelty. Link to comment Share on other sites More sharing options...
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