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Stainless bolt replacement in calipers? I have just bought some of these Gp Billets for the SP5 and looking at replacing the bolts that hold the two halves together with stainless or Ti 'cos the standard ones ALWAYS rust(in fact are rusting in the picture of a new caliper!!)!SS of course is the cheaper option but is never used in high stress areas ie caliper mounting bolts,but would it be ok for this use?Your opinions please. |
Be aware that there are many grades of stainless steel, I get mine from Dave Middleton (he advertises in Classic Bike) and have to say that I have yet to break one. I got some cheaper ones a couple of years ago and have had two 8mm engine bolts break already. You have been warned! |
Thanks Chris, I use Dave as well! |
Get some titanium from probolt. Email them direct or phone the boss Kev. |
DO NOT USE TITANIUM!!! I put some Ti caliper mounting bolts in my Brembo monoblocs - after just 1 week, I managed to get three out - the head of the fourth cracked and 7 drills later it was still stuck on there!!! Had to buy a cobalt drillbit - when it did come off - I found out that the bolt had seized on just the HEAD!!!! This happened even though the bolts were thoroughly greased before putting them in. Use Stainless - just to be safe. Khushy PS - the Ti bolts were bought from ProBolt. [Edited on 6-11-2005 by khushy] [Edited on 6-11-2005 by khushy] |
best advise,is to contact the brembo importer !www.gprdirect.com theres no substitute for oe stuff,after all,they're brakes ! |
I did contact grp.They didn't know what the bolts were in the monoblocs.Khushy's experience speaks volumes.Plus i wouldn't touch pro-bolts titanium for anything other than pretty stuff!! |
I've used A4 stainless in these applications for years now..... Recommended to me by a TT scrutineer..... |
Get the right grade of stainless and you'll be fine. Plenty of copper slip round the heads tho.... |
Stainless has less tensile strength than convential steel bolts. i would think twice about using them in sucha high stress area. titanium alloy bolts are also a risk unless you go for high tensile grades of tianium fasteners. Pro-bolt are OK for cosmetic applications but appear too soft for high stress areas. If you cab get high grade Ti alloy fasteners then these are an ideal choice (I recommend Poggipolini - although the British contact is mercurial! i.e. promises to get stuff and then goes off the radar!). JHP usually have a selection of Poggipolini. Don't skimp on cost for usch an important application. |
I'm thinking along the same lines myself Rich !!! We were both involved in an earlier thread however ...... http://www.ducatisportingclub.com/xm....php?tid=16715 Study the words of Shazaam! wisely, grasshopper !!! |
Stealth,I'm not sure that the bolts that actually bolt the calipers together IS such a high stress area.Certainly not in "shear" which is where SS is weaker than conventional steel.If i go for Ti,as you say Poggipolini is the way forward,just that if high quality SS was as good,then that would do!!££££££££!! |
Reading between the lines for a cheapo like me, it sounds like Cadmium plated steel or high tensile steel might be the way to go for the mounting bolts. SS (A4 grade 80 as mentioned) might well be ok strength wise but the implication is that for long term use there might be a corrosion issue with Aluminium. Frank |
happy to be corrected on the level of stress on caliper bolts - I just don't think I would leave it to any chance by having low tensile materials holding the buggers on. strong is more important than shiny although .....if you can get get strong and shiny then...............................obviously time for my cocoa:rolleye: |
Stealth,i TOTALLY agree!When it comes to holding them on.I am actually talking about holding them TOGETHER,which(not being that clued up on metalurgy,or it's spelling!) doesn't seem to invoke the same levels of stress and therefore will allow a lower strenghth bolt ie SS. Frank,i have used SS everywhere on all my Dukes and never had an issue with reaction between the metals.Maybe it's because they are not in long enough!! |
Oh... holding them together. Now I understand. Sorry - like I said time for cocoa. What's wrong with glue? :sing: |
Yes Jasp, having said all the above I've used SS bolts on my 6-pot calipers and have not had a problem - but, I've not had them apart either. I used plenty of anti-sieze and didnt have any problems: http://homepage.ntlworld.com/flsntl/...s/page0002.htm I did use high tensile steel for the mounting bolts (and nyloc nuts - belt and braces eh?). But I'll obviously need something more 'bling' for my P4's :):):) Gold cadmium plating perhaps - LOL..... Frank |
Frank,i may have some HIGH QUALITY Ti ones for you.Give me a ring.:roll: |
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Don't underestimate the amount of stress "holding them together" involves. If you try to think laterally, when you apply braking force to the caliper, the equal and opposite reaction is to try to force the calipers apart. Therefore the bolts "holding them together" are actually a high stress item. For my calipers, I used aircraft standard SS bolts, but got them through a now defunct source. If you do a search on high tensile SS bolts, I'm sure you'll find something similar. |
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That's true, but it's a tensile stress, not shear in that instance. However, I don't know how stainless compares to titanium or steel in that respect. |
Even the better grades of stainless are nowhere near as strong (in shear or tension) as the steel used in plated allen screws (Grade 12.9). I'd bear this in mind when considering replacing any bolts. I'd be wary of replacing caliper clamping bolts at the best of times, though. They will have been carefully torqued up to equal tightness. [Edited on 7-11-2005 by moto748] |
Jasper - the rusty bolts on my own brembo billets is a constant source of frustration (although when cleaned up and WD40'd they look fine from a distance), but when I mentioned to Rich L (Louigi) about replacing them his response was very cautious. My hand may be forced though coz the r/h caliper is weeping a small amount of fluid (im guessing there is an o ring behind the bolts) so i'll let you know what I do.. Nat |
I have talked to a few people and have now even got the torque settings.I am going the A4(high tensile) stainless route,removing one bolt at a time.I can't see this being a problem.The calipers should not move with three other bolts holding them together.I hope. |
From http://www.easywebstore.co.uk/stigfa...tID~34484.aspx "Is stainless suitable to replace high-tensile bolts? No. The vast majority of stainless fasteners listed on this site are grade A2-70, and have approximately 85% of the tensile strength of grade 8.8 steel bolts. As such, stainless fasteners are only recommended for non-stressed applications, which effectively rules out brake calipers, suspension mountings, brake discs, seatbelt anchors and propshaft bolts. We cannot advise on the suitability of replacing any OEM fasteners with stainless, or accept any responsibility for your actions in so doing. On your own head be it...... " |
I am replacing with A4 not A2. |
For SS specs etc check out this website for advice. http://home.jtan.com/~joe/KIAT/kiat_2.htm |
This is a reply I did from a similar post a bit back - normal Zinc plated bolts have a tensile strength of 500 Newtons/mm2 stainless steel basically starts at 500 N/mm2 for class 50 up to 800 N/mm2 for class 80. High tensile bolts are about 800 N/mm2 - usually stamped 8.8 on the head. So if you want to be really sure about the strength get some stainless steel grade A4 class 80. Alloy fasteners have a huge range due to the various metals available, but are unlikely to be over class 80 on a bike. also you have to be carefull about putting stainless bolts into alloy as disimilar metals react with each other causing corrosion, this can be prevented using copaslip or similar, you then have to reduce the tightening torque to copensate for the lubricate tread - to about 60% of the stated torque. |
Jasper, let me know what you eventually end up with as I'd like to order some. I've had a brembo billet on the shelf in my living room for the last year (the pair to my DD l/h caliper) and even the bolts on that have gone rusty!! Incidentally, I'll be out at the brembo factory shortly so I'll ask why they fit such crappy bolts! :lol: Cheers, Ali |
I seem to recall that we had problems previously when using s/s in the presence of ammonia - the s/s apparently becomes brittle to the point of useless. Granted it was a saturated area inside a glovebox but just a thought if your cleaning the s/s with ammonia based product. There's never a chemist around when you want one is there. |
Their top spec race calipers use titanium bolts (unless they're monoblocs, of course). Why not use some of those? |
Felix,i was looking at doing that but then this corrosion/reaction of metals raised it's head!!I'm still convinced SS is an option if the correct spec is used,as is Ti. |
Just use A4 S/S with some copper slip and you will have no problems, most suppliers of S/S will offer either A2 or A4, S/S is not expensive but never use S/S for engine bolts as it has a courser thread than normal metric engine bolts and hence can work loose easier. I found this out when I bought a set to put on my Jota and was warned about this problem by a very knowlegable chap many years ago, remember that S/S does not have the same tensile streanth as mild steel for such applications like retaining bols etc. You will have no trouble with A4 on your calipers. |
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Sorry but this simply isn't true. Stainless steel is a material, not a 'type' of bolt. Thread patterns are manufactured to to fixed standards: a metric coarse thread is a metrids coarse thread, whether the bolt is made from stainless steel mild steel, brass, or Plasticene. That's not to say that you can't get a bolt in stainless with a different thread to normal metric coarse, but the idea that stainless threads are intrinsically different is just plain wrong. And I re-iterate that even A4 stainless is nowhere near as strong as the stuff steel allen bolts are made from. |
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A4 does not determine the strength of the bolt, it's the class that does that eg. an A4 class 80 bolt has a very high tensile strength - see my post a bit higher up . |
I have ordered some A4 class 80 bolts.I am pretty damn sure that they will be strong enough for this use and am willing to take the risk.Especially as there are a few people out there that have done it with no significant problems(as long as well coppaslipped).I may go the Ti route if i can find some money!! |
They will be absolutely fine |
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Ask them how they machine the piston pockets in monoblock calipers! I've been an engineer, admittidly aircraft, for 30 odd years and I'll be jiggered if I can work out how they do it. |
Right,you can't get A4/80-non in the country!!You can get A2/70-80.A4 is marine(nothing to do with the strength!!).So,a2 70-80 it is!!Here is some reading: If Stainless isn’t as strong as high tensile steel is it going to be strong enough? This is our MOST faq. Firstly it should be made clear that if for whatever reason you require high tensile (HT) bolts you should use original equipment. Secondly if we believed a bolt was not strong enough for a particular application we would not sell it to you. HT steel is used by factories because it is cheap, convenient and saves assembly time. We ran a motorcycle fitted with standard A2 bolts on discs and fork castings etc which were tested on a daily basis for many months and found no problems whatsoever. Not really a surprise when you consider both the hub and the yokes are low tensile cast alloy - the threads on the fastener are actually stronger than the threads in the material. If you need further reassurance - in the seven years we have been selling stainless we have not had a report of a single failure because the bolt wasn’t strong enough. A2 Class 70-80 (BS970 bar & hexagon equivalents T303/T304) The 'A2' denotes the alloy type. A2 is often referred to as 18/8 (18% Chrome/8% Nickel) or Type 304. This is the most common form of stainless steel fastener fabrication, it offers excellent general corrosion resistance and is the minimum specifcation we supply. Class 70-80 refers to the strength range. There are two strength ranges available, Class 60 and 70-80. Unlike some of our competition we sell only fasteners made from the higher strength range. A4 Class 70-80 (BS970 bar & hexagon equivalents T316) A4 is also referred to as 18/10/3 (2% extra Nickel added 3% molybdenum) or Type316. This is regarded by specifiers as 'marine grade' or 'enhanced corrosion resistant' stainless and is designed for constant immersion in salt water or 'stronger' acids. I have had to bulk order these(3 sets) so if anyone wants 8.let me know(Yes Rob,your first!!) :) |
You can purchase A4 fasteners from RS components, however there is minimum order quantity. They only go up to 6mm diameter - length 40mm. A bag of 50 costs £10 +VAT |
Mistake. RS components sell Hex socket in A4 available from M3 to M12 however they become expensive as you move up in size. For example M12 * 70mm (MOQ 10) costing £41 + VAT for 10 |
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