I forgot to mention spalding fasteners 01522 753444 very helpful and very reasonably priced , they cover ALL thread forms !
Hi Ducatiderek. That’s really strange- we both have 2022 Specials but mine has Torx bolts and yours has Allen bolts. Have you owned the bike from new?
Hi. The plot thickens. I’ve just received 2 replacement caliper fixing bolts from Piaggio and they are Allen bolts not Torx bolts. Maybe my original bolts are what was first used for the 850s and then they switched to Allen bolts - who knows how things work in Italy!
Out of interest, are there any markings on your new bolts ? 12.9, for instance ?
I’ve ordered a Torx Plus set so will be able to verify if the bolt heads are that - but looking at the ‘Plus’ star pattern I can see how a ‘normal’ Torx bit would just round out the hole.
I’m now expecting other fasteners to be ‘Plus’ so getting the ‘Plus’ bit set is desirable.
Arrgh not that old chestnut…yes, in theory SS is weaker in shear. In practice, has anybody ever seen a stainless brake/frame fastener fail in normal use?
When I rebuilt my SP1000 I used stainless bolts both on the calipers and the frame. Cue much tooth-sucking and nay-saying at the local club meet.
I am, however, still very much alive. Not one of those fasteners ever failed.
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Indeed, as Speedy points out this is an old chestnut
Compare the tensile strength of 304 stainless bolts - 515 Mpa to the OEM high tensile steel (probably 8.8 grade - whose yield strength is 640 Mpa) and you tell me if that 19% reduction will make any difference in the real world. An M10 metric fine bolt in stainless will have a thread shear resistance of 19.5 kN
Just think about 19.5 kN - that’s close to 2 tonnes force per bolt
Who’s riding your bike - 10 gorillas??
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Oh if anyone asks I’m a professional mechanical engineer of more than 40 year’s experience
Whilst I don’t carry out stress calculations on a daily basis these days, I certainly do at least weekly. For example last week for a mine hoist headgear bearing housing fixing bolts for a South American copper mine
So in conclusion, the stainless bolts will have a slightly lower ultimate tensile strength compared to the OEM plated high tensile steel bolts, but in real world operating conditions this will have no detrimental effect, but make sure you use a calibrated torque wrench to correctly tighten them!!
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did they have locktite on them?
Hi Sid. Nope. The threads were completely dry.
If you’re concerned about the bolts loosening in service, and they have been supplied without any threadlocker on their threads, simply buy a small tube of Loctite threadlocker, apply sparingly, torque to the recommended tightening torque with a torque wrench (invaluable when using steel bolts in tapped alloy so you don’t strip threads) and job done !
Which was rather my point. I’m not an expert, so I go by the published charts, and the published charts say do not tighten stainless as if it was high tensile, because it isn’t. Ergo a torque wrench is essential, do not assume. Or alternatively know how much you can do up stainless by experience.
I was told off years ago by a head mechanic and racer/lead trackday instructor for over tightening my caliper bolts at a service. He held up my bolt against a new ( Honda ) bolt and you could really see the stretch, frightening. Apparently Honda put these bolts in on purpose to stop people overtightening them without it being picked up in a service ( and I suspect subsequently being blamed in the case of a failure ). Maybe Guzzi did the same? I use SS but for the last set I got High Tensile SS bolts which I hadn’t heard of before from a supplier near Bicester.
Have tried Racebolts UK. ?
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Theres a lot can be said about Bolts - My opinion If you want to be 100% safe use 8.8 or 12.9 rated bolts - Allen head are perfectly acceptable - Unbrako or HoloKrome are the top names. You should be able to get BZP (zinc plated) but even then they won’t stay rustless for too long. They are critical fasteners but not actually heavily loaded so Stainless is an acceptable alternative. A2 or A4 grade Titanium has no real advantage apart from Pub Kudos. Orbital fasteners are another good company to use. Try and avoid Chinese import stuff.
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I agree with what Guzzimax says - And for what its worth I’m also a mechanical engineer with - Holy cow am I that old!! Just read the rest of this thread and a couple of points - Yes check the threads they are probably metric fine. Note that a lot of sellers quote ‘High tensile stainless’ - Thats Bullsh!t just means they don’t know what they are selling. As stated A2 and A4 are a bit below 8.8 bolts in tensile strength. Off the cuff Its not likely you could break them by over-torquing them before they stripped the thread in an Aluminium fork leg!
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I can now confirm, on the V7 850 Special (2021+), as OEM these are Torx Plus socket head bolts, bit size TP45. That’s what fits in the 'oles …
Its JIS versus Phillips all over again!
I’ve just followed all this discussion and feel i want to contribute from a different point of view…
Not to challenge anybody and certainly not those engineers but is my take…
For the caliper mounting bolts to shear, the machine must be going at such forward velocity and much hydraulic force applied on the lever causing the front brakes to lock the front wheel whilst the weight of the rider and the bike keeps the rear end down avoiding a forward somersault and all that energy nowhere to go but to strain and snap not one but two 10mm diameter mounting bolts sitting behind a fork stanchion.
When is that going to happen?
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