Hi All I am asking for advice on the calliper bolt length for a 2016 DVT mts. I have received titanium bolts from Race Bolt described as for 2010-2016. The bike is a 2016 (66) model. When they arrived they are M10 x 1.25 x 55 the length should be 60. My question is will the reduced length work or will it compromise the strength of the fixing? Any doubt and I will return them for the correct size! Thanks in advance. Mark
I don't know the bike, but in general if you put the same torque through less threads then you risk thread stripping. You have changed the bolt material and so it will be the fork thread that strips. Rather you than me.
Don't get all scientific! Just me speaking off the top of my head is enough information (nearly)!!!!!!!!!!!!!!!!!!!
The key info was in the text. 1x bolt dia for steel, 2x for aluminium as a guideline. So if its a 10mm steel bolt going into steel, then 10mm will normally suffice. If its 10mm steel into a weaker alloy eg aluminium then a new factor comes in of 2x bolt dia ie 20mm of overlap. These are just guidelines which would then also be affected by thread form/pitch etc.
so the conclusion is that really the diameter of the hole should be much greater if a steel bolt is replaced with a Titanium bolt?
No, the depth of hole is relative to the number of threads required for material stability. The diameter will have more to do with the tensile and shear capabilities of the bolt itself, not whether you could pull the bolt out of the hole stripping the threads. (though dia will have some impact on thread contact area)
Sorry, I wasn't thinking it through - and I must really go back and read the citation properly! But in essence, are you saying that to replace a steel bolt with a Ti one, then if you still do up to the same tightening torque (although that is another debate) the thread length should be longer and definitely not shorter?
The weakest link in this scenario, as long as the titanium type is of sufficient failure capacity for the job, is the aluminium. The guideline recommends an overlap of twice the diameter of the bolt for aluminium to give the max loading capacity available by the threads. 10mm dia hole in aluminium needs approx 20mm of thread overlap. More than that and there is no real benefit, less than that and a failure "could" see the thread stripped out by tension. It could be that the tightening torque from Ducati gives only 50% of the material limits for the hole, which would then allow us to have less minimum thread overlap.
They are grade 5 titanium bolts. I confess I’m not very mechanically minded so does your final paragraph mean 55mm should be sufficient length?
Bolt length is pretty irrelevant. Its how much of the threads go into the hole when assembled. If its a 10mm dia bolt, then 20mm of thread into hole should be fine. If less than that then there will be compromise, but whether it is to a critical level would need to be calculated by some boffin. With the normal bolt, how much goes in the fork? 20mm, 25, 30? If the original only gave 20, then the shorter will give 15, and therefore will not satisfy the 2x diameter guideline = 20mm ( for bolt dia of 10mm). If the original goes in 25mm, then a 5mm shorter bolt will give 20mm thread overlap so satisfies the guidelines. Pls note this is all ballpark theory, if you are concerned, don't fit them. Personally, I would worry more about the titanium quality than the thread overlap. If you can torque up to spec and nothing strips, there was enough thread overlap. If the titanium strength is shit, then the bolts could fail under braking, and that would have very little to do with whether there was 15 or 20mm thread overlap. Not commenting on grade 5etc, but more on actual quality as opposed to advertised.
Thanks so much for that. Much easier to understand for the mechanically dyslexic. The bolts are advertised as grade 5 but how do you tell?
What I don't get is why put yourself through this hassle and expense? The original bolt material is strong enough - unless you don't trust Ducati - but if you don't then why ride them? Titanium is more heat resistant but this is irrelevant as heat is not an issue. And it is lighter. You will be saving less weight than taking a p1ss. I don't get why fat bikers are so obsessed with weight saving on their bike when losing body weight is free and easy if you just eat less!
I would have thought the DVT model bolts would be different to the 2010 to 2015 brake bolts as the calipers are not the same. My guess is you don't have the correct bolts for your bike.
My calliper bolts from a 20 year old ST2 and a 13 year old ST2. Neither bike has been cleaned in years. No rust and all fine. I dare say that a wash and polish wouldn't hurt. I've been to loads of bike events in the past and we often go and have a gander at the bike park. We have never ever inspected calliper bolts. Who give a f....? And if people are so worried about weight why is there always such a long queue at the burgher van?
