Caliper rebuild with Stainless bolts....
Discussion
Your M8 bolts will have a minor diameter of about 7mm, so that gives them an area of about 38mm^2. Your stainless has a tensile yield of 450 N/mm^2, and the bolts should only experience tensile loading, so we'll use that figure.
This gives us a yield force of about 17,000N for each bolt. Assuming the caliper has 2 bolts, this becomes 34,000N for the caliper.
Your typical front brake hydraulic ratio is about 30:1. It will be quite considerably lower for a rear brake, let's say 10:1?
So in order to yield your stainless bolts, you'll need to be putting 3400 Newtons of force on your rear brake lever, which is near enough 340kg. Please let me know if you break them, I don't want to be bumping into you in a dark alley!
Also, if the current bolts don't have any markings on them, they're unlikely to be high tensile bolts. I.e. Your stainless bolts are probably stronger anyway!
This gives us a yield force of about 17,000N for each bolt. Assuming the caliper has 2 bolts, this becomes 34,000N for the caliper.
Your typical front brake hydraulic ratio is about 30:1. It will be quite considerably lower for a rear brake, let's say 10:1?
So in order to yield your stainless bolts, you'll need to be putting 3400 Newtons of force on your rear brake lever, which is near enough 340kg. Please let me know if you break them, I don't want to be bumping into you in a dark alley!
Also, if the current bolts don't have any markings on them, they're unlikely to be high tensile bolts. I.e. Your stainless bolts are probably stronger anyway!
getitupya said:
Does no one here know the difference between "shear" and "tensile" strength?....ONC mechanical engineering level!
Assuming that the caliper bolts we're talking about are the ones holding the caliper together, rather than the ones attaching it to the bike, then you'd be pretty hard pressed to get any shear stresses!getitupya said:
Does no one here know the difference between "shear" and "tensile" strength?....ONC mechanical engineering level!
I do, Why do you ask?The bolts holding the two halves of the caliper together will be under tension.
![](http://thumbsnap.com/sc/Aa541pM4.jpg[/img]</a> <a href="http://thumbsnap.com/fPGq1F4W" Target="_blank">[img]http://thumbsnap.com/sc/fPGq1F4W.jpg)
I assume it was these bolts Catso was referring to as he said "Dismantled" & "using stainless bolts to hold a caliper together?", rather than the bolts securing the caliper to the bike.
Edited by Grommit on Wednesday 20th October 00:26
I have changed the bolts that anchor both the front callipers to my Yamaha Fazer front fork legs, I would guess that the week point in the set up would be the alloy mounting in the fork legs and not the S/Steel bolts them selves. I have also changed the domed headed bolts that hold my rear sprocket on for Hex head S/Steel as well, if you do this make sure that there is enough clearance for the hex headed bolts to pass through the calliper unhindered.
Oh! by the way I'm not an expert in any way and you must make your own decisions as I did, I mentioned it to the motorcycle MOT station and they did not see a problem with either mod.
Oh! by the way I'm not an expert in any way and you must make your own decisions as I did, I mentioned it to the motorcycle MOT station and they did not see a problem with either mod.
Ive used stainless bolts to mount calipers 'and' to secure both halves of the calipers together and im still here!I did actually have the same concerns once as the op,think it was while i was restoring an old Z,someone told me you get high tensile stainless so on that one occasion i'm sure thats what i went with?Maybe a false memory though,like the time Beyonce sat on ma face!
Hooli said:
catso said:
bimsb6 said:
i would change them in an instant and never give it another thought ,harrison billet calipers have always used stainless bolts in their calipers .
That's what I'm going to do. So the next question, since stainless will bind in alloy - do I use threadlock or anti-seize grease on the bolts? 
http://www.bosunbobs.com/en/Llewellyn-Ryland-Dural...
LiquidGnome said:
Just curious...why don't some of you use the rear brake that much? I change the back pads more than the front!
It depends on the wheelbase and COG of your bike but most sportsbikes will lift the rear under hard braking, making the rear of only limited use. It sounds like you're not using enough front brake.
rsv gone! said:
LiquidGnome said:
Just curious...why don't some of you use the rear brake that much? I change the back pads more than the front!
It depends on the wheelbase and COG of your bike but most sportsbikes will lift the rear under hard braking, making the rear of only limited use. It sounds like you're not using enough front brake.
Don't: http://www.bssa.org.uk/topics.php?article=122
Raw tensile strength is one thing, but you're missing the fact that austenitic steel work hardens, and this could be potentially fatal in a brake caliper.
Raw tensile strength is one thing, but you're missing the fact that austenitic steel work hardens, and this could be potentially fatal in a brake caliper.
grahamr88 said:
Your M8 bolts will have a minor diameter of about 7mm, so that gives them an area of about 38mm^2. Your stainless has a tensile yield of 450 N/mm^2, and the bolts should only experience tensile loading, so we'll use that figure.
This gives us a yield force of about 17,000N for each bolt. Assuming the caliper has 2 bolts, this becomes 34,000N for the caliper.
Your typical front brake hydraulic ratio is about 30:1. It will be quite considerably lower for a rear brake, let's say 10:1?
So in order to yield your stainless bolts, you'll need to be putting 3400 Newtons of force on your rear brake lever, which is near enough 340kg. Please let me know if you break them, I don't want to be bumping into you in a dark alley!
Also, if the current bolts don't have any markings on them, they're unlikely to be high tensile bolts. I.e. Your stainless bolts are probably stronger anyway!
I'm currently designing a few pipe supports, various PFC's and RSA's, held onto beams with nothing much more than a few M16's, whilst doing these supports I have to calculate the weight of the steel work, pipes and contents similar to what you have done, not to mention any counter lever effect the support might have. Every time I'm fThis gives us a yield force of about 17,000N for each bolt. Assuming the caliper has 2 bolts, this becomes 34,000N for the caliper.
Your typical front brake hydraulic ratio is about 30:1. It will be quite considerably lower for a rear brake, let's say 10:1?
So in order to yield your stainless bolts, you'll need to be putting 3400 Newtons of force on your rear brake lever, which is near enough 340kg. Please let me know if you break them, I don't want to be bumping into you in a dark alley!
Also, if the current bolts don't have any markings on them, they're unlikely to be high tensile bolts. I.e. Your stainless bolts are probably stronger anyway!
king staggered just how much a m16 or m10 can take. 
I vaguely recall 8.8 being stamped on many plated steel bolts.
Copper slip or Loktite: not sure, but I think the grease option will have an effect on the torque setting for the bolts; this is data you should be able to get from Ducati. Also, I believe there are different types of Loktite, depending on application/temperature etc.
Doesn't the Ducati manual have this info??
Copper slip or Loktite: not sure, but I think the grease option will have an effect on the torque setting for the bolts; this is data you should be able to get from Ducati. Also, I believe there are different types of Loktite, depending on application/temperature etc.
Doesn't the Ducati manual have this info??
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