Bike: 2007 Triumph 675 w/ stock brakes.
So I wanted to do some twiddling and the caliper bolts were looking a touch rough, so I justified the purchase of some pro-bolt TI, race spec bolts.
Easy enough... the caliper bolts are M10X1.25X65.
But when my nice (they really are nice) new bolts arrived I noted some differences.
The stock bolts flair as soon as the threading stops to about 11mm od - they will not pass beyond the threading on any sizing gauge I have. The Pro-bolts actually cut in a tiny amount after the thread portion and then flair to a spot on 10mm about 5mm from the head of the bolt.
The bolt holes in the calipers are sized for the larger stock bolts and so the TI bolts leave more play room when the bolts are just finger tight, and only that last 5 +/- mm of the bolt is what's making direct contact with the bolt.
Obviously, when the bolts are torqued to spec (25Nm) I cannot wiggle the calipers. But I do wonder if this difference in bolt shape (shouldered out just at the top) and smaller OD is going to make troubles when real braking forces are applied to the system.
I know I can over think items like this... but it is my brakes on a track bike so I'd like to be sure either way.
To actually answer your question I'd have to know how much contact there is with the shouldered part of the bolt inside the caliper bore.
I suspect as long as the bolts are tight it doesn't matter.
Can you show pics of the 2 bolts?
Is there anything other than the bolts to align the calipers to the forks; ring-dowels or the like?
Quote from: Speeddog on November 20, 2013, 07:48:30 AM
Can you show pics of the 2 bolts?
Once I get home, yes.
Quote from: Speeddog on November 20, 2013, 07:48:30 AM
Is there anything other than the bolts to align the calipers to the forks; ring-dowels or the like?
There is a bit of a recess in the caliper body that the bolt head fits snugly into, in both cases so they *seem* to align as accurately with one bolt set as the other. But beyond that, no there's not any guides, pins, grooves etc unless there's something hiding in the bolt hole though the caliper.
JIS threaded?
Quickly recalling what I remember from school, the smaller bolts would see all tension/compression loading where the stock bolts being tight would also have shear...
But since on an axial caliper, the braking force loads the bottom bolt in tension trying to pull the caliper off the fork slider, the top bolt theoretically sees no force at all...all the braking force is exerted on the two flush faces trying to push the caliper into the fork slider...
On an axial rotor, its 100% shear on the bolts.
I would say that other than allignment (like keeping your pads wearing parallel) there would be no issue whatsoever. I would get them loose fit, squeeze the front brake to self allign them, and snug them up with pressure holding the pads alligned. then release and do your final torque.
**Disclaimer: No engineering analysis has been performed so if your bolts break and you die...tell your wife to go after the bolt company. ;D**
Well, they are Ti bolts, vs steel so the mechanical properties of the metal are markedly different...
And they are radial mounts - should have mentioned that from the get go.
Quote from: Slide Panda on November 20, 2013, 08:46:27 AM
Well, they are Ti bolts, vs steel so the mechanical properties of the metal are markedly different...
And they are radial mounts - should have mentioned that from the get go.
My bad. I was hacking away at the keyboard and forgot to consult my brain. When i said Axial in the second paragraph...I meant Radial...
Yes. You have very different material properties. But the advantage (in this case) to radial brakes is that much of the braking force is transmitted to that top mating surface in compression, this essentially makes the top bolt an alignment pin and nothing more.
As requested, photo
left- stock bolt.
18mm OD on the head
10.7mm OD on the body down to the threading
Right - TI bolt
17 mm OD head
5.5 mm of 9.9 mm OD then tapering down to
9.0 mm OD until the threads.
(https://dl.dropboxusercontent.com/u/35831615/2013-11-20%2018.05.17.jpg)
As said before, alignment is the problem. There is definitely some wiggle room left with that shoulder. The decision is yours.
I *could* use the stock ones as alignment tools to get the caliper on with the new bolts and correctly positioned... But obviously don't want things shift and go bad when trying to bleed off 150mph...
Just posted to the triumph 675 board as well. We'll see if they have knowledge of 'more correct' ti bolts. Or if I should just abandon this farkle route.
Ok the 675 folks pointed me to a different part number for stainless bolts, that then let me track to Ti bolts with all the correct dimensions. They don't have pre-done safety wire holes... but guess on can't win them all
How easily does Ti drill?
I know it tears the hell out of band saw blades.
No clue... Kev? Calling MonsterLover...