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Has anyone used aluminium bolts on the caliper Is this too high a stress point I know that Ti is manditory for the seatpost, stem and rotors but what about the two bolts that hold the caliper they are 6mm if that makes a difference. thanks
 

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Some Formula brakes used them. They were good quality bolts that were not threaded all the way though. Mine have been fine for about 4 years. Definitely a place to use a torque wrench too.
 

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I love Pisgah
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I'm running all alum with some Formula B4s(same oem bolts B R H mentioned). Raced the crap out of them since early 03. Even raced on one caliper mnting bolt up front once since the other backed out. Good enough for me. Also use alum with some Hayes Mags. The longarse caliper "Breakdown" bolts(20mm x 6mm) were swapped for alum, as well as the rear centering bolts(caliper to adapter plate). The rest is all ti but would run it all alum just as well.

Having said all that..the alum hardware is on 2 dedicated race bikes. I prolly wouldn't bother if it wasn't oem on anything else but a WW project of some sort. But I would run all ti otherwise:). Ti just holds up better from day to day use in the long run.
 

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After rethinking the same situation a couple of times I'd say it'd depend on which kind of brakes and fork you've got. If postmount I would go Ti, IS then I'd go alu....
 

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Terkel said:
After rethinking the same situation a couple of times I'd say it'd depend on which kind of brakes and fork you've got. If postmount I would go Ti, IS then I'd go alu....
That's opposite of what I would say. Post-mount caliper mounting bolts really do nothing except keep the caliper from moving around. All the force of braking drives the caliper into the posts, so there is no real load on the bolts. Heck, you might be able to get away with nylon bolts there (but I myself wouldn't try that).
However, IS caliper mounting bolts are perpendicular to the force axis, so they experience strong shear forces under hard braking. This is where I would want the shear resistance of ti, rather than aluminum.
To test this out, try this: grab your brake lever, and remove the caliper mounting bolts (with the other hand). Now try to roll the bike forward. The post mount setup won't go anywhere, as it is being driven into the posts- the IS setup, though, will rotate a bit until the caliper smacks into the leg of the fork.

miles
 

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aseletzky said:
Has anyone used aluminium bolts on the caliper Is this too high a stress point I know that Ti is manditory for the seatpost, stem and rotors but what about the two bolts that hold the caliper they are 6mm if that makes a difference. thanks
Speaking of rotor bolts, here's a question to throw out. First, some background.
The current standard is six bolts, right? However, some brakes have had fewer- as few as three for the original AMP (bought by RockShox) brakes.
The force acting on the rotor bolts is a shear force- there is no side load (under normal conditions) either pulling the rotor off the hub or pushing it on.
Aluminum is kinda crummy as far as shear goes, and ti is much better. Steel, though, is king in this regard.

All this leads up to the question:
Is it a stronger and lighter setup to maybe use two steel (opposite each other, of course) and four aluminum bolts vs six ti bolts? It certainly would be a lot cheaper...

Maybe I'll go answer part of my question and weigh the two alternatives.

miles
 

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I've broken Formula al bolts. Not riding, just trying to get them as tight as I need them to be to feel safe riding them. I also break al V cable bolts. as much as I like non-performance reducing weight saving, al bolts really are a pain to me. And no, a $$$ torque wrench is not an option. It's a bike for crying out loud. I went riding bikes for a reason, and using torque wrenches to install a stupid bolt was not one of it.
 

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Ever tried riding your bike ;) up a really steep section, you can barely run up. So you use your brakes and due to gravity your bike and yourself gets pulled down trying to pull your front postmount assembly apart :D Nice ehh :eekster: On the rear it would depend on where your disctabs are mounted.

Miles wrote:
IS caliper mounting bolts are perpendicular to the force axis,Yes so they experience strong shear forces under hard braking. Only if your bolts are loose. The high friction between caliber and forkmount prohibit the caliber from whacking those little bolts to pieces. It's exactly the same idea with rotors bolts.
 

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i can only tell what has worked for me (64 kg):

PM: full alloy, since there are no shear forces. The bolts just keep the caliper in place

IS: ti up front, alloy on the rear caliper (because there's only about 30% brake power)


FWIW i use bolts with a rolled thread instead of a cut thread and change them every 2 years (5.000 km)
 
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