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Brake rotor bolt circle?

maxyedor

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Oct 20, 2005
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Bent a rotor pretty bad last night, so I'm just going to cut a new one at work today, but forgot to grab the bent one on my way out the door. Can't find the dimensions anywhere, maybe I just suck at the internet, but WTF is the point of an International Standard if you can't find it via Google?

Nybody know the bolt circle off the top of their head? Thanks in advance.
 

stoney

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http://en.wikipedia.org/wiki/Bicycle_brake#Disc_sizes

Standards

Centerlock (Shimano proprietary)
International Standard (IS) (in widespread use) 44mm BCD
AMP 6-bolt (AMP proprietary, obsolete)
Cannondale's 4-bolt pattern (obsolete)
Freewheel thread (used by Mountain Cycles and others; obsolete)
Hope Technology's 5-bolt pattern (Hope proprietary, obsolete)
Hope Technology's 3-bolt pattern (Hope proprietary)
Rohloff's 4-bolt pattern (proprietary, 65mm, same as some chainrings)
Rock Shox 3-bolt pattern (proprietary, obsolete)
 
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maxyedor

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Thanks, what I thought was blanchard ground stainless was actually 6AL4V Ti, so I didn't bother cutting it, just rode the other bikes. Have to grab my stainless from the other building and and tweak my design a little bit for added bling, I'll cut one Monday.
 

maxyedor

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Waterjet, the laser is too busy with production work, harder for me to use it for "R&D". Lagging on cutting them, found my spare rotor and been busy making cool stuff that goes boom.

Does anybody know the actual reason for grinding the rotors? I understand needing consistent thickness, and wanting them to be flat, but raw material is plenty even and they warp to hell the first time you get them hot anyway. All my ground material is for space-ship parts, so it's gotta be perfect, but a brake rotor?
 

jonKranked

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something something consistent surface texture something something friction based functional part something something
 

jonKranked

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and no. they don't "warp to hell" the first time you use them. if that were true, you'd see people swapping rotors mid-ride.
 

maxyedor

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Maybe warp to hell is a bit exaggerated, but mine always warp a little, I can true them and get rid of any rub, then after a ride, they're back to rubbing. Seems pointless to grind them when simple use tweaks them way further out of flat than the raw material. It looks cool, but so would tumbling and tumbling would be way cheaper.
 

jonKranked

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i did some googling earlier, found on a moto forum that the grind is to create micro-texturing to get better performance vs a non ground surface
 

maxyedor

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Sounds like it may help with bed-in, but only if you have new pads and rotors, otherwise 1 decent down-hill and that texture is gone forever. So it really just seems like it's a cool way to justify charging $40 for a $3 part. Think I'll save the fancy material for fancier parts.
 

atrokz

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Yes you should grind them. It will help with bedding everything in and provide a more even surface for pad contact. This all depends on the finish you're getting from the sheet though. If it's already ground, then don't bother.

Also, shouldn't this be heat treated stainless to some degree and not just in the annealed state? Since rotors rust to some degree, I'm thinking 4 series stainless. Would that make sense or are they all just annealed? I should throw one up on my Rc tester to see.
 

jonKranked

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That seems nertz since the effect would last, oh, an hour of braking time...
Sounds like it may help with bed-in, but only if you have new pads and rotors, otherwise 1 decent down-hill and that texture is gone forever. So it really just seems like it's a cool way to justify charging $40 for a $3 part. Think I'll save the fancy material for fancier parts.
you'd think that, but pads wear much much quicker than rotors, even with metallic pads. and as aktroz pointed out, its more for bed in.

the only time i ever saw a rotor actually wear down was when a set of brake pads on a buddy's bike completely wore down to the metal backing and started grinding on the rotor.
 

jonKranked

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also, a lot of trials riders still using rim brakes grind the braking surfaces of the rims, and those grinds last a long effing time.
 

maxyedor

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also, why are you asking a bunch of mtb arm chair engineers instead of google? :confused:
Google is just a more complicated way of asking a bunch of armchair MTB engineers. Google couldn't even find me the IS pattern, plus I get distracted and start google naked chicks and videos of things exploding.

Yes you should grind them. It will help with bedding everything in and provide a more even surface for pad contact. This all depends on the finish you're getting from the sheet though. If it's already ground, then don't bother.

Also, shouldn't this be heat treated stainless to some degree and not just in the annealed state? Since rotors rust to some degree, I'm thinking 4 series stainless. Would that make sense or are they all just annealed? I should throw one up on my Rc tester to see.
Wouldn't re-grind the pre-ground sheet, but depending on what material I go with I may not have ground sheet in-stock. If I actually order material then it costs me money, and what's the point of free parts if you have to pay for them?

I believe most, if not all rotors are at a minimum cut from half-hard sheet. I've seen rusty rotors, but never with a higher end rotor, so I don't think Magura/Hope/Avid use the same material as say, Aztec. Wouldn't surprise me if the cheap aftermarket, entry-level and Target-bike rotors are 4xx but high end performance stuff is 3xx.

I'm also starting to think they grind them in part because they laser cut them. That's a lot of cutting on a thin piece, so I'm sure they warp due to heat. Waterjet should have no warpage.

also, a lot of trials riders still using rim brakes grind the braking surfaces of the rims, and those grinds last a long effing time.
Pad compound plays a major role in that. Rim brakes are a soft pad as the rim isn't supposed to wear, the disc is a "Wear item" despite the fact that it wears very, very little.

w00dy, thanks for the link.
 
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jonKranked

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Pad compound plays a major role in that. Rim brakes are a soft pad as the rim isn't supposed to wear, the disc is a "Wear item" despite the fact that it wears very, very little.
rim brake pads for use with ground rims are hard as hell. lots of specialized compounds, the better ones run upwards of $50 a set. granted they're still softer than disc pads, but they're nothing like regular pads for v-brakes
 

atrokz

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Wouldn't re-grind the pre-ground sheet, but depending on what material I go with I may not have ground sheet in-stock. If I actually order material then it costs me money, and what's the point of free parts if you have to pay for them?

I believe most, if not all rotors are at a minimum cut from half-hard sheet. I've seen rusty rotors, but never with a higher end rotor, so I don't think Magura/Hope/Avid use the same material as say, Aztec. Wouldn't surprise me if the cheap aftermarket, entry-level and Target-bike rotors are 4xx but high end performance stuff is 3xx.

I'm also starting to think they grind them in part because they laser cut them. That's a lot of cutting on a thin piece, so I'm sure they warp due to heat. Waterjet should have no warpage.



Pad compound plays a major role in that. Rim brakes are a soft pad as the rim isn't supposed to wear, the disc is a "Wear item" despite the fact that it wears very, very little.

w00dy, thanks for the link.
Gotcha. Yea, free is always the best price! If you're waterjetting them, you'll just have the burrs to deal with but that's easy enough on it's own.

With regards to steel. I was under the impression it was all heat treated 4xx as 3xx usually isn't very heat treatable what with low to no carbon content whereas most 4xx have adequate amounts of carbon. Getting half hard sheet (in the 40Rc range) would eliminate any need though and is definitely the right direction. I'm just guestimating here, and at the end of the day any sst would work, just wear quicker and you'd see that right away.

Going to come up with any neat designs to integrate into the rotor? Might as well if you're going through the trouble of making them to begin with!
 

maxyedor

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rim brake pads for use with ground rims are hard as hell. lots of specialized compounds, the better ones run upwards of $50 a set. granted they're still softer than disc pads, but they're nothing like regular pads for v-brakes
Good to know, the last high end V-brakes I messed with were my HS33s back in 2000ish, and if I'm remembering right, they used a pad similar to a normal V-brake, they worked bitchin!


Gotcha. Yea, free is always the best price! If you're waterjetting them, you'll just have the burrs to deal with but that's easy enough on it's own.

With regards to steel. I was under the impression it was all heat treated 4xx as 3xx usually isn't very heat treatable what with low to no carbon content whereas most 4xx have adequate amounts of carbon. Getting half hard sheet (in the 40Rc range) would eliminate any need though and is definitely the right direction. I'm just guestimating here, and at the end of the day any sst would work, just wear quicker and you'd see that right away.

Going to come up with any neat designs to integrate into the rotor? Might as well if you're going through the trouble of making them to begin with!
I have a virtually unlimited supply of .080" 300 series half hard, so I think that's the route I'll go. Ti sounds cool, but it's such a poor conductor that I think I may start having brake fade issues. Not sure there's a pad compound that will work with ceramic, also pretty sure I don't want that fragile of a rotor, but that's a possibility too since I've got it laying around.

Trying to find a balance I like between swept area and airflow. Other than that I'll be doing some form of wavy rotor, they've always performed the best for me. Of course I'll also be making one covered in penises to sneak onto my friend's bikes when they pester me about tuning their hoopties up.