Front rotor mounting buttons.

elkymutt

elkymutt

Well-known member
I got a question that I've been asking for a couple years now that I can't find a decent answer to...

On all the bikes I have come across with two rotors on the front wheel, none of the rotor "buttons" has ever lined up with the other when looking straight through the front wheel (obviously looking from the side), in effect, none of the actual holes in the rotor line up (on the swept area of the rotor)

What's up with this? Heat dissipation purposes? Improving braking in the wet/rain?

Cheers
 
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elkymutt said:
I got a question that I've been asking for a couple years now that I can't find a decent answer to...

On all the bikes I have come across with two rotors on the front wheel, none of the "buttons" has ever lined up with the other when looking straight through the front wheel (obviously looking from the side)

What's up with this? Heat dissipation purposes? Improving braking in the wet/rain?

Cheers
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On most bike you can make them line up, simply by rotating to the right spot before bolting them on...Im picky so I do that on my bikes
 
Because it doesn't matter to performance if they line up or not.

They'll line up every time if you have the same multiple of mounting bolts as buttons (5 bolts, 10 buttons for example), but that's probably rare.
 
fastar1 said:
Because it doesn't matter to performance if they line up or not.

They'll line up every time if you have the same multiple of mounting bolts as buttons (5 bolts, 10 buttons for example), but that's probably rare.
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Yeah, I've heard this before and it makes sense.

Is this the only reason?
 
Well I suppose we could further analyse the same point, and say that they don't design them to line up every time because that would mean adding more bolts or buttons than are strictly necessary. By memory, I belive my front rotors mount on 5 bolts and 7 buttons. Any more would add cost and weight.
 
fastar1 said:
Well I suppose we could further analyse the same point, and say that they don't design them to line up every time because that would mean adding more bolts or buttons than are strictly necessary. By memory, I belive my front rotors mount on 5 bolts and 7 buttons. Any more would add cost and weight.
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I think the issue is most companies besides Honda do not manufacture their rotors to be directional, meaning there is a different rotor for left or right side mounting...Honda does and I know for sure you can make them line up....
 
I honestly don't think there is a rationale as to the alignment of the button holes in the rotors. As they say they'll line up all the time if there is the same numbers of buttons as bolt holes. If there's not the same number then you CAN make them line up by rotating the rotors before mounting.

The real question is what determines the number of buttons and mounting bolts? The manufacturer determine the number of mounting bolts while the rotor manufacturer determines the number of buttons.

Depending on the design and technology the rotor manufacturer will change the number of buttons over time. For example EBC went to a "Square Drive" technology where the sides of their buttons were flat, thus making it much more difficult for front to back forces (such as braking) to wear them.
 
Yeah, one year a manufacturer will say their current rotor has fewer mounting points (buttons) to decrease weight, while the next revision of the bike there might be 33% more buttons claiming better heat dissipation...
 
WOw...anal bunch. Who cares? You can't see them when riding,:LOL
 
Yeah, one year a manufacturer will claim fewer buttons decreases unsprung weight and the next major revision of the braking system, they will suggest the extra buttons added is for better heat dissipation.

If a manufacturer decides to go with a particular button pattern, why can't they space the buttons out equally so only one rotor needs to be stamped out? No confusion, no rebolting hassle....
 
A lot of wheels will stagger the rotors and you can't line them up. But my ghad, man... surely you have better things to do with your time, like... ride?
 
Shaman said:
A lot of wheels will stagger the rotors and you can't line them up. But my ghad, man... surely you have better things to do with your time, like... ride?
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This isn't productive...

I don't get to ride much between November and march. Do you?

So when you aren't on the bike, you stop asking questions?

Sorry to hear how you think...
 
Yeah, but this would be dead last on a long list of issues I'd think about first.

BTW most rotor bolts are single-use. You may need to replace them outright if you take the rotors off. If you re-use the bolts, use LOADS of blue loctite on them. When you think you have too much on, add some.
 
what are you guys smoking? when you come down, just go and wax your bike, dont worry about things like this!
 
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