What's with this rotor?

[kevin_stevens]

This guy pulled up in front of the cheese-steak shop where we were having lunch and wandered off with his buddy to another store.  After awhile I took a closer look and realized that the hole pattern in this rotor is a pretty complex pattern.  His friend's bagger (I think also a Road King) was the same.

Is this pattern a sensor ring of some kind for ABS or speedometer, or what's it about?  I want to bash it, but need to understand it better first.  

KeS

[atadaskew]

It's just a clever, and stock, way to lighten the rotor and reduce the unsprung weight.
Sure it would help more if the wheel and steel fender didn't weigh 60lbs butt still..

[mugwump58]

I would have thought the drilling would be symetrical. Perhaps it's a mod that I wouldn't understand

[spd2918]

Duh, them are "speed holes."

[chornbe]

Balancing it?

It's not ABS sensing.

That's an earlier one than the '09 that's in my shop at the moment. The '09 in the garage has a very different pattern, but then the '08s and '09s have whole new brakes from previous models.

[Prubert]

The holes help the disc flex like a floating rotor.

[Geoff]

The model year shown doesn't have ABS. I'd say the holes are for balancing purposes. Is the red color on the rotor a reflection or marking dye?

[fhaze]

It doesn't really matter..the damn thing will never get used anyway.

[chornbe]

The model year shown doesn't have ABS. I'd say the holes are for balancing purposes. Is the red color on the rotor a reflection or marking dye?

Looks like reflection.

It doesn't really matter..the damn thing will never get used anyway.

Fair point. Those things are dangerous.

[kevin_stevens]

Balancing it?

It's not ABS sensing.

That's an earlier one than the '09 that's in my shop at the moment. The '09 in the garage has a very different pattern, but then the '08s and '09s have whole new brakes from previous models.

I would doubt balancing just because both bike's rotors were exactly the same.

KeS

[kevin_stevens]

The model year shown doesn't have ABS. I'd say the holes are for balancing purposes. Is the red color on the rotor a reflection or marking dye?

Reflection.

KeS

[Playinthestreet]

Same drill pattern as my 07 E-Glide, and if I remember correctly, my 01 Dyna Glide T-Sport.  Who cares?  It stops the bike.  

[kevin_stevens]

Same drill pattern as my 07 E-Glide, and if I remember correctly, my 01 Dyna Glide T-Sport.  Who cares?  It stops the bike.  

Well, obviously I care, enough to start the thread, anyway.  I like to know the reasons for things.  

KeS

[mugwump58]

Inquiring minds want to know.

[Prubert]

Some of it is for looks and some of it is to help the disk from deforming as it heats/cools during use.

It tries to do the same thing that a full floating disk does....

[mugwump58]

I would have thought the drilling would have to be symetrical to maintain balance.

[nferr]

I would have thought the drilling would have to be symetrical to maintain balance.

Looks over function in the Harley world.

[chornbe]

Looks over function in the Harley world.

  Huh?

Symmetrical would look good. That's certainly not for looks.

[st ryder]

Some of it is for looks and some of it is to help the disk from deforming as it heats/cools during use.

It tries to do the same thing that a full floating disk does....

Scheez, you gave the correct answer twice now and they still don't get it!   Yes, the pattern  allows for expansion of the rotor so it's warp resistant like a 2 piece semi/full floating rotor.    

 

[Mookie]

Scheez, you gave the correct answer twice now and they still don't get it!   Yes, the pattern  allows for expansion of the rotor so it's warp resistant like a 2 piece semi/full floating rotor.    

 

What does having an uneven pattern (is it even a pattern?) have to do with expansion?  Holes or no holes the metal will expand and contract, I fail to see the relationship.  Full floating rotors float, non floating rotors don't.

The only reasons to have holes, that I know of,  are for venting (cooling) or for cleaning the swept area of the brake pad as you're braking.

 

[kevin_stevens]

Scheez, you gave the correct answer twice now and they still don't get it!   Yes, the pattern  allows for expansion of the rotor so it's warp resistant like a 2 piece semi/full floating rotor.    

 

An answer that doesn't make any sense isn't much of an anwer.  How does an asymmetric pattern of rotor holes "allow for expansion of the rotor so it's warp resistant"?  Concise and rational explanation, or link please.

KeS

[st ryder]

An answer that doesn't make any sense isn't much of an anwer.  How does an asymmetric pattern of rotor holes "allow for expansion of the rotor so it's warp resistant"?  Concise and rational explanation, or link please.

KeS

Just because it doesn't make sense to you doesn't mean the answer's not correct. It's in the "swoosh" shape, which is what you were asking about, yes? If you ever owned a HD, you'd know about their brake rotors. Don't believe me? That's your prerogative. You know how to surf the net, do your own research for more details.

[mxvet57]

Scheez, you gave the correct answer twice now and they still don't get it!   Yes, the pattern  allows for expansion of the rotor so it's warp resistant like a 2 piece semi/full floating rotor.    

 

Works the same way as a wave rotor on dirt bikes.

[kevin_stevens]

Just because it doesn't make sense to you doesn't mean the answer's not correct. It's in the "swoosh" shape, which is what you were asking about, yes? If you ever owned a HD, you'd know about their brake rotors. Don't believe me? That's your prerogative. You know how to surf the net, do your own research for more details.

No, I'm asking about the asymmetric holes drilled in the swept area, not the symmetric mounting tabs.  Throwing out a flat declarative statement with no background or explanation, on such an apparently unrelated point, isn't helpful and makes it seem that you're just repeating some rumor you heard.  I can't find any reference to the hole pattern, or I wouldn't have posted it here in the first place.

KeS

[st ryder]

No, I'm asking about the asymmetric holes drilled in the swept area, not the symmetric mounting tabs.  Throwing out a flat declarative statement with no background or explanation, on such an apparently unrelated point, isn't helpful and makes it seem that you're just repeating some rumor you heard.  I can't find any reference to the hole pattern, or I wouldn't have posted it here in the first place.

KeS

I'm not sure about the asymetrical cross drilled holes in the sweep area *specifically*, but if it's part of the design, which it is,  then it's part of a design that was made to resist warping. Here's a link you couldn't find that helps explain the rationale behind the rotor's deisgn, which I believe covers an explantation for the pattern of the cross drilled holes, ie they are drilled that way as part of the asymetrical design. This is the last time I do research for you. Next time, I'll let you do research that "refudiates" my statements, fair enough?  



"Challenged to maintain cost targets without compromising styling appeal and performance, Hayes committed to making a one-piece design work. Engineers grappled with how to cope with the high temperatures (up to 1200F) that the surface of the rotor experiences. "Normally, we'd just make the rotor thicker, since the delta T is inversely proportional to the thickness, but again the small envelope we had to work within did not allow for that,".

Instead, engineers came up with an unusual geometry, which allows the rotor to expand radially without compromising braking integrity. As a traditional one-piece rotor attempts to expand from the thermal energies, it becomes susceptible to warping. The problem is that the outer rub area expands at a quicker rate than the hub or center area, resulting in thermal stress that can crack and warp the rotor.

A two-piece rotor gets around this problem by insulating the heat to the outer ring only. The ring is permitted to float on the pins, which enables it to expand and contract freely from the hub of the rotor. However, there is a cost and higher-weight penalty. Two separate rings and several mount pins can double the price of a typical rotor. Furthermore, minimizing the weight in the front end of a motorcycle improves handling. As a consequence, engineers typically try to minimize the amount of unsprung weight.

The key to success for Hayes' one-piece rotor is its non-symmetrical pattern. Its overlapping arms are designed to permit radial expansion up to nearly 0.080 inch in diameter. These arms act like a spring, allowing the rotor to expand and then contract to its original size without warping. By eliminating the possibility of warping the rotors, Hayes engineers were able to use a fixed mount caliper, which improves the brake's responsiveness and helps to eliminate both pad drag and noise."

http://www.hayesbrake.com/DesignNews/designnews_article_JAVA.html

[kevin_stevens]

I'm not sure about the asymetrical cross drilled holes in the sweep area *specifically*, but if it's part of the design, which it is,  then it's part of a design that was made to resist warping. Here's a link you couldn't find that helps explain the rationale behind the rotor's deisgn, which I believe covers an explantation for the pattern of the cross drilled holes, ie they are drilled that way as part of the design. This is the last time I do research for you. Next time, I'll let you do research that "refudiates" my statements, fair enough?  

Next time you can actually just avoid the thread if you're going to be so consistently unpleasant.    But thanks for the link.

KeS

[st ryder]

Next time you can actually just avoid the thread if you're going to be so consistently unpleasant.    But thanks for the link.

KeS

The answer to your question was provied *twice* before I got involved if only to provide some support to the poster of those correct answers who you (and others) ignored. Next time you start a thread, better warn potential posters you don't accept answers that don't make sense to you, regardless if they are correct; that you require they provide proof.  Perhaps you should show some respect for other people's experiences/knowledge base and accept that there are others out there who know a thing or two about stuff that you don't, "Thomas."

[spd2918]

An answer that doesn't make any sense isn't much of an anwer.  How does an asymmetric pattern of rotor holes "allow for expansion of the rotor so it's warp resistant"?  Concise and rational explanation, or link please.

KeS

No, I'm asking about the asymmetric holes drilled in the swept area, not the symmetric mounting tabs.  Throwing out a flat declarative statement with no background or explanation, on such an apparently unrelated point, isn't helpful and makes it seem that you're just repeating some rumor you heard.  I can't find any reference to the hole pattern, or I wouldn't have posted it here in the first place.

KeS

Next time you can actually just avoid the thread if you're going to be so consistently unpleasant.    But thanks for the link.

KeS

I think he backed up what he wrote.  He answered the question, so let's not be pissy, m'kay?

[chornbe]

Well, speaking from outside - cause I love alls youse guyses - Kevin asked, was answered, but without links. Honestly, it's an easy point about which to be skeptical. ST posted link / quoted text, and now Kevin's got the supporting info he was asking for... which didn't happen until ST's last post.

It's all good.

[st ryder]

Well, speaking from outside - cause I love alls youse guyses - Kevin asked, was answered, but without links. Honestly, it's an easy point about which to be skeptical. ST posted link / quoted text, and now Kevin's got the supporting info he was asking for... which didn't happen until ST's last post.

It's all good.

No, it's not all good: The thing is, the answer to the question was provided twice by Prubert, and all the "I want/need to know/that doesn't make sense" readers ignored him altogether. No even a polite "thanks for that", or a "really, do you know how they work?" or even, "hmm, thanks for that. I guess I'll have to look into it somemore because I can't get my mind around it." No, he gets ignored. I get "called-out" on my answer that supports his answer, because it "doesn't make sense." I didn't realise there's a posting standard that states we all have to back up our answers to be taken legitimately. And if one would like links/proof, one can ask if they are available more respectfully, instead of "where's your proof?" But ultimately, the answer could have been found without this thread even existing. It "doesn't make sense" when a person comes, asks a question and then rejects the answers as not good enough.   A disingenuous "thanks for the link" doesn't mollify the hubris.

 

 

[chornbe]

I enjoyed reading your link. I didn't understand the asymmetrical thing, either.

So genuinely... thanks for the link.

Too much bickering around here lately. Let's all take a step back and a deep breath.  

[kevin_stevens]

Well, this has been a thoroughly unpleasant and uninformative experience.  

It reminds me very much of the Badweatherbikers Buell forum, which I also avoid as much as possible.  I still don't understand why or how the pattern of rotor holes affects the expandability of the rotor, and I don't think the linked article explains it, either - it talks about the mounting tabs.

I'm going to lock the thread, put ST-Ryder on ignore, and try to forget the whole thing ever happened.  Sorry I ever asked.

KeS