how do rotors work

[aceblueheeler1992]

hey
i have seen all the different sizes of rotars
but what is the difference in size , like i see the sasquatch's with 8" and then i see stp's with 6" so whats the diference between rotar size. what does it do

 

[Fisher]

its Rotor,

The larger rotors become less hot.
Also does the slower spinning rotor have something to do with it?
Edit: meant a faster spinning rotor for 8"

 

[JSPhoto]

Well, i'll say what i know, and then probably be corrected but here we go
Larger rotors do the following and probably a little more i dont know:
- More stopping power
- Cool Easier
- Tend to clean up a bit easier while movie (more a design thing)

Ok, so they give you more stopping power by increasing the amount of torque produced to teh hub, much like lengthening the handle on a spanner allows you to use less force to move something (not gunna go all tech with formulas and shit unless you want me to)

The cooling is simply because there is more surface area for the heat to be expelled, and each rotation takes longer meaning there is more time for the metal to cool, and the 8" disk will spin faster than the 6" disk as the radius is larger, so the faster speed will also give a better cooling effect

The cleaning thing, well thats just something I have found through using them they tend to not clog up as much when its all muddy and crappy.

Alot fo STPs and street bikes also have 6" rotors because they tend to warp less and less easily bend and they dont get in the way as much whilst doing that the streeties do , so hoping chairs etc.

Sorry if I went all technical there, I have been studying helicopter aerodynamics and i'm still in maths/physics mode.

Hope it was in some way useful

 

[Sean]

And "teh" award for awesome rotor technicallity post goes to... Karnige182.

I believe you can get 5" rotors now too, good for the street rider and weight weenie alike.

 

[Zyphryss]

Yep, I know Avid makes a 5" rotor, and Hayes make a 9" one.
And I've heard rumours of carbon rotors, too!

 

[JSPhoto]

And "teh" award for awesome rotor technicallity post goes to... Karnige182.

I believe you can get 5" rotors now too, good for the street rider and weight weenie alike.

Correct
And yes I are knowingly-ness , i'm sure there are a thousand more reasons why large rotors are used, but they are what i know, I await ango and S. to get some input in here, perhap if the title was 'rotors' it may get more attention

Yep, I know Avid makes a 5" rotor, and Hayes make a 9" one.
And I've heard rumours of carbon rotors, too!

As stated correct, I was gunna point out avid made some, but you beat me to it! Avid are the kings of strange rotor sizes. I believe someone out there also makes a 10" disk to fit on rediculous forks such as super monsters and risse forks, but not 100% on that.

 

[|Matt|]

I couldn't be bothered reading the other posts, Karnige's seemed to be pretty knowledgeable though.

Larger rotors = more leverage on the wheel. Think of it like trying to undo a tight bolt with a 5cm long allen key, then attempting the same bolt but with a 20cm long allen key. An 8 or 9 inch rotor has more leverage on a wheel than a 5 or 6 inch rotor so it stops the wheel faster.

However, overkilling the rotor size will result in you flying over the bars or locking the wheel rather than stopping if you can't control your braking well.

Larger rotors also cool faster which helps reduce brake fade and such on big descents where braking is almost constant.

 

[JSPhoto]

I couldn't be bothered reading the other posts, Karnige's seemed to be pretty knowledgeable though.

Matt thinks i'm knowledgable! *blushes* haha!

As for everything else you said, I think we agree, so its good, things are looking like I may acctually be right. And I had an awesome memory of large rotors, went form gay cable brakes with 6" rotor to 8" rotors with codes, just lightly tapped the brakes and kaboom, I went over the top haha.

 

[|Matt|]

And I had an awesome memory of large rotors, went form gay cable brakes with 6" rotor to 8" rotors with codes, just lightly tapped the brakes and kaboom, I went over the top haha.

I um... did that at a train station once when I was doing a brutal as endo. I landed it perfectly, on my ass and my bike landed in my lap. Apparently it looked heaps pro....

 

[stu.111]

Car rotors and motorbike rotors work best at a optumim tempreture thats not cold or hot, is this true with mtb rotors too? Meaning can you go over board on rotor sizes if your not careful? i.e. leave the 8s for downhill use not free riding or all mountain.I was woundering as im about to buy new rotors and was thinking about going up a size front and rear

 

[JSPhoto]

I um... did that at a train station once when I was doing a brutal as endo. I landed it perfectly, on my ass and my bike landed in my lap. Apparently it looked heaps pro....

Bahaha!! Thats awesome! I completed mine infront of such people as the swanns and woody, I had a fair decent audience, dam state races, even coming from hayes 9s to codes is a huge difference! but thats more the calliper than the rotor, dual piston makes a huge difference (or quad piston whatever the hell they are! i'm not really sure)

 

[JSPhoto]

Car rotors and motorbike rotors work best at a optumim tempreture thats not cold or hot, is this true with mtb rotors too? Meaning can you go over board on rotor sizes if your not careful? i.e. leave the 8s for downhill use not free riding or all mountain.I was woundering as im about to buy new rotors and was thinking about going up a size front and rear

It is true! the rotors should be warm for sure! for FR I would think 7" back, 8" front, AM I would think 6" back and 8" front still, the 8" front gives you the extra stopping power you will/may need and the 6" for Am is just to slow you down coming downthe hills as you go up them just as much, the 7" for FR is for more stopping power and cooling, but heaps of FR bikes also run 8" its really user preference, it depends on the brakes just as much as the rotor really, when it comes to stopping power etc, the rotor will just aid the amount of time the caliper will be at its maximum stopping ability.

 

[|Matt|]

Car rotors and motorbike rotors work best at a optumim tempreture thats not cold or hot, is this true with mtb rotors too?

I'd imagine so. I'd say its similar to tires working better on the road when they're hot and sticky, so maybe warm rotors and brake pads are a bit more porous and 'sticky' when they're warm.

 

[jailbait]

Car rotors and motorbike rotors work best at a optumim tempreture thats not cold or hot, is this true with mtb rotors too? Meaning can you go over board on rotor sizes if your not careful? i.e. leave the 8s for downhill use not free riding or all mountain.I was woundering as im about to buy new rotors and was thinking about going up a size front and rear

Yes however if you try braking fairly briskly on the road with an 8 inch on your bike then touching it, you will still burn your hand.

I don't think you could go overboard in that respect.

 

[Gruntled]

I like to stick with my 8" rotors for stopping power in all types of riding. The better your brakes grab, the better you stop. I like being able to lock up either wheel in an instant, and using one finger on my brake lever.

 

[Viv92]

Car rotors and motorbike rotors work best at a optumim tempreture thats not cold or hot, is this true with mtb rotors too? Meaning can you go over board on rotor sizes if your not careful? i.e. leave the 8s for downhill use not free riding or all mountain.I was woundering as im about to buy new rotors and was thinking about going up a size front and rear

Maybe, but the large rotor will still be more powerful. I use an 8" front, and do a fair bit of XC and DH, and it's definitely better for both than the 6" I had before.

 

[takai]

Car rotors and motorbike rotors work best at a optumim tempreture thats not cold or hot, is this true with mtb rotors too? Meaning can you go over board on rotor sizes if your not careful? i.e. leave the 8s for downhill use not free riding or all mountain.I was woundering as im about to buy new rotors and was thinking about going up a size front and rear

Not quite. The pads in your calipers will work best at a certain operating range. Ceramics have a higher heat range than Organics, which means that usually you have to be going faster and braking harder to keep the heat in them and keep them working.
On the flipside, you can easily overheat pads, for example Organic pads tend to top out after long descents and the pad material glazes over and you get shyte* braking performance.

*this is the technical term

Maybe, but the large rotor will still be more powerful. I use an 8" front, and do a fair bit of XC and DH, and it's definitely better for both than the 6" I had before.

Yes, it will be more powerful, although it depends on what sort of pads you have in. My 8" front with EBC Reds on the downhill bike stops like crap when its not hot, stops far worse than the 6" rear with organics on the same bike. Once its heated up on the other hand...

 

[bumpygreen]

Pads

Which pads are people using?

 

[RaID]

The cooling is simply because there is more surface area for the heat to be expelled, and each rotation takes longer meaning there is more time for the metal to cool, and the 8" disk will spin faster than the 6" disk as the radius is larger, so the faster speed will also give a better cooling effect

Both 6" and 8" rotors or whatever size rotors rotate at the same speed as the wheel
think about it. Their angular speed is the same, the linear speed at the end of the rotor changes with radius.

 

[frostbite]

I dont think going larger in rotor size really matters unless you're a weight weenie. You're not going to have issues with them not being in 'optimal riding temperature' or something. I run 8" front 7" rear and its pretty much good for everything. Takes a little getting used to the power on the front brake but its all good.