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Disc Brake Sizes


EigerSA
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I want to order disc brakes from crc, but not sure about the sizes of the rotors. I'm guessing large rotor better braking or maybe cooling? should front and back be the same or different sizes? Sizes I see are 160mm, 185mm or 203mm. So what's best? oh and a wavy or round disc, does it make a difference?

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160mm generally the standard, some have larger on the front, especially AM or downhill, but there is the weight penalty. You also need the right adapters (gets a bit messy, front and back are different). I have 160 fr and rear on my XC Scalpel and 180 / 160 on my AM Prophet. Got a 200mm as well as a spare, but that's a big mofo.

 

Take a look at the Hope floating rotors, they allow for thermal expansion, done very well for me.

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so 185mm on the front and 160mm on the back? what if I just use 185 front and back, wouldn't it just make it easier?

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Also check what max size is supported for your fork. Some forks don't allow the bigger rotors.

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160mm generally the standard, some have larger on the front, especially AM or downhill, but there is the weight penalty. You also need the right adapters (gets a bit messy, front and back are different). I have 160 fr and rear on my XC Scalpel and 180 / 160 on my AM Prophet. Got a 200mm as well as a spare, but that's a big mofo.Take a look at the Hope floating rotors, they allow for thermal expansion, done very well for me.

 

+1 on that! I have 203mm Hope Floating Rotors on the front and back of my DH bike. Work like a charm!

 

so 185mm on the front and 160mm on the back? what if I just use 185 front and back, wouldn't it just make it easier?

 

185mm front and 160mm back is a nice combo. This gives one some stopping power along with feel. Large rotors on the back wheel (which is the less effective braking wheel) will cause the brak to lock with less braking force. And a locke up rear wheel is not the best way to try come to a stop.

 

So yeah, the 185mm on the front will give the stopping power, and the 160mm on the rear will allow fo the 'feel'.

 

I run this combo on my 4X bike and it works great. Also just look at motorbikes (motocross or superbikes)... they run larger rotors (and sometimes even more powerful calipers) up front.

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I read somewhere that bigger disks equals better cooling only, not better braking. Makes sense if I think about it - but ultimately cooler brakes is going to be better braking.

 

You will also need different size adapters which may or may not come with the brakes.

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I read somewhere that bigger disks equals better cooling only, not better braking. Makes sense if I think about it - but ultimately cooler brakes is going to be better braking.

 

You will also need different size adapters which may or may not come with the brakes.

 

it happens to be both. Simple mechanics. Torque = Force x distance. So the bigger the further away from the centre that the force is applied, the greater the torque.

Edited by patches
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