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Bigger rotors and stopping power


banna

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In theory putting larger rotors wont be harder but actually softer on your brake disks. It like trying to stop a spinning record with your finger. The closer to the middle the harder you have to push down to stop it. The further out to the edge, the less force is needed for the same stopping power. That is also why V-brakes are also light on the rubber blocks and dont burn up on the first go.

 

Go for it!!

 

Ever take a look at a Buell brake disk, they thought of this looooong ago.

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Glad you answered. The same comes to play on your axle. The bigger the rotor the bigger the forces on the axle. What axles are your using on the downhill bike? Thru axle type or normal QR axles. I think the OP should be warned about the possible danger for failure as well.

 

I call complete BS. There is no way that the forces seen by the axle is a function of the rotor size. So much for BA Brugbou aka Civil engineering

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I call complete BS. There is no way that the forces seen by the axle is a function of the rotor size. So much for BA Brugbou aka Civil engineering

 

 

Ha ha ha....interesting!!

 

Only way I'll be convinced is if someone can come up with some maths (i.e facts)to either prove or disprove this statement about increased forces on the axle...

 

I'm inclined to think not much more "force" on axle, regardless of rotor size?? But i might be wrong here...

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Well, because the axle is running on bearings, the force would be exerted on the 6 rotor mounting bolts (or centrelock)... woudn't it? (I may be wrong?!)

 

But axle wise, my DH bike has a 20mm thru axle in the front, and a 150x12mm thru axle at the back (both Hope Pro II's)

 

Come to think of it there never were any problems with rim braking wheels and their diameter are much larger. When I upgraded the MTB wheels to disk wheels on the MTB Tandem I was warned that agrressive riding may compromise the QR. There was a discusion on www.bikeforums.net where various people responded. including Christoff Timm, who is a rather knowledgeable Tandem enthusiast. According to a few people who responded there was a few cases of QR snapping during aggressive riding. The problem seemed to be be in the warping of the fork diring aggressive riding. I have no proof of this and it was menstioned during the discussion.

 

I decided to stay with my Marzocchi Z1 fork with QR using 180mm rotors as wel will never be involved in aggressive riding with our MTB Tandem although we have now learned to bunnyhop the bike!

Edited by eccentric1
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I call complete BS. There is no way that the forces seen by the axle is a function of the rotor size. So much for BA Brugbou aka Civil engineering

 

Seems you have knowledge to share and we are not writing exams, you are welcome to join, please do!

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Come to think of it there never were any problems with rim braking wheels and their diameter are much larger. When I upgraded the MTB wheels to disk wheels on the MTB Tandem I was warned that agrressive riding may compromise the QR. There was a discusion on www.bikeforums.net where various people responded. including Christoff Timm, who is a rather knowledgeable Tandem enthusiast. According to a few people who responded there was a few cases of QR snapping during aggressive riding. I decided to stay with my Marzocchi Z1 fork with QR using 180mm rotors as wel will never be involved in aggressive riding with our MTB Tandem although we have now learned to bunnyhop the bike!

 

Oh yeah... when it comes to QR on the front wheel... I know some studies were done regardting the direction of the force exerted by a disc brake and how that could unseat the QR.

 

More details here

 

Basically it's because the braking forces the wheel downwards, whereas a V-brake will force the wheel forwards.

 

I run 20mm thru axles on on both my bikes (but that's due to the nature of their use).

 

But hey... you can bunnyhop a tandem with 2-up?! way impressive! Me and some riding buddies are looking for someone willing to jump a tandem... you keen :lol:

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Oh yeah... when it comes to QR on the front wheel... I know some studies were done regardting the direction of the force exerted by a disc brake and how that could unseat the QR.

 

More details here

 

Basically it's because the braking forces the wheel downwards, whereas a V-brake will force the wheel forwards.

 

I run 20mm thru axles on on both my bikes (but that's due to the nature of their use).

 

But hey... you can bunnyhop a tandem with 2-up?! way impressive! Me and some riding buddies are looking for someone willing to jump a tandem... you keen :lol:

 

The Yanks have made a Tandem Rigid forks with the disk mounting on the right hand side facing forward to combat these forces.

 

We only do bunny hops in the dark dep recesses of forests where no eye can see us. I must say we do look silly in our bunny uniforms! Jumping we came close to in Angola where they put berms across the road to stop people from damaging the newly built road. I managed to lift the front wheel but EM promised me that I will have ride alone in the future if I ever do that again!

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Ha ha ha....interesting!!

 

Only way I'll be convinced is if someone can come up with some maths (i.e facts)to either prove or disprove this statement about increased forces on the axle...

 

I'm inclined to think not much more "force" on axle, regardless of rotor size?? But i might be wrong here...

 

I refuse to have to provide "maths" for something that is so glaringly obvious. It is common sense. I'm right.

 

But let me spoon-feed BigH: Braking is braking, the max braking force you can generate is a function of the tyre traction on the ground. How you get there i.e. rotor size is irrelevant. If you skid your front or rear tyre with a 140mm or 203mm imparts the same force in the axle.

 

I suspect Forks are limited in disk diameter as the location of the brake caliper moves significantly with bigger disks causing much higher forces on the mounting points on the fork.

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Ands probabaly more costly to design seperate forks with caliper mountings at different positions than the stock standard ones??

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I call complete BS. There is no way that the forces seen by the axle is a function of the rotor size. So much for BA Brugbou aka Civil engineering

 

QFT.

The forces will translate into the hub, not the axle. There are sliding surfaces there remember. but honestly, this is only a concern if the hub is made of paper :rolleyes:

 

i see what u ACTUALLY meant, you just worded it very poorly Eccentric. What you were failnig to direct our attention to initially was a problem locating the wheel securely when using disc brakes. that's NOT the same thing as disk brakes structurally affecting the axle in a generic sense, which is what i think most of us concluded from your initial post. hahhaa..that little thing called context..

Edited by Capricorn
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Guest Omega Man

 

Ever take a look at a Buell brake disk, they thought of this looooong ago.

Buell run a single rim mounted disc. Apparently the braking power is similar to the usual 2 smaller diameter rotors.

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QFT.

The forces will translate into the hub, not the axle. There are sliding surfaces there remember. but honestly, this is only a concern if the hub is made of paper :rolleyes:

 

i see what u ACTUALLY meant, you just worded it very poorly Eccentric. What you were failnig to direct our attention to initially was a problem locating the wheel securely when using disc brakes. that's NOT the same thing as disk brakes structurally affecting the axle in a generic sense, which is what i think most of us concluded from your initial post. hahhaa..that little thing called context..

 

Ik zal deze technische kwesties in mijn moeder tong in de toekomst vertellen, maar deze Hubber genaamd kiphardlopenvoormij zal zelfs dat niet begrijpen!

post-24908-0-80821300-1314783806.png

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QFT.

The forces will translate into the hub, not the axle. There are sliding surfaces there remember. but honestly, this is only a concern if the hub is made of paper :rolleyes:

 

i see what u ACTUALLY meant, you just worded it very poorly Eccentric. What you were failnig to direct our attention to initially was a problem locating the wheel securely when using disc brakes. that's NOT the same thing as disk brakes structurally affecting the axle in a generic sense, which is what i think most of us concluded from your initial post. hahhaa..that little thing called context..

 

Even the problem of the front wheel coming off is again not a function of rotor size. Even the forces seen by the hub is not rotor size related..

 

Basically what I'm trying to get at is that rotor size affect very little apart from the rotor itself..

Edited by chickenrun4me
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Just for my own understanding (and appologies, I'm an accountant, not an engineer), so if you put a bigger rotor on, are you actually generating more stopping power, or does it only feel that way, because the force that you need to exert via the brake levers is less to get the same stopping force? Not sure if I'm making sense?

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