# disc brake rotors bend, when I brake?



## chimpanzee00 (Dec 16, 2006)

I have a Diamondback Topango Comp Disc, bought it in 2004.

I just got back from a mtn ride, & I heard loud squeaking after changing gears.

I noticed the disc rotors bend when I engage the brakes (both front & rear). Is this normal? Or, should the rotors not bend? I was at a LBS, & I did a test with 1 of their MTBs. The rotors did NOT bend, when I hit the brakes.


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## ljsmith (Oct 26, 2007)

This is normal. On all disc brakes that I know of, the outboard pad pushes the disc into the inboard pad. So technically it is being bent into the inboard pad. If the brakes are adjusted properly the outboard pad won't have to push the rotor very far for it to make contact with the inboard pad. So if yours has to push (bend) the rotor a lot you probably need to adjust the inboard pad.


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## boomn (Jul 6, 2007)

Mechanical disc brakes will bend the rotor because of what ljsmith described.

Hydraulic disc brakes have pistons on both sides that push equally. The one you saw at the lbs had hydraulic discs


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## Steve030687 (Jan 7, 2007)

The bending of the rotor depends on the brake caliper, but it is not as clear cut as Hydro vs. Linear. For example, Avid's BB5 push from one side and bend the rotors and the BB7 comes at the rotor from both sides.


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## kramnnim (Sep 2, 2007)

Um...BB7's "push from one side" like the BB5's...


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## Prophet Julio (May 8, 2008)

What kind of brakes do you have? The caliper should be centered if you have two pistons. If the system is not aligned properly you will get "the howl". Easy to fix, go to The Brakes forum.


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## Steve030687 (Jan 7, 2007)

kramnnim said:


> Um...BB7's "push from one side" like the BB5's...


I could have swore that was one of the major differences between the BB5 and BB7. Not like I study these things.


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## kramnnim (Sep 2, 2007)

BB7's have an adjustment knobs for both in and outboard pads...BB5's just have one knob, for the inboard... They use different pads, as well...


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## Prophet Julio (May 8, 2008)

If you go to Brake Time Forum there is a link to a You Tube video that shows the whole sequence for installing and adjusting the BB7's. They are easy to do, and a good brake to have. Good luck.


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## Prophet Julio (May 8, 2008)

Should have attached the link.






Good luck.


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## snaky69 (Mar 8, 2005)

ljsmith said:


> This is normal. On all disc brakes that I know of, the outboard pad pushes the disc into the inboard pad. So technically it is being bent into the inboard pad. If the brakes are adjusted properly the outboard pad won't have to push the rotor very far for it to make contact with the inboard pad. So if yours has to push (bend) the rotor a lot you probably need to adjust the inboard pad.


That is only true with low end hydraulic disk brakes(namely the Hayes Sole) and mechanical brakes.

On all other hydraulic brakes from medium to high-end both pads move onto the rotor, so the rotor doesn't budge.


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## MTN MAN (Feb 6, 2008)

*aye im an idiot*

and i put the front brake on while the front wheel was off. I can get the wheel on and it spins(for about 2 seconds) Is there any way to fix this like prying the pads on the disc brakes or some thing?


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## new2this (Nov 26, 2006)

*watch the video or go to Avids site ...*



MTN MAN said:


> and i put the front brake on while the front wheel was off. I can get the wheel on and it spins(for about 2 seconds) Is there any way to fix this like prying the pads on the disc brakes or some thing?


and read the instructions, BB7 is one of the EASIEST set ups there is. It really is easier to review the instructions and/or follow the vid.

Thats if you have BB5/BB7 if they are Hayes or another brand track the instructions down and follow them it really is not to difficult you just need to do it in order (with the wheel on) When set up properly you should have no rubbing and very little deflection of the rotor.

Good luck


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## cteampride (Jan 19, 2008)

Ive got some shimano disks on my bike.

Yes the rotors bend slightly. Seems like the pad that pushes the rotor will wear out a lot faster though. If you think about it, bending the rotor provides a lot of breaking power in itself vs just squeezing the rotor without it bending. However, seems like poor design - thats what you get with cheep breaks i guess.


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## MTN MAN (Feb 6, 2008)

the brakes i have are avid juicy 7. and what video are you talking about:skep:


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## snaky69 (Mar 8, 2005)

MTN MAN said:


> the brakes i have are avid juicy 7. and what video are you talking about:skep:


Yes, take the wheel off and use a flat blade bladed screwdriver, be very careful not to damage the pads. Works is side to side slowly and the pads will slowly pull apart.

Put the wheel back on, tighten it down.

Now, unscrew slightly the caliper bolts that hold onto the adapter on your fork. Enough so that you can move the caliper around a bit with your fingers. Put it in place correctly, squeeze the brake lever as far as it will go, and tighten those bolts again.

You've now reset and centered your pistons.


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## MTN MAN (Feb 6, 2008)

wuw dude thanks an assload id be screwed with out ur peoples comments


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## new2this (Nov 26, 2006)

*sorry assumed*



MTN MAN said:


> the brakes i have are avid juicy 7. and what video are you talking about:skep:


:madman: that you had mechanicals.. up a few posts there was a link to a you tube video Snaky gave good instructions.

The only thing I would add... grab the brake to center and HOLD it whilst you tighten the caliper bolts down.

with those juciy 7s you should be able to dial them in real nice like. :thumbsup:


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## MTN MAN (Feb 6, 2008)

wow i was just about to ask that.:thumbsup:


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## cmc4130 (Jan 30, 2008)

I have a cheap Hayes mechanical disc brake on an extra bike, and I noticed that it pushes/bends the rotor inwards a lot more than my Avid BB5 on one bike and my Avid BB7 on another bike. The BB7 seems to work the best.

looks like this:

https://vid255.photobucket.com/albums/hh138/upsetbmx/Hayes%20mechanical%20disc%20brake_zpswel3fbpu.mp4


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## TheGweed (Jan 30, 2010)

Holy thread resurrection batman!


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## tigris99 (Aug 26, 2012)

If it pushes them over too far adjust the brakes. Means the inner pad is too far away....

Sent from my XT1565 using Tapatalk


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## Oh My Sack! (Aug 21, 2006)

TheGweed said:


> Holy thread resurrection batman!


WOW! Bush 43 was President when this first ended. Epic resurrection indeed! :lol:


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## jeffj (Jan 13, 2004)

cmc4130 said:


> I have a cheap Hayes mechanical disc brake on an extra bike, and I noticed that it pushes/bends the rotor inwards a lot more than my Avid BB5 on one bike and my Avid BB7 on another bike. The BB7 seems to work the best.
> 
> looks like this:
> 
> https://vid255.photobucket.com/albums/hh138/upsetbmx/Hayes%20mechanical%20disc%20brake_zpswel3fbpu.mp4





tigris99 said:


> If it pushes them over too far adjust the brakes. Means the inner pad is too far away....
> 
> Sent from my XT1565 using Tapatalk


The less deflection of the rotor when braking the better so long as it doesn't rub. That is because the more that the rotor is deflected, it contacts the pad at an angle and will cause uneven wear on the pad(s). It will also stop better with less deflection, or more specifically, having the pads as close to the rotors as possible without rubbing is what will perform the best. Theoretically, brakes that have the piston moving inward from both sides will make the uneven wear issue a non-factor. There are some mechanical disc brakes (such as the TRP Spyre) that are made this way.

If you have the Hayes MX4 mechanical disc brakes, these are not the worst mechanical disc brakes out there. I would rate them somewhere between the Avid BB7 and BB5, which are some of the better mechanical disc brakes from 'BITD', so you should be able to get them to work reasonably well.


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## cmc4130 (Jan 30, 2008)

tigris99 said:


> If it pushes them over too far adjust the brakes. Means the inner pad is too far away....


Yes, that's right. I was only barely able to move the inner pad closer (turning the Allen bolt, but it seems maxed out--maybe the Inner pad (or both pads) are just cashed. I thought I replaced them not too long ago.... but there was a weekend of DH flow trail, so maybe they're done! It seems like this adjustment works better with Avid BB7.


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## tigris99 (Aug 26, 2012)

Some brakes have a tiny set screw that locks the inner pad in place that you have to loosen to adjust. Actually I think it's rather common except avids toolless adjustment. It's there so the inner adjuster can't come loose on its own. Look at the caliper closely for a hole or set screw sticking out that uses a tiny Allen wrench.

Move up to decent hydro brakes and this isn't an issue anymore. Shimano m615s are cheaper than BB7s half the time and perform very close to XT level brakes.

Sent from my XT1565 using Tapatalk


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