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The Hell You Say!!
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2,956 Posts
Discussion Starter · #1 ·
Just recently noticed that when I pull the front brake lever it pulses. Ive got plenty of lever and its very firm and the bike stops...just a weird pulsing. Would that mean that there is air in the lines or maybe a MC?
 

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The Hell You Say!!
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2,956 Posts
Discussion Starter · #6 ·
So the bet is that if I have a warped rotor youll buy me a new set?? Cause those fookers are expensive!! I figured it might be. Im just going to upgrade to a set of wavy rotors and gonna get new pads while Im at it.
 

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740 Posts
These rotors suck...common issue on the ZX7, ZX9, first gen 636 and Z1000, they're all the same. Seems they pretty much all warp in time.

Mine have a slight pulse, can only really notice it at low speeds. It used to kind of bother me, but it hasn't gotten any worse in the last 20k miles, and it's not wearing my pads out (now have almost 20k on a set of EBC HH pads and they're still 50%), so I'm not really jumping to drop $500 on new wave rotors.
 

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The Hell You Say!!
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2,956 Posts
Discussion Starter · #13 ·
I'm really not all that worried about it. I had more vibration in my truck when braking (before I did a full brake job) than I do in my lever and it doesn't mess with the bike at all. Probably just ride this way for the rest of the season. I have some changes in mind this winter and new brakes will probably be one of them.
 

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ignorant cunt
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4 Posts
Warped discs or rotors is a myth.

That is, the disc or rotor itself isn't actually warped if you're experiencing 'pulsing' at the lever on a bike or the foot pedal on a car.

If you think about it logically, a physically warped disc or rotor needs to pass through the pads even when the brake isn't applied. If the discs/rotor was physically warped then you'd also experience the brakes binding or a few pumps to bring the pads in. The warp would need to seperate the pads more than normal to not experience a pulsing.

If your only symptom is a pulsing when the brake is applied then this is not a 'warped' disc/rotor & there's no need to junk the old for new.

What is most likely to have happened is the pads have burnt onto the surface of the disc when both are extremely hot. Like if you've been ragging it somewhat but then spend a few seconds stationary with the brakes applied. The area that the pads have touched the disc are slightly more grippy than the rest of the disc. Hence when the brake is applied you get a sensation of pulsing.

Skimming the disc will solve the problem but it's not as cheap or easy as some other methods.

If you ever come across the problem in future then a simple Google on warped discs/rotors will throw up some easy & cheap solutions.
 
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Warped discs are not a myth ...fact

Bike discs do warp & what you feel at the lever is the brake pistons being pushed back slightly or the brake binding slightly every time the high spot or warped area passes between them ..... take a suspected warped disk off & lay it on a flat surface to check, glass is good for this if you don't have a surface plate

In most cases skimming an old warped a bike disc is not advisable as there is a minimum thickness stamped on them & by going below this you risk the chance of the disc cracking ..... really not good which is why the min thickness stamp is there!

Loose or seized bobbins on floating discs can give the same symptoms & can be pressed to tighten them up or freed off but its a pain to get them all the same & only really recommended as a quick temporary fix
 

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ignorant cunt
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4 Posts
Read & weep. What is commonly referred to as 'warped discs' is very rarely an actual warped disc. A physically warped disc would not display the symptom of pulsing at the lever.

https://en.wikipedia.org/wiki/Disc_brake#Run-out

http://www.stoptech.com/technical-support/technical-white-papers/-warped-brake-disc-and-other-myths

These are just 2 of the many articles available on the subject, if you want more, including from very many highly respected sources like manufacturers such as Brembo, AP & Beringer or many named brake specialists working in F1, MotoGP, WSB etc . . . Then you simply need to Google "warped rotors" or "warped discs" and look for RESPECTED sources of information.

When a pulsing at the lever is the symptom a physically warped disc is not the cause. It is a myth perpetuated by the uninformed. Like 'gel seats are more comfortable for long distance riding'.

Physically warped discs will show you symptoms very differant to a pulsing at the lever.
 

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The friendly Ghost.
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13,172 Posts
I have a minorly warped rotor sitting down stairs in my garage. It rubbed ever so slightly on the pads when not applied and when applied, would pulse like all hell.

I swapped the rotor for a fancy non-warped one and scrubbed the surface really quick with sand paper and viola! No more pulse and no more slight rub when not applied.


Most rotors that get re-surfaced (think thick car rotors) are actually chucked up into a mini lathe and then trued back to a known flat plane. The high spots and warpages are just cut out of the surface's outer layer. You can't do this easily with motorcycle rotors due to the min thickness being so close to the factory thickness for lower rotational inertia.
 
G

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Warped discs or rotors is a myth.

That is, the disc or rotor itself isn't actually warped if you're experiencing 'pulsing' at the lever on a bike or the foot pedal on a car.
:bsflag:
This is where we disagree, I have a couple of warped bike discs here & have changed a dozen or so that are physically warped & one of the symptoms of them being warped is pulsing at the lever as explained previously

I agree there can be other reasons for pulsing but to state that discs don't warp is plain wrong ! A google search reveals that most of the information you are basing your opinion on is relating to cars which have much thicker discs ... the 2 links you provide relate to cars..... & this is a bike site :)
 

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The Hell You Say!!
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2,956 Posts
Discussion Starter · #19 ·
As much as I appreciate the help Chas, I have to agree with 4cups. The disc is physically warped and like he said, to state that rotors don't warp, especially bike rotors, is like saying all white people listen to taylor swift. Its an absolute and by definition, absolutes are almost always wrong. I know for a fact that my rotor is actually warped.

BTW, I don't know about everyone else, but I do not consider Wikipedia a reliable source. Just my .02

Not trying to open a can of worms or piss anyone off, but this thread has already been resolved LONG before you signed up and you aren't off to a good start by opening a can of worms like that with your 1st and 2nd post
 

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ignorant cunt
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4 Posts
As much as I appreciate the help Chas, I have to agree with 4cups. The disc is physically warped and like he said, to state that rotors don't warp, especially bike rotors, is like saying all white people listen to taylor swift. Its an absolute and by definition, absolutes are almost always wrong. I know for a fact that my rotor is actually warped.

BTW, I don't know about everyone else, but I do not consider Wikipedia a reliable source. Just my .02

Not trying to open a can of worms or piss anyone off, but this thread has already been resolved LONG before you signed up and you aren't off to a good start by opening a can of worms like that with your 1st and 2nd post
So it's "actually warped" then?

I'd be interested in how you know that, on the basis that 2mins ago you were asking the internets about pulsing levers & now you can suddenly measure your rotor to a 0.02mm accuracy !

Like you, I don't want to pi$$ on anyones strawberries, but this site comes up in Google results . . . & some folk might be needlessly throwing away serviceable brake discs because they think they're 'warped'.

They are not.

They suffer from a little spot of pad burn, which can be resolved very easily & very, very cheaply, without buying wavy davy melted down washing machines in fake packaging off eBay.

If anyone reads this whose discs/rotors are warped, then please at least Google the subject before committing yourself to replacing them . . . because all the advice I've read here so far is that cheapo discs off eBay are OK so long as they're wavy & therefore kool.
 
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