How to know if rotors are warped?

[2fidyswag]

Being a noob I didn't check my pads regularly. Out of the blue last time I rode when I would come to a stop the bike would vibrate, it did that for about two stops and I went home. I looked online and saw it may be the rotors, so I took it outfront of my house and did a little test ride. And it didn't do it anymore. However whenever I walk the bike into my garage as the wheel turns at a certain point you hear a tiny bit of a grind. So I've parked the bike and inspected the rotors but they seem to look the same as my rear. Obviously I need to get new pads in there as quick as possible, but how do I know if I need a new rotor? I was gonna change the pads myself but now that I'm questioning my rotor I'm thinking of taking it to a local shop because I know the guy. Any ideas on what to do? I heard that when pads are super low they sometimes will grind, so it's not the metal on metal.


2011 ninja 250, 7k miles. haven't changed pads entire life of bike.

[tubarney]

Your rotors are fine. Put the new pads on, if there is some serious binding then you have a problem.

With the new pads, jump on the bike and start of really slow, increasing your speed. If the bike brakes at any time then its warped.

Its pretty hard to warp a rotor, especially in 7k miles.

With that much milage, you should just be needing new pads, you should even get another 3-6k miles from the pads depending on how hard you brake.

How much is left on your pads?

[2fidyswag]

The back looks fine, the front appears to have literally nothing for a pad. It looks totally gone. I never noticed a braking problem really until the other night so I didn't ride. And when I walk the bike it makes a rubbing noise

[nickjpass]

Not sure, but if you lift your wheel, spin it, and the wheel DOESNT spin freely, it's warped.

[2fidyswag]

so if it is warped, do I have to buy a brand new rotor, what are my options. I don't see why it'd be a problem. If I was stopping ago earlier today without issues and don't ride it anymore until my new pads come in I thinnk it'll be fine? can they machine rotors?

[2fidyswag]

I guess what I am getting at is besides the other night where I stopped twice and at the very end of my stop I felt a slight shudder. It was the first time I eveer felt it/ or noticed it. I went home right away, and tested it out again the next day and it seemed to be fine. However I saw the pad was not even noticable. So I parked the bike. So since stopping wasn't really an issue to begin with shouldnt I be fine if I dont ride till my new pads come in?

[nickjpass]

Chances are, your rotor is fine. This is only my opinion from what I've read (I don't actually have access to your bike lol). Many times, a rider will think something is wrong with his bike, when really, it's perfectly fine. It could just have been the road surface. Small bumps and cracks and the road can cause your handlebars to 'shutter'. Since I'm not sure, don't take only my opinion. Have some one like @alex.s chime in.

[2fidyswag]

Ok thanks ha. I'm stressing out because I really don't wanna spend more money on a rotor. Im already down $220 this month from a speeding ticket yesterday

[nickjpass]

Speeding ticket on a 250? Try hard. LOL. Stop speeding, would your mother be proud of you?

[2fidyswag]

Speeding ticket in my civic. Of all the vehicles I own, I get pulled over in the slow civic ha

[tubarney]

When you put the brand new pads on it should rub a little bit. Just not enough for it to do anything when your rolling the bike down a hill or something.

I hear aftermarket rotors are cheaper than OEM.

[alex.s]

Link to original page on YouTube.

[nickjpass]

Thanks @alex.s

[rojoracing53]

All one piece rotors are going to warp, it's simple physics. On the 250 they always warp toward to out side, I have a few idea as to why but haven't proved any of them yet.

Everything has a breaking point and a certain level of flexibility before reaching that point. Your rotors are going to warp and if you continue to keep warping them in the same direction they will eventually reach their breaking point and fracture. I had this idea that if you flip your rotors at regular intervals your can warp the rotor back the other direction and keep it from going one way to far. This wouldn't be a fix but more of a preventative maintenance thing to extend the life of something that is made to be disposable. If your an engineer or maybe have an understanding of thermal expansion and material growth you should be able to figure out the finer detail on your own. I figure trying to explain the whole the why and how of it here would be lost on most.

What I have done so far was at my first front pad change I flipped my front rotor which had already warped about 1/2" from center to outer edge. I was careful to take it easy for the first ride to make sure there was going to be problems. I believe I put on an additional 1000 miles or so before swapping the entire front braking system on the bike to another design completely for unrelated reasons. In those 1000 miles there were no observed problems and the rotor started to straiten itself out but sadly that's where my test was put on hold.

With this flipping method your rotors OD will grow and it will continue to apply strain to the materials structure but I suspect you could extend the life of your rotors by as much a 3x the normal service limits.

[alex.s]

Originally Posted by rojoracing53

your can warp the rotor back the other direction

the thickness of the metal is warping because of heat from the pads when you sit still after hard braking.

[rojoracing53]

Originally Posted by alex.s

the thickness of the metal is warping because of heat from the pads when you sit still after hard braking.

Not sure which type of warping the OP is referring to but the type I'm talking about is Dishing evenly like a dinner plate.

[alex.s]

gotcha. you mean the kind that eats into the pads so you start digging into metal on one side faster than the other. but that shouldn't really vibrate too bad on the brakes i dont think? just gives that horrible uneven wear right? warped thickness from one end vs the other like in the video i posted makes really bad pulsing vibration in the forks when on the brakes.