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Discussion Starter · #1 ·
I don't know what went wrong but brand new front rotors and now I have a pulsing feel when I hit the brakes. I used a torque wrench thread lock and even cleaned the calipers pads and new rotors to no avail. Unless I come up with a solution. The old ones are goin on and the new ones are heading back. Any bright ideas besides a match and a gallon of gas?
 

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First I'd suggest taking a breather, its just motorcycle mechanics, no reason to have a heart attack over it :) - think "zen"

After you've chilled a bit perhaps you should check your rotors, make sure they aren't warped or worn weird, new pads are going to be nice a smooth and if your old rotors were worn strange that would likely cause vibration. Rotors should be floating free (can wiggle left/right a couple millimeters).

I'd recommend a brake bleed if you haven't if your previous pads were real thin and the new pads are obviously thick so the calipers will handle them differently... Unlikely culprit but worth a shot.

Also make sure the pads are seated properly- There are some little metal "spring" clips (not sure what you'd call them) but they help to hold the pads position- its easy for those to get placed incorrectly and cause the pad to drag or do weird stuff.

Hope that helps!
 

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First I'd suggest taking a breather, its just motorcycle mechanics, no reason to have a heart attack over it :) - think "zen"

After you've chilled a bit perhaps you should check your rotors, make sure they aren't warped or worn weird, new pads are going to be nice a smooth and if your old rotors were worn strange that would likely cause vibration. Rotors should be floating free (can wiggle left/right a couple millimeters).

I'd recommend a brake bleed if you haven't if your previous pads were real thin and the new pads are obviously thick so the calipers will handle them differently... Unlikely culprit but worth a shot.

Also make sure the pads are seated properly- There are some little metal "spring" clips (not sure what you'd call them) but they help to hold the pads position- its easy for those to get placed incorrectly and cause the pad to drag or do weird stuff.

Hope that helps!
I think you missed the part where he says he has new rotors, I assume he's using the old pads. If that's the case, probably better to put some new pads in as well, I would think (?)
 

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Discussion Starter · #4 ·
Well thank you gentlemen for your suggestions. I tried to bleed the brakes no luck. I am hesitant to spend more money on parts to fix a problem that was. Not there at the start of the job. After three redo's a bleed a cleaning and many inspections and retorques I decided to put the old disks back on. Works great again. I looked at the way the old rotors sat on the rig and they are flush at the center. The new ones are a mm or 2 above the rim. Do you think the extra mm could have caused the problem or do you think I just got bad rotors? I did not see any evidence they are warped but I'm not a calibrated instrument either. :ears:
 

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You should change to new pads when you change rotors. The old pads are probably contoured to the irregularities of the old ones. You could try sanding the pads a bit and see if that helps, before you buy new ones.
 

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Discussion Starter · #8 ·
Well I have new pads on the way. I honestly would be a little surprised. Just the way the pulsing is makes me think rotors. As for why new discs but no pads easy the discs are flimsy and are falling apart they have alot of wiggle where they should not. I will admit my failings as a human being if the Pads fix it though and will have learned a valuable lesson.
 

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You should change to new pads when you change rotors. The old pads are probably contoured to the irregularities of the old ones. You could try sanding the pads a bit and see if that helps, before you buy new ones.
This.

As a quick test, you can sand the current pads flat using a flat, glass surface and even pressure. And double check to the surface of the rotors to make sure there's no irregularities on it from uneven pad material transfer. Assuming you have adequate pad material left do to so, you should be able to sand enough to get a fresh, unmolested surface to contact the discs.

Also, some of the reasoning in this thread doesn't follow. Pads are stationary, regardless of any irregularities they may have on their surface. You can gouge and warp a set of pads all you want; but they won't pulse unless they are being swept over an irregular surface...like a bad rotor. New rotors aren't guaranteed to be true; they are subject to manufacturing issues like everything else.

What do we know? With old pads and old rotors, he gets no pulsing. With old pads and new rotors, he gets pulsing. The only that that has changed is the rotors in this situation, and it was their addition that has caused issues.

Now is it good practice to change pads and rotors at the same time? Of course. But the OP's symptoms are that of an out of true rotor.

I'd be more than happy to be proven wrong.
 

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When issues like that come up, I use this:



This can tell you exactly what the rotor run-out is and if it's bad or not. Or if the rotor isn't mounted properly.

Instruments like this aren't expensive and give better answers than anything else.
 

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Okay so some how I inverted pads and rotor inmy mind and made the post all screwy but... seems like the points the same.

New rotor could be warped, but more importantly you should also do your pads as well since they are shaped and "used" to the old rotor... they will run weird on the new rotor.

Glad you are getting it figured out! Best of luck-
 

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pulsing brakes are more frequently caused by uneven grip between the pads and the rotor than by a warped rotor. the pads need to 'bed' to the rotor, and in doing so they transfer a thin film of pad material onto the rotor surface. if this is uneven, so is the braking force, and the brakes pulse.

Rock Dodgers advice to check runout is appropriate. this will eliminate or confirm the 'warped rotor' possibility. a mechanic can quickly, easily, and cheaply do this, if you lack the instrument.

provided the rotor is true, the challenge then is to get a consistent film of pad material onto your new rotors. honing the pads flat (per opmike's advice) would be the first step. then just follow normal bedding procedures, i.e., repeated harder and harder braking events (without stopping), building heat in the brakes without using them overly hard. the advantage of using new pads is that they start flat and true, whereas your old ones will have 'grooved' to the irregularities of the old rotors. I suspect that's the underlying cause.
 

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You can 'rent' a dial gauge at most major autoparts store. You put down a deposit, then they refund it when you bring the tool back. There shouldn't be any actual charge for this service.

Check the run-out on the rotors to verify they're not all wiggly. If they're 'actual' new rotors they should be in good shape, but some 'new' ones that have been sitting for a few years could have warped due to storage on edge or some other factors.

Pads and rotors wear into one another. When you change one, the surfaces don't meet each other very well. Especially in your case, where you changed the rotors but not the pads. The pads take on most of the wear irregularities, so when you mate them to a fresh rotor their contact surface can be rather poor and uneven.

Lastly, when you get your new pads and rotors setup you'll want to do a quick break-in, or bedding, procedure. There's about 500 ways to do this, but they all involve a series of increasingly hard stops from 30-40mph to 5mph or so, and then repeating. Usually a series of 10 or so - though make sure you don't overheat your brakes. If the pads glaze, you'll have to take them off and scrub off the glazing. Try to use your rear brake for when you need to come to a complete stop. If you hold hot pads and rotors together, the pad material will tend to transfer a bit too heavily to the rotor, giving a raised surface on the rotor.
 
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