Grinding edge on brake rotor | GTAMotorcycle.com

Grinding edge on brake rotor

sburns

sburns

Well-known member
Hey all

My rear brake rotor has a bit of edge on it from pad digging into it. I was thinking to grind it off. But I don't have a grinder. Only these disks you can buy which attach to the end of drill with a special bit. Is it a waste of time to try and do it this way. Or do I need a real grinder.

As for why I just don't go out an buy a new rotor. I have been trying to track down this sweak on the rear end of the bike. I have narrowed it down to the brake. My thought being this grove from this edge on the rotor is causing the pad to wiggle. Also I rather try this approach and see if is solves/or at least get me on the right track before just doing the replacement. The rotor itself still seems pretty thick.

Thoughts I know you have them!
 
Measure the thickness of the rotor with calipers or a micrometer? Seems thick doesn't tell you whether it is in tolerance.

How did a pad dig in? I am assuming you have pad slapped it at some point (replace pads, leave rotor)? How hot have you gotten the rear brake? I would be tempted to get it hot enough you can smell it and then ride around for a while not touching it to allow it to cool off. Other more rational/experienced members may chime in that this is a bad idea.

How much is a rotor? The hone looks like it's about $50 (and I'm not sure you will ever need it again, I've never needed or wanted one).
 
Last edited:
If you have a groove at the edge of your rotor that means the rotor surface isn't flat which means you need to
a) replace the rotor
b) resurface the rotor on a lathe or blanchard grinder

If the two rotor surfaces aren't 100% parallel it could cause the brakes to squeak
 
GreyGhost said:
Measure the thickness of the rotor with calipers or a micrometer? Seems thick doesn't tell you whether it is in tolerance.

How did a pad dig in? I am assuming you have pad slapped it at some point (replace pads, leave rotor)? How hot have you gotten the rear brake? I would be tempted to get it hot enough you can smell it and then ride around for a while not touching it to allow it to cool off. Other more rational/experienced members may chime in that this is a bad idea.

How much is a rotor? The hone looks like it's about $50 (and I'm not sure you will ever need it again, I've never needed or wanted one).
Click to expand...
I use the rear brake a lot. Yes just replace pads not rotor. I've been through 3 sets of rear pads since getting the bike. I think the second set caused the grove since it wasn't a HD set and wore out quicker then the other sets.
 
bitzz said:
If you have a groove at the edge of your rotor that means the rotor surface isn't flat which means you need to
a) replace the rotor
b) resurface the rotor on a lathe or blanchard grinder

If the two rotor surfaces aren't 100% parallel it could cause the brakes to squeak
Click to expand...
Thanks seems I am getting to the bottom of this mystery sweak. Beside my bad idea.
 
I thought that motorcycle rotors weren't thick enough that you could grind them down safely, whereas car rotors were?
 
Baggsy said:
I thought that motorcycle rotors weren't thick enough that you could grind them down safely, whereas car rotors were?
Click to expand...
I think he is referring to using a flex hone. It just removes the glaze and puts a non directional pattern back into the surface.
 
I'd measure the rotor with a micrometer to determine if it is in spec. Do the pads sweep the edge of the rotor or just below? If just below the edge then in normal wear you're going to get a bit of a ridge as the rotor wears. Aftermarket pads may be more aggressive and chew up an OEM rotor, false economy. How many KM did you run to use 3 sets of pads? How many front pads sets did you changes in the same timeframe? Sounds like abnormally fast wear, are the rear brakes dragging.
 
Are you talking about a small lip right on the edge of the rotor? Or a ridge in the centre of the rotor face (like a record)? If it's just a lip at the edge, you're good to remove it with whatever means you have at your disposal (using some damn sense though).
 
Renboy said:
Are you talking about a small lip right on the edge of the rotor? Or a ridge in the centre of the rotor face (like a record)? If it's just a lip at the edge, you're good to remove it with whatever means you have at your disposal (using some damn sense though).
Click to expand...
Strongly disagree. If the rotor is worn leaving a ridge of unworn material, measure and most likely replace it.
Removing the ridge does what?
 
If there's a lip it means the main friction surface of the rotor has been worn down. Machining the rotor isn't a thing for motorcycles, replacement is. Rotors aren't that expensive.

In related news..

sburns said:
I use the rear brake a lot. Yes just replace pads not rotor. I've been through 3 sets of rear pads since getting the bike. I think the second set caused the grove since it wasn't a HD set and wore out quicker then the other sets.
Click to expand...

Are your brakes linked on that bike? Using on the rear brake (to the point of going through pads this fast) is a very, very bad practice. The rear brake only produces about 30% of the braking power of the front, and in a panic situation just hammering on the rear will not help you much. Problem with habitually using the rears is that in said panic situation your brain will just automatically go there.

The only time I even touch my rear brakes is during low speed maneuvering (an amazingly effective technique I learned during one of the advanced rider courses I went to) or during very heavy braking, IE coming into a corner hot and fast and needing to bleed speed fast, or an an emergency situation. Even then with linked brakes touching the rear brake is only secondary to front, but that's another story.

70% of your braking comes from the front wheel. Every rider should use that as their primary means of braking, without question.
 
Wingboy said:
Strongly disagree. If the rotor is worn leaving a ridge of unworn material, measure and most likely replace it.
Removing the ridge does what?
Click to expand...
From my interpretation of his description is he wants to know if it's causing a noise, and if so, he's going to replace the rotor. The lip is there because the pad isn't making (enough) contact with the rotor so removing it does nothing as far as braking is concerned.
 
PrivatePilot said:
If there's a lip it means the main friction surface of the rotor has been worn down. Machining the rotor isn't a thing for motorcycles, replacement is. Rotors aren't that expensive.

In related news..



Are your brakes linked on that bike? Using on the rear brake (to the point of going through pads this fast) is a very, very bad practice. The rear brake only produces about 30% of the braking power of the front, and in a panic situation just hammering on the rear will not help you much. Problem with habitually using the rears is that in said panic situation your brain will just automatically go there.

The only time I even touch my rear brakes is during low speed maneuvering (an amazingly effective technique I learned during one of the advanced rider courses I went to) or during very heavy braking, IE coming into a corner hot and fast and needing to bleed speed fast, or an an emergency situation. Even then with linked brakes touching the rear brake is only secondary to front, but that's another story.

70% of your braking comes from the front wheel. Every rider should use that as their primary means of braking, without question.
Click to expand...
Maybe he tracks his Harley and runs into the grass...a lot. In just about any other case though, I agree the rears are more for decoration.
 
Renboy said:
From my interpretation of his description is he wants to know if it's causing a noise, and if so, he's going to replace the rotor. The lip is there because the pad isn't making (enough) contact with the rotor so removing it does nothing as far as braking is concerned.
Click to expand...
What machining process would you suggest he use to do this?
 
Renboy said:
From my interpretation of his description is he wants to know if it's causing a noise, and if so, he's going to replace the rotor. The lip is there because the pad isn't making (enough) contact with the rotor so removing it does nothing as far as braking is concerned.
Click to expand...
Ding Ding Ding!!! We have a winner. I was going to use the grinding as a troubleshooting technique, not a as permanent solution. The rotor is going to be replaced.
 
sburns said:
Ding Ding Ding!!! We have a winner. I was going to use the grinding as a troubleshooting technique, not a as permanent solution. The rotor is going to be replaced.
Click to expand...
I often take a failed tool apart, not to fix it, but to find out why it broke and if the break was preventable.
 
A buddy rides his harley the same, 90% rear.
He gets his pads in packs of 3. They must be from china. He's on his 3rd set of rear pads this year already.
 
sburns said:
Ding Ding Ding!!! We have a winner. I was going to use the grinding as a troubleshooting technique, not a as permanent solution. The rotor is going to be replaced.
Click to expand...
To take off a ridge, I would use a file not a hone. If you are feeling extra lazy and this is right at the edge of the rotor, a light touch with a grinder on a spinning disc will turn the ridge into a valley in seconds.
 
You must log in or register to reply here.

Back
Top Bottom