Front Brake Rotor Drag

fulltime wrench
Edited Date/Time 5/3/2015 9:11am
The front rotor on my YZF drags the pads constantly. I can spin the wheel fast as I can but it comes to a stop in just a few seconds.

The rotor is a Galfer SKW with about 10hrs on it. Its not bent, I put the stock rotor back on to experiment and it also drags. If I pull the caliper off, the wheel is very free. It will actually bob back and forth as it slows down until the rim lock is bottom center. Pads have 20hrs on them and are in good shape. I resurfaced them with 180 grit sandpaper on a piece of glass, they are flat. Caliper pins are clean, straight, lubed and have very little wear. Pad pin is new. I flush my brakes every five hours so the system isn't full of goo. The rotor flange on the hub is clean and checked flat with a straight edge.

I saw a video a while back where Tickle's mechanic spun his front wheel and it kept spinning freely. I want my wheel like that.

Anyone have any tips or tricks to try before I order piston seals and possibly pistons depending on their condition?
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Jrewing
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Jrewing 4/30/2015 10:35pm
4/30/2015 10:35pm
Too much fluid in the reservoir? Mine spins all day.
fulltime wrench 4/30/2015 10:54pm
4/30/2015 10:54pm
Jrewing wrote:
Too much fluid in the reservoir? Mine spins all day.
Nope. Fluid level just below top of sight glass window, nice bubble with the cap on and tight.
Jrewing
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Jrewing 5/1/2015 3:04am
5/1/2015 3:04am Edited Date/Time 5/1/2015 5:57am
No dirt behind lever. I've had a tip over and had a tiny bit of dirt that stopped the lever from full return. The piston wasnt clearing the compensator port properly. Maybe aftermarket lever could affect it?
Pull backwards on the lever and see if the wheel spins better
markit
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markit 5/1/2015 5:42am
5/1/2015 5:42am
Jrewing wrote:
No dirt behind lever. I've had a tip over and had a tiny bit of dirt that stopped the lever from full return. The piston wasnt...
No dirt behind lever. I've had a tip over and had a tiny bit of dirt that stopped the lever from full return. The piston wasnt clearing the compensator port properly. Maybe aftermarket lever could affect it?
Pull backwards on the lever and see if the wheel spins better
Yea i had one of my KXs when I took all the slack out of the lever it would drag like yours.

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fulltime wrench 5/1/2015 7:33am
5/1/2015 7:33am
I removed the lever, still drags.

I'm thinking if I pull the pistons I will find crud packed up to the seal. The caliper is 10 years old with never a rebuild.

mb
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mb 5/1/2015 11:15am
5/1/2015 11:15am
I would take apart the caliper & grease everything up. Inspect for wear & replace parts if necessary.
mxtech1
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mxtech1 5/1/2015 1:30pm
5/1/2015 1:30pm
You need to be realistic here. Most factory bikes are running ceramic bearings throughout the bike, including the wheels. Ceramic bearings have an astronomically low amount of friction compared to the cheap, used, steel bearings found on your bike. I have worked on bikes with these bearings and the drag is incredibly low and the wheel will spin for a long time.

On a normal bike, a front tire should spin freely for 3-5 seconds before stopping. That is pretty good. It sounds to me that your bike is fine and you don't have any problems, you are just expecting to achieve a result that is unobtainable with your current parts.

It would still be a good idea to pull your pistons out to clean them and replace with new seals. You would be surprised how gunky they get even with good maintenance.

Another trick for a serious racer is to cut the metal spring out of the hub seals. This will allow the wheel to spin with less friction because the hub seal is not applying pressure to the axle, but I don't recommend this because it drastically reduces the life of the bearings due to exposure.
FGR01
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FGR01 5/1/2015 2:02pm
5/1/2015 2:02pm
I don't think he's being unrealistic. If everything is in proper shape the wheel should spin free. I get the impression he's smart enough to know when the brake is dragging more than normal.

It's possible the caliper mounting lugs on the fork are bent or the caliper mounting bracket itself is bent. I've seen both happen a few times. My buddy bent the mounting lugs a little by hitting the caliper on a rock on a left turn with a deep rut. He replaced nearly every damn part until he realized the lugs were bent. He ended up using a straight edge sanding stone on the mounting surfaces to bring them back into alignment.
fulltime wrench 5/1/2015 2:37pm
5/1/2015 2:37pm
Mxtech,

Thanks for the reply. I know I don't have a "problem", and I think I am being realistic. The wheel spins very free with the caliper off, 20 sec or so. Its not a matter of ceramic bearings or "cheap" steel bearings. The friction stopping the wheels rotation is not in the bearings, its from the pads dragging on the rotor. The dragging is excessive, and not normal.



Jrewing
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Jrewing 5/1/2015 3:43pm
5/1/2015 3:43pm
Thought I read you'd built the calipers. Yeah defs do that.
MaxPower
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MaxPower 5/1/2015 4:45pm
5/1/2015 4:45pm
Cut the spring out of the seal? Are you being serious? You are talking about a dirt bike not a bicycle used in time trials. Take those stupid seals out completely , you can save almost 12g of useless weight too
NorcalVet
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NorcalVet 5/1/2015 6:12pm
5/1/2015 6:12pm
Sort of off topic @ the OP

How's the skw OS rotor set up?
- thinking of ordering for my rm 250
- seems to good of a price vs performance?

Gonna order new pads also, probably sintered?
fulltime wrench 5/1/2015 6:36pm
5/1/2015 6:36pm
NorcalVet wrote:
Sort of off topic @ the OP How's the skw OS rotor set up? - thinking of ordering for my rm 250 - seems to good...
Sort of off topic @ the OP

How's the skw OS rotor set up?
- thinking of ordering for my rm 250
- seems to good of a price vs performance?

Gonna order new pads also, probably sintered?
I really like it. Fit and finish is nice and the bracket is machined well. Probably the best $135 I've spent on my bike. Stops my heavy ass steel framed YZF in a hurry, significantly better than stock. I coupled it with a stainless braided direct route line and yes I use sintered metal pads. The biggest difference it made for me was some right hand corners where I was having to use some rear brake to assist the front in slowing down. I could rely more on the front brake and leave the rear alone to get my foot up earlier and transition into the corner smoother.

I'm very picky with my brakes, especially the front, which is partly why I want to get the dragging eliminated. I flush them out all the time and I absolutely cannot ride someone else bike if their brakes are sub-par.
fulltime wrench 5/1/2015 6:44pm
5/1/2015 6:44pm
FGR01 wrote:
I don't think he's being unrealistic. If everything is in proper shape the wheel should spin free. I get the impression he's smart enough to know...
I don't think he's being unrealistic. If everything is in proper shape the wheel should spin free. I get the impression he's smart enough to know when the brake is dragging more than normal.

It's possible the caliper mounting lugs on the fork are bent or the caliper mounting bracket itself is bent. I've seen both happen a few times. My buddy bent the mounting lugs a little by hitting the caliper on a rock on a left turn with a deep rut. He replaced nearly every damn part until he realized the lugs were bent. He ended up using a straight edge sanding stone on the mounting surfaces to bring them back into alignment.
I must have missed your post. Thanks for the suggestion. The caliper mounting lugs are straight and square and the mounting bracket is new with the OS rotor without any crashes or rocky riding time on it.
NorcalVet
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NorcalVet 5/1/2015 6:46pm
5/1/2015 6:46pm
fulltime wrench wrote:
I really like it. Fit and finish is nice and the bracket is machined well. Probably the best $135 I've spent on my bike. Stops my...
I really like it. Fit and finish is nice and the bracket is machined well. Probably the best $135 I've spent on my bike. Stops my heavy ass steel framed YZF in a hurry, significantly better than stock. I coupled it with a stainless braided direct route line and yes I use sintered metal pads. The biggest difference it made for me was some right hand corners where I was having to use some rear brake to assist the front in slowing down. I could rely more on the front brake and leave the rear alone to get my foot up earlier and transition into the corner smoother.

I'm very picky with my brakes, especially the front, which is partly why I want to get the dragging eliminated. I flush them out all the time and I absolutely cannot ride someone else bike if their brakes are sub-par.
Thanks for the feedback
- now I have to order them tonight and some pads and enough left over for a read rotor and pads Cool
markit
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markit 5/2/2015 3:39pm
5/2/2015 3:39pm
MaxPower wrote:
Cut the spring out of the seal? Are you being serious? You are talking about a dirt bike not a bicycle used in time trials. Take...
Cut the spring out of the seal? Are you being serious? You are talking about a dirt bike not a bicycle used in time trials. Take those stupid seals out completely , you can save almost 12g of useless weight too
Yea im a serious racer so i take my seals out and run open bearings.
moto899ca
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moto899ca 5/3/2015 9:11am
5/3/2015 9:11am
MaxPower wrote:
Cut the spring out of the seal? Are you being serious? You are talking about a dirt bike not a bicycle used in time trials. Take...
Cut the spring out of the seal? Are you being serious? You are talking about a dirt bike not a bicycle used in time trials. Take those stupid seals out completely , you can save almost 12g of useless weight too
markit wrote:
Yea im a serious racer so i take my seals out and run open bearings.
I dont even run an air filter, those things just hold back air from making it into the engine. #seriousracersonly

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