I'm getting an excessive shaking or shimmy when I apply the front brakes, I suspect it's a bent or warped rotor, Any suggestions on how to determine which one?

 

Get the wheel off the ground,with a flashlight watch the brake pads as you spin the wheel. The warped side will move the pads back and forth. I'd replace both rotors though.

 

Thanks

 

Remember to use brand new rotor bolts when you replace those warped rotors.

 

Rotors just don't up and warp. Maybe a sticking caliper piston caused it.

 

If your bushings on the front forks a loose or worn will cause the same issue during breaking.

 

I'll sell you the low miles, true take-offs from my 09 SG for $25 plus cost of shipping.

Jef

 

Of course it's best to jack it up and use a dial indicator to check the runout. I find I can feel it when it's over about 3-4thousandths, Harley says 8 is the replacement threshold which is just ridiculous. When you say "Shimmy" do you mean like an up and down "bucking" or a left to right "wiggle"?

 

A test to rule out the fork bearings is to get up to a good speed, lightly hold the bars and just let off the gas, don't brake and decelerate with the engine, thus shifting the weight to the front of the bike. If you get a good shimmy without applying the brakes it's most likely the fork bearings.

 

You don't say how many miles are on those rotors but before I replace anything I would sand both sides of the rotors with some light sandpaper and then wash them with warm soapy water. If they still "grab" I would rub them down with some aerosol brake cleaner and a rag to make sure I got all the crud/rust off the metal rotors.

If what you are describing as a shimmy is not "grabbing" of the rotors by the brake pads, then your fork head bearings may be loose and causing the wobble. If this is the case, then you can perform what is known as a "swing away test". For this you will need a lift in order to raise the front wheel off the ground. It is described in the service manual.