Turning Brake Rotor?

Hey XJers

Sorry this might be stupid question...but I noticed that my front brake rotor is pretty rough. Seams like a lot of grooves compared to any car rotor I've seen. Can you get these turned or is it better just to get new? Thickness? If you can turn them, do you have to take them to a motor cycle shop to do so? I have new pads to install, so I thought I would take care of this as well.


Thanks in advance for any help!

Louie

 

not enuf thickness to turn out right in my exprience. just get new ones

 

They can be turned down, but the amount they remove will more than likely make the rotor too thin and it will warp as soon as it gets too hot.
I had one turned down and it was successful only because the grooves were not very deep. I noticed some of the grooves were still in the rotor, but less pronounced after it was done, but it looked a hell of alot better.
I would take a rotor to an automotive shop that does car rotors and see if thye will do it (mine did) and the worst that can happen is it will heat up and warp eventually. Worth a try.

 

Thanks for the info! I appreciate it.

 

I was able to turn mine down. I used to work as a tool and die apprentice and used the shop equipment. The process is involved - here's how I did it.

Centered it up in the chuck - of course.
Slow RPM's with a rounded lathe bit.
I had to put base electromagnets all around the back of the rotor to give it some weight and keep it from chattering.
Lots of oil.

It takes constant adjustment of the magnets to keep the rotor from chattering. I had good results but the setup was elaborate.

I would not suggest doing it and I wouldn't do it again.

 

Thanks Fraps. My brother works at a shop and said he would try it for me.

 

Taken from the XJCD repair manual for the 650

Maximum deflection: 0.15 mm ( 0.006 in )
Minimum disc thickness: 6.5 mm ( 0.26 in )

The section on the 750 gives the same deflection but allows minimum thickness down to 4.5 mm ( 0.18 in )

I could not locate any information on turning the disc

 

You don't really need to turn them just to clean them up. I used a sanding disc in my electric drill to polish mine up. It will take off groves if they aren't too deep but be careful not to take off too much in one place because you want the whole surface to be smooth when you're done.

 

Replacement is the recommended solution. Not cheap. Look for some good used ones at the local bike yard or Flea-Bay.

 

I was told that they CANT be turned on a lathe.. Not because of the thickness, but the material. The rotors are some sort of hardened steel alloy, which is much harder than the iron which makes up regular car rotors. If you put them on a lathe it will destroy the bits (which the machinist won't be too happy about), AND chew up the rotor. If they really need to be resurfaced (ie. has grooves that are deeper than you can scuff out with a whizzer wheel), you need to take them to a shop that has a flywheel grinder. As long as the rotor is mounted true on the turntable, (and the grooves dont go real deep) you will end up with a factory-finished rotor, and it only grinds a few hundredths off.

 

A good machine shop that can surface flywheels can also resurface those discs. I wouldn't use a grinder or drill as you might cause your brakes to grab unevenly

 

I had mine done at a machine shop. They used a flywheel resurfacer to take off a minimual ammount. They were still within specs, it was a great improvement. The guy that did mine was familiar with them, he said they were similar to his race car rotors.

 

As above flywheel grinder BUT there is a problem These are not very magnetic (hard to hold) And the shops charge same price as having a Flywheel resurfaced.. $50 in my world For EACH side.
Making aftermarket replacements like those from Mikesxs.com seem a bargain.

 

As the saying goes: "You're damned if you do; and damned if you don't!"

If you have to Turn the Rotor, its likely that you be right on the edge of thinness and highly susceptible to warping the thing in short order.

I'd do as ArizonaSteve suggests. Sand down the roughness.

If you can find a gut at an AutoBody Shop that will "Clean-up" the face of the Rotor with a Dual-Action (D-A) Sander ... you'll spare the Roror from need to be cut.

Otherwise ... I'd suggest you pop for a NEW Rotor or two. Those Front Brakes are where you place your life every time you kick-up the sidestand and go someplace.

Having FAITH in your Brakes is the Most Important consideration to deal with. Pay the money for a new part.

Stay away from the worry that you can't rely on the brakes when you really, really need them!

 

Thanks guys for all of the input. I appreciate it!

Louie