Turning rotors

[tradeshowjoe]

I had some input from a mechanic friend of mine that I can not get my rotors turned. However, I noticed Miriam Cycles has the ability to turn motors on their web page. Just looking for some solid advice on this simple matter. Thanks.

[Jerry]

Most auto shops cannot turn motorcycle rotos. MC rotors are a harder material. I had luck taking mine to a machine shop that could work with them. Cost was $30.00 for a pair.

Shop manager said they used a large precision grinder for the work, not a lathe as is common in auto applications.

Tolerance for the rotors is quite small...don't have the number handy, but is only about +- .004. If your rotors are quite warped, turning or grinding them will reduce them below the minimum thickness, meaning you will have to replace them.

Keep in mind that you should remove the same amount of material from both sides of the rotor. .002 per side isn't much!

Try yellow pages under machine shops. Some will have a setup charge then a time charge, others will quote you a flat hourly rate. Shop did mine in about 30 minutes on a flat hourly rate.

[Robert Haller]

You can also keep your eye on ebay. Rotors show up there from time to time. I got a good set cheap that way.

[sixtysix]

The XS rotors are very close to minimum specs when new, almost any rear disc you will find is out of spec from wear already. I had a couple of rotors turned by a machine shop, they actually turned them and it left a kind of rough finish, I sold the bike a year ago and just looked at it yesterday, the rotors feel smooth but still have lines in them. Seem to be OK though. The proper procedure for turning an XS rotor is to surface grind it, from what I am told. There are also new (floating) rotors out there for sale from EBC but they are like $200 each or something rediculous.

[JP]

Originally posted by Jerry
Tolerance for the rotors is quite small...don't have the number handy, but is only about +- .004. If your rotors are quite warped, turning or grinding them will reduce them below the minimum thickness, meaning you will have to replace them.

Keep in mind that you should remove the same amount of material from both sides of the rotor. .002 per side isn't much!

You're right. A sheet of notebook paper is about .005-.006" thick. ONE sheet.

[xExcessive 1120]

Turning Rotors

In following availablility of parts on eBay for XS & FJ1100s, the going price for a good set of rotors is often less than the price of turning. In 44,000+ mi on my Ist 79 XS100F, I had almost no noticeable wear on the front disks, and I use my front brakes hard. xExcessive 1120

[Bill__Woods]

Hello,
I am an auto mechanic by trade. I have machined some rotors (on an ordinary brake lathe) off my friends xs750 special. they turned out fine. I have a drill atachment with flexible fingers with stones on them, it is made to put a non-directional finish on rotors after machining. Gringing is the prefered way to machine rotors or flywheels.
good luck on your bike, and brakes!

[rockyr74]

The flywheel comment is dead on. Find a shop that grinds flywheels and they can probably do your rotors too. I can imagine that turning hard slotted rotors with a lathe would be very tough on the bit.

I'm not in agreement about taking the same off of both sides - I don't see what difference it would make since they are single plane - this is more important on dual plane car rotors. I do agree that both sides need to be kissed to make sure they remain parallel.

Sometimes a kiss is all a rotor needs to stop pulsating or grabbiness. Forget about removing grooves or straightening perceptable warp - not enough meat - buy used ones.

New rotors are "stupid money" expensive - about 160 ea.

If anyone comes up with a vendor that does mail away rotor grinding, post to this list - I am sure he will gets lots of business.