Rear Rotor Decision

[DeanR]

My rear brake rotor now has a pretty good ridge on its edge. Thickness is now 6.12 mm (6.0 mm is minimum, 7.46 mm new)
Option 1 - new OEM $350 at Amazon … wow
Option 2 - new EBC $110 at Amazon
Option 3 - used OEM which I think I took off a spare wheel a number of years ago, 6.47 mm Looks to be in ok shape but I’ve not used it.
Option 4 - used EBC (I think) 7.42 mm but has a pronounced groove on one side. I think I took that off a spare wheel as well. See picture
or
I could pull the wheel off the other ST, rotor at 7.16 mm. Both wheels will need new tires anyway. Not sure if final drive splines would be an issue when swapping wheels between bikes. I suspect not. Both final drives and both spiders should be in great shape.

Leaning toward the used OEM but the EBC is a lot thicker. Or just get a new EBC as long as people have had ok luck with them. Or any other thoughts on rotors?

I always use OEM pads.

Rust should clean up but sure makes for ugly close up pictures!

 

[Larry Fine]

Option 5 - stop using the rear brake.

Seriously, I would vote for Option 3.

That rotor in Option 4 is chewed up.

 

[jfheath]

Note that front discs with new OEM pads do not have much room for anything else. If discs are thicker there may not be room in the caliper. Its probably not an issue but you may want to find out.

 

[ToddC]

What did you do to those rotors...?

 

[Larry Fine]

What did you do to those rotors...?

Whatever he used, it has the reverse profile of the rotor's surface.

It might look something like this:

 

[DeanR]

What did you do to those rotors...?

Nothing Todd. It was acquired, not mine. Been sitting on a shelf.
Both pictures are of the same EBC rotor. Sorry about the picture size but posting just thumbnails never seems to work..

Option 5 - stop using the rear brake.

I don't use a lot of rear brake. My wear is from 100k + miles.

 

[kiltman]

I got one off of eBay from China. Very happy with it.

 

[Larry Fine]

Sorry about the picture size but posting just thumbnails never seems to work.

After you enter each pic, you can click on it and drag corners to resize.

 

[rwthomas1]

Option 3! The price is right!

 

[dwalby]

If you have them all in possession, which is what I think you are saying, I'd go with the EBC with the gouge in it and sand the gouge out. I don't think those rotors are very hard, so I'd mount it on the wheel, get an orbital hand sander and sand the surface smooth. That gouge isn't very deep, I think it would probably sand out fairly easily, and you'd end up with probably something in the 7.2-7.3mm thickness range when you were done.

I can't remember the details, but I seem to remember having to touch up a rotor decades ago on either a car or bike and it sanded quite easily as I recall. Or, I'm just getting old and dreamed it.

Its worth a try because it will only take a few minutes to see how quickly the surface is (or isn't) being cleaned and with a hand sander it should be flat enough when you're done. The pads will bed in to take up any imperfections anyway.

edit: on second thought, no need to mount it on the wheel before sanding it, and that would keep the wheel cleaner as well. Hard to tell from the pictures how deep the groove is, one pic looks pretty shallow, the other looks a bit deeper.

The 6.47mm OEM would also be usable, but its 2/3rds worn out. Depending on how much you use the rear brake that could still last a long time.

 

[Upt' North]

The old OEM seems to have plenty of life left in it. Why wouldn't you.

 

[RobbieAG]

The OEM without grooves.

 

[ST1100Y]

What did you do to those rotors...?

23 years of fun... ?

With that in mind I'd opt for the OEM thing... it was well worth it's money and the new will again serve 2 decades...

 

[dtcoleman]

Hey Dean.
Maybe reach out to Uncle Phil. He must know a (or some) sourse(s) for 1100 parts. Worth a shot.
FYI. I wouldn't attempt grinding or sanding out the grooves like suggested. Apparently rotors on motorcycle should not be turned. Just replace.
My 2 cents.
Dave

 

[dwalby]

FYI. I wouldn't attempt grinding or sanding out the grooves like suggested. Apparently rotors on motorcycle should not be turned. Just replace.

The main reason motorcycle rotors aren't typically turned is there's not much metal to remove before they're at their wear limit, so there's little practical reason to do so. I suspect there's also the consideration of needing a special mounting fixture to attach motorcycle rotors to a lathe, probably a different one for each bike, and nobody makes them in the first place. Sanding the metal away isn't really all that different from what the brake pads are doing, its just doing it faster.

here's a video of a guy who does it with a drill press, jump to about 14:00 to watch his technique. I think as long as you're not too heavy-handed in one particular area and make sure you keep the surface thickness even all around the rotor, its possible to clean one up.

 

[DeanR]

23 years of fun... ?
With that in mind I'd opt for the OEM thing... it was well worth it's money and the new will again serve 2 decades...

Yea, but I won't !

here's a video of a guy who does it with a drill press, jump to about 14:00 to watch his technique.

He never really showed doing the rotor surface imperfections, was mainly interested in making them all nice and shiney.
I'll likely go with that used OEM, and see how it behaves on the bike. Probably won't make it shiney though.

 

[dwalby]

I'll likely go with that used OEM, and see how it behaves on the bike. Probably won't make it shiney though.

yeah, that's the quickest and easiest, and as long as it isn't warped or pulsating you're done. Still has enough meat on the bone to last you a while.

I'm curious as to how easy it would be to flatten out the groove in the EBC though, as a purely academic pursuit. And its useless in its current form anyway so there's nothing to lose.

 

[Beeflips]

The main reason motorcycle rotors aren't typically turned is there's not much metal to remove before they're at their wear limit

I had mine ground on a grinder with flood coolant, still flat within .003, I think .012 is the max spec.
If it's ground (which I would recommend over turning) you have a lot more control and can sneak up on it more accurately.
Thin materials must be kept cool when machining whether grinding or turning, or it will warp all over.
I'll check my thickness once, can't remember the exact number. And I'll try to get a couple of pictures on here.