New or used brake rotor?

[beemuker]

My front brakes pulse and I have determined my left front rotor is slightly warped. Looks like a new one [EBC] is about $200, and used ones on fleabay go for 60-100. Is there a problem with having one new and one original? The bike has very low miles [14k] . advice?

[Chaos]

The EBC's have a different look to them so aesthetically that may be a problem. 

[The Mighty Gryphon]

I replaced one of the front discs on my K75RT with a used one, and 20,000 miles later it is still working well. 

I don't know if it really makes any difference, but using a good used disc will have both discs more uniform in hardness, thickness, stopping power, and, yes, appearance.

As long as it isn't warped or thinner than spec, I would have no problem installing a used disc.  I use organic kevlar pads so disc wear is minimal.  This allows me to use discs that are near to the service limit in thickness and still get acceptable longevity out of them.

[Martin]

I have successfully straightened warped discs. We are talking minor warping not major buckles. If you don't have patience and restraint read no further and get another disc. :nono Be warned it is a slow process requiring lot's and lot's patience and a delicate touch, and only works on solid rotors not floating ones. Set the bike up so the front wheel is off the ground. You need to remove the calipers and attach a dial gauge indicator (DGI) with whatever you can rig up solidly to the top caliper retaining bolt. It needs to be set up so it runs on the outer most edge of the disc, and can be rotated away from the disc when adjusting the warp. This will only work if the disc has a smooth track to run on, if it doesn't forget it. With the DGI set up to run on this track rotate the disc a determine where the warp is and how big it is and mark with a pencil this part will be repeated after each adjustment. To remove the warp you will need a piece of  broom handle 10" - 12" long and a plastic hammer. The next bit requires patience and a delicate touch. Rotate the DGI so it is clear of the disc and place the end of the broom handle on the outer most edge of the disc carrier (not on the disc) where you marked the position of the warp, and tap gently with the plastic hammer.  If the warp is bulging out from the centre you need to tap it in. If it is bulging in need to tap it out. When tapping it out, the broom handle will be running at an angle this is the reason for it's length. You need to realign the DGI after every tap and check that you have moved it and by how much. Under no circumstances belt it or hit it hard, you will eventually get a feel as to how hard to tap it believe me it won't be a lot. Hitting it hard will only push it too far and will require you to tap it back the other way. You need to avoid tapping it to and fro, this will happen occasionally but needs to be reduced to the minimum. You are aiming for a figure under .007", well under this can be achieved with patience.
Regards Martin.

[Chaos]

This opens a whole realm of possibilities.  One disc could be optimized for cold or wet stopping with cast iron disc and organic pads, the other for racetrack conditions with a carbon fiber disc.  Best of all worlds! :clap:

[beemuker]

I have successfully straightened warped discs. We are talking minor warping not major buckles. If you don't have patience and restraint read no further and get another disc. :nono Be warned it is a slow process requiring lot's and lot's patience and a delicate touch, and only works on solid rotors not floating ones. Set the bike up so the front wheel is off the ground. You need to remove the calipers and attach a dial gauge indicator (DGI) with whatever you can rig up solidly to the top caliper retaining bolt. It needs to be set up so it runs on the outer most edge of the disc, and can be rotated away from the disc when adjusting the warp. This will only work if the disc has a smooth track to run on, if it doesn't forget it. With the DGI set up to run on this track rotate the disc a determine where the warp is and how big it is and mark with a pencil this part will be repeated after each adjustment. To remove the warp you will need a piece of  broom handle 10" - 12" long and a plastic hammer. The next bit requires patience and a delicate touch. Rotate the DGI so it is clear of the disc and place the end of the broom handle on the outer most edge of the disc carrier (not on the disc) where you marked the position of the warp, and tap gently with the plastic hammer.  If the warp is bulging out from the centre you need to tap it in. If it is bulging in need to tap it out. When tapping it out, the broom handle will be running at an angle this is the reason for it's length. You need to realign the DGI after every tap and check that you have moved it and by how much. Under no circumstances belt it or hit it hard, you will eventually get a feel as to how hard to tap it believe me it won't be a lot. Hitting it hard will only push it too far and will require you to tap it back the other way. You need to avoid tapping it to and fro, this will happen occasionally but needs to be reduced to the minimum. You are aiming for a figure under .007", well under this can be achieved with patience.
Regards Martin.

Patience and restraint were in short supply when I was being incubated, so I think I may take my chances with a used one. But I'll go have a look at it again and see if I can measure how far it's out.

[Martin]

Beemuker old saying softly, softly catchee monkee. Or the earth is slow but the oxen is patient. :dunno :hehehe
Regards Martin.

[Laitch]

My front brakes pulse and I have determined my left front rotor is slightly warped.

How did you determine that?

[Filmcamera]

Maybe get a used one for now and add two new EBC ones to your wishlist on Amazon. I did that and when I added them the price was $196 each but by checking weekly I managed to get them for $86 each when someone wanted to get rid of some old stock.

[beemuker]

How did you determine that?

I held a stationary object [screwdriver]  close to rotors and rotated the wheel.

[Laitch]

I held a stationary object [screwdriver]  close to rotors and rotated the wheel.

You hold it with your teeth or clamped in a toolbox?  :giggles

[Martin]

Picture of extremely expensive 20 year old BMW disc alignment tool pat pending.
Regards Martin.

BMW rotor alignment tool.jpg (60.89 kB . 768x576 - viewed 296 times)

[rbm]

Part number, Martin?  Want to search the Max BMW catalog. :hehehe

[Martin]

Sorry Rob they are no longer available. The very special wood they were made from comes from a protected species of tree, and it is now illegal to harvest them. I do however have the remaining length of this extremely rare timber, and I could be persuaded to part with a piece if the cash incentive is large enough. There is also a deluxe version available covered in heat shrink, however this is even dearer, as the heat shrink that is used comes from the intestines of the extinct Thylacine. There is however some hope as there have been reports of Thylacine sightings up north, the sightings are unconfirmed and we won't have verification until somebody shoots one.
Regards Martin.

[beemuker]

you guys have way too much time on  your hands

[Laitch]

you guys have way too much time on  your hands

Welcome to the club!