Rotor Rehab

[abe456]

My 99 r11rt has dreveloped a shudder in the front brake lever. Changed pads, cleaned the rotors with brake cleaner until they were shiny new looking. Of course, the shudder is still there. I'm betting it's bent or warped rotors. I dont own a dial indicator, so I can quantify the problem.

I hate to toss these rotors for new ones, local brake shop could not think of a way to accurately resurface the rotor faces.

I searched the posts on this issue, and results are not encoraging. Replace or live with it. Given the price BMW/GALFER wants, I will need some Obama bail-out money for a pair of these rotors. EBAY has a few rotors for sale, but before I do that:

Can anyone think of something else to try, given the rotors are headed for the recycle bin?

[GSAddict]

Stop at a machine shop and have someone put a dial indicator on the rotors before condemning them

[abe456]

Put a dial indicator on the rotors, sure enough, got 1 high spot on right rotor, 1 questionable spot on left rotor.

So I bought a right rotor off Ebay, when it arrived it was obviously worn out and way too loose. Back to the seller.

I found a machine shop that can mill and machine the rotors, I was wondering if anyone else has done this. I've heard the rotor faces are heat treated to resist wear, and milling them may not work.

Please help Mr. Wizard!

[rvbeemer]

Go to a machine shop that has a surface grinder. Ask them if they can grind your rotor(s) if you take them off. Do not grind them under the given min. thickness stamped on the rotors. That is really the only way to do what you want to do. Good luck!
Ronnie

[MotorradMike]

Hi Abe:

I stopped resurfacing rotors on my cars because it didn't last all that long and the aftermarket rotors got really cheap.

I've never heard of anyone surface grinding rotors. I suspect it will result in pulsing brakes due to the linear grind pattern but what do I know. Rotors are usually done on a lathe.

Check out aftermarket parts from EBC. Folks on this forum have tried them and you could do a search on EBC.

[breyfogle]

You could also check with BeemerBoneyard for used rotors.

[PGlaves]

Hi Abe:

I stopped resurfacing rotors on my cars because it didn't last all that long and the aftermarket rotors got really cheap.

I've never heard of anyone surface grinding rotors. I suspect it will result in pulsing brakes due to the linear grind pattern but what do I know. Rotors are usually done on a lathe.

Check out aftermarket parts from EBC. Folks on this forum have tried them and you could do a search on EBC.

The last time I had (car) rotors refinished it was done on a machine that both turned the rotor and spun a flat grinding stone too. Everything was spinning around. The finished surface had no real discernible pattern other than some very fine swirl marks all over it. This was at a brake specialty shop.

I am doubtful that you will get a satisfactory result attempting to refinish BMW OEM rotors. By the time they are smooth and true they are usually too thin.

[abe456]

Ok, I wont pursue refinishing the rotors. I think PGlaves has a good point, it prolly just won't get the job done.

EBC has rotors that will fit this model (99R1100RT) available on the net for $150 bucks plus shipping. I ran a search of posts and didnt find anyone who has tried these.


So......anybody out there have experience with EBC rotors?

[breyfogle]

So......anybody out there have experience with EBC rotors?

In a somewhat different application, I put a set of new EBC rotors on my K75S a year ago. My experience makes me question EBC's quality control. For a K75, the EBC rotors come pre-mounted on new carriers. When I installed the new carrier/rotors, neither side ran true which resulted in a very pronounced frontend shudder anytime the brakes were applied. To EBC's credit, they did replace one of the two new rotors free of charge. The frontend shudder is much reduced but still noticable. Good enough for a 20 year old commuter bike. If I had to replace the rotors on my R1100RS any time soon, I would probably not choose EBC as a first choice. Your results may differ.

[abe456]

Well dang it. I just cant get there from here. Guess I will have to become an EBay lurker (again) and try to find a good pair of used ones.


Thanks for the advice, at least I know what my real options are now.

[rvbeemer]

Hi Abe:

I stopped resurfacing rotors on my cars because it didn't last all that long and the aftermarket rotors got really cheap.

I've never heard of anyone surface grinding rotors. I suspect it will result in pulsing brakes due to the linear grind pattern but what do I know. Rotors are usually done on a lathe.

Check out aftermarket parts from EBC. Folks on this forum have tried them and you could do a search on EBC.

Mike,
The rotors on a car are made of cast iron, therefore they are turned on a brake lathe. Motorcycle rotors are made of steel. They have a tendendcy to get very hard due to heat plus the fact that they are very thin it is hard to turn them in a lathe as both sides need to be turned at the same time to stay concentric. Grinding is the only logical way to renew steel rotors if a person chooses to renew. How do I know? I've been working as a machinist for over 30 years. I have ground rotors , flywheels and such on a surface grinder before with excellent results. As I told Abe, watch the thickness. I don't recommend this for warped or bent rotors but for worn or galled rotors it'll get you by in a pinch or if your cheap. Personally, I buy new ones.
Ronnie

[MotorradMike]

This thread has doubled my knowledge on brake rotors. I've often wondered at the thickness of my BMW rotors. The Yamaha has thick rotors.

Anyway, thanks all. I hope Abe got out of it what he wanted.

I am pretty frugal but I'm willing to spend whatever on brakes.

[PattiB]

I just had a complete front end brake job on my R1100R and the pads, rotors and labor came to almost $800!!!!!!!!!!!! The rotors were EBC's and you have to always use their pads as replacements according to the warranty. I was considering upgrading to the Spiegler SS brake line kit but that would have added another $230 not to mention what the labor $229 would have been.

You might want to see if Re-Psycle can help: www.re-psycle.com/ they might have something slightly used or even new. They are very helpful and friendly and contact you right away...:thumb

Patti B
R1100R '00
F650 '99

[abe456]

A friend of mine runs a machine shop, has a huge lathe with a fixture that the rotors bolted on with no problem, no eccentricity or wobble. The lathe is used for turning flat, thin rotary plates for Bridgestone Tire and other companies. When I left the shop they were running a laser check for highspots. They have the tools to level the surfaces and fininsh the surface with a rotary stone, and sprays to keep the rotors cool. Best of all, no charge if they cant succeed.

Who knows, may have found a way to have these rotors turned true after all. Will post results in a day or two. If it works, I'm quittin' my day job and starting a "Rotors R Us" business.

[GSAddict]

A friend of mine runs a machine shop, has a huge lathe with a fixture that the rotors bolted on with no problem, no eccentricity or wobble. The lathe is used for turning flat, thin rotary plates for Bridgestone Tire and other companies. When I left the shop they were running a laser check for highspots. They have the tools to level the surfaces and fininsh the surface with a rotary stone, and sprays to keep the rotors cool. Best of all, no charge if they cant succeed.

Who knows, may have found a way to have these rotors turned true after all. Will post results in a day or two. If it works, I'm quittin' my day job and starting a "Rotors R Us" business.

That sounds like it would work but what about the minimum thickness specification?
Not much extra meat on those rotors.

[Motowalt]

give a call to framestraight.com
They may be able to straighten your rotors if they are bent/warped.
They did a pair for my Duc a couple years ago and didn't charge that much.
May be worth a try.

[abe456]

Machine shop could not mount the rotors on the lathe with minimal eccentricity. We discussed developing an arbor fixture that would hold the rotor exactly concentric with radius from center. They are willing to develop an arbor fixture to do this, provided I pay them a $500 setup fee.

They also noted from close material examination that the rotors are likely surface hardened. Their metallurgy engineer says surface hardening techniques vary widely, but could account for the high spots from non uniform wear if the surface hardening is not properly applied.

They have carbide cutting tools which can shave the rotors to extremely close tolerance, with a cooling bath to avoid heating the rotor. This would mean, tho, that some or all of the surface hardened metal would likely be removed. No way to tell without destructive examination. They do not have the means to re-apply surface hardening in any sort of uniform manner. Whether or not the shaved rotor needs surface hardening is a good question.


So that's it, doesnt look like re-furbish is a good option at this point. But i had fun chasing this down, and learned a few things.

[abe456]

Got 2 rotors off Ebay for $100 bucks and shipping. Braking is smooth as a baby's butt. But I wish there was a way to refurb these rotors. It just dont make sense to toss them in the scrap pile.