Brake rotor machining + replacement

wheel_of_steel

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My rotors are quite worn, grooved, and have a lip on them. I'm in the research phase for replacing them and thought I would share my findings and see what others have done.
  • Nobody wants or is able to machine them. I contacted a bunch of bike, car, brake, and machine shops. Being a weird shape, automotive brake lathes can't do it, and machine shops don't consider it financially viable to make the necessary jigs to either lathe them or use a milling machine to grind the surfaces.
  • For replacement, you have four main options (prices in AUD). Genuine is $512, brembo series oro is $280, a secondhand item is $165 from a wrecker, and a chinese ebay item is $100.
So for those of you who have replaced your rotor(s), what did you do? I don't trust that an ebay rotor will be particularly safe or resistant to abuse.
 

670cc

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I don’t know the exact numbers without measuring, but it‘s my understanding that the original rotor thickness compared to the minimum thickness service limit (which I believe is stamped on the rotor) does not allow for significant machining to be done.

I was in need of a replacement front rotor for my NC700X. I explored options. I found and bought a used OEM rotor on eBay, probably from a salvage operation. That used rotor performs flawlessly and is still in use.
 

itsmenc700

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I am strongly in the dont machine rotor camp.
If when I am replacing brakes on my cars, I do all my own brake work, the rotors look a little squirrely, I just replace them.
It costs about the same or less, and much less hassle.
Having said that - how many miles do you have on that rotor for it to need replacing?
 

MZ5

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My rotors are quite worn, grooved, and have a lip on them. I'm in the research phase for replacing them and thought I would share my findings and see what others have done.
  • Nobody wants or is able to machine them. I contacted a bunch of bike, car, brake, and machine shops. Being a weird shape, automotive brake lathes can't do it, and machine shops don't consider it financially viable to make the necessary jigs to either lathe them or use a milling machine to grind the surfaces.
  • For replacement, you have four main options (prices in AUD). Genuine is $512, brembo series oro is $280, a secondhand item is $165 from a wrecker, and a chinese ebay item is $100.
So for those of you who have replaced your rotor(s), what did you do? I don't trust that an ebay rotor will be particularly safe or resistant to abuse.

With that particular choice set, the only thing I would personally NOT do, is the Chinese FleaBay one. I doubt I could stomach over $500 for a Honda rotor, so I'd probably go with the Brembo or the used one. YMMV.
 

wheel_of_steel

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I am strongly in the dont machine rotor camp.
If when I am replacing brakes on my cars, I do all my own brake work, the rotors look a little squirrely, I just replace them.
It costs about the same or less, and much less hassle.
Having said that - how many miles do you have on that rotor for it to need replacing?
  • My bike has 40k miles on it and has just worn out its third set of sintered brake pads (oem, EBC, vesrah). The brakes have been used hard, it was an instructor bike doing lots of emergency stops, and then it did about six track days after that.
  • I found an italian website called carpimoto that sold me the pair of front and rear brembo rotors for 255 AUD shipped. I have gone with this option and will be trying a new set of newfren organic touring pads front and rear.

The back story
  • I noticed around 12k ago that the rotor had quite a lip on it, so I wanted to move away from sintered pads and switch to organics.
  • I replaced the ebc HH pads (nice bite, but notorious for chewing rotors) with some vesrah "organic" pads. Actually the seller incorrectly listed the vesrah VD-172 pads as organic, when they are in fact sintered. I didn't cross-reference the part number to vesrah's website so it's my fault for not checking. The correct part number for vesrah organic front pads is SD-172.
  • According to my rubbish calipers, the rotor is down to 4mm in the swept area, with grooves penetrating deeper than that, and the lip at the edge of the rotor is about 4.4mm. Minimum thickness is 4mm. New spec is about 5.2mm.
  • Machining the stock rotor would be a nice way to support skilled local labour instead of just importing manufactured goods. But in this instance, it's just not viable to pursue that path.
  • I don't mind paying $50 for a used consumable, but after doing a national search, $165 for a used rotor was the best price I could find. I think that's quite poor value for money.
 
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New Commuter700

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Wow, I'm shocked. I had not priced them before. It's like I told the salesman when I bought the bike, bikes are more expensive than cars despite having half the wheels. That said I will probably be replacing mine next year and I'll probably go with the Galfer rotors.
 

Janus

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Wow, I'm shocked. I had not priced them before. It's like I told the salesman when I bought the bike, bikes are more expensive than cars despite having half the wheels. That said I will probably be replacing mine next year and I'll probably go with the Galfer rotors.
I still haven't spent enough on my NC to get a subcompact economy rollerskate. Even if I include my top tier kit as an exclusive expense just for the NC and not my other bikes too.

I also get better mileage and enjoyment out of the bike. I would never roll down the PCH in a Chevy Aveo! Or any Chevrolet tbqh
 

brb

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Sintered pads are what most MFG are using now because they develop more heat(friction) that gives more stopping power. The down side is the wear to the rotors that should not be machined because the thickness of the rotor is what allows it to absorb and dissipate that heat without warping. Most will agree that factory parts are higher quality than aftermarket but that price point can be steep. Aftermarket(generic) rotors has to meet the same req. as stock. I am sure most of your cars have replacement rotors(china) that stop fine so why not your motorcycle are we that vain. I have used 2 sets of factory pads and 1 set of EBC sintered to date, front & rears approx 15K each time. My next brake job will include new rotors front and back from Amazon with some organic pads. Using organic on past bikes I noticed that the lever felt like power assist and did not need to warm up and riding in the rain they were superior.
 

throttlegirl

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My front rotor was also worn down, grooved, with a lip. I replaced it with a SFS brand sold on Amazon for 82.00. Shipped from Turkey. Installed before our cross country trip and have had no issues. 90,000 miles and a daily commuter so I assume that was what caused all the wear on the original. Figured I'd give the cheaper one a try first before going OEM and happy I did so far. That OEM price almost knocked me off my chair when I saw it, lol!
 

dduelin

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Everyone is different in how and where they ride. Both my NCs at 30,000 miles were on original pads and rotors, no where near replacement.
 

670cc

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Everyone is different in how and where they ride. Both my NCs at 30,000 miles were on original pads and rotors, no where near replacement.
Right. I’m at 47,000 miles, and original front and rear pads are only half worn.

The front rotor required replacement because I apparently, accidentally bent it ever so slightly doing a tire change.
 

Janus

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I had to replace my rear pad around 36000 miles, but I dragged my rear a lot in heavy traffic and used it exclusively while coming down my steep driveway. Shop said the front pad looked brand new, rotors were fine.
 

mrbios

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I have been "machining" rotors for years with an angle grinder. I use it to knock down the outer lip and sometimes a little on the inner lip. Next, I've had good luck lightly "wiping" the main part of the rotor with the side of a think cutting disk on an angle grinder to dull the finish and counteract the record groves. You can safely go a little below the mm limit stamped in to the rotor if you mainly do normal riding vs aggressive braking from hard riding.

I have never heard of mc rotors are ever resurfaced on a brake lathe. NC's have low maintenance costs and only a single rotor I don't see spending $300 ever 40K miles or so for a new front rotor as a big deal.
 

showkey

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Sanding or grinding the rotors is a really really bad idea.

Total indicated run out measured witha dial indicator is .012”. So excessive runout will cause pulsating and brake shutter or shudder.
Thickness variation in the disk is a missing specification in the manual but is usually about .002-.004” total variation.

Those allowable runout numbers are very low when it includes mounting and wheel runout as the rotor is mounted to the wheel. It the reason it’s easy to “bend a rotor“ even slightly out of spec while changing a tire can happen. So hand grinding is not going to work !! Also Honda motorcycle rotors can not be cut on lathe. They are very hard alloy and there is very little “meat” to cut or machine grind.

Most NC and other Honda bikeswill never need a rotor service or replacement in 100k of normal use.
 

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