Badly scored rotors

[headshrink]

I'm monitoring my brakes for the eventual service. I noticed my rotors are getting pretty badly scored, and when I was last at the dealer, the service manager said the rotors should be replaced..... that was 3K miles ago. They do look bad, I'm not questioning that, but this is also a slow time for my business, so I am looking into options. I hear you can get rotors turned-down by a machine shop, but neither dealer nor auto parts shop would admit to that. If I did find a place to do that, would the cost/benifit be that different than just slapping new ones on?

[kkim]

dunno, how much is a new rotor and what's the cost to turn them? pictures of you present rotor? there is a wear limit before you need to replace them, are you close to that limit?

[Snake]

It seems strange that the rotors would get that badly score with your bike being as new as it is. How many miles do you have on it?
Like KKim said price both options and you may want to measure how deep the scores are to see if you have enough rotor still left to turn.

[Banzai]

Unless you've got REALLY high miles, use brake pads like water over Niagra, got a rock stuck between the pad and rotor and embedded it into the pad, or have faulty rotors, chances are they're trying to get you to pay up for something that ain't at it's wear limit. ANYONE who says you're at your wear limit without at least measuring them and telling you what those measurements are is trying to steal money out of your pocket. At the very least, a micometer or a set of vernier calipers is necessary. Either or both can be had, with plenty enough accuracy for the average human, from Harbor Freight for under $20. I would suggest the digital calipers, as they have hundreds of uses (OK, maybe not hundreds, but you'll find them nice to have)!

Sorry if that comes across strong, but I absolutely HATE shops that think because it's a Ninja 250, and 1/2 of all Ninja 250 owners are new riders/first time owners, that they can just tell you to buy crap and you'll do it because you're too stupid or inexperienced to know better, especially high mileage bikes. Happens around here all the time, and they're just stealing money from the poor folks who just don't know any better.

Deep scores in brake rotors are normal, as long as they're relatively shallow and pretty much uniform and are not inhibiting breaking ability. Pictures would help us help you.

The front rotor new is 5mm, with a wear limit of 4mm. The rear is 5mm new with a wear limit of 4.5mm. Typically you measure across the shiny bright wear surface with the full jaws of a set of vernier calipers in at least 3-4 places to determine the overall condition of your rotors. This will give you a measurement to start judging the depth of the deepest scoring, but anything that falls into the category of "you could park a Buick in there" is too deep. Most anything shallower than that is OK as long as the high measurement is within the wear limit. You'd be amazed how bad rotors can look and STILL be within tolerance and FULLY EFFECTIVE, regardless of scoring.

Turning bike rotors traditionally isn't done. The way they're made, they're not turned. The blank is stamped out of the steel, then it's put on a surfacing machine, and then the edges are dressed, if necessary.

Unlike the lathe that is used to turn car rotors, the surfacer provides a solid surface on which to machine the part to ensure that it won't warp, and it also uses a different cutting method. You can, and most machinists will, get a bike rotor hot enough to warp it in any but the most expensive CNC lathes. Even then, it's a 50/50 shot due to set up errors in getting it perfectly set in the lathe. Been there, done that back when I had basically unlimited access to some of the best CNC equipment that the US Navy ever bought, and the best aviation machinists you can imagine. The best that a REALLY good machinist is going to do is about .002 run out over something as large as a dinner plate sized rotor, and that much error is enough to cause erratic braking as the centering of the brake caliper tries to compensate at high speed. Never mind the added friction and heat will degrade your brake fluid quicker, too.

They shouldn't be resurfaced again, either, because it alters the thickness of the entire rotor hub where it mounts to the wheel.

Basically, rotors are like pads, wear items. Use until it's at it's wear limit, and repalce.

Again, please post pictures and we'll help more. If you have access to a set of micrometers or calipers, you can measure them for yourself and, knowing the wear limits as stamped on the rotors, decide for yourself if it's time to replace them. Measure in several places around the rotor on the bright shiny contact surface (not trying to sound condescending, but I've seen service techs measure them wrong many times)

As for where to get them, I wouldn't trust anyone selling something on Ebay to measure correctly, as they have no vested interest in your safety once they have your money. I'd want to see them in person (or at least some damn fine pictures) before paying up any money. Oh, and be sure that they're flat, too. Simply dropping a tire/wheel assembly over onto something and it landing on the rotor is enough to warp it if it hits wrong (yeah, I'm responsible for that happening once, long ago, too, to another bike I owned), and for dang sure a wreck that totals the bike enough to part it out is enough, too!

Me, I'm not willing to play "Bet your life" on brakes to be penny wise and dollar foolish. My replacements, when necessary, are either going to come from a local wreck where I can inspect them for scoring and flatness, or new from on online vender.

[headshrink]

I have about 9,700 miles. Most are commuting miles 50/50 street/highway, utilizing engine braking where possible.

I just took a bunch of pics, and will try to post the best ones. I found it difficult to get good ones that accurately show the rotors condition.

First, the front rotor:








Now, the rear rotor:

[Alex]

Mine has looked exactly like that from very early on. If braking performance is fine, the rotor isn't warped, pad life is reasonable, and rotor thickness is over the wear limit, I wouldn't worry about it at all.

[kkim]

Originally Posted by Alex

Mine has looked exactly like that from very early on. If braking performance is fine, the rotor isn't warped, pad life is reasonable, and rotor thickness is over the wear limit, I wouldn't worry about it at all.

...but the service manager said the should be replaced!

[Alex]

Well in that case, break out the checkbook.

[headshrink]

Originally Posted by Alex

Well in that case, break out the checkbook.

I COULD do that.... but it wouldn't be worth the paper it is written on.

So I am fine then?



(I just noticed they typo in the title. Darn, I wish I could edit that)
- thanks to whoever took care of that.

[Banzai]

YES, you're fine. They look normal.

[randomwalk101]

that looks perfectly normal...dude you're rocking on 10K miles..let the b*tch wears out a little!!! hehehe..

btw, have you done a valve adjustment yet?

[headshrink]

Originally Posted by randomwalk101

that looks perfectly normal...dude you're rocking on 10K miles..let the b*tch wears out a little!!! hehehe..

btw, have you done a valve adjustment yet?

Supposedly it was inspected during the 7K mile service. They said it was fine, although one was very close to service limit and most likely would need to be done next time.