We have a set of race rotors with slight vibration and I was wondering if we have the capability to turn them on the metal lathe. I have taken the course, but not sure if someone has done it. Also, is there even a set of jaws to accept it.
I’ve heard tell that turning rotors can be done here, but it’s worth noting that O’Screwit auto parts will turn rotors for $15 each, as long as they’re not drilled or slotted. (Which are dumb features anyway and should make their users feel bad) At that rate, I’d rather drop a set off and go do something else while the specialty tool does its work.
EDIT:
On-car turning requires going to a shop that has such lathes, and they charge muuuuch more. It’s only worth the effort if the car has captive rotors or bearing-in-rotor design, both of which are hallmarks of some Hondas and Fords, but are atypical in other brands.
Slotted rotors also add to cost of manufacture, and both styles are less serviceable than standard vented rotors, while also increasing pad wear.
Both of these features were initially developed to improve rotor heat dissipation and allow for outgassing of brake pad material, which would otherwise become trapped between the pad and rotor as it vaporized.
With the advent of modern brake pad compound and design, in addition to improved venting geometry, these types of brakes offer no benefit for anyone but actual racing drivers, for whom the cost, serviceability, and operating lifespan are not a concern next to the potential fractions of a second off a steady lap time that the slightly improved performance a properly-designed and manufactured rotor can provide. If you have a Finnish name I can’t pronounce and your plans involve 8 dudes ripping your brake pads out and tossing new ones in in a couple hours, go ahead and let those guys put a set of drilled and slotted rotors on the car. Otherwise, consider more conventional brakes.
I had a Jeep Grand Cherokee that would warp the front factory rotors every 25K miles. After 3 sets of rotors, I put a set of PowerStop cross-drilled rotors on it and they were still on it 100K miles later.
We never saw any signs of cracking or fatigue and never had brake issues using them. No fatigue, they were faster to grip after deep water, etc.
Interesting : is the photo of the rotor that has gone far past the serviceability and has cracks - not a shocker based on that photo.
Not surprising tho - typical photo used for those that either don’t know how to maintain a brake system or worse opt for the lowest priced “high performance” part when shopping for new (in this case brakes) parts for their car.
I’ve installed brakes on countless cars and other vehicles i.e aircraft, and some have been with properly drilled factory or high QUALITY rotors, and have yet to have a crack issue on a street car or modified car when owned and driven/piloted by an intelligent individual / team.
A non drilled rotor can suffer the same fate as the above photo shows with heat cracks, excessive bluing and grooves from going past the service life. Abuse/ignorance…
Heat and gas dissipation are key in braking - no or low heat dissipation leads to a drop in braking ability (race or street).
The chamfered leading and trailing edges, and the slot in the middle allow brake material to escape, while the vents in the rotor increase surface area and in many cases are engineered to draw air through to increase cooling.
More advanced designs exist for very minor increases in cost that add performance without sacrificing serviceability. This style of Bosch pad for example:
This rotor apparently came off a 993 after a single track day.
And this one from a stock Ferrari
Quality or not, you’re exacerbating your risk of cracking with cross-drilled rotors. But more often than not, your weekend warrior buying “high performance” brakes is picking up that ebay special. When that’s your budget, stick to Centric.
That one was a 1997 Grand Cherokee Limited. We put 227K on that one.
Out of curiosity, was the right side worse than the left? I’ve had 5 ZJs and 3 of them had a tendency for the right front caliper to stick.
They never had caliper float issues, all 3 of them bled down too slowly was the problem. My working hypothesis is the line for the front-right brake has some designed restriction that wasn’t accounted for, so if the square cut seal starts to wear or the rubber hose starts to swell, the caliper won’t bleed quickly enough. Didn’t have any issues with the other 3 corners on all 5 ZJs, just the right front on the Laredo, Orvis, and the second 5.9 Limited, at very different mileage numbers. (250k, 80k, and 190k respectively) And issues persisted after replacing related parts.
Anyway, I found that even on ZJs, which have brakes lifted directly from their 1000-lbs-lighter XJ predecessor, OE-style Centric pads and rotors improved braking performance significantly. My niner could out-stop my WJ, which isn’t supposed to be a thing what with the WJ having much bigger brakes, but there it is. Compound makes a difference. In my opinion, a big enough difference that you’re chasing margins with drilled/slotted rotors of dubious quality and increased cost. And I am a big fan of settling for 90% effect at 50% input.
Rotors have been turned on the DMS metal lathe. Aven Stewart came last week in with third party replacement rotors for a car, the make and model of which I forget; but what happened is they were about a quarter inch too big in the diameter. These were ordinary style rotors without holes or slotting. We supported the rotor in the three jaw chuck by winding it outward and grabbing the inside of the center hub hole. This provided secure support. Each was turned down about a quarter inch of diameter, starting near 10" diameter. The lathe can not work anything over 13" diameter.
What we didn’t do was re-face the rotors and I haven’t personally seen anybody do that on the DMS lathe. It should be possible though. One thing comes to mind, however, the facing would have to stop short of the inside hole because of the chuck jaws holding it. So there would be a tiny lip adjacent the hub. But the brake pads normally don’t apply themselves at that part of the rotor.
There are micrometers for checking that the rotors don’t get thinned beyond manufacturer’s minimum specification. Whether or not this is worth while compared to having a brake shop do it is another matter.
In Avens case, he had the replacement rotors and the car was already up on the lift with rotors off when it was discovered that the replacements were a wee bit too big. Then the lathe action was a worth while recovery.
I’ve had good luck with the EBC green stuff semi organics - they ain’t lying about the brake dust tho. I consider my forever blackened front rims a daily reminder to be thankful for how hard they work (and how much I hate getting stuck behind short braking soccer moms in blacked out escalades during rush hour). Not for nothing - but I’m kind of amazed nobody mentioned rotational mass (as nominal as it might be) in this brake discussion… just sayin
The weight difference between drilled/slotted and standard rotors is negligible. You have to start chasing 2-piece and ceramic rotor designs to start making up weight differences at a given size. Which is definitely worth it as performance climbs to the point where money is no factor. But until that point, go for lighter wheels and tires. Again, marginal returns and so forth.
vibration can be caused by the pads not bedding correctly or the piston seals not pulling back far eneogh
Does it get better or worst when up to temp on the track ?
I have a couple badly glazed rotors that are otherwise fairly new. I think they got overcooked on the track with less than optimal (street) pads. I’m thinking that it doesn’t need to actually be turned, but just have the glazing ground off. It’s certainly feasible to do a grind down manually on the car, but haven’t done it before. I have since switched to XP10 pads and rotors have become a standard wear item…
As to slotted/drilled vs solid. I’m very convinced that both sides of the argument hold true. There are still gains to be had from drilled or modified rotors, but the entire system of rotor, pad and caliper need to work in concert with one another. The vast majority of the stance crowd that just slaps a set of cheap drilled disks on their car and pairs them with whatever craptacular pads is very likely decreasing the actual performance of their vehicle from my limited research and knowledge. That said, the 911 that is abandoned out back has drilled rotors and I’d be willing to bet that the engineers at Porsche have done a test or two to optimize the braking of that particular model line (911 ain’t new!).
EDIT: I’m also of the understanding that most race rotors have gone through some cryogenic or other hardening processes. No clue if that changes the game for machining (probably not) OR if machining would heat the metal of the rotor to the point that it changed the metallurgy some undesirable amount.
Surely they don’t believe they are improving their performance by dropping their suspension so low they have camber angles of 10-15 deg. or more. I think the only thing those guys are improving is their chances of a blowout.
That said, I know a LOT of guys who run S2000 for track days galore and or actual racers. They all run cheap centric blanks (if they have stock calipers) as the drilled rotors crack way before the cheapest solid blanks.