sdevine

My rotors were warped, and I had my mechanic machine them down and they were fine for about a year. Now my steering wheel is beginning to wobble at high speed breaking again. Should i get the rotors machined again? Or should I replace them? What would cause this problem to reoccur?

The ODB

Replace them with new ones. machining makes them thinner and warp even faster.

warping is caused from heat. Slowing down quickly from very high speeds causes the heat.

Vader

Besides, replacement rotors aren't much more expensive than resurfacing, and you never have to worry if the "hard spots" were machined through or not.

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Later,
Vader
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Pukka

If you replace the rotors, get new ones that are cross-drilled or slotted. This helps keep them cool as well as improves the look

TomP

I try to reduce the heat mentioned by ODB.. when I come to a stop off a highway, I try to stop back a car length. I keep the brakes on, then I roll up a bit, and put the brakes on, roll up, put the brakes on... I like to think I'm distributing that heat evenly on the rotor. (laughs) Of course maybe I'm just warping the Hell out of 'em that way, but I'd like to think it helps.


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
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Doug E

If you happen to have a 5 speed, use the tranny to slow you down.

I had a rotor warping problem with a sunbird I had a few years back. I did the front brakes 2 times in 2 years because the rotors warped. I got a better set of pads (Raybestos I think) the second time and its been fine ever since.

sdevine

Yes, its a 5speed and i do downshift, My brake pads are like new with 108k miles on them, never been replaced. So Maybe thats the problem?

86TransAmTPI

Does anyone know where you can get these cross-drilled or slotted rotors?Thanks,Al in NJ

Check out My Trans Am:
http://hometown.aol.com/italianknight178/index.html

Tab92bird

When your mechanic machined your old rotors, he should have looked up the minimum thickness your particular rotors can be machined to. Machining rotors already under minimum spec is not only illegal (it is here in TX, but I assume it's just a state law), but it leaves the rotors susceptible to warping because of less mass to distrubute the heat.
Usually warping is caused by either out-of-spec rotors, as I mentioned above, or sticking brake pads. look for hot spots on the rotor; if they are on the inside the caliper is to blame, on the outside it is your brake hardware.
As for cross-drilled and slotted rotors, they may work better overall, but keep in mind that they cannot be turned (machined). This means when your brake pads wear down, plan on investing on another $150+ for new rotors.
Hope this is of use,
Brandon

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White '92 Firebird w/ 305 TBI. Open element w/ non drop base, increased fuel pressure, TBI spacer, Hedman Hedders & y-pipe, no cat, cat-back exhaust

Apeiron

Drilling and slotting the rotors isn't for cooling, it's to allow pad gasses to escape to prevent fading. New pads tend not to suffer from this anyway.

GearHead1973

When you buy new rotors stay away from the China made ones they are usually warped out of the box or warp in just a few hundred miles. When I worked for a parts store shops would put them on brake lathe to check for trueness and it wasnt uncommon to have to send the driver back with a few rotors until they got ones that werent warped. The better ones will be from U.S. or usually Canada like the original ones.

Guest

Looks like its covered from everywhere...

The rotor spec is on the rotor itself, IIRC its 24.5mm min thickness. Something that could cause it is brake calipers that are binding/sticking. Make sure the hardware is clean, and put new o-rings in the caliper and some synthetic grease designed for it. Also check out your idler arm, make sure its tight because a worn idler will cause the problem to become much more pronounced.

slayer2000

iTrader: (1)

tab92bird,
Why can't drilled or slotted rotors be turned? I'm a machinist and I've turned alot of parts with interupted cuts and have never had any problems. Is there a reason brake rotors can't be? I'm not tring to be a smart *** or anything but I am thinking about geting a set of cross drilled rotors but I might think twice if they can't be machined.

sdevine

What do hotspots look like. I see no discoloration, but i do see several circles about 3/4 of an inch in diameter in various places.

Damon

Slayer- That's an intersting comment. I have been told by local shops they can't turn down my PowerSlot rotors, becuase of the cuts in them. Now wer're talking local GARAGES, not a machine shop but they told me the cutter would "skip" when it hit the open area and wouldn't give a flush cut when it reengaged- essentially it would "feather" the edges.

I never doubted them becuase it seemed to make sense and I was in no position to argue. I'd like to hear your thoughts.

Corry

Slotted I can see, if you grind 'em you'll make the slots more shallow, putting them out of spec, and maybe causing them problems. There is no reason a surface grinder can't grind the slots/holes. I too have operated a few surface grinder in my life Hell, usually you are starting w/ an uneven surface, thats why you're grinding it! If it will cost you less (i.e. you can do it yourself, and have no one to sue but yourself) you should be able to grind your own, but most shops don't want to be responsible for your brakes failing.

As for where can you get these wonderful brakes? Well, I can't seem to fin 'em anymore, but bear brakes are considered to be close to the top of quality/performance braking. Someone on here has got to know of a retailer


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Corry Lazarowitz
clazarow@voicenet.com
clazarowitz@hotmail.com
1987 Pontiac Trans AM (GTA?) 350 TPI
SLP 1 3/4" headers, 3" cat back (stock cat MSD ignition.
MSD Blaster SS coil.
3.73 Rear end gears
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Bosh +4 Spark Plugs (Don't know if they really help but hell!)
Holley AFPR
More soon when funds are avail...

Guest

It depends on the machine they are using for cutting, and how much they are trying to take off as to if they can cut the rotor or not. Most of them are using a new machine, I forget the name... Accu-something, and the whole selling point on that thing was so you could make a one pass cut taking off like .050 a side at a time. Thats crazy IMO. If you were to cut off a normal amount, like .010 max per side, and then make a second cut of .001 or .002 per side, it would work fine no matter what the surface was like, slotted, holes, whatever. You can use other methods for surfacing, but the idea with rotors is to do both sides at once with a machine designed for cutting rotors so that both sides of the rotor are parallel. Thats probably the most important thing when cutting a rotor. Cutting in smaller increments always makes for a better cut, I found that taking off about .003-.004 per side and then making a final pass with .0005-.001 off each side and grinding with a sander to take the edge off and put a swirl finish on the rotors worked best.
I did this for about 8 years and have done my share of slotted/cross drilled rotors. They are a little more difficult to do because of the holes and the bits like to jump if stuff is loose or you are trying to take too much off, but it can be done if you take smaller cuts and make a final pass taking off very little.

sdevine, hot spots can be hard to see sometimes. Sometimes they are a discolored spot on the rotor that is blue or even purple, and other times they are a very shiny, if not polished, metal spot about 1/16" in diameter or smaller (not always round) that are very hard compared to the rest of the rotor. These are more common with brake drums, but do occur on rotors sometimes as well. IMO anything that has had those kind of hot spots rather than discolored areas should just be pitched for new ones.

[This message has been edited by madmax (edited April 14, 2001).]

slayer2000

iTrader: (1)

The part's I machine typically call for paralellism of .001 or less. I have a piece of steel that I made with a drilled and tapped hole in the end of it. I just chuck it in the lathe, indicate it in and then bolt the rotor to it. but like I said I don't know much about drilled or slotted rotors. With the tooling I've got interupted cuts are no problem as long as the feeds and speeds are correct. carbide tools are a little sensitive to cuts like that but they can be used okay

89GTA5spd

you can pick up slotted/drilled rotors in JC Whitney w/ free shipping. They are on sale now and cost less than most rotors do at major parts stores.