I bought a pair of drilled rotors from KVR, and installed them, along with new pads, bearings, etc. However, the car shakes badly when I brake, to the point it has a couple times made the cd player skip....I have done everything (adjusted bearings, cleaned and lubed caliper slide pins, etc) and now I'm sure it it because a rotor might be warped (wasn't trued after crossdrilling)

How can I true them?? I think the conventional method of truing on a lathe would make a mess with the holes, and probably would need to chamfer every hole afterwards.

Should I better look for a decking machine or something like that at an engine rebuilding shop? has anyone done something like this?

 

I've never had drilled rotors so I can't say for sure, just what I think would work. I would have them milled and them just make sure you clean them up real good and get all the metal shavings out of the holes. However, if they're new then it sounds like you have another problem.

 

contact KVR and tell them what happened. if you bought them recently they might replace them for you

 

Just because they are new doesn't necessarily mean they are true... You can turn them on a lathe with no problems, just try to take off as little material as possible (this will minimize the chance of f'ing it up)...

 

Well, they are not new right now, had them on for a couple months, but with the old rotors, I didn't have that problem, just didn't have enough braking power.

Along these months, I have fixed or changed a lot of other things, like pad backing plates, new wheel bearings (properly adjusted 3 times), hyperflex braided brake lines, replaced brake fluid, new tie rods and idler arm, rear shocks, rear brakes fully rebuilt, new tires, wheel/tire combos balanced, had it aligned, etc. Still, the shaking remains...
Anyway, the people I bought them from, don't seem to stand behind their product, so I think it is going to be cheaper to have them trued, than to get another set of new rotors from somebody else.

 

It's like $20 a rotor to mill them, so I'd say just mill them and forget it if they won't stand behind their product.

 

you can turn them on a normal brake lathe just fine.

put them on the lathe and take off a TINY amount of material. if it grabs in some areas, and not in others, then its warped.... otherwise its somthing else.


warped rotors however, do not cause a vibration like that when you are using the brakes. they usually pulse the pedal, lock up easier, ect... but they dont "shake"

 

O yes they will shake the **** out of the front of the car if there warped bad enough. I've seen a lot of warped rotors that shake a car to death

 

Yes they can!

Most brake shops will generally have an extra surcharge to turn drilled or slotted rotors because its alittle harder on the cutting bit (so they claim). Most drilled rotors are camfer enough in the holes that a few turns will still leave adequate camfer of the holes- just depends how bad they are. This is a perfect example as to why the corect compound pad should be used with expensive drilled rotors. Do not ever run a pad with material in it that is harder than the rotor (like most semi-metalic pads)

Edit: also- always have BRAND NEW rotors turned before you install them. They are almost never perfect out of the box.

 

is it possible to turn slotted rotors?

 

Since I own a machine shop, I'll tell you their claims are true. It's called an "interruped cut" and tends to break or chip the carbide inserts on the cutting tool. So they charge more for replacement of the cutting tool they will probably break doing your rotors.

A brake lathe is much different than a standard engine lathe. There is no adjustable feed rate on the brake lathes I've seen, so the carbide insert will chip and the normal feed rate. If they could slow the feed down and reduce the chip load, it would be less of a problem chipping the inserts.

 

Thank you for confirming that Alloy. I don't like to post a "fact" if I am not an expert in that field. I stated above "so they claim" so everyone would know what I posted was 2nd hand knowledge.
Dean

 

Well, thanks everybody, I had the drilled rotors turned last saturday, and the vibration is completely gone. I went to the beach, and I was able to get the car to 110 mph and it is ok now.

The only thing, is that I felt a bit of reduced brake power (guess the pads were worn kinda weird, matched to the warped rotor; so now they have a bit of less contact area with the straight rotor.

Should I replace the pads with new ones, to prevent the oddly worn pad (they look flat though) from making a groove or something on the freshly turned rotors? or should I just let them wear until they wear-match to the rotors?

 

I would replace them. You wouldn't want to damage a fresh rotor with some $20 pads.... Besides it doesn't take but 1/2 hour to change the pads if you've done it a few times.