Slotted brake rotors and vibration

[Gubi]

Ever since I replaced the front rotors on my Milano with slotted ones, I've had a bit of a vibration/buzz when doing stops from high speed. Not too bad, but it definitely wasn't there before.

I checked the runout of the rotors and they are 0.002" and 0.003", which is within the spec of 0.003". Is this a common issue with slotted rotors? Or do I just need to get the disc runout a little tighter?

[Gubi]

Anyone? Anyone? Something-something economics? Something-doo economics?

Bueller?

[MarcusHMM]

Well, two things to check, and I am not an expert so I could be way off base.

First when you did the rotor did you make sure they were clean and grease free when you put them on?

Second, did you break in or seat the pads properly as directed by the manufacturer and did the pads have a chamfered leading edge to then when you installed them?

Just my thoughts and I could be wrong and probably am.

Marcus

[Gubi]

Good thoughts, but yes, I'm sure the rotors were clean and I bedded the pads properly. The rotors and pads still look fine.

This is the first time I've used slotted rotors, though, so I guess I'm just wondering if it's something inherent to the slots.

[Tifosi]

Never noticed anything like what you describe when I swapped over to slots up front 2 summers ago.

Is it something you feel in the pedal, or the whole car in general?

Did you get the hub bearings properly tightened, with said bearings being freshly grease packed, in really good to new condition beforehand?

Caliper pistons index?

What pad material did you choose? (stock, ceramic, semi-metallic, etc. while it shouldn't make a difference, sometimes it indeed can, especially if there's something really soft in there that can put dust into the slots faster than it can evacuate said dust from the slots)

And just for giggles, didja happen to check each and every slot to ensure that there wasn't a raised feather edge on it? (feather might be the wrong word. More like 'little ramps arounf the perifery of the slot')

Honestly though, I can't imagine feeling a (early on) buzz due to slots during high speed stops, as (to my mind anyway) the rotors would be spinning so fast that it simply would be too high a frequency to feel (number of slots going past pucks SO fast that they'd be indistiguishable from each other)


I suppose one could pull them off and have a light skim cut done so that it would ensure any feathering were gone and take care of the runout at the same time, but wouldn't actually do anything if the source were elsewhere.

[JoeCab]

Occasionally we get complaints of a "woofle-woofle" sound with the drilled/slotted rotors when coming to complete stop, but I've not heard of any problems at high speeds.

Is this more of a vibration in the pedal or a sound?

[Gubi]

It's more of a sound and feeling in the car, not a vibration in the pedal itself. It's subtle, so maybe I'm just being paranoid. Sounds like this is not typical, though.

Pads are Ferodo street pads. Bearings are packed and properly adjusted. Rotors are installed on the right sides with the slots going the right way.

I think I'll pull the pads off this weekend to inspect them again, maybe file the leading edge a bit more, check the rotor slots for ridges.

[Gubi]

Hmmm. Pads and rotors look good. Filed the leading edge a bit and it didn't make a difference. Bearings preload seem fine.

Mongo dunno. I've got to take it in for an alignment after I replace the caster bushings, so I'll probably just have them check it out then. Maybe I just need to get the disc runout a bit closer to zero.

[gt601]

Hey Mongo. Where did you get the rotors? I had a similar experience with the IAP discs. I installed two sets and they were both bad. It's been several years though.

Paul

( not bashing IAP, but thats where I got them)

[aldo]

Probably has no effect on vibration but I've often wondered; are slotted rotors directional?

I've seen manufactures installation instructions contradict each other as to which way the slots should face?

[bianchi1]

just for a short time.. flip the disk, left side to right, right to left..so if the vibration stays.

[Gubi]

Quote:

Originally Posted by gt601 Hey Mongo. Where did you get the rotors? I had a similar experience with the IAP discs. I installed two sets and they were both bad. It's been several years though.

[dscottj]

Ok, I put slotted & drilled on our family truckster (PT Cruiser) because they were supposedly more resistant to warping. I'm not sure what it is about my wife's driving style, but all she has to do is sit behind the wheel of a car and the brake disks seem to turn into pringles chips. Including this (then) brand-new car.

At any rate, I put slotted & drilled disks on and sure enough, they're definitely noisier than "standard." It's not awful, but it's definitely there, especially toward the end of a really long pull-down. Imagine running your finger over a smooth disk. Now imagine it running over one with pits and grooves. That's the difference, to me at least. PPLLRRRRRRRFFMMMMBBBB, sort of thing. Sounds a lot like what you're experiencing.

Worked for me, because it beat the alternative. Rotors that aren't smooth... well, to me it felt like I pitched a wheel weight off every time I hit the brake pedal. The spider got so bad if I hit the brakes HARD I was worried something was going to get vibrated off.

[Alfissimo Int.]

Quote:

Originally Posted by Gubi Yeah, they are in fact IAP purchased. I got them end of 2007 it looks like. Well that would kind of suck. I assume I could get them slightly turned to true them?

[JoeCab]

Quote:

Originally Posted by aldo Probably has no effect on vibration but I've often wondered; are slotted rotors directional? I've seen manufactures installation instructions contradict each other as to which way the slots should face?