dtran002

Hey all, I just want some ideas. Here is the problem: My 95 Accord 4cyl Lx somehow always shake like mad when I hit the brake at higher speed (40mph+). I used brembo cross drilled and slotted rotor, oem size, and the shake wont start again until for a long time. After awhile, I changed to regular blank rotor, and the brand name of it was Mountain something....Anyway, after a month, the car started to shake crazy when I brake. So what I want to ask is should I get the brembo cross drilled and slotted again or the brembo blank. Im afraid if I get the blank, it going to shake again sooner than the cross drilledd. Anyone experience with the brembo blank on the 95 Accord?

high_society

I just posted on a similar question. Basically, you had the right idea with the drilled and slotted rotor. Better heat dissipation should prevent warpage. But if you're having problems with the expensive drilled/slotted rotors then something else is wrong. Did the car shake only when braking? Was there vibration at high speed?
I noticed with my blank OEM Honda rotors that warping was sort of temporary. It used to get all out of whack and vibrate really bad, then after some more normal driving, go back to normal and not vibrate at all. I assumed that meant the rotor was chaning shape a lot, which isn't good at all. That much flexing and bending in the rotor will eventually cause it to crack or break.

TheMuffinMan

iTrader: (1)

You are warping the rotors. That is why they are shaking.

There is absolutely no need to have drilled/slotted/etc and in fact all drilled Brembo's are done by another company, not them. If you're continuing to have the problem I'd look at your calipers for issues. Brembo blanks are more than sufficient.

Also you should note what kind of pad you are using.

high_society

There's no benefit to drilled or slotted rotors? I always thought they helped move dirt off of the braking surface and also helped keep your brakes cooler. I guess you would only reap that kind of benefit from heavy use of the brakes; such as tracking your car.
Either way, I have slotted rotors. They look cool even if they don't help.

TheMuffinMan

iTrader: (1)

They won't help to the extent you'll notice it on a street car. I'm sure someone will try to argue it, but other than eating up a pad more and having a greater chance at cracking/warping they don't have an advantage.

I have the NSX calipers and brembo blanks and I can assure you it stops well.

high_society

But they don't look as cool... lulz

P_Adams

I just posted this to another thread. It applys here also:

1988 thru 1992 Sterlings (Accura drive trains) had a recuring problem with what the Brit's called brake judder. Repeated rotor replacements were most common until they issued a bulletin whereby either a torque wrench was used or a torque limiter was affixed to any impact gun.
They found that unever torque to the lug nuts could indeed cause the rotor to act much like an LP record warping from heat. Although still parallel, the fiction surfaces would wobble from side to side causing unever clamping forces (thus the vibration)
Another factor can be thermal shock; often caused by the sudden cooling of a very hot object - much like a hot brake rotor going thru a puddle. My favorite example is that long braking approach to a highway off ramp and the subsiquent puddle you hit. Instant ^%$&#

P

dtran002

Well, either rotor, the car still shake after awhile. It just my experienced with the cross drilled and slotted rotor from Brembo actually lasted longer before the shaking occur again comparing to the blank one. I know Brembo does not drill the rotor, but I'm just tired of the shaking after the new rotor change if I get the blank one. As far as look, it not my concern, at least not anymore hahaha...Thanks P Adam for the info, I always thought it has to do with the calipers, uneven clamping pressure cause the rotor to warp.

TouringAccord

unfortunately, that is the exact thinking some people use when buying drilled/slotted rotors.

function > form

TouringAccord

I've heard of this before as well. Thats why I always use a torque wrench when putting my wheels on. And if I ever take my car or my girls car into a shop I always specify they use a torque wrench and not the impact when putting the wheels back on. I usually get some weird looks but I don't care.

johnlear

Improving heat dissipation is a good thing, and increasing the surface area of the rotor will increase the area from which heat can radiate into space and conduct into the surrounding air, so in theory will assist in keeping the rotors cooler.

Drilled (or cast in) holes in the rotor may either increase or decrease the surface area of the rotor depending on the size of the hole(s) and the thickness of metal through which they are drilled, so may be beneficial or detrimental depending on hole size (smaller holes = better holes). Slots do increase the surface area.

However, the increase in surface area from either holes or slots is very slight and the affect on cooling infintesimal (and if drilled holes are too large will actually inhibit heat loss due to reduction in surface area).

The purpose of holes and slots is to allow 'out-gasses' (i.e. visible smoke and othe invisible gasses) from overheated pads to more readily escape from between the pads and rotor surfaces. Such gas causes the pads to lose contact with the rotors and thus lose friction, the pads in effect 'aquaplaning' on a microscopically thin layer of high pressure gasses (i.e. 'pad fade').

Warping might be a product of some section of the rotor cooling at a significantly faster rate than another section. If you have hot brakes and then park the car (or even sit at the lights..) part of the rotor will be between the pads and a larger section exposed to air, and the section of rotor exposed to air will cool faster than the section 'insulated' by the pads...

With hot(ter) brakes it's a good idea to drive around slowly for a few minutes to allow the rotors to cool off evenly over the entire rotor.

P_Adams

They also fall into the old "more is better" trap.
The reason Cross Drilled Rotors have had such a bad rap early on, was that those offering them did three (3) things wrong:
1) To many holes (weakened the rotor)
2) Wrong drill pattern (avoid straight lines)
3) Didn't champher (radiused) the holes (formed heat cracks)

I prefer slotted rotors. Not only do they allow de-gassing, but they are self cleaning as well.
If I have to have them remachined, I have them ground on the car.
I prefer Grinding as opposed to cutting because it avoids those phonograph record-like lines which can lead to noise and premature brake pad wear.

P

johnlear

Also, drilling the holes isn't a good thing. Holes should be cast into the blank because a cast iron surface has a hard 'skin' that is resistant to cracking, i.e. a crack is much less likely to initiate in a cast hole than in a drilled hole.

This applies to both cast and forged components, being why stressed forgings and castings that have been polished should then be shot peened, i.e. to compress the surface to create an 'artificial' hard skin similar to the 'natural' hard as cast / forged skin. I've never heard of the machined surface of a brake rotor being shot peened, but I wonder if it's ever done...

Slots are better than holes, curved slots are better than straight slots, slots that start and finish within the machined surface area of the rotor are better than slots that extend to the edge of the machined surface area. In this context 'better' means less prone to cracking. Probably the most resistant to cracking would be the 'J' slots that seem to be becoming more common (for good reason).