BrakeExpert

I would like to talk about rotors and redrilling the lug pattern. The bolt pattern / lug pattern of our Hondas are typically 4x100, 4x114.3 and 5x114.3. When making a custom brake setup, sometimes you can simply take another Honda rotor, drill some holes into the hat, and bolt it right on.

Rotor bolt paterns

On our Hondas, wheels are held to the car by sliding the wheel over a hub and special nuts, called lug nuts, are tightened. These nuts have a certain pressure applied to them. When the pressure is applied, it is said that the lug nut is having torque applied on it. Torque is a twisting force, it is applied to the lug nut with a special wrench called a torque wrench, that ensures each of the 4 or 5 lug nuts has the same and correct amount of tightness to push the wheel against the rotor and hub. Of the recent Hondas, there are 4 standard bolt patterns: 4x100, 4x114.3, 5x114.3 and 5x120. These are a code, the first number indicating the number of lug studs and nuts, the second indicating the distance between two opposed lug studs in millimeters. In a 4x100, there are 4 lug nuts, the corners at 100mm apart center to center, and in a 5x114.3, there are 5, each nut has two lug nuts spaced 114.3 mm apart from it at most.

All Honda lug holes from the factory are 1/2" exactly and all lug studs are M12x1.5 in dimension. Almost all OEM lug nuts use an acorn style (of the three styles of lug nuts, there are flat, acorn, and angled. Most of the aftermarket wheels we use take angled.)

Brake rotor installation

Almost all Hondas use a 1 piece rotor. It looks like a top hat from the side and is located between the hub and the wheel. Most OEM Honda stock rotors have holes for each of the lug studs to go through, a big hole in the center that the rotor rests on the hub with, two threaded holes, and two beveled holes. Those of us with Hondas are lucky, since our rotors all have these threaded holes which push the rotor agains the hub to remove if its gotten stuck on over time, and the two beveled holes, in which special retaining screws are screwed into. These hold the rotor in place, but are not necessary on any stock brake system. When the car is in motion, the only thing keeping the rotor in place is the wheel and hub sandwiching it in place from the torque applied on the lug nuts. The pressure is dispersed over the entire contact area. For this reason, "redrilled" rotors are completely safe. Since the lug nuts are sandwiching the rotor inbetween the wheel and hub, the lug holes are not even touching the lug studs. The lug holes are 1/2" and the lug stud is smaller, allowing an equal gap about a millimeter around the edge of the lug stud. Since the lug studs are not bearing a sideways load, the lug holes can be made larger if needed and will still operate the same. Some people worry that 'overlapping holes' due to a redrill in bolt pattern are not safe. Remember that the lug holes are merely holes - they exist ONLY to allow the lug stud to get through the rotor and the wheel to allow for a lug nut to be put on and apply pressure to the wheel at 4 or 5 points. These oversized or overlapped holes in no way affects the vibration, load, or structural integrity of the rotor at all. Some of you may have seen cross drilled brake rotors where the contact area has teeny beveled holes that can crack. This is on the contact area which has a lot more heat applied, and friction wearing the surface causing the hole to gradually shrink relative to the surface because of normal wear. The lug holes have no friction applied and do not crack.

On a side note, the term 'redrilled rotors' is a bit misleading, as any rotor that is redrilled with an overlapping hole is likely drilled with a mill end, since an angled drill bit would 'walk' and vibrate the machine, not allowing a hole to be made (at least not easily.)

Having a rotor that is hub-centric is the key

The important part of a rotor in a brake system is that it is mounted correctly. As it is merely being held in place, this is easy, but on a custom brake setup, sometimes there are other factors.
Since the lug studs are not load bearing and do not touch the rotor, when the wheel is being put on, something needs to keep the rotor in place while the wheel is being mounted. With stock Hondas, the retainer screws do this, but they are NOT NEEDED. This is because the rotor is hub-centric. On all stock systems, the centerbore of the rotor and the raised center of the hub is the same, so when the lug nuts are being tightened, the rotor stays seated on the centerbore. If a rotor with a larger centerbore is used, and retainer screws are not possible due to a redrill, the rotor will have a radial vibration since it cannot be mounted correctly. The rotor will then sit on the lug studs until mounted, and that bit of play in the lug holes will have the rotor offset relative to the hub. This will cause vibration and when braking from high speeds, you will feel the pedal and the car pulsate. To rememdy this, you may use a ring shaped material to center the rotor. These can be made of plastic, iron, or in my case, aluminum. The ring will sit on the hub's center and then the rotor is put on. The ring holds the rotor in place while the wheel's lug nuts are being tightened. Remember that all the lug nuts should always be torqued to the same and proper torque specification. On a Civic, Its about 75 lb-ft for aluminum wheels, 80 lb-ft for steel wheels. With overlapped holes in a redrilled rotor, remember that the pressure will be dispersed over the whole rotor hat, so torquing lug nuts is essential, but it is just as critical for every car to have all the lug nuts torqued correctly. Having one loose and one too tight will cause uneven pressure on any brake system and lead to lateral vibration immediatly and increase over time, requiring the rotors to be turned on a brake lathe, or replaced sooner than necessary.

EH2Kevin

This is great information. Thank you!

unusual71

nice writing, I redrilled S2000 rotors to 4X100 and put two years of abuse on them with zero issues. I think the original purpose of the retaining screws is positioning when using a brake lathe.

spAdam

iTrader: (1)

+1 here for redrilled rotors. I ran redrilled Prelude vtec ones on my EJ1 from 1998-2009 with 0 issues.

BrakeExpert

No the screw holes aren't used for a brake lathe, they hold the rotor centered, so when you take off the caliper, the rotor doesn't move. Lots of makes of cars don't use them. on STOCK brake applications, they aren't needed.

Salami

All 4 bolt Honda-Acura's have a lug nut torque of 80 ft lbs. Is does not make difference of what the wheel material is.

EE2bitsk

nice info dude. non-torqueing wheels down is a huge no no.
been torqueing all mine at 75lbs since 05(when I started driving) and been fine.

bnetkillzone

Lots of good info

unusual71

alright. I was looking at brake lathe stuff as a friend was selling one and I read that manufacturers use the screws to hold the rotor to the hub so that they can mount them, run the brake lathe and then install the wheel without the rotor losing position. makes sense to me but my name isn't Brake Expert either lol

GOOCH-JDM-ITR

great info. How hard is it to actually re-drill the rotors (are they steel)? Do they require a drill press? I have a 98 GSR w/spoon calipers and warped my current rotors so I'm trying to figure out if I should buy them redrilled again(fastbrakes-SpecR), redrill myself(Prelude rotors to 4x100), or just buy rotors that are 2mm too small (MiniCooper07-280mm) and not have to drill. Also what is your feeling on "coatings" on the hats of the rotors. Thanks