Redrilling rotor stud holes

[Omega]

The rotors I would like to use are for a 4.75" lug pattern. Obviously ours are 4.5", so I need to drill a different set of holes.

I would like to know of, if any pitfalls of doing this.

 

[Defiant]

Not recommended. Stress risers, cracks, disintegration, disaster. Ask Todd TCE.

Similar to:

http://www.dsmtuners.com/forums/showthread.php?t=141849

 

[gsxboostin]

I'm just curious....but why do you want to use a bigger rotor? I mean why not just save time and hassle and just buy rotors with stock lug pattern? -Matt

 

[Todd TCE]

Scary story.

But the question was about re driling the hat for an alternate bolt pattern, not the rotor surface.

This should not prove to be an issue at all if done properly. Drill to spec and chamfer the holes and I'm certain you'll be fine. Or a good machine shop can slot the existing one a bit to fit the current pattern. There are many multi drilled hats and iron hat/rotors in service from various suppliers.

More important is if you do this you'll need to be sure the center bore matches your current vehicle. That will keep the rotor running true.

How you go about fitting said larger rotor into the existing caliper....welll that's up to you.

 

[Defiant]

^ ^ ^ That's the answer I'd trust.

Thanks, Todd~~

 

[Omega]

Thanks Todd... I would prefer to redrill over slot though.


Speaking of the center bore:

The rotor bore is slightly bigger than the hub. Off the top of my head the dia. difference was around .13". I'll need to make a spacer ring to center it up.

If anyone knows of a rotor with a DSM center bore that is 12.75 x 1.25 I am all ears.

 

[Jehu]

As long as you have a machine shop doing this and not with a handdrill, it should be fine.

 

[Todd TCE]

2G center bore is 2.640"
3G center bore is 2.712"

Some 'later' 2Gs came with the the later 3G bearing. It's seen by way of a second step on the up turn area of the center. Plays hell with kits too! Hats don't seat properly. AND Mists sells this larger one as the only stock replacement when I checked a year ago.....

I've got alum centering rings that are 2.64 ID and 3.06 OD if that will work for you. When they do the holes ask them to open up the center bore.

 

[Omega]

Right, with the parts in front of me the hub OD is 2.643 (including surface rust) The rotor has an ID of 2.778 (with a couple of thou "slop"). Unfortunately the center bore on the hub is smaller than the CB on the rotor.

Thanks for the offer on the rings, but the OD is too big.

I am going to call a local speed shop tomorrow to see if he can redrill the rotor. Not sure what I am going to do about the spacer. Perhaps Mcaster-Carr has some pipe that I can turn down.

When properly placing a caliper (with pads) on a rotor... Should the pad be flush to the rotor edge or should it be an 1/8 in or so? I know it would depend on the distance between the caliper and rotor edge, but is there a rule of thumb?

 

[Todd TCE]

Be easier to enlarge the iron holes....

Centering rings? .138/2= .069 wall? PITA. So thin they are hard to make. Can be done, but you won't get a leading edge radius on it for the hub.

If the hub has a threaded hole for securing the rotor put this in the new rotor and use it. Between that and the stud holes you'd be ok.

Put the pad just at the edge. Max ER (effective radius)

 

[Omega]

The speed shop has no problem redrilling the rotor for me.

So your saying that the lugs will center the rotor enough that I won't have to worry about the hub and center bore being wrong? I guess I could have the holes drilled a hair under what the factory dia is to center it even better.

Thanks for the help.

 

[Todd TCE]

The speed shop has no problem redrilling the rotor for me.

So your saying that the lugs will center the rotor enough that I won't have to worry about the hub and center bore being wrong? I guess I could have the holes drilled a hair under what the factory dia is to center it even better.

Thanks for the help.

No, quite the opposite. I'd take hub centric over stud any day. Unless you have a centering bolt you can replicate on it as well. Then when in place the wheel pressure will prevent it from moving as well as carry the rotational load.