brake rotor redrill

[that-guy]

so i have a customer who is adiment that this specific brake system goes onto his car, however the rotors are made to a 5 lug bolt pattern, and the customer's car uses a 4 lug setup. not budging at all on doing a 5 lug conversion, the only option appears to be to drill the 4 lug pattern into the 5 lug rotor hat. doing some drawing, one of the holes will perfectly intersect with one of the existing, the other 3 will need to be drilled out. you can see in the picture where the new holes will be (shaded in red)

the two holes that you see are close, there is a 1/8" gap between the two

my question is, how safe is this to do, and if it is safe, what process would i take to drill into these (what kind of drill bits, speed, etc...)???

 

[mayday0017]

This just sounds like a bad idea.... Wondering if grabbing a stick welder and filling those holes full of weld and grinding flush before drilling the new holes would be a good idea... What exactly is the point anyways? He put some other brand make model components on and now wants the rotors to match but doesn't want to spend the money on converting to 5 lug?

 

[that-guy]

regardless of his reason for wanting to use this brake setup but staying 4 lug, what reasoning is there to not drill a second pattern into it?

 

[Stooge]

i know of many vehicles that have had a like number of lugs changed to a different pattern, but dont really hear of changing the number of lugs by drilling them out. possibly cutting the wheel studs flush, welding them in and grinding it smooth to keep material there, assuming the wheel studs are part of the rotor and not a seperate modular hub. does the wheel backspacing not allow for an adapter to be used ? these guys will build whatever you want and can make them pretty thin to accomodate alot of limiting applications, and made in the US. http://www.motorsport-tech.com/wheel_adapters.html
i know you already made a template, but just throwing this out there for other readers, that Rotten Leonard also makes lug pattern template kits for cheap and comes with everything needed. http://www.rottenleonard.com/Menu.html

 

[bsaint]

I would rather drill new holes with lots of coolant than weld on a brake rotor.

 

[that-guy]

no spacers or adapters. wheels are apparently already picked out and the offset is right where he wants it...long story short, these brakes are off of the same model car, but bigger to compensate for more power. so he wants these rotors and calipers, but wants to stay with the 4 lug setup instead of swap to 5 lug hubs

 

[that-guy]

I would rather drill new holes with lots of coolant than weld on a brake rotor.

i would NEVER weld onto a brake rotor

 

[king nero]

This is done frequently, drilling a new pattern on brake rotors (and filing out the coinciding hole). check some car related forums, or someone on here will likely back me up on this.

 

[P_856]

my question is, how safe is this to do, and if it is safe, what process would i take to drill into these (what kind of drill bits, speed, etc...)???

I've seen this done plenty of times, I'm sure it's not as safe as doing a proper 5- lug conversion but I have never heard of any brake rotor failure related accidents.

The best and easiest way to drill those out would be on a drill press with a good bit that's designed for metal since the rotor is made of harden steel. Make sure to clamp the rotor down so it doesn't move.

By any chance is the customers car a Nissan 240sx?

 

[mayday0017]

240sx was my guess too

 

[that-guy]

I've seen this done plenty of times, I'm sure it's not as safe as doing a proper 5- lug conversion but I have never heard of any brake rotor failure related accidents.

The best and easiest way to drill those out would be on a drill press with a good bit that's designed for metal since the rotor is made of harden steel. Make sure to clamp the rotor down so it doesn't move.

By any chance is the customers car a Nissan 240sx?

no, not a 240...I have a large set of Cobalt bits and was thinking i would just start small and work my way up to the final size, using plenty of cutting oil

 

[NHBandit]

I don't see a problem. Don't weld on it, just drill the holes and call it a day.

 

[that-guy]

gonna give this a shot tomorrow and report back...i'm hoping that the Cobalt bits will go through it easily enough so long as i take my time and keep it lubricated

 

[Tripp2012]

I would think long and hard on this from a liability stand point before I would redrill anything brake related.

 

[mayday0017]

I would be scared of the 2 bolts that will be holding all of the force of the car snapping if they are under a sudden load such as slamming on the brakes or flooring it on a high HP car. The other 2 bolts almost won't count as being there at all seeing that they will be right next to 2 more holes....

I'm guessing the reason people are so scared of welding up the brakes is they are worried about them warping? If that's the only reason doesn't sound to hard to solve that problem.

 

[mayday0017]

Looks like the 1 hole you are keeping will have to be slightly slotted as well...

 

[that-guy]

I would be scared of the 2 bolts that will be holding all of the force of the car snapping if they are under a sudden load such as slamming on the brakes or flooring it on a high HP car. The other 2 bolts almost won't count as being there at all seeing that they will be right next to 2 more holes....

I'm guessing the reason people are so scared of welding up the brakes is they are worried about them warping? If that's the only reason doesn't sound to hard to solve that problem.

well think about this, if one will shear, they will all shear, and if its that 1/8" that is concerning, to move through that 1/8", it will have to move 1/8" all the way around, and i think the studs would shear before the rotor would ever have a problem

 

[lilscorpion]

I've welded in slugs (when needed) and re-drilled rotors, axles, and hubs before. No biggie and easy. Liability risk is up to you. I've never had a problem, failure, etc. I use a knee mill to get the patterns centered however, in the case of a drum that really only gets sandwiched between the wheel and the hub, the pattern doesn't need to be perfect.

 

[k p]

Does the 5-lug and the 4-lug pattern share the same distance from the center of the rotor (same radius)?

 

[LandR]

Don't do it.

3 reasons:
Welding can warp the rotor requiring resurfacing.
It can unbalance the rotor. Harmonic vibrations on rotors are not a good idea.
Its a modified car. Any customer that has high hp and is unwilling to do the correct brake upgrade is asking for problems and is already a potential liability.
What pads or calipers are they running? This will affect rotor force.

Correctly fitting rotors are cheap even high performance ones. Do it right. Brake failures aren't pretty.

 

[MoonRise]

Skip all the drama and just get 4-bolt rotors. Done.

 

[zkling]

What car is it going on?

In theory, the studs do nothing to hole the rotor from turning, but the clamping force from the wheel on top + lug nuts torqued properly = clamping force that prevents the rotor from turning. So in THEORY you could have a few slots in that thing and it would still work. However the more material removed --> Lesser clamping area.

As for actually drilling it, yea it is somewhat common practice. I've done quite a few for folks. Some cars are really $$$$ to upgrade a brake system on thus drilling becomes common. About the only thing you really have to worry about it the balance due to material removed. Which is seldom an issue.

I've always done it in the mill, indicate off the center bore, slightly oversized holes for stud clearance, slight chamfer on both sides of the new hole for that professional look.

I would rather drill new holes with lots of coolant than weld on a brake rotor.

yea you wouldn't want to heat a rotor up now.

 

[LandR]

Sounds like an integra or other JDM brand but could also be a dodge product srt-4

 

[stratman977]

Could you get a 6 lug rotor in that bolt circle? Use 2 holes and the other 2 would be 1/2 way between two existing.

I have this issue with the rims on my old subaru cause the bolt pattern is 4x140 which is impossible to find rims for and the stock 13" tires are getting harder to come by these days.

 

[kbs2244]

If this is an even somewhat popular thing I am sure there is a company making high performance 4 hole rotors.

 

[aka Larry]

I run 13" Corvette rotors on my track-driven Z-24 on track. The bolt pattern and hub center bore is different of course, but I've re-drilled many of them for the front and back with no issues. I had custom adapters made to keep the rotors hubcentric so the bolt holes don't really do much. One the rotor is sandwiched between the wheel and hub, it ain't going anywhere. Also lots of the custom hats designed for 2-piece rotors have multiple bolt patterns. Many racers run these with no issues as well.

 

[pmason0]

Seen that you did it, just wondering what is the car used for. Those two holes don't have much mass on the one side. Then again I road race one of my cars and would never think re-drilling holes, too much punishment, used to go through a few sets of rotors up front until I added cooling and changed pads.

 

[petawawarace]

There would be no problem doing this. First off, the thin section between the new holes and the old holes are only an issue on one (the force pushes the stud towards the solid section on the other one)

If you were really worried, make some plugs to go in the old holes, and tack weld them in. All they need to do is stop the thin section from opening up the new holes. Tacking them in will not induce enough heat to cause any issues.

 

[tearlessj]

Just drill it, no need to weld it. I ran a 1/2 bolt through the one hole the lined up, then centered the center bore. Then it was lined up good enough to drill. Don't over think it.

 

[that-guy]

so its obvious that this conversation has more opinions than facts, and coming from a structural stand point, this seems plenty safe considering the mass of the rotor and power it would possibly need to stop (mostly street driving with occasional auto-x and drag racing) now the question is, what drill bit to use? i am going to try some Cobalt bits this afternoon and see how those work. i would think they should be fine as they cut through stainless if i use a slow speed, cutting oil, and moderate pressure

 

[mayday0017]

I agree that there are very few facts here and mostly opinions, but I do think it is funny the guy who decides it is "Plenty safe from a structrual stand point" is the same person whose very first question was "how safe is this to do, and if it is safe". If you were that set on doing it you should of just asked how to drill through a rotor.

Do what you want to do, but just redrilling is in no doubt a half *** way of doing this. There may or may not be any adverse effects from doing this but many people have jumpped off a bridge in my home town some had lots of fun, some it took the fun right out of them.

Side note, I doubt that it will break but I don't believe in "Rigging things" on a customers car even if they ask me to and pay for it. It is just asking for bad press down the road when someone else see's it.

 

[PMT314]

Does the 5-lug and the 4-lug pattern share the same distance from the center of the rotor (same radius)?

Following what K P said, if the patterns are not the same diameter and you try to use one existing hole, would that not make the rotor off center and allow it to move in more of an elliptical fashion?

 

[that-guy]

I agree that there are very few facts here and mostly opinions, but I do think it is funny the guy who decides it is "Plenty safe from a structrual stand point" is the same person whose very first question was "how safe is this to do, and if it is safe". If you were that set on doing it you should of just asked how to drill through a rotor.

Do what you want to do, but just redrilling is in no doubt a half *** way of doing this. There may or may not be any adverse effects from doing this but many people have jumpped off a bridge in my home town some had lots of fun, some it took the fun right out of them.

Side note, I doubt that it will break but I don't believe in "Rigging things" on a customers car even if they ask me to and pay for it. It is just asking for bad press down the road when someone else see's it.

i am saying this after the fact. this is after asking the question, after hearing everything in this thread, and after doing my own research. doing mechanical design for aircraft on a daily basis, this would not be ideal, however the rotor material is more than strong enough for the stress it will be under...I'm aware that at this point i am more defending myself than asking the root question, but i also do nothing to anybodies vehicles that i wouldnt do to my own

Following what K P said, if the patterns are not the same diameter and you try to use one existing hole, would that not make the rotor off center and allow it to move in more of an elliptical fashion?

the center of the hub is the same size since they were made for the same vehicle, just in different lug configurations. taking my measurments and plotting it out using CAD software (which again i use on a daily basis) everything adds up, so i see no issues with this now after asking the root question

 

[Lambo nut]

Redrilling rotors are done all the time in the kit car world. In most of the cases there are no other option to achieve the desired outcome.

Kevin

 

[porschedude996TT]

Look at the forces applied to the rotor hat. The bolts are in tension (to hold the wheel on) and the rotor is sandwiched in between the axle hub and the wheel. The wheel in most cases is centered on the hub which carries the up and down load or in shear. The bolts as they affect the rotor are held in shear, and only when there is breaking action. Most structural guidence on edge distance is 1-1/2 the diameter on what is called "tear-out" meaning how much material is in the way of the bolt being pulled out the side of said material. So with either 5 or 4 bolts on the hat to deal with the brake forces to the bolts in shear, there is no worry. Don't weld and don't worry.

I would drill them on an index head either on a mill or a lathe. Trying this by hand or on a drill press may lead to having to drill out the whole larger to the point that bolt will not be in shear to the rotor.

 

[mayday0017]

Hm... looks like I was wrong. It will still look kinda rigged to anyone who pulls the wheel off but functionally will be fine. Below is an explination to the question of calculating the the shear force on wheel studs. The below explains this is a bolted joint and the force should never be on the studs themself.

If the bolted joint is working correctly (e.g. the wheel studs are properly torqued) there should be no force acting on the wheel studs other than tension from preloading them. Any exteral forces should be taken by friction in the joint in the forms of shear, tension/compression, torsion about the bolt pattern, and bending. All externally applied forces should be less than the preload applied to the joint by the torqued/tensioned wheel studs. You should design the bolted joint to have enough wheel studs with enough tension to never slip or move; if it does, your design fails.

 

[Doug Arthurs]

If I wanted to fill the unused holes I would try tapping the holes to close thread size then loctite a threaded plug in. Since no welding get would be involved there would be no warping. If the loctite won't take the heat then make the plugs less then full depth thread and the will jam tight and self lock. Then just grind the plug flush with the rotor. I also think it is not really a job for a drill press but a milling machine with a rotab. Of course I am a little prejudiced because I have one of each.

 

[raddksn]

what about when these rotors ware below specks, I vote for converting to somthing easly found (off the shelf no mods.)!

 

[240sxguy]

I have a set of wheels that's dual drilled for 4x114 & 5x114. They look exactly like your diagram. These are wheels from a reputable company who wouldn't do it if they thought it was unsafe.

 

[Lambo nut]

what about when these rotors ware below specks, I vote for converting to somthing easly found (off the shelf no mods.)!

Then you would have to drill another set. As I noted before, in some of these cases there are no other ways to achieve the result desired. With kit cars it is usually going from one bolt pattern size to another, not so much a 4 to 5 bolt or the other way around, but the need of redrilling is the same.

Kevin