Drilled Rotors? Nope!

[Max Power]

I've got a new set of rotors for the next brake change... I'm thinking about having them cross drilled, 10 sets of three holes, 30 holes each, 60 holes total. I could probably do it on my drill press for the price of a few drill bits. Or I could pay a machine shop guy prolly <50 cents a hole. Anything that would help bring the beast to a halt quicker is WELCOME. I'm not sure what size hole though... maybe 3/8, I need to do more research.

the reasons are best explained here...

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2408689233

of course mine wouldn't be slotted.

I do hear that they eat up pads quicker, but thats ok w/ me. Anybody have any experience here? What do you guys think?

[ April 30, 2003, 06:34 PM: Message edited by: Hugh Jazz ]

[turtlejoe]

I have heard that drilled rotors do indeed eat up pads quicker, and that they also tend to fill up with mud and crud when off-road. That may not matter if you drive mostly on the street though.

I improved my braking by adding a dual diaphragm booster from a J-20 and am quite happy. Some on the forum have changed over to the GM HydroBoost system with even better results.

Do a search for hydroboost and/or dual diaphragm and you should find plenty of information.

[Go3Team]

I would think that the holes are there only to dissapate heat from slowing down from high speeds, such as drag racing, etc. I don't think they would improve braking from slower speeds as these Jeeps are accustomed to. I would look into the above comment before shelling out the cash on those.

[Stuka]

they actually have pooring breaking ability in most cases. You need at least a 4 piston claiper to have enough gripping force to counter act the missing surface area. They eat standard pads *WAY* faster, they are designed for use with race pads, which dont work until they are hot. In a race car with race pads, you actually ride the breaks for the first lap to heat them up so they actually will work.

[The Anti-Chrysler]

Ditto on recommending the dual-diaphragm booster first.

Also, try replacing your front calipers if they are old. They are GM, and are about 12 bucks for rebuilts. Old ones with bad seals and dirty bores can stick and lead to bad braking performance.

Also, replacing rubber lines is a good practice if they are old.

Rear self adjusting brakes seldom do just that. Tighten them as necessary.

The holes drilled into a rotor definitely would not be 3/8". More like 3/16"

Holes will likely not help a vehicle like yours in everyday driving situations.

[RWalker]

Drilling the rotors could actually weaken them and make them warp easier.

[bvibert]

Drilled rotors are more prone to cracking too. Don't do it, its not worth it... unless your FSJ is secretly a race car :rolleyes: ;)

[The Anti-Chrysler]

Preoperly drilled holes won't help warp them, but they won't help performance. They actually help dissipate heat (allow air to circulate through), which would reduce warping.

Rotors that are "scored" (cut grooves from inside to out) can help braking performance by cleaning the pad and producing a more aggressive surface, but don't last too long and will reduce pad life considerably.

[Max Power]

Thanks everyone for your posts.

Brembo sells brake kits that have drilled rotors and 4 piston calipers, and these brakes do work better when they are hot, Stuka was right on both points.
My jeep stops adequetly now,but since I've already got new rotors to replace my current (way under spec) ones...

I read with great interest the dual diaphram swap, its on the to do list.

Here is an excellent article about drilled rotors, hope you can forgive the fact that its an isuzu.

http://www.off-road.com/isuzu/womb_brakes.html

Heres some reviews of powerstop rotors, (I've aleady got new stocker rotors, but this is pretty close, these are slotted tho) in the 15 reviews, about half were negative, good reading tho.

http://www.carreview.com/pscParts/Brakes/Power,Stop,Cross,Drilled,Rotors/PRD_1053_1579crx.aspx

Thanks

Robert

[Stolen76]

just my .02... the way it was explained to me is that the slots help gasses escape during heavy braking. gas build up from the heat and friction actually reduces the force on the rotor by pushing the pad back.
I delivered pizza for quite awhile and wuold run 800 - 1000 mile a week. hard braking on busy roads in heavy traffic. When I would do a brake job, I'd cut a vertical groove in the pad to allow the gasses to escape. Everyone I worked with did the same with good results. It was a trick passed down from a taxi shop. I'm still not sure if it was psychological effect or real performance, but I did notice a difference in heavy traffic.

[RamJetFSJ]

I wouldnt do it your self, or just have a machinist do it. To much chance of failure. the good brand rotors that have it done, have the holes champfured, so theres less stress, and less chance of cracking. If you really want them, Id just get slotted rotors. They do the same thing, but with less problems. they will clean out better, and work better when wet. I believe Napa sells slotted rotors for Chevy 44, which is the same as the Jeep.

But your not going to get much stopping from the slots or cross drills. Maybe a little better initial stopping power, and less brake fade, but thats about it.

And you will need to run a harder performance pad or they will get chewed up fast. I like Porterfields Carbon-Kevlar street pad. Thats what I run with my slotted rotors on my Dodge Dakota 4x4.

[Max Power]

The mtn passes here (both on and off road) sometimes really do call for some long, demanding high heat braking situations. I think that the right pad with a drilled/slotted rotor could decrease both rotor temperature and stopping distances.

I'm not going to make any rash decisions, I've got at least another year on my current brake setup, allowing me ample time for research and discussion.

Thanks all.

[scotty]

sounds like ALOT more little places to have to pry mud out of with a screwdriver in doing post-wheeling maintenance tongue.gif

[Serious Johnson]

Drilled rotors can actually reduce effective cooling because of decreased rotor mass and thus thermal inertia. They can also crack and even catastrophically fail in extreme situations.

I run them on the lightly-loaded solid rear rotors on my sports car purely to reduce unsprung mass, but don't expect, and have never seen any other performance benefit.

Modern pads do not off-gas to an extent requiring added escape paths beyond the single radial notch seen in some OEM pads. Slotted rotors can improve initial wet bite quite a bit, and improve pad friction by continually shaving the pad surface. Of course, this will increase pad wear.

Bottom line, unless you have fade issues, there's little to be gained and a fair bit to be lost by deviating from OEM.

I wouldn't mind upgrading the brakes on my Wag because I pull an Airstream in the mountains, and the **** things sometimes fade to the point that I have to rely on the trailer brakes to slow the rig. My first path of inquiry will be to someone like Carbotech to see if they'll make replacements for my stock pads & shoes.

:-

[CaliGWagon]

FWIW, I roadrace and autocross my M3, and I run slotted rotors. Drilled rotors are just abour dangerous as they tend to crack, warp and occasionally come apart. The ONLY acceptable rotors with holes in them have the holes CAST into them. Everything else is just for show.

Slotted rotors are noisier but they do help releive gas buildup (no puns)if you are running a road course or the like.

For the FSJ. Bigger would be better, better clamping would be next, but plain old discs are great.

[Jeepadilly]

I just did a complete brake job on Bear including two bran-spankin-new rotors in front (pressed onto the old hubs)...new wheel lugs...and rebuilt calipers...and if I stopped any faster, the FD would have to scrape me off the inside of my windshield!!!! Forget the holy rotors and mind the advise of the Pros above me...Regards
Brian ;)

[Max Power]

Thanks everyone fo their expertise and opinions, after ample research here and otherwise, I drilled rotors are not only a bad idea, they are a misnomer, b/c as pointed out earlier in this post, the hols should be CAST in the rotor (and then be machined) plus it seriously compromises the integrity of the rotor.

On the subject of grooved rotors, though they may offer some small benefit in wet weather/extreme heat braking, I don't think that the benefits justify the added hassle.

thanks again,
Robert