Slotted rotors?

I was wondering if they are advantageous at all for offroading. My rotors are getting a little worn down now, and since I am replacing them anyways, I am thinking about slotted, but I am a little concerned that the slots will just fill with sand and mud and not be advantageous but maybe even worse? Any advice anyone?

If you do alot of off-roading I would think they would be a really bad idea. They are designed to help dissapate heat, off road I thing would just collection points for mud, dirt, sand, whatever. They don't really have any self cleaning ability.

yeah that seems to make sense to me. :cheers:

Not so fast.....

The slots are not primarily for cooling, if at all. They add little to the surface area available for cooling. They are a compromise from drilled rotors, which allowed some cooling, but tend to crack if done poorly. The two primary expected benefits are shedding water for better wet performance, and shedding gas which under severe use causes the pads to float and thus increase pedal effort.

I think the gut reaction that the slots would somehow fill up with junk is unfounded. The slots are not that big/deep and considering the spinning and heat and pads wiping the rotors, there would be negligable "stuff" staying in there and if it did, you'de be no worse off than unslotted rotors.

I think its a wash wrt offroading and it would take rigorous testing to prove anything significant. Unfortunately there is little imperical evidence it would improve road performance also. Drilled-yes, slotted-marginal. But for a no-cost trade-off, maybe OK.

Isn't the floating from the pads creating gas only really associated with the racing/hi performance pads - and only when under extreme duty?



To me slots, holes, etc are just gimmicks made popular by people I call 'ricers'.

Gimmicks....no. Always practical...no.

As with everything else you get what you pay for. Slotted rotors would a ver good option if you dont wheel very much, but like others i would worry about it getting packed with mud, though the gasses try to escape would clear some of it.

Drilled and slotted are awesome, but only if you are willing tp spend the money on really good rotors. Racing teams dont take notes from 'ricers'.

haha all good stuff. I live in Alberta, so I wheel as much as possible for the few months that the ground has thawed out. I think the gains of cooling aren't really worth it if I am going to spend the money on good slotted/drilled rotors. I think I'm going to stick with a good old plain rotor.

The drilled and/or slotted rotors do not do much at low speeds, such as wheeling. Theyre designed mostly for several heavy duty high speed stops. This is why race cars used slotted, but drilled are weaker and more prone to crack. On a street car theyre pretty much useless.

I've been using the same set of Power Slot rotors for 4 years and they work just fine- both on and off road.I paid around $77/ea and they are the best wearing rotors I've ever used.After 4 years of hard use they still are as smooth as when they were new.All I've had to do is change brake pads every couple of years.I have the dust covers/backing plates removed from the inboard side so dirt doesn't get trapped and cooling is increased.They haven't warped, grooved or anything else along those lines.They've finally got enough wear on them that I'll actually get them turned, for the first time, sometime in the next 6 months.The only complaint I have is that they squeak a lot when heated up.

i got slotted rotors and they seem to work fine for me and i go offroading??

Dirt track racers run slotted and crossdrilled rotors, but they change them all the time. They claim it helps to keep mud and debris from damaging the pad surface.

I get enough sand/mud in my brakes I cannot imagine how noisy they would become if slotted or drilled rotors were on it.so many more entry points for grt to get into

If you run mainly in sand, they might fill up off-road. If you run mainly in mud (especially if you like to sink your tyres,) I wouldn't bother going slotted. Drilled might still clean itself out, or at least you'd wipe the surface clean when you applied the brakes - the holes would still be packed with mud.

Yes, drilling and slotting the rotors increases available surface area for cooling. However, it also creates stress risers, if the holes are left with fairly sharp edges.

A good drilled rotor will have the surfaces of the hole "rounded over" to create a smooth transition from the rotor surface to the through hole. A good slotted rotor will have a slot with a round bottom and round edges - smoother lines reduce stress concentrations. Smoother lines also reduce heat risers - which causes more stress.

Unless you can inspect them before you install them, or you can be assured that there aren't any sharp edges left from the drilling/slotting process, I'd stay away. I think Race Shopper does XJ rotors with an acceptable drill/slot pattern - but it's been a while since I've looked. (www.raceshopper.com, I think.)

The repuration for cracking that these rotors have is simply because people by cheap drilled/slotted rotors, and have the problems I've mentioned above. Something like that, that gets that hot, is going to crack - and it's going to start at the sharp edge of whatever. No surprise there - it's just a reputation that was started by riceboyz getting cheap crap for their piles of trash, and compounded by the people who sell them their cheap crap to install. Most riceboy parts I've seen would go straight into my scrap bin, if they showed up in my garage. I can always melt them down and cast them into something useful, if the need arises.

Moral? Buy cheap, get cheap. Especially on critical systems - like brakes! - it's worth it to spend a few extra bucks to get parts made correctly, with sound engineering behind them.

I'd run drilled/slotted rotors on my rigs - but mine are primarily "road warriors," and in Ghey Area traffic, I need every advantage I can get...

Once again, they are NOT for cooling.

Yes, the high speed crowd is concerned with the gas issue, but thier brakes are very good and thus the higher "bar" they meet before performance suffers. Junko brakes (read OEM) will get in over thier head at much more mundane speeds. Brake fade happens on OEM brakes after one stop, good brakes takes dozens if at all. So yes, we see fade on jeeps all the times, pull a trailor and your toast. "Extreme duty" for a Porsche happens above 150, for a Jeep around 45.

Agree with the comment about cheap junk. Rotors engineered with drilled or slots work great, rotors thrown on the drill press will break. Brakes have become a cosmetic statement and I am very suspect of available parts, are they cosmetic or real performance items?

An anecdotal comment about cracked or broken rotors is taken with a grain. It cannot be determined why that happened; bad engineering, bad heat treatment, bad habits? I wouldnt expect any 'merican manufacturer to be at the leading edge of brake engineering. Auto trans? Sitting at the stop light with your foot on the brakes when they are hot? Can you spell warped rotors? Yes. Not caused by slots.

Shogun said:

Once again, they are NOT for cooling.

Yes, the high speed crowd is concerned with the gas issue, but thier brakes are very good and thus the higher "bar" they meet before performance suffers. Junko brakes (read OEM) will get in over thier head at much more mundane speeds. Brake fade happens on OEM brakes after one stop, good brakes takes dozens if at all. So yes, we see fade on jeeps all the times, pull a trailor and your toast. "Extreme duty" for a Porsche happens above 150, for a Jeep around 45.

Agree with the comment about cheap junk. Rotors engineered with drilled or slots work great, rotors thrown on the drill press will break. Brakes have become a cosmetic statement and I am very suspect of available parts, are they cosmetic or real performance items?

An anecdotal comment about cracked or broken rotors is taken with a grain. It cannot be determined why that happened; bad engineering, bad heat treatment, bad habits? I wouldnt expect any 'merican manufacturer to be at the leading edge of brake engineering. Auto trans? Sitting at the stop light with your foot on the brakes when they are hot? Can you spell warped rotors? Yes. Not caused by slots.

Click to expand...

Since rotors don't tend to be heat treated (mainly machined from cast,) we can cross that one off of the list.

Bad habits? Entirely possible. I once dated a woman who insisted on driving with both feet - not because it was a stick (I didn't teach her to drive one - I had enough headaches...) but because she was somehow convinced that you had to always be on one pedal or the other.

I changed brakes on her car - all four wheels' worth! - right about every nine months. Mine lasted for years - but she never made the connection.

There are several reasons why I quit dating her, but that was one of them - couldn't teach her anything...

Rotors engineered with drilling or slots shouldn't break - but most drilled rotors are just thrown into a CNC machine with a drill bit or a longish end mill (which is more likely - the mill won't walk) and just done. Little to no finish work - if you're lucky, they drill the rotor, then grind the surfaces - rather than grind the surfaces, drill the rotor, then debur.

Most reports from the field (particularly negative ones!) are taken with an appropriate grain of salt on my end - after all, what's to say that it wasn't a one-off defect, or that the operator didn't cause the failure? If I don't know the operator's habits, for instance, that's a larger grain of salt. If it's someone I've known and ridden with for a number of years, the grain shrinks rather drastically.

Negative reports from "da riceboyz" are almost automatically ignored, ditto most things read in "riceboy rags."

Flipside - there's an old saying that goes, "If one person calls you a jackass, you can probably ignore it. If a dozen people call you a jackass, perhaps you should find out why." Consistently negative reports are going to warrant further investigation on my part - since there just may be something wrong (the chances are that the reports could have come from a number of incompetent operators - but I'll figure that out if and when.)

A lot of brake failures are also caused by not "bedding" the pads properly during break-in. This can result in pads cracking, "chunking" (parts of the friction breaking loose,) or just plain shattering (happened to that prior g/f I mentioned earlier - nothing I could do there.) This isn't the fault of the brake materials - pre-bedded pads get spendy fast! - but of the operator and/or installer (the installer should cover proper break-in with the operator.)

Replacing the pads and the rotors at the same time is a particular cause of failure - due to not bedding the pads. If you replace the friction members as a set, then break-in becomes critical - not only do you have to warm the friction material up gradually (to control outgassing,) but you also have to allow the cast material of the rotors/drums to "normalize" from the amourphous cast state - or they'll crack.

I'll typically clean up the drums/rotors the night before - removing all of the rust inhibitor! - and then take them inside. Put them in the oven to 400*F for one hour, turn the oven off, and allow them to cool (in the oven with the door shut!- the more gradually they cool, the better!) overnight. Do not pre-heat the oven first! This doesn't replace bedding, nor is it as accurate as a heat-treat oven, but it's worked for me for years, and it removes one potential problem during breaking. Usually, tho, I can get a nickel taken off each side of the old rotor and reinstall - which helps the pads break in a bit better, and the rotor is already normalised. Without normalising, there are myriad internal stresses within the rotor - from the casting and from the machining processes - and they're also going to be magnified by sudden heating and cooling. Your oven doesn't get hot enough to help the pads, tho - so follow instructions on breaking those in.

Ive got Powerslots for about five years, and havnt had a problem with sand, mud, dirt, dust, gravel, or other flotsam thats bound to find the crannies. Yes, I wheel quite a bit on all these terrains in thier seasons, and the vehicle is a DD as well. I replace the pads regularly, and havnt yet seen evidence of foreign matter damage on pad or rotor. Just my own personal experience with slotted rotors.

Just like the other Power Slot users that have posted...mine have been outstanding for years without any problems. No 'theory' here, just first hand experience.
Being in the desert, I see sand and rarely any mud, but nothing has ever becomed lodged into the slots.

If this were a high performance sports vehicle,..i could see it. I look at large heavy duty work trucks (ie F450, Chevy HD and the like) and they dont have drilled or slotted rotors. Instead the rotor is deeper, and seems to have gaps inbetween, allmost like having two disks, seperated by supporting spokes, if you will. This is of course on vehicles made for towing , and STOPPING ,..heavy loads.I would rather go for that , allthough one would need new calipers nad what not as well.Its more than a rotor change. I just dont believe you could gain any brakign performance from that little change. Especially if you go cheap, just like has been stated. And im a fan of "when it wears out replace it with an upgrade" Because i buy 12 year old vehicles.
If you want to really upgrade the braking ...get a drag racing parachute :spin1: J/K
Or that vacuum booster upgrade ive been dying to do.
But slotted rotors???? Nah ill leave it for others....