Slotted/Driled Brake Disks??

Your brakes don't know whether or not the heat build-up is from racing or trying to hold back your coach's weight on a long decent. In this case I think your mechanic is making a good recommendation, especially if you feel the price is acceptable. Labor should be the same with the only difference being the cost of the new discs. He may also suggest a better quality disc brake pad also, which is better at dissipating heat.

I have researched a lot on this subject. From what I read there are very CHEAP POORLY done rotor modifications on the market that cause many problems. I would check some of the truck mod web sites.

Just some info

Let's back up-- the service brakes should NOT be used for controlling speed of descent. They should be used only to slow you down enough to grab a lower gear. Engine braking should keep your speed in check on those long descents.

Drilled or slotted disks do nothing to improve brake efficiency.. If anything they take away from the braking surface area and lower the braking ability.. They have been used on motorcycles for years and we are told that it helps braking in the rain, cooling, etc... But they do it for cosmetic reasons only..

Do not bother with them as on the street it is just a cosmetic item and has no actual real use.


Sloted and drilled rotors where first needed in the endurance racing work. The reason was to add channels for off gassing of the braking compouds during repetative high speed and very hard braking rusulting in temperatures. These are temperatures well above what even standard street pads could handle without delamination of the braking compound from the steel backing. These are also cars that do not last an entire race on a single set of brake pads and they must be changed mid race. This creates the off gassing of binding materials used in the pads through the race as the binding matieral cooks out as the pad wears.

In a street environment even on a large vehicle, it is not needed as you do not generate the temperatures often enough to have brake fade due to off gassing of the compound or binding matieral. Most brake fade even in RVs and trucks are actually heat fade which drilled or slotted rotors will not improve.

Ontop of that I found that drilled and slotted rotors unless they are high end cryo treated rotors, they have a quick failure time in race conditions. I now run a better brake compound on my race car and OEM replacement rotors and no longer have to deal with off gassing fade and they handle the heat just fine.

In the "for what it's worth" category, I replaced the rotors on my Ford truck with Napa high end rotors. Not drilled or slotted but better material and better machine-ing to prevent warping (ford rotors are notorious for warping). Just an all around better rotor. 80k miles later still true as can be and perform well. I also rarely use my brakes to control a descent. It's all about the engine braking in tow/haul mode. Just find a good rotor with good reviews. No need to go drilling a bunch of holes in a perfectly good piece of metal.

wolfe 10's post is right on target.

We do a lot of traveling out west and navigate quite a few mountain grades.

On grade descent we gear down use compression braking then apply service brakes intermittently to reduce speed.

Just had the original brake pads on our coach replaced at 88,950 miles and pads still had about 38% wear left.

Can only relate to cars. Slots and drilled do help with cooling and cleaning away the brake fines and thus stopping power.
In really high stress like racing some prefer the slots that don't go all the way through.
I see a lot of smoking and or fire brakes on semis coming down mountains. I don't know if it would help in their case. They need much larger brakes and brakes on steer axle.
there might be some definitive answer. It does work or race cars wouldn't use them.
the best of all world are the carbon ceramic disc and they are drilled. They wear longer and give way more stopping. Don't know if they are available for heavy vehicles except airplanes.
Would probably cost a grand each. I think they want 5 thousand to change over our AMG.
By brand name disc that are properly heat treated and if grooved or drilled great. Don't buy the sold cheap for cosmetic effect ones.

Thanks for the responses. The context provide by JamesBr is good. We're pretty good about using the engine, but this vehicle rear brakes seemed to be a little hot. And on long grades, the pumping action typically used to control speed when it gets out of hand leaves them hot. Except for the rear brakes for this vehicle, my brakes are long-running investments (thanks to Dad for teaching me to drive).

We have learned on this forum to keep the slides greased on the brakes: this was not done by the previous owner. We're catching a lot of maintenance items this year that the previous owner (a friend, and still a friend) was simply not aware were needed by calendar rather than by mileage.

We purchased it at (if I remember right) under 50k miles and are approaching 80k at this point.

We've replaced the caliper on the rear right with a Napa caliper, and going on some advise on the list for the age of our vehicle, are replacing the flex brake lines to the calipers before heading for So. Cal. next month. Hoping that we have an un-eventful travel.

So, deciding on the new Napa rotors. If the new caliper, lines, and a complete flush don't change the characteristics, it will be back to the drawing board, but maybe not for the drilled and slotted disks. But rather to determine what causes the wear not characteristic to any of my other vehicles in the last 30 years. :)

- Tim

Well, after returning on from the trip, which included the Tejon pass in southern California, having previously replaced the brake disks on the back and the shoes and calipers, and complete bleed of the brake system, I can say our brake dragging problem is resolved without slotted brake disks and our brakes no longer smell hot (the event which happened sometimes even in the city at slow rates.

I believe that the deferred maintenance by previous owners contributed to this and other issues which seem to have cropped up as we've used the coach much more than previous owners. We've put about 32 K clicks on the odometer since we purchased it, and greatly enjoy owning an RV.