Why No Bronco Cross Drilled/Slotted Rotors?

[BwoncoHowie]

I especially like the chrome plastic hub caps with the "cross drilled rotor" plastic thingy on the inside so that '84 Toyota Tercel blingers can look cool. I would love to put some of those bad boys on my Bronco!!

LMAO ! ;D ;D ;D

 

[HotWheels]

I've been running the Raybestos BruteStops for about 2 1/2 years. Stops faster than my wifes mercedes.

http://www.raybestos.com/brutestop.htm

 

[lars]

The only way you'll settle this one is with a back-to-back stopping test, using the same vehicle, same weather conditions, same tires, same road, same brake pads. None of the links I've seen did anything besides assert that "this is better or worse because some engineer said so". I'm a mechanical design engineer myself, and I've worked in numerous industries, all of which were cost-conscious. But we also needed to sell product, and sometimes that meant designs/features/parts that were there to be attractive or draw attention, even if they cost more.

I don't know of any plating that has a higher coefficient of friction than the base metal that it covers. Cast iron is one of the best rotor materials around. Go look at an expensive Porsche that' been sitting for a few hours on a damp day. The rotors are rusting. The various forms of iron used for casting brake parts will likely exhibit only minor variations in friction coefficient, and any plating applied will likely soon wear off or literally be torn off- the surface of the iron deflects under braking loads- due to hertzian contact stress, if you want to get technical. That deflection weakens the bond between the base metal and the plating. Once it's gone, you are back to cast iron-not a bad thing.

Years ago I attended a sports car race in Europe. In the evening. I could see the rotors on some of the cars glowing red. Pretty impressive. Those sorts of conditions are somewhat different than the ones we subject our Bronco brakes to. I'm sure they needed to do everything possible to avoid cracking/warping or other failure modes. Perhaps including cross-drilling or slotting or other forms of stress relieving.

I too have the big Ford calipers, and these days I'm using the Raybestos Brute Stop pads that hotwheels mentioned (part no. BD50M at Checker/Shucks/Kragen). I experimented with lots of pads before I settled on those. Some carbon metallic pads I tried were actually much better, but only when they were hot. Since I don't race on mountain roads much, they didn't do me much good. The Brute Stop pads will fade a bit compared to the metallics, but the stopping power at low brake temps is so much better that the trade off is worth it (to me, anyway). The guaranteed-forever pads that most places sell will indeed last forever. Unfortunately they won't stop you either.

I would bet that under controlled testing conducted in a manner that most people drive their EB's (mixed street, highway, offroad) that pad material would be found to make a much bigger difference in braking performance than rotors.

 

[GusI]

Cross-drilled / Slotted rotors are holdvers from an earlier time of brake technology. People needed them on "race cars" at one point and imprinted on the concept - they are all show these days and no go.

Pad gassing simply doesn't happen any more with today's compounds. Pad glazing is no longer an issue either. Due to these factors, neither drilling or slotting provide benefit for the average consumer.

There was a great discussion of this over on corner-carvers which, if you're willing to wade through the swearing and abuse, discusses at great length the way brakes work and what genearlly works best.

If you changed your rotors and found you're braking better - did you change your pads, too? Probably. Further, your pedal travel is going to be shorter and feel firmer, particularly if you bled the system at the same time.

Yes, cross-drilling is available on Porsches. This is primarily because the people buying the cars *want* them. Most porsches are not driven on the track nor at the limit of their braking abilities. Most replacement rotors sold to the high performance consumers, people who take their cars on track and require maximum performance and heat dissipation, are not drilled or slotted.

Sure, you see a few of them on track days - most of them are cracked. Chamfering does help, particularly compared to the older methods of producing the rotors, but they will not last as long as plain rotors.

A disc brake rotor does two thigns for your braking system:

1) provide friction surface for the pad
2) act as a heat sink

By reducing the friction surface available, you're reducing efficency. By reducing the size and capacity of the heat sink you're reducing braking capacity and efficiency.

Vented rotors, a whole different thing than slotted or drilled, do make a difference in terms of cooling. They are designed to draw air from the hub and out through the edge of the disc to cool it. Drilling these rotors actually *reduces* their air pumping capacity and reduces their ability to cool themselves.

Simply, there is no reason, other than looks, for a 30-year old truck to have anything but vented rotors on it with high quality pads and fluid. You will get better performance, pay less, and your parts will last longer.

 

[HotWheels]

what's with the books? Good info though. My bronco did not stop well before...now it does.

 

[HotWheels]

btw I had a 911T also....Posche cars are an offshoot of their racers...nothing more. My 1971 911T was raced Paris to Dakkar and won 6yrs straight. They are not made to be comfortable...kinda like a bronco....do a job right and sacrifice nothing.

 

[brutis72eb]

Im with 74Bronc.....I want to go with the bling factor;D Theres nothing like a piece of spinning plastic supporting those 35's!

 

[7? BRONCO]

Might as well chime in....everyone else is. I just spoke to Performance Friction (O.E. supplier for Porshe, BMW, etc) last week and they said slotted is the best choice when compared to drilled b/c they don't crack. Also, most people won't like drilled rotors b/c they actually cause noise below 30mph (noise most Bronco owners won't hear b/c of our engines nor any race car drivers)---kids buy them for the bling factor. He also stated (like many above) that today's brakes don't emit gases like the old days. Finally, he said the drills or slotts do help slow a car down b/c your pads 'grab' them --- hence, your pads will wear faster and probably your rotors, too.

 

[HotWheels]

I don't hear nothing but bronco rattlin'

 

[EricLar80]

If you guys are looking for something that wont warp under the influence of heat, look at what Porche is doing with their supercars. They are using a ceramic/metallic composite rotor instead of just cast iron or the like. The ceramic has very good heat characterictics and the metallic part keeps it from shattering into a million pieces. Unfortunatley they cost $3000 a piece, according to my brother in law who works at Porche as a service writer. I agree with Lars, in our situation, the pads probably have more influence than do the rotors.
-Eric

 

[Mikey]

Well....I did change both the pads and rotors on my Capri since the rotors were warped so that is a valid point.

I'm convinced to try the new pads on my Bronco first as the rotors can be had from iRotors.com as a special order for $159 + shipping. The Bronco's rotors are not warped so I'll try the pads first. I have no idea what pads I have as they came with the conversion I bought from a dude. May be cheapos.

Anyone try a solid vs. cross drilled/slotted rotor change on their Bronco with no other changes?

The Mustangs and Capri's brakes are marginal at best for stock 5.0L HO driving...especially with an AOD. My original brakse were 10 inch rotors which cracked. I upgraded to used Lincoln Continental VII brakes with oversized calipers and SVO m/c. These rotors warped so upgraded to the cross drilled and slotted rotors with the Bendix Titanium metallic pads and stainless steel caliper pin guides. This combo solved my daily mountain driving problems.

Soooooo....this led me to thinking about upgrading the rotors on the Bronco. I really am convinced to start with the pads. Then, later, the rotors but.....the rotors aren't warped so why bother? Bronco driving IS much different than driving a 5.0 Stang.

OK.......<whew!> what are the best pads? Two have voted for the Raybestos Brute Force. Any other takers?

My final note is that I do think the cross drilled and slotted rotors offer more than bling factor though not as much as a good set of pads. Cost difference is under a C note so it's in the noise level of the mod options.

I definitely don't fit this mod in with the tuna can exhaust on a ricer.....<that stuff absolutely cracks me up!!!>.....or the rear wing bigger than the foo foo mobile <anyone hear Mojo Nixon and Skid Roper?>....ha! ha!...I gotta quit cracking myself up!! Vroooomm! vrooommmm ha ha ha! Did you fart? No, it the thing driving next to us! Hahaha!!! heheheh!!! They're coming to take me away ha, ha, ha!!..........STOP IT!

Mikey ;D

 

[74bronc]

I feel a real life Bronco Driver test article idea coming on. Anyone want to donate some stock rotors and drilled rotors for me to abuse? I will do an unbiased test and write-up for the mag.

 

[blksn8k]

Not to beat a dead horse ;D but if you want to see abused brakes try watching a NASCAR race at Bristol or Martinsville where they have a suspension cam looking at the front brake rotors. I don't think you will see any slots or holes, just extremely thick rotors.

 

[76Broncofromhell]

It's true except for one part: They do run slots on the road-course cars. My dad has the #9 Bill Elliot road-racer and the correct rotors for it are slotted front and solid rear. They run a .350 wall on each facet of the rotor and the slots are very shallow. The secret is they run about 3/4" or lining on each pad.

 

[iwlbcnu]

Wow!
How long ago did you use those rotors? Were you running the 10 inch or the 11 inch rotors? What kind of pads? I converted to the 11 inch on my 86.
Mikey

Mikey, I have converted to 11", 73mm calipers, w/ SS sleeves and lines and Turbo Coupe rear discs w/ 93 Cobra master cylinder. I had them for 2 years and about 5000 miles, maybe 15 auto-x's.

I run Performance Friction pads on the car and Bronco and like them.

there is no way in heck you can compare a 150 plus mph brake system to a 70 and under mph system. A race car is using a pad that is degigned to be used w/ a certain type of rotor.

You want a good test, put that race car beside a bronco, and from 55mph see who stops better. You might be suprised, as the race cars pads are only made to work at the very high temps they maintain.

Something else, how many of you have completely flushed your brake fluid in the last 2 years???? That really helps pedal feel.

All in all, on a street vehicle, you need the MOST rotor surface availiable and a good pad.

 

[HotWheels]

like I said. my bronco stops great now...not so before the slotted rotors and pads. I do live in the rainy NW also....

 

[Mikey]

Where do you get the Performance Friction pads? Have a look at the Bendix Titanium pads and see how you think they compare to the Performance Friction pads. http://www.bendixbrakes.com/products.html

You guys have convinced me to start with the pads. Anyone know of a brake pad comparison article on the web?


I haven't done the rear discs on my 86 or the ss lines.


I have a friend with a Camaro that is about to change from solid to cross-drilled and slotted front rotors. He has some sort of acceleration computer thingy and will run a test for us. We will try to be very scientific as we both are flight test engineers.

STAY TUNED!!!!

I would love to see some sort of article in Bronco Driver on this. Thanks for all the inputs! Keep 'em coming!
Mikey

 

[HotWheels]

Brutestops...maybe I should be a poll....let us see who uses what no?

 

[GusI]

If you're intent on getting useful data from your comparison, I would highly recommend the following:

New plain rotors
New fancy - schmancy - expensive - bling rotors
2 sets of new pads
bleed brakes prior to test of *each* combination

Be sure to bed the brakes prior to actual testing:
6 stops from 35 MPH
4 stops from 45 MPH

Drive around without using brakes for 10 minutes to allow rotors to cool. Proceed to test stopping power of new brakes.

Note that many factors modify stopping distances:

Quality of tires
Quality of road
ambient temperature
road temperature
Water - any

You'll need to complete these tests within a couple hours of each other to be truly valid. Starting in the early afternoon might be best to allow some heat to get into the road to improve traction a bit, dpendending on where you're at.

My supposition of what you'll find: No meaningful difference. Remember, we're talking about a G-Tech, I presume. It's fairly accurate for what it is, but it's not an institutional quality instrument, nor is it completely calibrated. Differences of a few percentage points either way for the combinations is unlikely to mean anything.

 

[HotWheels]

we could just take a coupl'a of our rigs down to the shop and stop on rollers and see what we c.