: Slotted rotor performance?



N0DIH
06-15-05, 07:28 PM
Has anyone, on a 12in front brake car (I think all 77-96 RWD cars are), replaced the front rotors with the slotted or holey drilled rotors and compared braking performance?

Is there any other changes to the rotors that have any significant effect on braking? Better metal? Better cooling vanes?

So, if I am handy dandy with my drill press, a stencil and dremel, will I see the same performance with stock rotors drilling the same features?

I did some drilling on one rotor, not the other on the front of my Bonneville when the rotors were new. With new brakes. And after set of brakes, I could see no appreciable improvements or detriments other than the little hairline cracks all over the drilled one. Mind you the rotors were the Autozone made in China specials. Brake wear was not significantly different between the left and right, no pulling, nothing different. No odd wear on the rotors. These were drilled only, not chamfered.

Wondering if in street driving, this is nothing more than a hype like the tornado air foil...

Thanks!

carguy16
06-15-05, 09:16 PM
It's a big hype. I dont know what i was thinking, thinking about getting slotted rotors!

I dont know what I was thinking, thinking about getting disc brakes for the rear!

As someone said, get your drums adjusted, and get some good equipment for the front, you will be fine. I can say that is 100 percent correct, I had no idea this 4,400 pounds land yacht could stop this well, its amazing!

Nodih, If I were you, just revamp the whole front end brake system: new calipers, rotors, lines, and some Raybesto's Superstop pads, I feel like IM driving a sportscar with these new brakes! :thumbsup:

Slotted rotors are a waste of money, dont do it.


Has anyone, on a 12in front brake car (I think all 77-96 RWD cars are), replaced the front rotors with the slotted or holey drilled rotors and compared braking performance?

Is there any other changes to the rotors that have any significant effect on braking? Better metal? Better cooling vanes?

So, if I am handy dandy with my drill press, a stencil and dremel, will I see the same performance with stock rotors drilling the same features?

I did some drilling on one rotor, not the other on the front of my Bonneville when the rotors were new. With new brakes. And after set of brakes, I could see no appreciable improvements or detriments other than the little hairline cracks all over the drilled one. Mind you the rotors were the Autozone made in China specials. Brake wear was not significantly different between the left and right, no pulling, nothing different. No odd wear on the rotors. These were drilled only, not chamfered.

Wondering if in street driving, this is nothing more than a hype like the tornado air foil...

Thanks!

N0DIH
06-15-05, 10:25 PM
My fronts are ok, but I suspect the rears are lagging some, so I will work on that.

I am one that still ponders the 11.5 x 2.75" swap on the rear.

I know Katshot and others say that the % is 95% front 5% rear. But if the rear grab more, then it would help, right? Assuming the ABS doesn't kick in prematurely. But still it would be grabbing harder. You don't want ALL the force on the front. So if I add 50% or more improvement in braking force in the rear, that 5% can become 7.5% or even 10%, which has seen improvements on the Caprices/Impala's with the 4 wheel disc. The % isn't so much what I am looking for, it is the capacity. If I can add larger, I will automagically decrease pedal force needed to perform the same braking force. There is still a traction limit, so eventually there is a limit on how fast you can brake no matter what, that will be limited by the tires eventually.

And after thinking about it, no, you can't do the stealth bolt mod on the D body. Why? 4 Channel ABS, not 3. The stealth bolt mod is for the old combination valve, assy, not the 4 channel controller we have.

I can see the slots if I was autocrossing or road racing, and that coupled with brake cooling ducts, else, I think it is useless. The primary reason is the pads outgassing and causing a pressure between the pad and the rotor, which loses the clamping pressure.

Anyone have differing opinions? If there is something I am missing, please speak out!

As for 4 wheel disc, the 1979-1981 T/A's with 4WD were one of the best stopping cars on the planet, 70mph to 0 on 170 ft. Porche 911 teratory of the day. And that was with no ABS. Just a 4000 lb car and some 11 in brakes. We have 12in fronts and 11in drums in the back, add in 11-12 in disc in the back and we should be on par if not better than the 79-81 F Body. And I know that car well, they do brake well, even mine with rear drums (9in drums!).

For now, stock, later, ponder the disc setup. Or the big rear drums. And now, the question begs to be asked, which is better? Rear disc from a 9C1/Impala, or the 11.5X2.75 drums from a Limo/C1500 GM Truck? Which actually has more braking force?

carguy16
06-15-05, 10:37 PM
GOod way to see how you rear brakes fare too, if your parking brake is adjusted properly, while driving about 30, or when ever, apply the parking brake, see how well you slow. Just dont apply it so some one rear ends you because you have no brake lights.

My fronts are ok, but I suspect the rears are lagging some, so I will work on that.

I am one that still ponders the 11.5 x 2.75" swap on the rear.

I know Katshot and others say that the % is 95% front 5% rear. But if the rear grab more, then it would help, right? Assuming the ABS doesn't kick in prematurely. But still it would be grabbing harder. You don't want ALL the force on the front. So if I add 50% or more improvement in braking force in the rear, that 5% can become 7.5% or even 10%, which has seen improvements on the Caprices/Impala's with the 4 wheel disc. The % isn't so much what I am looking for, it is the capacity. If I can add larger, I will automagically decrease pedal force needed to perform the same braking force. There is still a traction limit, so eventually there is a limit on how fast you can brake no matter what, that will be limited by the tires eventually.

And after thinking about it, no, you can't do the stealth bolt mod on the D body. Why? 4 Channel ABS, not 3. The stealth bolt mod is for the old combination valve, assy, not the 4 channel controller we have.

I can see the slots if I was autocrossing or road racing, and that coupled with brake cooling ducts, else, I think it is useless. The primary reason is the pads outgassing and causing a pressure between the pad and the rotor, which loses the clamping pressure.

Anyone have differing opinions? If there is something I am missing, please speak out!

As for 4 wheel disc, the 1979-1981 T/A's with 4WD were one of the best stopping cars on the planet, 70mph to 0 on 170 ft. Porche 911 teratory of the day. And that was with no ABS. Just a 4000 lb car and some 11 in brakes. We have 12in fronts and 11in drums in the back, add in 11-12 in disc in the back and we should be on par if not better than the 79-81 F Body. And I know that car well, they do brake well, even mine with rear drums (9in drums!).

For now, stock, later, ponder the disc setup. Or the big rear drums. And now, the question begs to be asked, which is better? Rear disc from a 9C1/Impala, or the 11.5X2.75 drums from a Limo/C1500 GM Truck? Which actually has more braking force?

ocjmakaveli
06-15-05, 10:44 PM
It's a big hype. I dont know what i was thinking, thinking about getting slotted rotors!

I dont know what I was thinking, thinking about getting disc brakes for the rear!

As someone said, get your drums adjusted, and get some good equipment for the front, you will be fine. I can say that is 100 percent correct, I had no idea this 4,400 pounds land yacht could stop this well, its amazing!

Nodih, If I were you, just revamp the whole front end brake system: new calipers, rotors, lines, and some Raybesto's Superstop pads, I feel like IM driving a sportscar with these new brakes! :thumbsup:

Slotted rotors are a waste of money, dont do it.


carguy I know your young so I'll go easy on ya but..........

I think most of your comments have little to go on except other people's opinions and your own, none are based on self-experience or first hand experiences.

Rear discs do help out in many ways regardless of whether you know how to do the swap or regardless of whether or not the person has the money to do it, 4 wheel discs are better than 2-discs 2-drums braking systems. They feel better when braking there's a noticeable change in nosedive to say the least.

Slotted rotors were created for a reason................High performance driving which includes any driving which can cause brakes to heat up quickly and stay heated for long periods of time.

I think in comparison are new stock brakes better than old stock brakes?.......YES

Yet I would say from first hand experience that a NEW 4 wheel disc system is better than the stock disc-drum setup.

I would've loved to have slotted rotors because I know from proven tests that they help reduce rotor warping under heavy driving but I couldn't afford them at the time i did mine so i settled with standard rotors.

If you can afford them I would recommend slotted rotors because they do offer a performance advantage under heavy driving especially high speed driving.

You can always have a 'good' brake system but why settle for less if you can have the BEST?

carguy16
06-15-05, 11:25 PM
Right now with the front brakes working great, I dont notice the rear brakes any more. Before the front brakes were fixed, I could feel the rear end grabbing.

At any rate, who races Fleetwoods around?:cookoo:


carguy I know your young so I'll go easy on ya but..........

I think most of your comments have little to go on except other people's opinions and your own, none are based on self-experience or first hand experiences.

Rear discs do help out in many ways regardless of whether you know how to do the swap or regardless of whether or not the person has the money to do it, 4 wheel discs are better than 2-discs 2-drums braking systems. They feel better when braking there's a noticeable change in nosedive to say the least.

Slotted rotors were created for a reason................High performance driving which includes any driving which can cause brakes to heat up quickly and stay heated for long periods of time.

I think in comparison are new stock brakes better than old stock brakes?.......YES

Yet I would say from first hand experience that a NEW 4 wheel disc system is better than the stock disc-drum setup.

I would've loved to have slotted rotors because I know from proven tests that they help reduce rotor warping under heavy driving but I couldn't afford them at the time i did mine so i settled with standard rotors.

If you can afford them I would recommend slotted rotors because they do offer a performance advantage under heavy driving especially high speed driving.

You can always have a 'good' brake system but why settle for less if you can have the BEST?

carguy16
06-15-05, 11:57 PM
When I first got my car, I thought the brakes on it were normal, wrong. The drums in the back had worn shoes, and they were way out of adjustment.

Disc up front, things werent quite working properly...

Just basic work, its fine. Awnustly, with my drums working right in the rear there is less nose dive. Drums grab, disc grab as well, I think thats crap saying disc brakes in the rear reduce nose dive, if the drums are adjusted, you can feel the grab from the rear, thats from my experience, if not then when you come to a complete stop there is a bigger front nose dive...

I am satisfied with my brakes, I drive my car hard some times, and I can say I am now satisfied and confident.

ocjmakaveli
06-16-05, 01:18 AM
Right now with the front brakes working great, I dont notice the rear brakes any more. Before the front brakes were fixed, I could feel the rear end grabbing.

At any rate, who races Fleetwoods around?:cookoo:

A very proud group of people race their fleetwoods your just on the wrong forum but what if his needs were to race his fleetwood your just answering based on your needs and that your satisfied with stock brakes but the question at hand was are slotted better and they are.

The thing is you dismiss a better brake system just because you are satisfied with a much less effective version but that's not how it should be just because you are satisfied with one version you cannot dismiss another version just because.......

btw awnustly is spelled Honestly

One day you'll realize why people race their fleetwoods and seeing as how the impala ss is identical except for the suspension and the impala ss is typically a sports car I don't see any reason why a fleetwood can't or shouldn't be raced when it is equipped with the necessary parts.

ocjmakaveli
06-16-05, 01:26 AM
nodih overall I would recommend a rear disc conversion because it does help out on braking but YOU MUST do the stealth bolt mod AND proportioning valve mod too to get the proper braking.

If you have the money I would highly recommend getting bigger wheels I believe a minimum of 17" and get larger Front rotors do some research and you'll find them it should be around $1000 for larger rotors and all I believe.
there are a couple topics on this I'll get you the info on it later and give you the link.

http://www.tceperformanceproducts.com/

for bigger rotors impala ss brakes which are the exact same as fleetwoods in case you didn't know just look for impala ss brakes they all fit our fleetwoods.

heres a topic on bigger rotors rather than stock http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=23;t=000756

http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=23;t=001113 (http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=23;t=001113)

http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=23;t=001145 (http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=23;t=001145)

http://impalassforum.com/noncgi/ultimatebb.php?ubb=get_topic;f=23;t=001295 (http://impalassforum.com/noncgi/ultimatebb.php?ubb=get_topic;f=23;t=001295)

http://impalassforum.com/noncgi/ultimatebb.php?ubb=get_topic;f=6;t=001524 (http://impalassforum.com/noncgi/ultimatebb.php?ubb=get_topic;f=6;t=001524)


overall though go to http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=forum;f=23;DaysPrune=5 you can do a search for what your interest is whatever your looking for whether your interested in superchargers or nos etc. they have the best most knowledgeable guys that have all been there and done that you'll get the best knowledge on the fleetwood there most of it is based on the impala ss but since they are the same except for the stock suspension being slightly different (more softer on caddys) the principles are the same.

Let us know what you plan to do. Bottom line though for regular everyday driving just new parts and good pads are good enough. If you drive at high speeds though or brake hard repeatedly on a daily basis then you might look into those improved brake systems.

davesdeville
06-16-05, 03:16 AM
If you experiance brake fade from hard braking repeatedly then you should go with drilled/slotted rotors. Otherwise there's not much use. I didn't experiance any fade towards the end of 2 short laps of autocrossing in the ETC so I don't feel any need to upgrade.

N0DIH
06-16-05, 08:15 PM
nodih overall I would recommend a rear disc conversion because it does help out on braking but YOU MUST do the stealth bolt mod AND proportioning valve mod too to get the proper braking.

My comment on the stealth bolt mod. If you have a 93-96 Fleetwood with ABS. You CANNOT do it, it does not exist. The combination valve isn't there, that is a 3 Channel brake thing. We have 4 Channel.

So, how do we proportion the rear brakes to the front?

My plans for now, are good performance street. BUT, If I get my way, autocrossing again. I miss it, it was fun, and what a joy to run the biggest car out there for handling. And I feel that I CAN make the beast handle well. But the brakes will need to be top notch, hence why I am looking at either disc or the HD drums from the trucks. I can make drums be just as fade resistant as discs, not biggie there. My concern is braking power, which is more powerful? You cannot say that discs are better as a blanket statement. (not saying anyone is!) I would rather be at the limit of the tires than at the limit of the brakes.

I have the old backing plates for the old style disc, but the e-brakes were lousy on them. I like Navy Lifer's (Bill) setup better. Close in rotor size, older is thicker though. ABS is mandatory for me, won't have it be disabled for discs, so older may be out.

ocjmakaveli
06-17-05, 03:17 AM
My comment on the stealth bolt mod. If you have a 93-96 Fleetwood with ABS. You CANNOT do it, it does not exist. The combination valve isn't there, that is a 3 Channel brake thing. We have 4 Channel.

So, how do we proportion the rear brakes to the front?

My plans for now, are good performance street. BUT, If I get my way, autocrossing again. I miss it, it was fun, and what a joy to run the biggest car out there for handling. And I feel that I CAN make the beast handle well. But the brakes will need to be top notch, hence why I am looking at either disc or the HD drums from the trucks. I can make drums be just as fade resistant as discs, not biggie there. My concern is braking power, which is more powerful? You cannot say that discs are better as a blanket statement. (not saying anyone is!) I would rather be at the limit of the tires than at the limit of the brakes.

I have the old backing plates for the old style disc, but the e-brakes were lousy on them. I like Navy Lifer's (Bill) setup better. Close in rotor size, older is thicker though. ABS is mandatory for me, won't have it be disabled for discs, so older may be out.

you can adjust the proportioning IT has been done to the fleetwoods and I did it too the abs has nothing to do with proportioning.

the abs does not regulate how much stopping force each wheel has and only regulates the slipping

the valve that is replaced is the one under the master cylinder the MC has a screw in front and in rear of it. If you check under the fluid piece which is the metal body parts where the tubes goto you'll see you screw in front with a plastic black piece covering the bleed hole and one screw in back you can't see too well. You usually completely replace the front screw with a shorter one in order to control proportioning and then you modify the existing rear screw and grind it to make it narrower so that all 4 brakes brake at the same time. With drum-disc brakes the rear brakes are energized first and their is a 1-2 second delay you can't feel it with disc-drum systems but once you change to rear discs you can actually feel the rear braking and then it takes about 1-2 seconds for the fronts to start braking but this is fixed with the proportioning mod which allows fluid to flow to both front and back simultaneously.

Trust me it can be done just contact bill harper and he'll get you everything you need in order to maintain ABS functionality for about $700 besides the rotors and other small locally available items.

If you need pics of the stealth bolt and the other bolt which goes in teh rear let me know and I can post some. i'll try to get some off the net in a couple minutes.

ocjmakaveli
06-17-05, 03:24 AM
ok here goes all include pictures.


BTW if you do the rear discs which I guarantee won't dissapoint and worth the money YOU HAVE TO DO THE metering mod I didn't like the feel of the brakes before I did this mod so...... add rear discs($700-$1000 complete setup with abs) then stealth bolt mod($30) and metering mod(free just need grinder or the like) and some time or money for labor.

pages with stealth bolt mod pictures

http://www.goissca.org/~gofasst/brake_proportioning_mod.htm

http://impalassforum.com/noncgi/ultimatebb.php?ubb=get_topic;f=23;t=001099#000002

http://impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=23;t=001265

the pics may not be exact in a few cases but I can post pictures of mine if needed just let me know but trust me these screws are on teh fleetwood at least on my 94 fleet they are.

Good luck

ocjmakaveli
06-17-05, 03:26 AM
one last thing if you like the hard long complicated explanations for why this works then read this great informative post http://www.impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=23&t=000252have fun :golden:

N0DIH
06-17-05, 01:16 PM
Then I must be missing something, as I have looked at my brakes, the fluid comes out of 2 tubes to the master cyl, to the ABS controller, then to the brakes at each wheel. There is no place to do the stealth bolt mod, as I have read it on the Impala stuff, they have a combination valve. If we have one, I can't find it.

The link is now dead, so if anyone has more info or an archive of the page saved, PLEASE send it!
http://www.b-body.net/Technical/Brakes/ComboValveMod/index.html

This is all I can find now.
http://www.ssincityss.com/Break%20Bolt.htm

ocjmakaveli
06-17-05, 06:08 PM
It is very very possible that since you have the towing option that you may not have it but I'll upload pictures now and you can take a look at mine.i have the master cylinder then 2 lines goto another metal piece under it then to the abs pump thing.

i also highlighted the valve on the last picture

turbojimmy
06-17-05, 06:34 PM
If you experiance brake fade from hard braking repeatedly then you should go with drilled/slotted rotors. Otherwise there's not much use. I didn't experiance any fade towards the end of 2 short laps of autocrossing in the ETC so I don't feel any need to upgrade.

I noticed appreciable fade in my DTS when slowing from 80 MPH onto a tight ramp that I take every day. That and the shudder from warped rotors. Knowing my dad has struggled with warped OEM rotors on every Caddy he's owned, I put drilled Brembos up front on my car. No fade and no warping (yet).

Jim

N0DIH
06-17-05, 08:34 PM
Now I feel like a idiot! Plain as day, I have no idea how I could have missed it!

Open mouth, insert foot.....

It has a sticker on it, "LR" Any ideas what the code means? I wonder if a V4P car has different proportioning due to 7000# trailer capability. It would make some sense to allow more rear bias.

carguy16
06-17-05, 09:56 PM
What is that black plastic thing, that looks like an oil filter by the master cylinder? It goes below the throttle adjustment box(or cable for throttle)...

N0DIH
06-17-05, 10:44 PM
Looks like an aftermarket alarm, is it?

brougham
06-18-05, 12:59 AM
If you are just driving it normally I'd just use the normal parts. The brakes on mine work good. It needed new rotors 2 years ago and I have quiet stop ceramic brake pads because the normal ones squealed all the time and it was annoying. There's also a lot less brake dust with them.

ocjmakaveli
06-18-05, 01:39 AM
Looks like an aftermarket alarm, is it?

yes that is the siren for my aftermarket alarm :)

btw nodih I got around to installing my fuel filler lock and it works great I just connected it to the left rear door in the harness that comes in on the left pillar it was real easy and the colors were the same as the lock motor. Worst thing was I had to grind a hole through the rear in order to get the cable to go out but it wasnt too bad.

N0DIH
06-18-05, 02:40 AM
Mainly I do a lot of driving (upwards 600 miles a week) just to get to work and back. Sometimes in traffic (Chicagoland has plenty thanks to the tollway), and you notice the brakes when they get warm. They still stop, but you can tell that it is not 100%. Not fade, just not as much friction as I would like.

I am looking at getting back into some autocrossing, which will tax the brakes heavily on this big of a land yaght. So having bigger, IS better!

The questions I have:
1. Stay with stock 11x2 drums
2. Go to 1976 and older 12x2 drums (longer lever, more braking power)
3. Go to C1500/Limo 11.5x2.75. They were good enough for a limo, why not for a FWB?
4. Go with Bill Harper's 9C1 modified brake package
5. Go with the 76-78 Eldo/Toro rear disc setup

#5 is a quite easy swap, but has some e-brake reliability issues, which is somewhat of an issue to me. But they were basically the front calipers on the rear with a ebrake lever added. Cadillac had a 2 3/8" piston, whereas Pontiac on the T/A, and later smallish Eldo's had the 2in piston in the caliper.

#4 is somewhat pricey, but best in rear disc reliability

#3 is likely the strongest most powerful brakes.

#2 is a decent choice, but backing plates are getting rarer. The bolt on from the 71-76 Full Size wagons (std J55) and option B/C/D with J55. JM4 was our beloved 11x2.

#1 modify the stock brakes for improved cooling.

Any comments?

ocjmakaveli
06-18-05, 03:56 AM
the only thing i will say about the limo brakes are that the needs are very different although the limo drum brakes will stop a limo they will never be under the extreme use of autocross drivers.


I think that drums do cause fade no matter how big they are because they are enclosed and get very little cooling.

if your only worry is stopping better then limo drums are fine but anything that would require repeated heavy braking in hot weather I would recommend discs.

Honestly brake fade can happen just on a hot humid day in traffic when in chicago it can go from 65mph to 35mph to 65mph every minute on the expressway.

If you want it done right I would say bill harpers way is best although not the cheapest for sure.

second best would be the limo drums.....

third would be just replacing your stock system with all new parts and good performance brake pads

N0DIH
06-18-05, 10:19 AM
Actually, somewhere I have an article from Herb Adams where he raced his Camaro "Cheverra". He ran the stock 9x2 rear drums to 150mph in race conditions without fade issues. He ran a 396 at one point, and later I think he went to a 427. He did his mods on many of his cars with drums.

What he did was drill 2 2-3in holes in the backing plate, and ducted 1 to forced air in from underneath cooling duct, then drilled 5 holes in the drums, out closer to the edge between each lugnut hole. Voila! excellent brake cooling!

For the street likely the drum holes may be too much and accept too much water in a rain storm and running through puddles, but the backing plate holes and ducting up to them and the drum itself are streetable mods if ducted properly.

They used to make semi metallic drum shoes at one time. You don't want full metallics on the street, they don't work well cold.

So I am not against drums, they have less drag than discs and they are cheap and fairly easy to work with. But discs are often overall superior, and look better to boot.

http://pages.tias.com/9074/PictPage/1922549593.html
http://www.74-77camaro.com/Articles/shootout/great-camaro-shootout.htm

Quoted from that article:
"Also benefitting from the front air dam are the brakes. Ducts in the dam take air from behind the grill and force it into the front brake caplipers. Each front brake utilizes mettalic brake pads and backing plates which have a fitting for the attachment of the cooling ducts. In the rear, metallic linings are also used, with holes cut in both the brake drum and backing plate to keep air circulating through the system. Holes in the VSE wheels also help keep air moving through the brake system. It should be noted that the metallic linings were used because of the Willow Springs testing, and are not recommended for street driving where semi-metallic linings should be more than adequate."

"To aid in brake cooling, Adams drills five 1 1/2 inch holes through the brake drum and two other holes in the baking plate to allow air to flow through the drum and cool the linings. Note the adjustable Koni shock absorbers."