Customization/Safety question...

[richierich78]

I posted this in the general room as well but since it's not only a safety issue but a genuine improvement I felt it could go here as well...

I have an '07 LTZ with 24" and low-profile tires.

I always planned on putting "performance" brakes and rotors on my baby but I was going to wait until I needed brakes and just knock it all out.

Well, the other day I almost had an accident, car in front of me made a quick stop and I had to swerve into the wrong lane to avoid hitting them. (luckily there was no oncoming traffic or cops around). I wasn't necessarily too close but I might have been going too fast (obviously) for that particular situation.

I used to drive an Explorer (which is a whole lot smaller) and it would have come to a stop a whole lot quicker. We all know the 'hoe is a big girl and she needs a lot more force to stop.

So at that point I made the decision to get the brakes and rotors more sooner than later.

What do you guys recommend as far as improving performance and specific brands to by?

Please Dad, don't say, "You shouldn't be driving so fast..." :lol:

 

[Gambler]

What kind of budget are you looking at?

 

[richierich78]

For parts... I don't think more than 200 per wheel.

Honestly, I don't know what I'm getting into. I'm sure the "best" costs a fortune. But I need to know the right direction. I've never gotten "performance" before. On my old one I would just go to Auto Zone and replace it with standard brakes and rotors.

 

[Bear]

http://www.autoanything.com/brakes/20A50532A1.aspx

I am on the same boat here. Perhaps the Brembos are out of reach but the Baer set is not as bad, only thing is it has only 2 piston calipers, isn't that the same as stock? Would they really be an improvement in braking performance? If anyone knows of anything better please let me know, I am at 64,XXX miles and am on my 3rd set of rotors. I don't want to spend the money on the Brembos but the Baer set only has the 2 piston setup, am I concentrating too much on something unimportant? Any help would be GREATLY appreciated.

 

[richierich78]

http://www.autoanything.com/brakes/20A50532A1.aspx

I am on the same boat here. Perhaps the Brembos are out of reach but the Baer set is not as bad, only thing is it has only 2 piston calipers, isn't that the same as stock? Would they really be an improvement in braking performance? If anyone knows of anything better please let me know, I am at 64,XXX miles and am on my 3rd set of rotors. I don't want to spend the money on the Brembos but the Baer set only has the 2 piston setup, am I concentrating too much on something unimportant? Any help would be GREATLY appreciated.

I think the larger rotors and calipers should help a lot. Thanks for the link, now I have an idea of what I'm looking for and I'll check out some of the auto parts/performance shops in town and see what they're talking about.

I'll make sure I post my findings/results.

 

[JKmotorsports]

An upgrade in rotor and caliper size will definitely help. Larger diameter rotors offer the opportunity for larger calipers and pads. Larger pads and rotors equals more surface area friction to help stop. Also, the larger total piston surface area you have, the better the squeezing power of the calipers. 4-6 piston calipers are ideal for trucks with much larger and heavier tire and wheel combos.
Even if you were to upgrade to just larger rotors and move the stock calipers out with relocation brackets, that will help by providing better leverage for the calipers. Better leverage makes it easier for the calipers to slow down the momentum.
Slotted and cross-drilled rotors help keep the rotors cooler, lessening brake-fade. It also gives a place for the gas build-up to escape so your pads don't "float" during heavy braking. Also look for rotors with directional cooling vanes sandwiched between the rotor surfaces. This will help keep the rotors cooler as well.
Here's just a few good companies to look into for brake ungrades:
Baer, SSBC, Brembo, PowerStop, Wilwood, and Stoptech.

 

[strangeengine]

An upgrade in rotor and caliper size will definitely help. Larger diameter rotors offer the opportunity for larger calipers and pads. Larger pads and rotors equals more surface area friction to help stop.

While it seems like this would provide additional stopping power, it does not.

Friction is a function of the pad surface (the friction material) and the force applied to it normal to the rotor. If additional surface area resulted in more friction, you could just apply more force to the pads ("push the brake harder") and get the same end result.

Also, the larger total piston surface area you have, the better the squeezing power of the calipers. 4-6 piston calipers are ideal for trucks with much larger and heavier tire and wheel combos.

Umm, no. See above.

Multi-piston calipers are great for evenly distributing braking force across the pads, making for even pad wear and efficient force delivery, but they don't increase the braking ability (in spite of anything Brembo/StopTech/AP/Wilwood/Baer/etc would have you believe).

Some of this is a function of caliper design. BMW's ATE-sourced calipers, for example, are a sliding-caliper design with one large piston. If you used a fixed-caliper design, like Porsche, you would by definition use at least 2 pistons (one on each side, since the outer caliper piece does not slide). Presto, blingy "multi-piston" marketing speak!

The fixed-piston caliper is a better design than the single-piston sliding caliper, but not because of the higher piston count per se. The sliding caliper is tends to result in poorer brake pedal feel because the part of mechanism connected to the hydraulics is moving vs. the solidity of the fixed caliper (vast simplification, but you get the idea).

Even if you were to upgrade to just larger rotors and move the stock calipers out with relocation brackets, that will help by providing better leverage for the calipers. Better leverage makes it easier for the calipers to slow down the momentum.

You get slightly better "leverage" because the rotors are moving slower relative to the pad at wider diameters. However, the energy to be dissipated is the same, so ...

Slotted and cross-drilled rotors help keep the rotors cooler, lessening brake-fade. It also gives a place for the gas build-up to escape so your pads don't "float" during heavy braking.

Slotting and cross-drilling is 99% marketing bling. Pads don't out-gas the way they used to.

Cross-drilling is a great way to buy rotors frequently. In the case of basically all rotors but OEM Brembos fitted to Porsches (and possibly StopTechs), the holes are drilled. This weakens the metal and the rotors will eventually crack at the holes. Porsche rotors are cast and the holes are cast in place. This allows the iron molecules to arrange themselves around the holes and the crystalline structure of the metal is not disrupted by drilling holes in it.

Also look for rotors with directional cooling vanes sandwiched between the rotor surfaces. This will help keep the rotors cooler as well.

Totally legit and great advice. If you choose directionally vented rotors, make sure you install them in the correct directions! While it appears that you would want the rotors to "scoop" air from the perimeter, the opposite is actually true. You want the rotor to 'fling" air from the hub (center) to the edge.

Here's just a few good companies to look into for brake ungrades:
Baer, SSBC, Brembo, PowerStop, Wilwood, and Stoptech.

Brembo and StopTech are the top of that stack. From the racing world, add AP.

 

[JKmotorsports]

While it seems like this would provide additional stopping power, it does not.

Friction is a function of the pad surface (the friction material) and the force applied to it normal to the rotor. If additional surface area resulted in more friction, you could just apply more force to the pads ("push the brake harder") and get the same end result.
.

While I agree with some of the points you mentioned, some of it doesn't make sense, at least not from my experience of racing and working on cars anyway. The composition of the pads have a huge impact on the friction coefficient and stopping power sure, as well as the tires. But with all other factors being the same, if you have more of that material in contact with each other over a larger surface area, you generate more friction and increase the ability to transfer the momentum into another form of energy, heat. Generally the bigger diameter the disc, the bigger the pad area can be, the more friction can be generated. This is the swept area, and the more you have, the better.
Yes, you can push the brake pedal harder, but only to a certain point.
I do agree fixed are definitely better than floaters. But in addition to evenly distributing the force applied to the rotor and the better pedal feel, multi and larger pistoned calipers help dissipate heat quicker and can help amplify output of brake torque, given the piston bore in the master cylinder is large enough to help supply the needed hydraulic pressure to the larger and/or increased number of caliper pistons. Multi piston calipers are more efficient in delivering force just like you said, which means more friction from the added pressure means better stopping given everything else is equal.

 

[strangeengine]

While I agree with some of the points you mentioned, some of it doesn't make sense, at least not from my experience of racing and working on cars anyway. The composition of the pads have a huge impact on the friction coefficient and stopping power sure, as well as the tires.

No, the pad composition affects the heat range the pads work in. The friction coefficient rarely changes much.

But with all other factors being the same, if you have more of that material in contact with each other over a larger surface area, you generate more friction and increase the ability to transfer the momentum into another form of energy, heat. Generally the bigger diameter the disc, the bigger the pad area can be, the more friction can be generated. This is the swept area, and the more you have, the better.

No, this is a common misconception. Friction is a function of force normal to the rotor.

And, frankly, if you can lock the tires, you've got enough force anyway.

Yes, you can push the brake pedal harder, but only to a certain point.
I do agree fixed are definitely better than floaters. But in addition to evenly distributing the force applied to the rotor and the better pedal feel, multi and larger pistoned calipers help dissipate heat quicker and can help amplify output of brake torque, given the piston bore in the master cylinder is large enough to help supply the needed hydraulic pressure to the larger and/or increased number of caliper pistons. Multi piston calipers are more efficient in delivering force just like you said, which means more friction from the added pressure means better stopping given everything else is equal.

It's rounding error, though. Multiple pistons really just give you even pad life and great brake pedal feel. Oh, and bragging rights.

Your points are valid about heat dissipation, but we are talking about stopping distances and on the first stop it just doesn't matter. Heat soak is another issue, of course, and we care about that when racing we we brake a lot repeatedly with short cooling intervals, but less so when hauling our SUV down for a red light.

- Mark, also a racer

 

[JKmotorsports]

Brake tq ft/lbs = disc radius(in.) * clamping force * coefficient of friction / 12.
Plug numbers into the equation and you will see that a larger rotor does increase braking torque.

Brake pad composition and friction coeffiecient:
Different materials have different friction coefficients as well as different heat ranges. Most brake pads have a rating (two letters) that show roughly the coefficient of friction at two different temp levels, 200F and 600F.
The first letter represents the coefficient of friction at 200F, while the second represents friction coefficient at 600F.

E: .25 - .35
F: .35 - .45
G: .45 - .55

The higher the number, the better the ability of the pad to "bite". Of course, you also want to make sure the pads are within the heat range you will be using them in. Higher temp pads have a lower operating temp, so they will have a lower CF until they warm up, which is not safe for the streets.

Also, notice the slot down the middle of most high quality pads. Brake pads used to be made out of asbestos, which would give out gases when heated to extreme temperatures. These gases would get trapped between the pad and rotor and cause inefficient braking. Slotted and drilled rotors were designed to give the gases some place to go. Modern brake pads no longer out-gas after you have bedded them in. However, it is possible to have a small amount of brake pad material to burn off during heavy braking. When any organic material burns, there is a chemical reaction and it gives off vapors/gas. To make sure this doesn’t become a problem, quality brake pads have a slot down the middle to give the vapors or gas someplace to escape.

 

[strangeengine]

Agreed, but it's all academic if you can already lock the brakes. Additional brake torque becomes meaningless in that circumstance, as I've said a couple of times now.

Let me guess - you sell big brakes.

 

[JKmotorsports]

Agreed, but it's all academic if you can already lock the brakes. Additional brake torque becomes meaningless in that circumstance, as I've said a couple of times now.

Let me guess - you sell big brakes.

No, just putting out there what I have learned from teachings, research, and experience. And yes I agree with you, additional brake torque is meaningless if the wheels already lock. The facts (or opinions) I put out there weren't intended for everyone with larger wheels, hi-performance vehicles, etc, just in general.

For everyone concerned of their vehicle's braking ability with larger wheel combos: If your braking system has the ability to activate the abs system on your street driven daily driver during a panic stop on a dry road surface, then your brakes are more than likely sufficient enough for the task.:thumbsup:

 

[Bear]

No, just putting out there what I have learned from teachings, reasearch, and experience. And yes I agree with you, additional brake torque is meaningless if the wheels already lock. The facts (or opinions) I put out there weren't intended for everyone with larger wheels, hi-performance vehicles, etc, just in general.

For everyone concerned of their vehicle's braking ability with larger wheel combos: If your braking system has the ability to activate the abs system on your street driven daily driver during a panic stop on a dry road surface, then your brakes are more than likely sufficient enough for the task.:thumbsup:

All I am after is whether slotted and drilled rotors will diminish my trips to the parts bin and getting rotors. Mine have warped rather easily, I have factory 20's on the Yukon and am not really planning on upsizing, the ABS has kicked in for me before so I am confident I will stop, the warping is my problem, will a set of cheap Baer Alumas do the trick? The big brake kit comes with larger rotors and calipers than stock. It is in fact a 2 piston caliper and someone mentioned a 4-6 piston caliper being ideal. I can't find anywhere where it says the rotors are cast with the openings rather than drilled and someone stated in an earlier posts those rotors will in essence chip and crack at the holes if they are not cast in that manner. I don't want to throw $2,500 away if the 2 piston setup is less than ideal and the rotors are prone to cracking.....:umn::ktoe::confused2:

 

[JKmotorsports]

All I am after is whether slotted and drilled rotors will diminish my trips to the parts bin and getting rotors. Mine have warped rather easily, I have factory 20's on the Yukon and am not really planning on upsizing, the ABS has kicked in for me before so I am confident I will stop, the warping is my problem, will a set of cheap Baer Alumas do the trick? The big brake kit comes with larger rotors and calipers than stock. It is in fact a 2 piston caliper and someone mentioned a 4-6 piston caliper being ideal. I can't find anywhere where it says the rotors are cast with the openings rather than drilled and someone stated in an earlier posts those rotors will in essence chip and crack at the holes if they are not cast in that manner. I don't want to throw $2,500 away if the 2 piston setup is less than ideal and the rotors are prone to cracking.....:umn::ktoe::confused2:

Drilled rotors will usually develop minute cracks around the edges of the holes unless they are cast in place like strangeengine stated. Most companies that offer drilled rotors have chamfered edges around the holes that help alleviate the stress cracks some, but not completely. I've seen it plenty of times on cross-drilled rotors that have seen long or heavy use.
Take a look at this kit for an idea. It has larger, slotted rotors and relocation brackets for your stock calipers. If you're stopping just fine with your current stock setup but just want better, longer lasting rotors, something like this may be what you're looking for. There are several companies that offer upgraded, better quality rotors as stock replacements.