Brake Rotor Weight

[Sheepdog]

I'm still new to this forum and have been reading all the third gen stickies to bring myself up to nominal on T4R topics. I found the brake rotor info to be particularly interesting. Coming from a motorcycle background, the first thing I :dammit:thought about with the thicker rotors was increased unsprung weight. As I'm sure everyone is aware, unsprung weight places greater demands on the vehicle's suspension. In extreme cases, springs and shocks must be beefed up to regain control causing ride and wheel control to suffer. This leads to my questions:

1). Have owners who have completed this mod noticed a change in suspension compliance?

2) Is rotor warping mainly a problem for vehicles equipped with automatic transmissions, or are 5-speed 4Runners (and their advantage of compression braking) also affected?

3). Do slotted or drilled aftermarket rotors degrade braking performance?

I've done a bit of searching, but haven't yet found any quantifiable answers. I recently replaced the stock rotors on my Moto Guzzi with Grimeca rotors from an Aprilia RSV-4 and reduced unsprung weight by over 2 lbs. The change was so dramatic that I had to reduce compression and rebound dampening in my forks by 4 clicks. Does the vastly greater weight of my four-wheeler negate a relatively small weight gain?

 

[DC runner]

NO.

Stop right there. I am a lifetime biker and you can't bring that logic to a car... a car with a suspension designed to hold up the weight of a vehicle with several thousand pounds...

A rotor weighs, what, 10/15/20 pounds. That weight wasn't in any way impacting your suspension. In fact, you want a thicker and heavier rotor. A thin, light rotor will not dissipate heat as well and will warp.


Warping has 0 to do with transmission and everything to do with how you drive and how you maintain your vehicle. It could be due to a stuck caliper or someone who loves to ride their brakes in the summer when it is 110 degrees.

It isn't the transmission.


Don't waste money on slotted or drilled rotors. Performance rotors have a time and a place, but unless you upgrade your entire brake system; you need good, solid rotors. Some people enjoy the looks, for sure, but you won't see any braking improvement unless you upgrade calipers and the cylinder to physically grab the brake harder.

EDIT: Engine braking. I wanted to note on this as well, you actually get more efficient engine braking in an Automatic. The physical impact of "hydraulic" connection helps increase torque as well as increase engine braking. Also, drivers of Automatics tend to use engine braking more, as they have no alternative not to. You can easily press in the clutch to avoid it in a manual, but people don't usually pop over into N. The sole design of an automatic transmission using a fluid power transfer via the torque converter is all about energy multiplication. This 1. increases the power potential and 2. increases the effect of brake drag. As it isn't a 1:1 connection, unless the torque converter is locked up; it is smooth.


It is the two fans sitting across from each other.


What does your motorcycle weigh? 300 pounds? 400? A 4runner weighs around 3500 hundred pounds. A car suspension is designed for far heavier loads. A Rotor is literally the least of its worries. The engine alone weighs much, much, much, much more than that. Hell, if you consider the weight of coolant; the coolant in your car weighs more than a rotor.

 

[Sheepdog]

My Guzzi weighs over 650 lbs and my Triumph a little over 500. Both of them ride on only 2 wheels.

BMW would disagree with you about unsprung weight on 4 wheelers...they have spent a good deal of money finding out how to reduce unsprung weight on their cars and SUVs. These measures include alloy A-arms, alloy wheels, and right-sized brake components.

Automatic transmissions are quite efficient, but how many people downshift as they decelerate? I think most would agree that very few drivers do, instead using their brakes do the job. It is a fact that vehicles with manual transmissions experience longer brake pad/shoe life. I applied this fact when I formulated the question about brake warping with 5-speeds transmissions.

Coolant and engines are not carried in an unsprung position.

Drilled or slotted rotors allow greater cooling, the dissipation of brake pad residue, and they weigh less. To me, this represents gains in performance, but only if the reduction of swept area on the rotor does not increase stopping distance.

Listen, I'm not trying to disrespect anybody's decisions about how they set up their ride. I realize that the priorities of a dedicated rock-climber or motor trekker are probably different than mine. I pull (or cartop) boats, I explore forest service roads, and I carry the very precious cargo of my friends and loved ones. I want to make my 4Runner safe, reliable, and comfortable primarily on smooth paved roads, but also the odd unimproved route. Please help me to make decisions that are based on fact and in the best interest of my goals.
__________________
"i'd rather be ashes than dust."

 

[tylerbaird]

I read somewhere that the rotor warps because they were designed for the Tacoma, which obviously weighs less than the 4Runner. The brakes on these trucks are definitely not the greatest, which is why I will most likely be doing the Tundra Brake Upgrade when I do my brakes this spring. I have no idea when it comes to putting pressure on the suspension. All I know is that the TBU is one of the most favorable mods on these trucks.

 

[Qyota]

Let's clarify first that it is extremely rare for rotors to physically warp. The term "warp" is a misnomer for what is actually uneven pad material transfer. This creates areas on the rotor that are more and less "grabby" over the rotation of the rotor. So the pads stick and unstick as the rotor rotates, and that action reaches the driver as pulsation or shudder.

Now, the stock rotors aren't any more prone to pad material transfer than any other solid OEM brake rotor. They may be slightly too small for the application, I agree, but the physics are the same.

That said, there is no logical reason to employ lighter weight rotors on this vehicle. Minimal gains in unsprung weight will have little effect on acceleration, braking, or manuevering of such a large vehicle.

I agree, however, in using such technology on motorcycles and high performance cars. The advantage(s) on the 4runner would be unnoticeable.

 

[HCurphy]

1). Have owners who have completed this mod noticed a change in suspension compliance?Nope, not in the slightest.(had more brake dive at first but shock/springs fixed it)

2) Is rotor warping mainly a problem for vehicles equipped with automatic transmissions, or are 5-speed 4Runners (and their advantage of compression braking) also affected? I think all's equal for argument sake, any differences would probably be due more to driving habbits then anything

3). Do slotted or drilled aftermarket rotors degrade braking performance?
No expert here, but from my interweb research they do nothing either way for this application other then looks. (again, may dissipate heat/dust better, but differences would be minute.)

just my 2 cents.