rockstar143

iTrader: (6)

equilibrium point between helping and showing that your helping is more helpful than another person's experience and help. End result...shared knowledge, so I'm all for it.

Turbonut

iTrader: (1)

Matt, either you’ve been taking too much cough syrup or hanging around with Wacker too much.
Let me get this straight, put on the rotors, secure the wheels/tires, drive down the road and the rotor speeds will vary. Better check this theory.

I don’t care if the rotor is 18’” in diameter, 2’ square, or 15” x 18” oblong, as long as the brake pad location doesn’t change (distance from center) the rotor speed at that location will always be the same as determined by the rpm’s of the hub.

Wacker

Another fine example of failure to understand that, on a rotor with a properly sized center bore, this shouldn't be necessary. Once again for those that chose not to read the original post:

THIS IS ONLY THE CASE FOR ROTORS WITH AN IMPROPERLY SIZED CENTER BORE.

It may, however, be a good practice to always put them back in every time (when possible) if you aren't sure.

I will continue putting them back in and will be ordering replacements for my wife's TL since hers were removed by pervious owner and has these inferior rotors...with vibrations...and "off center" rotor wear. My TL (not the wife's) has the exact same rotors and (with screws put back in after instal) does not have the vibrations or odd rotor wear. Is this a coincidence since I proved that the center bore is too large? I think not.

Wacker

But the amount of rotor surface varies beyond the contact point of the pads in this particular case. This means that the surface beyond the wear area of the rotor is not equal around the entire circumstance of the rotor so the outer edge will have inconsistent speed...causing imbalance...and increases the potential for vibration...

Turbonut

iTrader: (1)

Looks like you're slowly coming to my way of thinking. Never said that the circumference wouldn't vary, but stated that in my opinion that the small difference wouldn’t create a vibration and during normal usage, any rotor will vary in weight distribution do to grooves, scores, pad transfer, rust, etc. Geez, if you look at the regular lugs compared to the special keyed locking lug nut, it's much heavier than the other lug nuts but doesn't create any vibration when installed.

Like I stated early on, remove the screws, drive the car and report back as to brake pad wear, or rotor wear as you suggested, and steering wheel vibration from the out of balance rotors.

I’m having new tires installed on the TL in the next couple of weeks when the weather clears, and at that time, just for kicks, I’ll put a dial indicator on the outside edge of the rotor and check.

ZOMGVTEK

The bottom line is quite a few vehicles never had anything but the wheel holding the rotor on from the factory.

While the potential for an issue is there, it's probably trivial under normal circumstances.

Having the screws missing bothers me, yet my previous vehicle had no screws in the rotors for ~6 years and nothing exploded.

Wacker

If your rotors have the proper size center bore, you will be wasting your time. What rotors are you running?

I hate cars

I see why you think speed will stay the same since distance to center of the HUB stays the same. However, if the rotor sags due to a poor fit on the hub, as the wheel and rotor make it's first half rotation the rotor is going to be offset in the upper position. It's not going to be running true.

This happens with some aftermarket wheels and/or spacers and you get a vibration. An offset rotor may or may not give a vibration, actually it will for sure make a vibration, whether or not it can be felt by the driver is unknown. I have 13" rotors. I remember when cars had 14" rims and those had to be balanced. Obviously the tires added considerable diameter but it still applies.

You will get a slight up and down motion from the rotor which can cause all kinds of problems. You're familiar with rotary engines. The rotor doesn't spin in a perfect circle, it spins around the eccentric shaft. It's the same basic motion the brake rotors will be making.

I hate cars

The lugs are on what, a 5" pattern? You don't see the difference in a 12" rotor running untrue at its outermost diameter? It's not the rotor that's untrue, even worse it's entire mass is offset and not true. This is much different than a heavy spot in the rotor. Plus you're making an assumption that the locking lug is a different weight than the others.

Grooves and scores in the rotor are radial. How would this cause an imbalance? It doesn't.

This really is simple. If you're having a hard time understanding, picture the same problem but amplified. Pretend there's 1" of play between the hub and rotor and studs and rotor. Install the rotor with no screws and it's sagging 1/2" low. You put the wheel on which locks it in this drastically offset position. Is it easier to picture what happens with the mass of the rotor and the forces on the brake pads and calipers? This is MUCH worse as far as imbalance goes than a simple heavy spot on the rotor. You have the entire mass offset so in essence you have an extreme heavy spot but also a matching light spot 180 degrees away and instead of the pads being pushed forward only they're now being pushed and pulled up and down.

paperboy42190

iTrader: (7)

big question: why are we buying improperly sized hub bore rotors to begin with? a good brand rotor that is properly made isn't that expensive...

Wacker

1) I didn't buy the rotors that are on this particular car.

2) Even if I would have, I had no clue the bores were oversized.

rockstar143

iTrader: (6)

I actually have the same rotors. I have no obvious issues with them. I put the rotor screws back in.

Okay, in all honesty, I wouldn't knock them because at the time I think I paid very little for all 4 drilled and slotted with new chamfered pads. They gave me the look i was going for behind my rims and they operate perfectly fine under normal driving conditions. That said, they are slightly warped since I can feel it when slowing down rapidly from a high speed. I try and avoid that scenario.

Turbonut

iTrader: (1)

You don't seem to understand as you're once again backtracking and stating something different as usual to cover your tracks, from different rotor speeds, that was an interesting theory, to now a 1/2" difference in run out to enhance your stance. Must say, that's quite a difference when compared to the <.030"(not even certain as to the amount of movement) we're discussing, but once again remember I haven't challenged anyone’s opinion that the circumference will not have run out, but in my opinion, the <.30” is not enough to cause a wheel imbalance as verified by the numerous people that have had the screws omitted, locking washers removed, etc. and never experienced any vibrations. Actually have not experienced anyone with “normal” rotors ever having a problem with rotor imbalance that resulted in steering wheel vibration.

As far as grooves being symmetrical that is not true. I've had cars come in with the pad backing almost through the rotor in areas, rotors that have been broken, pieces missing, vanes broken, rotor surface missing in areas, and during test drives have never had a steering wheel vibrating because of these conditions.

Time will tell.

I hate cars

I'm backtracking? As usual you don't have the IQ to understand basic brake functions so you result to insults. Do you want me to draw you a picture? I can do it in crayon if that's easier for you to understand. All I did was elaborate on my initial post and backed it up. The fact that you think I'm backtracking proves this is a concept you're not capable of understanding. Know your limits.

I don't know whether to try and explain and break it down some more because you just don't have the capability to understand.

I can rip your poor excuse for a post apart with you substituting "symmetrical" damage when I specifically said "radial" scoring.

I clearly mentioned to picture the rotor with 1" of play to make it easier for your small brain to comprehend the problem but you take that out of context as if I'm saying there can be a 1" rotor to hub clearance. You're a joke. You twist words around to win an argument that you've already lost. We're not here to win arguments, were here to solve problems but with your ego and small brain it stops the flow of good information.

We're not taking about runout of the rotor itself. Were talking about something much worse, runout caused by an offset rotor. You need to realize the difference.

If you're incapable of realizing an eccentric rotor is a bad thing and will put forces on the pads and calipers they were not designed to bear then the conversation stops here. Say you don't understand and we will move on.

If you don't understand that an offset rotor causes a balance issue and resulting vibrations, just admit it. Whether or not the driver can feel it depends on how bad it is but if it's out of balance there will be vibration no matter how small and it will be worse at high speeds.

If you don't understand that the rotor speed changes even with a consistent wheel speed when the rotor is offset and can cause low speed warpage like symptoms I don't know what to tell you. The rotor is effectively a different diameter at different points of rotation. The problem here is you don't understand and instead of asking for help you're doing whatever it takes to save face.

Weren't you going away? Not a man of your word I see.

Steven Bell

iTrader: (2)

Guys, please......can we PLEASE be civil and just get along?

YeuEmMaiMai

lol who you think we are? Rodney King?

Vlad_Type_S

iTrader: (3)

Actually I'll chime in. The problem is that if the hub is not centered, you create something called a rotating unbalance, specifically a static unbalance (http://en.wikipedia.org/wiki/Rotating_unbalance). The symptoms are vibrations and noise among others. NI wrote a nice white paper explaining how to model a rotating unbalance with their software, but within that paper, they explain the concept very well. (http://www.ni.com/white-paper/4381/en/)



The amount of side effects cause by the shift in center of gravity entirely depends on the amount of gravity offset. So whether or not you will get vibrations depends on the rotor. But it is possible.

Now let's examine how this effects pad/rotor wear. If the rotor was perfectly centered, the only brake pad/rotor wear occurs as a result of the rotor rotation. (IMG1.jpg) If it is not centered, a lateral wear is introduced. If you examine a fixed radius around the shaft (an ideal rotor), it creates a perfect circle whose center is at the shaft. If you select a fixed point on the unbalanced rotor, it will draw a perfect circle with it's center offset from the shaft. (IMG2.jpg) This causes an additional lateral friction on the rotor/pad that will result in irregular wear. Edit: As the imperfect rotor rotates, the edge of it will appear to move in and out of the center of the shaft with reference to the pads. I think that's a better description of what causes the apparent lateral wear.

Honestly, I didn't know the screws were there because I haven't swapped rotors yet. But it seems like a no-brainer to use them even if your rotors seem to fit perfectly because it reduces any chance of a rotational unbalance.

I hate cars

Very nice explanation. That's what I was trying to explain, but said much better. Nice illustration too. That's what I had in my head, just hadn't pulled out the crayons to draw it yet. That should clear it up, I can't imagine anymore arguments over this. The only question is the degree of imbalance, not if there is or is not one.

Like several said early on, if the rotor fits tight to the hub, screws aren't going the do anything which I think accounts for the majority of our rotors. If it doesn't fit tight, the tapered head of the screw (to the taper of the rotor hole) will center it for you.

I'm glad this subject was brought up because if I ever had this problem I probably would not have thought to use the screws.

Sorry Steven, I tried to be good.

Vlad_Type_S

iTrader: (3)

I HAZ CRAYONS!


I'm very glad this subject was brought up because I, too, wouldn't have thought to use the screws. Thanks OP!

Turbonut

iTrader: (1)

I was hesitant on issuing a reply as past history dictates that when one is in a debate with you, the thread has a tendency to go downhill quickly, but having said that, I’ll give it a try.

I always have agreed that if the rotor placement is off center there is no denying that the “orbit” of the rotor will be compromised, not a perfect brake pad wear pattern with a uniform lip. However, it’s my opinion that this condition will cause no problem. You seem to think that as the pads are contoured to the rotor shape, any deviation will result in the pads being jammed into the caliper pins or caliper body and exhibit abnormal wear to which I disagree. Let’s look at a centered rotor. The rotor is spinning at about 14 revolutions per second and when the brakes are applied, tremendous force is placed on the pads as they just don’t squeeze the rotor without consequences and even when braking lightly, the pads will move inside the caliper and create the dreaded squeal we’ve all been accustomed to hear as they move and the pad backing rubs on the piston. Also, keep in mind that all pads are not contoured to the shape of the rotor as some are square, some have straight bottoms, some straight tops etc. so these would contact the rotor at different angles and present no problems.

So I still contend that there will be no problems.

Guess that’s it from the East Coast.

I hate cars

When you apply the brakes you have steady state force on the pads in one direction. When the rotor is not running in a true circle you're forcing the pads up and down. If the rotor is spinning at 14 rpm the pads are trying to reciprocate 28 times a second instead of a steady force in one direction.

Look at the pictures, it shows the direction of force on the pads. The paper explains exactly what I've been trying to say. I can't believe this is still being discussed.

Turbonut

iTrader: (1)

We're talking about <.030" and it will not make the pads go up and down, if that was the case there could be no square pads as all pads would need to be the exact shape of the rotor.

I hate cars

Can you not see pictures on your computer? Look at the pads, look at the arrows. You're beating a dead horse. I'm sorry you can't comprehend but that's not my problem. I've explained it as well as I can. The paper posted by another member explained it and even had pictures. I don't know what else to say. Study the pictures.

nfnsquared

1. I highly doubt that 1mm of play in the BrakeMotive rotors is the causing vibration issues on TL's. If it was, considering the hundreds (if not thousands) of sales Brakemotive has made to TL owners, I'd expect to see post after post of this issue. And I don't....

2. The OP hasn't even tried running the rotors with the screws in yet. At this point, he's only guessing that his braking vibration is due to the 1mm of play....

Vlad_Type_S

iTrader: (3)

It may not cause a vibration, but it may cause a vibration. There is no proof of either case. But we certainly know that there IS a rotational unbalance and we certainly know that a rotational unbalance can cause vibrations. If mine was vibrating and I didn't have the screws in, I would put the screws in. I'm not saying that Brakemotive makes a bad rotor, and I'm not saying that it is causing the vibration. All I'm saying is... why the heck wouldn't you? It's in the science and costs $0.86 per wheel. Everyone is free to make their own choices with their cars, but why not mitigate a risk if it's almost no effort at all. Just saying.

Edit: Isn't this what troubleshooting is anyway? If you have a vibration, and you find something wrong that can cause a vibration, wouldn't you repair it so that it can no longer cause a vibration? If you have a vibration and find something that can cause a vibration and you ignore it.... I just don't understand that logic whatsoever.

Vibration.

I hate cars

Going along with that, you don't just have a "heavy" spot (not the right term I know) but you also have a corresponding light spot on the opposite side which compounds the problem. This would be 1mm off on both sides. About this 1mm and .030" thrown out there, has it been measured or is this a guess?

There IS an unbalance, that is not debatable. The only questionable part is if it's enough to be felt by the driver. Let's not forget the lateral movement causes uneven rotor speeds and that in itself can cause a vibration under braking, all balance issues aside. Both the speed and the lateral movement of the pads.

Vlad_Type_S

iTrader: (3)

^Excellent point. The lateral forces are apparent and a consequence of rotation, but it is absolutely true that the rotor will oscillate this apparent lateral force on the pad. The oscillating force on the pads occurs under braking and is perpendicular to a tangent of the rotor, thus applying a force on the pads toward and then away from the rotational axis, once each per revolution. The oscillation frequency depends on the rotational speed and the magnitude of the oscillation depends on the gravitational offset and brake force applied. Oscillations = vibrations. Now I would even argue that if there is an unbalance, there is certain to be a vibration, both as a result of a gravitational offset, and a second vibration introduced as the brakes are applied due to the apparent lateral force. But as IHC said, the question is whether or not the driver can feel it. I'm even more convinced than before to use the screws hahaha.

I'm looking forward to an update from OP to see if it helped.

Wacker

I own 2 (two) 2004 Acura TL's. Both have brakemotive rotors. One has the screws and no vibrations. The other does not have the screws and has vibrations. The wheels are balanced perfectly and tires (Potenza) are in wonderful shape so I can only assume the rotors may be the issue. The vibration happens at higher speeds. It is not felt through the rest of the car. It can only be felt in the steering wheel. The rotors on that particular car are warped as well causing the typical pulsing when braking. Since I rotated the tires and inspected the brakes (this is when I realized the screws were gone and notice play in the rotors) the pedal pulsation is noticeably worse. I can only assume it is because the rotors went back on in a different position. I am not in a hurry to replace the screws as I know these shit rotors are shot. When I decide to put on a new rotor/pad setup, I WILL be replacing the screws. It will be sooner than later as the wife hates the warped rotors on her car.

nfnsquared

Wait, first you reported "horrible vibrations while braking" and summarized that off center rotors were the cause. Now you are saying the vibrations only come at high speeds and are only felt through the steering wheel, nowhere else.

And now you include the little tidbit about these same rotors being warped and causing brake pedal pulsations.

Missing screws are not the issue...

Wacker

Holy hell!!! You guys are all the same! Would you stop for one minute and actually read my posts please?!?! Stop putting words in my mouth and insisting I'm making claims that I'm not. I guess I poorly chose my words on the first post. I was pointing out the fact that the rotors were warped and vibrated and that I would be replacing them and the screws. I should have specified that the rotors were already junk. I merely pointed out the fact that the rotors do not have a properly sized center bore and that this has the potential to cause vibration issues. At what point did I claim to have vibrations because of the screws? I didn't. I merely posted my findings and my thoughts on the issues it could cause. We all know that vibrations upon braking are either caused by warped rotors or rotors that are not seated flush on the hub. I pointed out a potential for a balance related vibration.

In the second post you quoted, I still didn't claim that the lack of screws was the source of the vibration. I related my symptoms and the obvious. Are the screws the actual source? Who knows. The potential, however, is definitely there.

If I would have known you dick heads were going to come in here and put words on my mouth and try to pick apart a proven theory, then I would have kept this finding to myself. I'm trying to educate people that there are inferior rotors out there and its best to always replace the screws. If you can't get that through your thick head, it's no longer my problem. I'm really getting sick of this forum. Someone tries to help, and a select few people shit all over a thread and ruin good info for everybody.

I'm done. Any more arguments trying to put words in my mouth will no longer be responded to. It's just childish. If you want to contribute, then contribute. Otherwise, I will not spend any time arguing any more.

Vlad_Type_S

iTrader: (3)

Damn bro! I was hoping you would put the screws on now. Changing one variable at a time will allow isolation of the issue and prove/disprove if the screws help and that would require the use of the shit rotors . But since the rotors are warped, I completely understand your course of action and it makes perfect sense. My inner scientist just wants to know everything hahaha. Honestly though, thanks again for posting this because I had no idea.

Wacker

There is no dispute that the screws will hold the rotors in the same place on the hub (while the wheel is off) if the center bore is oversized, as is the case with the brakemotive. If you already have the brakemotive without the screws, your rotors have probably already developed the off center wear pattern. Putting screws in now may lead to pedal vibrations till they seat again. I know just taking everything apart and inspecting caused my wife's pedal vibration when braking to worsen. It has been a week since I have driven her car, so I'm curious as to whether it has subsided some since the wear surface should have had time to seat again. I have always wondered how brakemotive could offer drilled and slotted sets cheaper than most budget blank sets. I'm wondering if they may be out of spec throw aways that they get inexpensively and drilled/slotted and sold. I'm also wondering if all of their rotors have the same sized bore as mine. I haven't checked my other ones that have the screws in them. I haven't had the need to tear them down as of yet since installation. They are starting to show some signs of warping though. I've been trying to take it easy on them to get as much life as possible out of them before they warp to the point that I can't stand it. I know it's inevitable though.