The below video I took earlier demonstrates that even though our hubs are hubcentric, brake rotors don't always have a perfect sized center bore. These aftermarket rotors on this 04 TL are a perfect example. You will notice that when I hold the rotor flush on the hub and force the rotor vertically up and down, there is about 1mm of movement. This is definately enough movement to cause vibrations and uneven brake wear. You can hear the rotor clunking up and down on the hub center bore in the vid. This is why it's important to put the tapered retaining screws back in when replacing rotors. These screws are designed in a way to center the rotor perfectly on the hub. This car was missing the screws when I bought it and has horrible vibrations when braking. I will be replacing these ASAP.

 

Never heard this before. AFAIK, their sole purpose is to hold the rotors in place on the assembly line until the wheels get installed.

Supporting documentation to back up your statement?

 

The screws do help locate the rotor and hold it in place while the wheel is removed. It should be OK to not run these, but I could see the potential for problems if the aftermarket or inferior quality rotor has an improperly sized center bore. Quite a few vehicles just rely on a tight fitting center bore, but typically things are there for a reason.

The screws just hold the rotor in place, it's the lugs that clamp the rotor onto the hub.

 

Did you not watch the video? The fact that there is at least 1mm of movement in the rotor on the hub should be enough documentation. You are right. The screws do hold everything together until the wheel is bolted on. What you fail to understand is that it holds it CENTERED until the wheel is bolted on to keep it all in place. This is why it is a tapered screw and not just a recessed flat bolt. Do you have an alternative way of guaranteeing that the rotors are perfectly centered before bolting the wheels on? If you do, I will need supporting documentation. Are you just trying to be difficult?

Exactly. If you bolt this assembly together while gravity dictates that the rotor is in the lowest position, it's guaranteed to be off center.

 

OP, I just asked a simple question on where you came up with such a claim. Now we know.

 

Great that you took the time to post the findings, but it won't cause a vibration or uneven wear of the pads. The wheel, when bolted down, will hold the rotor in place, and do we even know that the countersunk holes are precise enough to place the rotor in an absolute perfect position over the hub. There are also vehicles that don't have the countersunk screws, but just washer like retainers that are screwed over the stud(s). I try and retain the screws or washers, not to keep the rotor centered, but to keep the rotor in place when doing brake replacement.

 

I have never re-used them. Never will. Your video does nothing to persuade me.

 

giant pita to take out, never put them back in......

 

Yeah I had to drill a couple of mine out.

 

Impact driver works like a charm to get those out.

 

There is not a dispute about the wheel holding the hub on. Lol. This isn't about rotors falling off. I'm not an idiot. For you to say that an off center rotor will not cause vibrations at speed is showing your lack of thought on the issue. The rotor weighs several pounds. For that weight to not be centered.....why would it not cause vibrations? And it WILL cause uneven rotor wear. If the rotor is bolted up 1mm off center, then the edge of the rotor wear surface will be off by 1mm. Bolting wheels on will not correct this issue.

Your theory of this not causing vibrations is the same as bolting wheels with a different center bore on a smaller hub without adding hubcentric rings. If it is off center, it WILL vibrate. Same with the rotor.

I've never had issues getting the screws out. Then again. I've always used an impact bit tool you hit with a hammer. Just like Jase13 mentioned. Having the right tool for the job makes a big difference.

 

The first time I encountered them, I had to drill. After that, I got an impact driver and just put them back in. Its a few whacks to the impact driver with a mini sledge and they come right out ready to reuse. But yeah, without an impact driver they are tricky.

How big of a problem you face without running the screws depends on how close fitting the rotor is. For most people, it's probably never going to present an issue. I just prefer to have the screws in since it's not a big deal to remove with the proper tool. I have more of a problem with the lack of repeatability on rotor placement when you remove the wheel than the potential offset itself.

 

an off centered rotor may cause vibrations on high speed cruising, but I dont think it'll cause a braking-only vibration. for it to cause a braking-only vibration it would have to have movement during braking, and since the lug nuts are holding the wheels tight on the rotor, there isn't any movement in the rotor.

honestly though this "issue" could be solved if you bought some good quality rotors. My rotors fit snug on the hub with no movement at all. However, I still put the screws on because I don't like it when parts are "missing" on my car. I thread it down but put practically zero torque on it to minimize the chances of it getting seized

 

No, it shouldn't make a bit of difference under braking with fresh rotors. However, well used, or grooved rotors, will likely present the largest difference. If the rotor is grooved, which it most likely will be after a fair bit of use, the pads will also be worn into these groves. Remove the wheel, and without the screws to hold the rotor in place, it's exceedingly likely the rotor will be slightly misaligned with respect to the groves in the pads. This would cause braking only vibration. Some people only really replace rotors when they 'have' to and they can get quite bad. These are also the same people most likely to use cheap rotors and drill the screws.

I'm not sure how big of a deal it is, or how much it would be noticeable, but it will absolutely happen. If this happened on all 4 wheels, it might be noticeable. I wouldn't think it would be a big deal, but the possibility exists.

Quality rotors likely fixes most of the issue. I've never personally noticed rotors move around vertically more than a few thou, which is barely perceptible. The screws still won't hurt, but I wouldn't be too worried about it. The worst problem you should see probably is still very minor. Personally I'd just rather have the screws there and forget about it. I put a coat of ASL on them and tighten them back up really tight.

 

Well, I tried to polite in my reply, but as usual we seem to be dealing with, although maybe not an idiot (your terminology), but certainly far removed from a certified mechanic coming back with a curt reply. You do realize that if it is 1mm, that’s .039", so if you believe that can cause brake pads to wear, better do some research and with a 11+" rotor the weight distribution or off-center won't cause a balance problem. Also, what do you think happens to the rotor when in use? Does the rotor retain its perfect weight distribution, certainly not; grooves, lips, normal wear, pad transfer, will cause minimal weight variation and will have no ill effects on balance.

As far a wheel/tire off-center causing a vibration, the unit weights maybe 50 lbs with a 26" diameter, much different when compared to a 12" rotor. I'd say that's like comparing apples to oranges.

After some thought, remove and leave the screws out, drive the car and report back how severely the pads are wearing and how the steering wheel is vibrating from the out of balance condition. I'll look forward to your reply.

 

Where did the pad wear conversation come from? I never said anything about pad wear. Did I? Didn't think so... You are putting words in my mouth. Why would this cause excessive pad wear? You really do think I'm stupid. Every time I have mentioned wear, it has been rotor wear. Don't believe me? Read back. An off center rotor WILL wear off center. If not, then I will need your supporting documentation and elitist theory supporting why this will not occur.

In a perfect world, if we never took the wheels off of our cars, I'd say you were correct. We all get flats, have to rotate tires, and get wheels balanced. As previously stated (multiple times) the pads seat themselves with the rotor. They make groves that they run in. If you take the assy apart and don't get it together the exact same, you will have strange vibrations through the pedal till the pads and rotors re-seat. The old groves that are now off center will have to be worn off. Can you guarantee that a rotor with an improper sized center bore will line up the exact same every time the wheels are rotated if the screws are missing? No you can't. But you know what? If I leave the screw in, I can guarantee that my rotors will be in the EXACT. SAME. POSITION. EVERY. TIME. This will guarantee me even rotor wear.

It baffles me that you can deny this!!

 

You don't even know what you write, I rest my case.

 

So, anytime someone says "brake wear", you assume it's pads? Dually noted. But for the record. I NEVER WROTE BRAKE PAD WEAR. As a matter of fact I, and others, mention rotor wear specifically multiple times. Where are those quotes? It's funny this is the only point you choose to respond to.

 

:popcorn :

 

This is gonna get good

and even more

 

I've been trying so hard to ignore this one.

 

I think it's more the larger hole/tolerance of the brakemotive rotor. IIRC the oem rotor, I had to wiggle and jiggle to get back into place and it sat on the hub very tightly.

That said, I had the same decision to make after my revamp of the S2000 oem brakes...had to drill out the front 2 (someone before me stripped the heads, rears came right out) and decided to go to honda and get 8 new ones. I even coated in anti seize...being in Florida, I'm not worried about rust/salt causing the same scenario again.

Write or wrong, I appreciate you sharing the experience and warning of a potential issue, John.

 

holding it in is bad for your health

 

Another one that can't let it die. Ok, after 2 days you come back and say the brake wear you were referencing was not uneven brake pad wear, but uneven rotor wear. New one on me, but for the sake of argument let's assume that at the time you were referring to rotors and not the pads, please explain how the .030" condition is going to be problematic.

 

Ding ding ding round 1 is under way

 

Round 2 is almost underway. Radial runout and uneven rotor speeds vs non brake pedal pulsation. I'm just too damn sick to care right now.

 

Sorry. Not everyone can sit at our counters and wait for a response. I'm at my corporate office (SnapOn tools) for product development meetings this week.

Apparently you need pictures to understand the issue. I will work on a simple diagram for you to expalin my point. Can I guarantee it will be before 2 days? No. I'm pretty busy supporting our automotive, military, and industrial markets.

 

^ you know I changed the brakes on my car for the first time at 81,000 miles (2002 CL type S). The pads and rotors were replaced as a set. The car has 31K on the new brakes and I have ZERO issues with my rotors and pads. I also did not put the screws back in after I removed them. That was 4 years ago. my rear brakes also do not have the screws and again no issues when I change them every 55k miles. (now on my third set)

The car stops smoothly and in a straight line with no unusual noises.

 

Not all rotors will have the issue. This is related to some aftermarket rotors with off sized center bores.

 

Right, I think we call all agree at this point that EVERYONE would like their rotors perfectly centered and that if they are not, for whatever reason, we are not in for a catastrophic failure of any kind.

That said, thread title should just be changed to "if you have aftermarket rotors that aren't perfectly snug to hub, you may want to consider putting the centerring/mounting screws back in to ensure your rotor is as perfectly centered as possible".

Fair enough?

I think you're getting flack for the tone and absolute statements.

 

That's my thoughts. If the hub fits snug you don't need the screws which probably accounts for the majority. If it does not fit snugly the screws can help align it due to the taper instead of the rotor drooping to the lowest spot.

If it's off center it will lead to uneven rotor speeds on each revolution which probably won't be enough to matter but it's also going to push the pads up and down slightly which can lead to it's own problems. I would think once a wear pattern is established on the rotor it's not a huge deal but remove the rotor for a repair and reposition it when it goes back on and you're going to have trouble due to the already established incrorrect wear pattern vs the new incorrect wear pattern.

 

Yep.

 

Exactly ... Oh .. I'm screwed there .. the rotors I put on .. aftermarket ... never had the holes for the screws .. I'm buggered.. Oh wait .. that was 3 summers ago .. all is fine .

 

I can agree with this.

The only problem is: How many DIYers are perceptive enough to know when they need the screws or not? Best to just put them back.


Nail on the head. Thank you.

 

OK, group hug

 

Well that was anti climatic

 

That's because everyone's intentions were good!
:gheyhug:

 

That's only because I'm sick and too tired to push Turbonut's buttons.

 

Trust me, I could tell that you weren't in your usual form when you replied the first time. I also knew it wasn't with Wacker that you were looking to respond. Feel better, bud. This time of year is brutal (for everyone but Florida)

 

https://acurazine.com/forums/3g-tl-tires-wheels-suspension-97/6mm-disc-brake-retaining-screws-820767/

http://www.heeltoeauto.com/pitboard/?p=143