Static balance with CCM brake rotors attached

That's a good video. I just watched it last night.

Once I balance everything, I'm going to index the wheel to the brake rotor - probably the hub too, just for good measure.

Ray

 

I'm going to off these Michelin tires as soon as possible and put some Pirelli P Zero's on. The dealer put the Pilot Sports (or whatever they are) on there to sell the car, but I don't care much for them. They aren't horrible, but I just don't think they are as good as Pirelli.

Ray

 

I've been thinking a lot about balancing the wheels over the last few days and trying to understand exactly the differences between a static and dynamic balance and what is being accomplished via each method.

I still fall on the side of a "near perfect static balance" is probably better than just a so-so dynamic balance. But if you start to think about the dynamics of what is actually happening here, you can sort of start to see that a static balance should address the heart of the issue I think.

If you think of the wheel/tire as a cross section down the middle and try to understand where potential unbalanced locations can arise, you can see what would cause wobble vs. hop, etc. Given that the outer face of the rim is much more in line with the center plane of the wheel (and this is also where the bulk of the weight is spinning around its axis, due to the spoke, center lug area, TPMS, etc.) I think it makes the most sense to believe that this region of the rim is less subject to imbalances that would cause wobble and more susceptible to static imbalances that would simply cause one area of the entire assembly to want to rotate down, while the lighter area would want to rotate up.

So, any unbalance along those lines (i.e. the wheel/tire being heavier at say the 12 o'clock location than the 6 o'clock location) can easily be addressed by a static balance, exactly the same as with any motorcycle tire. Here again, I would much rather take a hand static balance to a single gram or less than a balance to the nearest 1/4 once by someone who only understands how to stick X number of lead weights to whatever approximate location a machine points to as being near the unbalanced area.

Now with regard to the part of the rim/tire that hangs farther away from the axis / mounting area for the lug bolts, I think that area (since it is leveraged out away from the main plane of the wheel) has a far higher ability to induce wobble. If you forget about the entire wheel for a second and simply picture it as a heavy point, off in space away from where the main axis of the wheel is, it becomes clear that any heavy spot would have plenty of leverage and centrifugal force to cause a wobble.

However, even in this case, a static balance would tend to show up this heavy spot, since it would have an overall impact on the rotational balance of the entire assembly you are working with. If there is a heavy spot (indeed, any place on the tire), then it will manifest itself as pulling the wheel down due to the pull of gravity.

So, that being the case, then the question becomes only "how far away from the mounting plane/asix of the wheel is the heavy spot?"

Now, the dynamic balancing machines attempt to identify this, as near as I understand, by using a lever off the center axis of the wheel, which is extended far to the left or right - then sensors detect and compute where the heavy spot must be by virtue of the wobble detected at two points on the lever/beam which extends out from the spinning tire. Despite the use of mathematics, I still think this is probably largely a best guess sort of scenario. I might be incorrect there, but I wonder how accurately the heavy spot can be isolated using this method.

So that brings me back to locating this same heavy spot via the static balance method. A heavy spot is a heavy spot. You can't change that. If it's in line with the main center plane mass of the wheel/tire assembly, then it will produce hop more than wobble. Conversely, if it's farther out on the edge of the wheel (particularly if it's out one the edge furthest from the mounting face / center vertical plane of the tire), then it will have the biggest impact as far as producing vibration or wobble. However, with that said, where the heavy spot is (left or right on the wheel) will have almost zero impact as far as how it affects where the wheel likes to come to rest as far as rotating down to its heaviest point during a static balance.

So, if that is correct, then the only question becomes how far left or right against the center vertical axis of the tire is the heavy spot? I think you can safely assume that the more pronounced the vibration is, the farther away from the center of mass plane of the tire it has to be. If that assumption is correct, then you can fine tune where the weights are placed simply by starting in the middle and - if the vibration is still present - moving the weight out a little further inboard or outboard until the vibration is fully offset. This might take a couple tries, but I don't think any adjustment in how much weight is being used would even be required, since you are still mainly addressing the static balance of the overall assembly here.

And, furthermore, even in the case where you have two heavy spots (one inboard on the tire/wheel and one more outboard), those could both be properly offset with a single weight in the approximate middle line of the wheel.

So, as my Dad used to say, "that's my story and I'm sticking to it"

Now, I was thinking about spinning the tire up on the static balancer to 1500 RPM's, which, by my rough calculations, would duplicate around 120 MPH, but I decided that's super dangerous. For one, if it fell off, I'd have a lot of energy in the wheel and tire and suddenly I'd have a loose tire trying to get out of my office at 120 MPH Probably not a good idea.

My other thought, beyond simply just going for a test drive, was to mount the tire on the car, then use one of my DC motors or something to spin the tire up as they do with the mounting machines; then use a dial test indicator to monitor the edge of the rim to see where it's wobbling at. However, I don't think it's going to come to that.

Unless my thinking is flawed here some place, I think a static balance will tackle 90% of the issue and then perhaps making some adjustments back and forth as far as placement of the weights (either moving them or spreading them out) will address the other 10% pretty well.

Again, if it doesn't work, I'll report back about that.

The other thing to keep in mind here is that wheels, rotors and tires are balanced during production. Tires are checked and anything too far out of order are rejected. So I don't believe that I'm dealing with horrible, grossly unbalanced items here. What I think mainly needs to be done is that the items in question simply need to be individually static balance, then matched to help offset each other's slight imbalances; then the entire assembly needs a final balance and then (maybe) some very slight alignment of where the weights are ultimately placed to help mitigate any wobble that could be felt on the road.

Now that the kids have left and I have my house back, I'm going to balance the actual mounting hub thing I bought and make sure it is balanced itself. Then I'm gong to take a wheel off the car and see if it will mount up and sit on the static balancer. I'll take photos or make videos as I go.

Again, if it works, great. If not, then at least it has been an interesting experiment and I can always go to a tire shop armed with a lot more knowledge and understanding.

Ray

 

Okay, here's the latest:

I pulled the front wheels/tires off the 458 last night, as well as one of the CCM rotors.

First thing I did was put the wheel/tire on the static balancer, to see just how good the balance from the dealership was, as I see a lot of people (not just on this thread, but all over Ferrarichat and just in life in general) always saying "leave that to the professionals; don't try this yourself, blah, blah, blah". All that might be fine... assuming you could still find any professionals in the world these days.

So, as delivered, the wheels were horribly out of balance. When placed on the static balancer I use for my motorcycle, the wheels immediately rotated to their heaviest spot. They rotated so fast that you'd almost think no balance had been done at all. In terms of static balance [at least for how I do my motorcycle tires], they were what I would consider to be grossly unbalanced.

So, again, this makes me believe that most people using dynamic balancers either don't know what they are doing or don't care - or both. The ultimate proof here will be how my car rides, but I still say that a good static balance will probably beat a shoddy dynamic balance any day of the week. We shall soon see if I'm mistaken or not.

Let me add here that both front wheels were roughly, equally out of balance.

After checking the original balance as delivered, I removed the wheel weights and cleaned up the rims, etc. I then did my own static balance. Even with just a quick balancing job, I was able to get the wheels much more into balance (i.e. the wheel will remain almost motionless, no matter what orientation you place it at).

Okay, so at this point, I decided to check the balance of the CCM rotor by itself. In order to check the rotor by itself, I had to use the adapter hub, so that the balancing axle and cones could pinch it. As it turns out, this wasn't required on the Ferrari rim, because I as able to secure it between the back of where it indexes onto the hub and the front where the wheel cap pops in. For the CCM rotor, however, the adapter was required, due to how thin the mounting part of the rotor is (i.e. the cones have nothing to pinch down onto). I started by calibrating the adapter's balance alone. It was out of balance by about 10 grams, so I balanced that first and also marked which lug nut when on which stud.

Next, I used the adapter to check the balance of the CCM rotor by itself. Since the rotor appears to have balancing cuts in it, I expected it to be a little more balanced that it actually turned out to be. I didn't use weights to determine exactly how out of balance it was, but I could guess maybe 5 grams or so. I checked the balance with and without the fixing bolt and fixing pin - not much difference.

At this stage, I marked the lightest point of the rotor for reference and then (using the adapter hub) combined the rotor and rim/tire assembly in such a manner so that the heaviest point of the rotor was opposite the lightest point of the rim/tire (when no weights were on the rim, of course).

I then checked the balance of the entire assembly (rim/tire/rotor) on the static balancer. Still out of balance. In total, in order to achieve a rough static balance that held the wheel from rotating to any heavy point, a total of approximately 53 grams were required (aka about 1.8 ounces).

I'll do a more precise static balance later, but this initial balancing sounds about in line with what one would expect, given the overall weight of both the rotor and rim/tire (and TPMS), etc. Keep in mind, as well, that I can only offset the weight of the rotor vs. rim/tire to the nearest lug bolt hole, which means it's not a perfect offset to cancel each other out.

Okay, so at this point things are looking okay. The only remaining question is where should I place the weight in order to achieve the best overall static as well as dynamic balance. I guess that will require some trial and error. My basic thinking is that if the error is out away from the vertical axis where the rotor and wheel spokes are, then I will have to place the offsetting weight more inboard. However, since most of the mass of the components is roughly inline with the mounting plane that is against the hub, my gut feeling is to err on the side of being in line with the spokes/rotor - so I'm going to start there and see how things feel on the road.

I'm also thinking I might build a very large caliper (using linear bearings and a long precision rod) so that I can measure the toe in/out of the front wheels, as the car sits on the ground. In reading over the default settings for the 458, I was a little surprised to see that the workshop manual calls for toe out. I feel like a hair of toe-in might make the car handle better at higher speeds - but that's for another thread

For now - and for anyone following along - the rotor and wheels are sitting in my office. Here are a few photos from last night. As soon as I have a chance, I'll pull the other rotor off and balance everything. With any luck, I'll have the car back together in the next few days and then I can report back how things went, good, bad or otherwise.

Thanks for all the input on the thread. Most appreciated!

Ray
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

I only run Pirelli's on my Yamaha. Wouldn't trust my life to anything else.

These Michelins may or may not be as good. I have not run the P Zero's on the 458. Also, I think part of my issue here is not the tires, but more the alignment of the car. I'm slowly addressing that, however.

As mentioned above, after doing the balance on the wheels/tires, my next project is going to be to make a huge caliper that I can use to measure the exact toe in/out setting on the car. The only other alternative that I can see is to reference against some perfectly square points on the frame or suspension components of the car - my guess is that there are some which would work, but I have to investigate a bit further in order to locate something which might work. At the end of the day, measuring across the forward and aft points of actual lip of the wheels seems like it's the most accurate approach, however.

As far as camber, if I'm not mistaken, it doesn't change during operation a multilink suspension system, so I don't think I need to mess around with that, after it being set at the Ferrari via the shims.

Ray

 

Well, having never been in a Rolls, I couldn't really comment. However, what I can say is that there is a big difference between vibration from the road (road feel) and vibration induced into the chassis due to an out-of-balanced wheel or damaged wheel. What I'm experiencing is clearly vibration due to something being either out of balance, or - as you touch upon - perhaps something being out of true/round.

With regard to the wheels being 100% true, I've checked that. One of the rims does appear to be very slightly out of true. I haven't put a dial test indicator or anything on it (yet), but I would guess maybe .020" or so. I will check it later and obtain an exact reading. I am also going to double check the shop manual to see what their allowable tolerances there are in that department.

It also appears that this same wheel has sustained an impact (most likely from a pot hole or something) on the inboard lip of the rim. I also see evidence of touch up paint back there, so this may be an issue for the dealership to address further. I cannot say if the rim has been previously straightened or not, but I will try to get to the bottom of it, if possible.

It's possible that what I'm seeing is merely a slightly deformed lip; if that's the case, it may not be the source of any vibration. When I break out the measuring equipment, I'm going to measure the inside diameter of the wheel, in order to see if the wheel is out of round dimensionally or if just the lip has been slightly knocked around. First step will be to attempt a better balancing job and then road test the car. I'll also report back regarding trueness of the rim later, as well.

In the meantime, if you're handing out joy rides in your Rolls Royce over there, please do keep me in mind

Ray

 

It's possible for sure. However, until I do further testing, it's hard to say for sure.

The vibration could also be from a poor balancing job, too. As mentioned, when I removed the wheels and checked the static balance, it didn't exactly impress me. I think the be thing to do is balance the tires as best I can using the static balance method, then road test the car to see if the vibration I was feeling is still present. If it is, then that points more towards issues relating to the rim not being 100% true.

I'm in my office now. As soon as my girlfriend heads out the door to go shopping, I'm going to measure the other rim and see how it stacks up as far as trueness, etc.

I'll follow up here in a few.

Ray

 

I've seen that done and I was actually thinking about trying that over here as well. However, when it gets down to 1mm or 2mm for toe-in/out, I sort of feel like I want something which doesn't have any flex involved (as line might).

I have to order some tools and such for the garage. I might look into ordering some parts, so that I can fabricate a large caliper or some other way to measure the suspension. The other thing I was thinking about was this: I have several large granite surface plates here; I was thinking about lying them down along side the wheels of the car and then measuring across (under the car) and aligning them. This would produce a perfectly square/flat plane to work from (assuming the ground is flat haha). I could then measure over to the lip of the wheel and measure the toe in/out.

I have a 24" caliper here, so I think I should be able to get a pretty accurate reading

Ray

 

I'm not sure what they are teaching in schools these days, but I don't think it's auto shop, welding nor any sort of mechanical engineering

With my specific case over here, it's starting to look more and more like the person who last balanced these wheels was just pushing buttons on a dynamic wheel balancing machine, without any real regard for how good or bad the final outcome was or what was really going on with regard to the balancing.

I'll tell you this much: I was surprised how out of balance the rim/tire was from a static balance standpoint. I'll also feel a lot better about having the brake rotor included in the picture here. I'm not sure if the rotor alone could produce an unbalanced state in the front end, but why risk it? I think taking the brake rotor into account while balancing the wheel/tire assembly makes the most logical sense to me.

Anyway, I'm about to stick some weights on and see how things turn out. I still have to pull the left hand CCM rotor off the car, which is not the worst job in the world, but also not as simple as you'd probably hope either

The jury is still out on whether or not the wheel is out of true enough to cause problems. I'm going to compare it to the other wheel here in a minute and then check the trueness of the rim once it's mounted back on the hub (since this will take out any alignment errors in my static balancing spindle).

I've also decided to adhere the wheel weighs in the axial plane of the mounting face, spokes and rotor, since this represents the largest concentrated mass that is spinning here. If there is still vibration, then I will mess around with sliding the weights further inboard to see if there is any material change.

The jury is also still out on whether the dealer is going to get a call regarding this rim or not.

I'll follow up soon here.

Thanks for all the input on this thread! Most appreciated, as always.

Ray