Static balance with CCM brake rotors attached

I think that's a good point. I don't notice the vibration much until about 80 or 90 MPH.

On my motorcycle, I had a very strange vibration that I couldn't track down for months. It only occurred when the bike past 50-55 MPH, then went away. It was sort of like a vibration wave that went from the front of the bike to the back, then vanished. I tried a few different things, but no luck. Then I spoke to a neighbor who used to race bikes. Without any hesitation, he said "it's the tires".

I said I had checked everything and he still just said "it's the tires". Sure enough, it was the tires. I installed new tires and it went away. Might have also partially been the balance, but who knows.

The point is that it just goes to show you how sensitive some things can be and how certain speeds can produce a resonance effect, etc.

With the 458, I think there is a fairly good chance the vibration I'm feeling is simply due to a sloppy balance at the tire shop (or dealer - not sure who installed the tires last on this car and/or if the dealer mounts their own tires).

Like I say, we shall see soon here.

Ray

 

Those "balance on the car" machines are interesting. I still think doing a very exact static balance is probably more accurate.

The BB thing is interesting, but not for me. Also, from what I have seen of it, it only works after you get up to speed. If you stop or slow down, it takes a while for the BB's to find their home and reduce vibration again.

Ray

 

Here's a video I uploaded to YouTube, which shows me balancing one of the Ferrari 458 wheels w/ its CCM brake rotor:

https://www.youtube.com/watch?v=DIj4YUbLuDQ

I still need to pull the other rotor off the car, but at least one wheel assembly is balanced pretty well (I would say within 2-3 grams of being perfect). I thought everyone might get a kick out of seeing how it's going over here tonight.



Ray
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Finally got around to doing some more work in the garage. It's been cold and rainy here, so I haven't really been all that interested in working on the car.

Tonight, I re-mounted the right side CCM brake rotor and reinstalled the pads, etc.

I used the opportunity to double check the runout on the wheel and was happy to find that it's much more true than I feared. I think my initial readings were more a function of my mounting axle (which I plan to upgrade later on, due to some flex it seems to have). Anyway, when taking the reading with the rim mounted on the hub, it's +.004" max and -.009" max at the two most extreme measures.

That seems well within acceptable limits for a used street wheel.

I'm going to call it a night, but will probably finish things up tomorrow if it's warm again. I'm also going to see about measuring toe in/out - assuming the vibration issue has been resolved - soon here.

As far as measuring toe in/out, the only two methods I can really come up with (that would work well I think) is the fishing line method off posts around the car or just fabricating a giant sliding vernier style caliper and taking a measurement off the lip of the wheels. I had held out some hope of measuring to those little flat round points back on the body (behind the wheel/tire), but I don't think that's going to work out too well. I suspect those are flat spots which a laser measuring device uses at the factory (in order to verify that the sub panels have been attached within tolerances). I thought I might measure from those flat surfaces over to the CCM brake rotor, but it doesn't really lend itself to accurate measuring with all the cables and such back there.

Anyway, at least the rim I was worried about isn't as large an issue as I had originally feared.

Ray
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Well, I finished the static balance on both wheels last night, remounted everything and test drove the car today - briefly up to about 120 MPH on any empty stretch of road.

So, the vibration is still present. In fact, it might be worse now - although only marginally, unless that's just my imagination. It feels like vibration from the front end and it feels like it's due to unbalanced wheels.

The static balance I did was accurate to within 5-7 grams by my estimation. I did opt to mount the wheel weights on the outboard lip, which now I'm thinking might be part of the problem. So, after dinner, I'm going to return to the garage, pull both front wheels off again and remount the weights inboard to see if that changes anything.

If that doesn't make a difference, I'm going to also check the balance on the rear wheels and then start asking if anyone local to Monterey would like to swap front wheels with me for a minute to see if my wheels are actually the source of the problem

I'll follow up further on this thread, after I do the next test drive with the weights remounted in the same location but on the inner lip of both front wheels.

Ray

 

I've always had great luck with Pirelli tires. Currently the car has Michelins on it.

Ray

 

Okay, so here is the latest...

I removed the wheel weights and repositioned them as far inboard as they would go.

I just test drove the car and there is definitely a very noticeable improvement. In fact, I would say that about 90% of the original vibration, which I was perviously feeling above 80 MPH, is now gone. There's still a very, very faint feeling of the previous vibration. However, it feels so distant that it's almost not even discernible any longer. Most of what I'm feeling now, via the steering wheel, could probably best be described as road feel, more than anything else.

So I think this tells me that I'm on the right track here. The fact that the weights are having more of a positive impact inboard tells me that static balance isn't the only issue here, but wobble is also.

Next, I think I'm going to increase the amount of weight used slightly (perhaps another 7 or 15 grams) to see if that helps to counter balance things a little further. I may also try moving the weights to the center line of the rims (or perhaps dividing up half inboard and half outboard) just to see what sort of results this might produce.

So definitely a step in the right direction from what I can tell.

I'll follow up here as I do a bit more testing. I'm also thinking about checking the balance of the rear wheels, although I think I may have to increase the spacing on my static balancer in order to fit the rear wheels on.

Ray

 

So I added 10 grams of weight on each of the front wheels (in the same location as the existing weights), just as a test, in order to see if this had any sort of impact either way. The result was an increase in vibration, although only modestly.

So this indicates to me that I'm on the right track here. I've just removed the additional 10 grams and will drive the car a bit further. I'm also thinking about pulling the wheels off again and doing another static balance - although this time without including the CCM brake rotors. I'm not sure if balancing the wheels with the brake rotor is helping or hurting.

On one hand, balancing with the rotor could be producing a more accurately balanced package as a unit. However, on the other hand, inclusion of the rotor could be masking or altering where the wheel/tire really needs to have weight placed. I'm going to do a little more testing here shortly.

Another thing I might do is "focus" the wheel weights in a more concentrated area. Currently, I have a strip of 7 gram weights all in a line. This spreads out the distribution of the balancing weights - perhaps too much. So I was thinking I might either switch to larger 10 gram weights or run the 7 gram weights side by side. If I do try that, I will do it when I check the static balance again.

The other thing is the toe in/out setting. In reading about how to tune race car suspension, it seems that having too much toe out is what is probably causing the car to feel a little unstable at high speed and under acceleration. In my reading, it seems that toe out is often used in order to increase handling in corners. However, this seems to come at straight line stability, which is what I'm more interested in. I was also reading that toe out can be aggregated under acceleration, since there can be a spreading effect caused.

I've decided that running fishing line and measuring off the wheels (in several different points) is probably about as accurate as any other method of measuring the car, so I may give that a try tomorrow. The only thing I can really come up with that might be more exacting is building a very large vernier caliper, using some precision rods or something.

Anyway, at least I feel like I'm starting to understand what is going on with how the car feels and also that I'm beginning to get a handle on what changes I probably need to make in order to make the 458 feel as stable at speed as my 360 did

Ray

 

I would guess your wager there is probably pretty accurate.

In researching all this, I have read about the dynamic balancing machines - although I have yet to download and read any operation manuals (that sounds like fun and a good idea actually). My basic assumption is like you say: probably most people operating these dynamic wheel balancing machines have very little training beyond pushing a button here or there. Based on my last two experiences at Costco (with balancing tires for two of my SUV's), I feel like most people incharge of operating these balancing machines maybe don't fully understand what they're doing.

For my motorcycle, I built my own tire mounting fixture, so that I could mount and balance my own tires without having to turn my carbonfiber rims over to someone else. Since I still have all those tools, I was giving some thought to making an adapter which would allow me to mount and dismount the tires for the Ferrari also.

If my static balancing here works out, then this would allow me to totally handle tire changes myself on the 458.

With regard to the toe in/out, thanks for the information there. I'm going to measure the current settings on my car shortly and I will report back. Based on everything I have read so far, my thinking is that I want to try running about 1.0 or 1.5mm of toe in on the front, just as a test.

Thank you again for your input; most appreciated.

Ray

 

Look at the bright side Brian, the number of posts to display per page is user configurable.



Ray

 

Thanks!

Ray

 

More on adjusting the toe in/out setting:

I took some measurements and did some calculations tonight, in order to obtain the exact distance of each wheel center cap from the center line of the car. Attached is my worksheet for anyone interested. Please note, I have diamond cut wheels; so the width measurements of the rims and to the rim lips are based on my actual rims here. The remainder of the measurements are taken from the published data in the 458 Italia owners' manual.

With these measurements - and knowing that the rear center cap sits exactly .130" deeper towards the center line of the car than the front center cap - I will be able to setup a string that is exactly parallel along each side of the car.

I actually am planning to use the Sticky RX wheel mounting tool as the basis of this. On the front wheel, I'm going to install one tool exactly at 3 o'clock and then rotate the rear wheel so that a second one can be installed exactly at 9 o'clock. Doing this will allow me to tension a string or fishing line between the two tools and exactly across the center line of both wheel caps. From there it will be a simple matter to use my measurements and align the string exactly parallel to the center line of the vehicle.

From there, by placing a machinists rule along the lip of the rim, I will be able to compare its orientation to the line produced by the string and thus be able to exactly measure the front and rear wheel toe in/out settings.

Ray
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Let me know how that method works out for ya, if you actually ever attempt to use it to measure or adjust your toe settings

Unfortunately, using the method you have outlined here - especially short of having a floor that is as flat as a surface plate - wouldn't really be precise enough to measure the toe in/out figures accurately enough. It might be accurate enough to hang a picture frame on the wall level, but when it comes to the very small adjustments used on the Ferrari for setting the toe, camber, etc., I think you'd quickly realize your margin of error would be far too great.

The centerline of the car isn't being measured; it's provided as part of the track numbers for the car from Ferrari and I'm using it as a reference when measuring the rims and their orientation relative to the car itself. Check the first few pages of the owner's manual for further information.

Camber doesn't change as much on a modern multi-link suspension systems as it does on older cars, when going through its range of motion on the road, so leaving the current settings from Ferrari is probably okay for now. Nevertheless, that's an area I plan to at least measure soon. But there again, just using a laser level, a T-square and your garage floor will not produce an accurate enough reading when it comes to the degrees of camber for the suspension. It requires using a more accurate digital angle gauge.

Also, to change the camber on the 458, I believe it requires using shims. My gut feeling is that the camber setting from the factory is probably just fine for the street - and altering that setting wouldn't make much difference for a street car which spends the majority of its life driving in basically a straight line (i.e. with its suspension unloaded as far as cornering goes).

The main point here is that toe in/out probably has the biggest impact on how the car feels/drives (outside of the track) and it's the easiest to adjust - so long as you can accurately measure it. What better way to measure it than against the car itself - and with a degree of accuracy approaching 1/10th of a mm?

I'm not sure caster is adjustable on the 458, without the addition of after market parts.

Ray

 

No, I've never paid to have my car aligned. Just bought news tires, put them on, declined the alignment nonsense and taken my chances that everything was still fine from the factory.

As far as checking/aligning the suspension on my 458, I'm going to stick with the method I'm developing here. I believe it's fundamentally sound and so far, at least, it appears to be yielding accurate results from what I can see.

Did anyone happen to notice (from the worksheet I posted above) that my "as taken" measurements off the car itself perfectly cross reference against the stated measurements of the car to an accuracy of .00 mm? A hundredth of a millimeter! Com'on; that even sort of surprised me!

I mean, sure I'd love to just use my garage floor and a T-square to accomplish all this too - and, in fact, those were some of my initial thoughts on how to approach all this as well. However, at the end of the day, if you really think about that approach, you'll quickly realize that those methods are inherently flawed. There is simply far too much potential to introduce a greater error into the entire equation than the actual small measurements you are trying to obtain in the first place.

If you are seriously engaged in racing over there, then perhaps you have all sort of fancy "race ready" suspension alignment fixtures and jigs and stuff that you can use, which are all designed to compensate for those subtleties. I don't race, so I don't have access to all that stuff. I have mainly measuring tools related to lathe and milling machine operations - and some fishing line - so I am going to have to figure out a way to employ those to accomplish this.

Let me point out - and remind anyone who may come across this thread in the future - that, in the workshop manual for setting up the car, Ferrari specifies these alignment parameters down to +/- 0.2 and 0.4 degrees when it comes to camber and caster, respectively, and +/- 0.25 mm for the toe-in/out settings. So we are dealing with a pretty high degree of accuracy here to begin with.

The best method I can come up with is either measure the lip of each wheel against the one across from it, or setup lines parallel to the car's center line and measure everything off of that.

Even with my method, I'm making a couple of minor assumptions: First, I'm assuming that the center line of all four wheels is accurate to the center line of the car (as stated by Ferrari) - and furthermore, due to this (and on account of the measured widths of the rims) that all four center caps will be exactly the distance I think they should be relative to the center line of the car.

Second, I recognize that even something as slight as a tiny variation of the thickness of the shims used by Ferrari to setup the initial camber of the car could potentially throw things off ever, ever so slightly (although, there, I think any error induced would be on the order of 10,000th's of an inch). Additionally, since my front rims are out of perfect true by about 0.010" (depending on exactly where I place my measuring tools), it's entirely possible that my resulting measurements might also be off by around that much (potentially) per side - unless I take steps to adjust for this (something which I may look into doing).

Anyway, beyond those couple of points, if anyone can see any major shortcomings with the method I have proposed, please feel free to chime in. I've spent the last week laying in bed at night going over all this in my head many times, and - at least so far - I cannot find any major flaws with my method or approach I've outlined here.

I'm attaching a page from the workshop manual for reference.

I'd also like to point out something else: despite how accurate one method is over another, at the end of the day, all this merely boils down to a test drive and seeing "how it feels" on the road or track. When you realize that, you also realize that what's most important here is not so much the measuring, but the tuning.

Ray
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I'm about to go finish balancing the wheels. I've come to the conclusion that most likely the weights need to be inboard on the lip of the rim, as uncompensated weight out in this area has the most potential to induce wobble and vibration as compared to the rest of the rim.

Where the dynamic wheel balances shine is identifying exactly where to place the weights (on the inner vs. outer lip), but I think they fall short compared to static balancing when it comes to the accuracy of exactly how much weight is needed.

My gut feeling is that I can be more accurate with the static balance part and then basically hunt around in the dark, so to speak, moving the weight required a little further towards the inner vs. outer lip, in order to pin point exactly where the weight needs to sit. That's what I'm in the process of sorting out now and it seems to be producing positive results.

In thinking about it, I feel like in most cases, the culprit will usually be unbalanced weight on the inner lip of the rim, since weight there has leverage on its side, whereas weight inline with the center axis plane of the rim doesn't. This means uneven weight inline with the mounting plane of the hub would probably produce hop moreso than wobble, and wobble is what is felt moreso than anything else back through the steering of the car.

The latter point there (about hop vs. wobble) probably also explains why balancing the rotor w/ the wheel might not be as important as I originally thought it might.

Ray