What variation in weight is normal within a set of Campagnolos?

Buon giorno tutti,

The subject line contains my question - has anyone weighed each of their set of Campagnolo rims?

And I'm asking for a Bora owner I recently befriended .. so primarily about the 1970's magnesium rims for the 4-lug Bora or even a Khamsin.. I guess the Indy and Ghibli have them too..
I'm NOT talking about the difference in weight between the different STYLES, but the variation within a single set of 4 (or 5 if you inlaced the spare).
Within one single set of 4 rims - how much variation have you found?

My new Bora owner has one rim that is 3-4 lbs LIGHTER than the rest of his set..

Grazie,
- Art

 

Do any of you know anything about Campagnolo using aluminum alloy for their Bora rims?

We have gathered more information and are working under the theory that the majority of my friend's Bora rims are aluminum, while the one outlier is magnesium.

BACKGROUND:
The Bora owner damaged a rim many years ago so he bought another Bora rim and stuck in back as the spare.
Fast forward and recently he sent the 4 rims on the Bora, plus the spare, out for powdercoating.
He got them back from the shop with the tires now removed, the reduced weight of one was noticeable. He estimated 3-4 lbs lighter than the rest.
He had new tires mounted on all 5 freshly powdercoated rims, all the same type of tire.
Then he got curious about the weight difference.
He inspected all the rims carefully and found no markings, or design, or feature that distinguished the one oddball rim.

He got in touch with me via a mutual friend.
I had him confirm he still had the original damaged rim we could use as a 'control', then isolate the weight of each freshly powdercoated rim.
Today he put the "tired" rims on a scale to measure each.
He took the total weight, looked up the weight of the tires he bought, and deducted the tire weight:

Results:
3 rims weigh 20.8lbs.
1 rim weighs 21.3lbs.
1 rim weighs 14.3lbs.
As a control, I had him pull his old damaged original rim out of storage (with no tire mounted on it), and it weighs.... 20.8lbs.

The delta of +/-7lbs is equal to the delta in density between aluminum and magnesium - roughly 33%.

Tomorrow the owner is going to confirm whether the old original damaged 20.8lb rim is aluminum.
- Art

 

The relative difference in weight is impressive.
I am surprised however there is absolutely no distinctive feature in the casting of the wheels, mag or alu.
Usually the mag castings are rougher than the alloy castings, and there are often cast markings or specificities on the wheel, especially on the inside. Also thickness differences in e.g. ribs.
Have you thought also of a possible difference in tire weights?

 

We should know today whether the one original damaged 20.8lb rim is alum or magn.

- The tires are something we can't control for without dismounting them vs. testing the metal is pretty easy and should be accurate.
(It seems impossible for modern production methods to result in a 7lb delta on a single tire, so for now we are focusing on the material of the rims. The density difference of 33% between alum and magnesium is too accurate to be overlooked).

Thanks, I will suggest the owner look carefully at the insides of the rims.
- I have not inspected or seen the rims myself, but the Bora owner has looked as close as he is able and sees no distinguishing marks, stamps, or features that separates the one 14.3lb rim from the others. He says they are identical in every way. I agree this is mystifying.

Yes, the appearance of raw magnesium is different from raw aluminum.
- Today he will scrutinize the damaged original 'control' rim - taking photos of the damage and metal samples to establish whether it is aluminum or magnesium. We have a friend who says he can offer an evaluation of how the metal is damaged - how brittle vs ductile the damage it appears - to assist identifying the metal. If the sample and photos prove inconclusive, he will take metal samples from the "pockets" on the back of ALL of the rims.

I suggested the owner call the powdercoating shop today because they would have noticed the metal of the one rim appearing different from the others, and that prepping magnesium is a very different process than for aluminum. He replied that he told the shop all the rims were magnesium, so he expects they were all prepped the same. I think if he calls the shop they might still remember one being different.

I'll share more info as it comes in.
- Art

 

Art,

I'd never powder coat an older magnesium alloy wheel. My newer magnesium wheels on my Ghibli Open Cup were simply painted. Those were track only rims. You want to be able to see anything developing and powder might hide that. People who tried to use them on the road version of those cars had lots of crack failures. I ended up getting aluminum 3pc racing wheels custom made for that car so that the originals could be preserved and any track incidents could be easily be repaired. But the weight difference is enormous and you can actually feel the car accelerate better with the mag rims. It's substantial. Refinishing my Espada's Campagnolos was an enormous task. Those are a beautiful design but a terrible casting. The reproductions are all aluminum which is what most restorers use on the Miuras.

That weight difference is quite alarming, something is quite screwy. Dismounting all the tires is a big PITA but I think it's called for. I never have refinished the rims on my Bora and I had one that developed a slow leak so it got sidelined. Sorry but it's in very long term storage at this point so I do not have access. Otherwise I'd weigh it for you. Someone must know the number maybe McGraths?

 

B Shorey here (bs), I'm the guy with the wheels Art mentioned. Some of you might remember me from the days of the old Yahoo Group list.

Anyhow, the wheels are all restored and powder coated, that's done and there's no going back. New tires on all five of them. The weight difference is definitely in the wheel, not the tire, and fwiw it's 6-1/2 lbs. It was the guy at the tire shop who picked up on the weight difference, I grabbed one of each before the tires were mounted and it was significant. At that point I probably should have just gone home with the wheels and perhaps cut them all up for some proper metallurgical analysis and the good of humanity, but I'm hoping to drive my Bora again after 10+ years, so I went ahead and got the tires mounted.

I have chiseled a small chip from the damaged wheel and have sent it off to a metallurgist friend of mine and Arts. So soon we will know the compound of the heavy wheels that were original to my Bora. Then the mystery becomes what the heck is the other wheel made of.

The odd wheel was purchased maybe 15 years ago from EBay. Some of you also might remember that, a bunch of us on the Maserati Yahoo Group who only needed a single wheel each got together and purchased a set of wheels that showed up on EBay, and we each ended up with one. So somewhere, there are 3-4 other Bora owners who might have the same mystery as myself.

The markings are identical on all wheels. I can provide pics if you want. There is zero indication that this odd wheel is anything different from the other five, other than the significant weight difference. If I learn that this lighter wheel is some modern repro, I'd actually be more than happy to buy another four of them and make them the working set of wheels for my Bora.

bs

 

Looking forward to hearing the results Brian. So why not send a small sample of the other one as well?

 

Two reasons. First, I've got no problem taking a chisel to a busted wheel, but I do have a problem taking a chisel to a perfectly good (and expensive) wheel. And second, all but the physically broken one have been powder coated.

bs

 

It has to be that intrusive/destructive?

 

Don't know. But I'd have to scrape through the new powder coating to get any kind of a sample, and I'm not willing to do that. I took a fingernail size sliver from the broken wheel to send to the metallurgist.

In hind sight, I'd have done this before the powder coating. But as nobody picked up on it until after the powder coating, here we are.

bs

 

The hub faces of the wheels surely aren't powder coated right?

Just a thought ...

Hope your car is finally getting close?

 

They are. Given the whole porosity thing, my understanding is that you can't leave any area exposed. Anyhow, a friend out here who does high level restorations on Alfas used a shop that he does business with, between the two of them they've forgotten more about this stuff than I'll ever know. I trust their abilities, they know what needs to go on the face, the hub, the mating surfaces, etc etc.

The car is very close. I moved to Ca 10 years ago, the car has been sitting in New England since I left. I finally gave up on the shop that was supposed to paint it back east and dragged it out here last fall. I've got the calipers off and apart right now, whomever rebuilt them I think didn't use proper LHM rubber bits, so they were all seeping. And of course I've now realized, that even though I have not driven it in a decade, I should probably be replacing/refreshing the accumulators that I replaced and refreshed maybe 12 years ago before I start pouring LHM back into the system. Why not, I just replaced the old tires that probably only had 200 miles on them.. It never ends, does it?

Anyhow, going to pull them off this weekend and send them somewhere, and maybe try to get the calipers back together and put back on the car.

I've owned this car for 20+ years and have probably put less than a thousand miles on it, none in the past decade. Now that it's here in Ca with me, that's going to change.

Whoo hoo!!

bs

 

Well you really do not want powdercoating on any of the surfaces which are used to secure the wheel to the hub as it can fracture under torque tightening and then you'll have quite a problem. I watched a very new Lotus Elise go right off the end of the long straight runway at Lime Rock because the guy had not observed this caution. That includes the lug nut recesses especially.

 

We might have an answer suggested by Maserati...
..just waiting on some information to be confirmed by Brian the owner, and Jim the metallurgist.

1. - Yep. When I refinished my Bora rims in 2018, I ended up enameling them the Sikken CF7090 silver. We learned from a powdercoating attempt that contaminants (probably LHM) had seeped into the magnesium pores. It was not able to be adequately cleaned. The oils would vaporize in the autoclave and blow the coating off. So I'm enameling the Khamsin too. But - I have had success powdercoating uncontaminated magnesium Campagnolos. Two sets of Alfa rims have come out just fine powder coated.

2. - Yes, the 7lb difference is extreme. I happened to speak with two restoration specialists today. The first one, Jim Simpson at ODD Parts Fabrication was mind-blown over the 7lb difference. He recalls Campagnolo using different alloys for 'Superleggera' applications. He referred me to Matteo at ReOriginals who I just talked with, and who welcomed the mystery. Matteo called me back after talking with Maserati Italy because he had to talk with them anyway about a Tipo 151 he is restoring. Maserati suggested an answer that will take a short while to confirm.

3. - If we have our answer, we'll share it here and with MIE, and Chris at McGraths so they can look out for lightweight Bora rims.

Ciao,
- Art

 

In the meantime, here are some photos Brian shared of his busted OEM rim he pulled from a decade in storage, used as the 'control'. This is one of the 'heavier' 20.8lb rims... Something took a BIG chunk out of the bead.. and the dark color of the raw metal sure looks like magnesium.

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Not much more clarity today, but I'll share the update...

The suggestion by Maserati Italy was the lightweight rim is a 'manichino - mannequin in English - which is the term Italians use for their sand casting 'plugs'. These casting plugs were made of a non-structural alloy of unknown density except they were fractionally larger than the production magnesiums. The manichinos were used to create the production molds, and therefore would have the exact same appearance and markings as the magnesium production rims. The magnesium poured into the production molds would shrink to the correct size.

Brian has measured each of his rims and they are all 16.5" outside-to-outside, which is the exact same dimension as the sample measurement I took of one of mine. So we looked into exactly *what* the dimensional difference would be...

- Maserati/Matteo suggests the manichino rim wouldn't be so large it couldn't still take a tire (let's recall here that Brian has tires mounted on all rims, including the lightweight mystery rim, but excepting the damaged 'control' rim).. and that you can't detect the difference just by looking... OK, those are anecdotal.
- An online search reveals magnesium shrinks 2.96-4.20 percent liquid volume. It appears that liquid volume shrinkage translates linearly to the diameter's dimension. If that's true, then the 16.5" diameter times +/-3% shrinkage = minimum 0.495" difference, which would surely be apparent in Brian's measurements of his rim(s).

This seems to show the rim isn't a manichino, but until we can confirm the 'fractional' difference in dimension, the theory isn't ruled out completely.

One next step is for Brian to get a sample of the lightweight rim to our Metallurgist friend for an analysis of the alloy.

In the meantime, Brian, - don't drive on the lightweight rim.!
- Art

 

..maybe this could come in handy...

https://alloytester.com/metal-analyzers

 

Jim The Metallurgist shared that sand casting processes are able to compensate for shrinkage by the use of 'insulated risers' - which feed molten metal into the mold as it hardens - which is why the plugs may be virtually the same dimension.. Here is a video how this works.. not that I understand all of it..

https://m.youtube.com/watch?v=aaofoYWiwCk

- Art

 

https://www.matsuk12.us/cms/lib/AK01000953/Centricity/domain/3676/Physical%20Science%20Web%20Page/Ch%2013/Story_of_Archimedes.pdf

 

I think Harbor Freight has those for $22.00 now ...

 

Since we've been talking about alloy wheels and how they get properly treated I wondered what people think of this methodology.

Repairing and refinishing alloy wheels for daily drivers is a big deal here in the NE of the USA.
There's a place in Fairfield, NJ that will take your car, put it up on jack stands, remove the wheels, repair and replace the tires all in a one stop two day operation. $160/wheel for 20".

I have need to refinish all 4 wheels on a car I just bought. It needs new tires as well so I find this very appealing.

Upon inquiring I learned that all they do is powder coat. That's OK with me for modern wheels. When I asked if they powder coat inside and out (I'd heard that they do not) he said they do the front and back of the wheels plus about 1/2" into the bead area. I was flabbergasted as to why they don't do the entire rim. I even asked if I could pay more to have that done. He said no and told me that they don't because it's a waste of money.

Something sounds fishy about this. So I'll end up with raw bead blasted alloy inside the tire. How can that not cause problems and why are they really doing it this way?
I've also heard that some American OEM wheels are finished this way?

 

Maybe they don't do the bead area because:
- it's hidden;
- alloy does not oxidise (apart from an ultra thin layer of aluminum oxide) and remains perfectly air-tight; and
- they only refurbish the bead areas in contact with the tire, to avoid leaks.

Mag would be a different story as it may become porous, crack and leak througout the material.
A professional chromate treatment by a specialist is the only valid protection of mag to avoid these issues.

 

They claim they do go into the bead area but how far is open to debate IMHO. They got a bit testy when I began asking these questions.

The lack of corrosion on aluminum rims on the bead area has not been my experience. I have a set of 3 piece Hayashi rims on my 84 Biturbo that I bought new in 1985 and they've worked out great but about 4 years ago it was time had to rebuild them and in the process I developed some slow leaks which my very reputable tire shop suggested was due to improper sealing of the two split rims so I chased that twice and then we looked at the bead area which wasn't perfectly surfaced even after I had tried to clean it up a bit. The spun aluminum rim halves never had any finish just a great polishing on the outside halves. So we then tried some bead sealer and all the slow leaking was gone. That has never seen road salt and only snow in the California Sierra mountains where they don't use salt. It's road salt that causes these rims to be refinished now.

My tire installer of 25 years who is hooked up with all the sports car clubs has a ton of experience and it's he who old me that OEM rims from some of the American car manufacturers were using rims made WO a protective finish on the inside. He also rightly points out that moisture does collect inside of tires over time, hell sealer they use probably is water based.

I find the OEM rims thing hard to beleive but I also can't explain this vendor's methodology and he's the 900 lb Gorilla in this business around here. I think I'll look at some more vendors.

 

Yes, I seems to me these shops are popping up quickly... Assume they are counting on quantity, not quality, and deal with aluminum only.. If so, they will reject any job that wastes their time ...including your questions. LOL. Instead, they are focusing their marketing efforts on the ample supply of suburban customers wanting to spruce up their rims for a few bucks. I think some business folks have found a lucrative market and the word is spreading.

.. look at the bead-edge of a tire. It's not much more than 1/2", so this doesn't seem inconsistent with the quality of work they are offering.

 

I've moved on to another place that actually does the entire rim for the same price. But this approach seems fraught with potential issues. It's a good reminder that it's still very much a caveat emptor world out there.
Homework is tedious and time consuming but typically quite necessary.

I still can't fathom the weight difference in Brian's wheels. Something doesn't add up. Let us keep Hercule Poirot on the case!