[///Malcontent]

If you're following my Track Bike thread, you know I purchased a set of essentially unused PVM forged magnesium wheels for that bike. I've been trading e-mails with the manufacturer and they tell me due to the date code, the wheels are more than three years old and no longer safe to use. I've sent them a number of questions regarding this advice but I'm also soliciting information here.

I know magnesium can be tricky and is prone to severe oxidation if left uncoated. And being these are very light weight wheels, it's possible they are stressed closer to their strength limit and may be more susceptible to fatigue.

Has anyone received similar warnings from PVM and/or other manufacturers? The OEM Marchesinis don't come with similar warnings, from what I can find in my documentation.

I'm considering having non-destructive testing done yearly just for peace of mind. Has anyone done so as well?

What practices are people who also purchased forged mag. PVM wheels following?

Am I being a ninny? (I suspect possibly.)

 

[Shazaam!]

... they tell me due to the date code, the wheels are more than three years old and no longer safe to use.

Obviously, this is legal-speak. Even if the wheels sat on a shelf for three years, PVM is stating they are no longer liable if they fail. Since they don't know what kind of service the wheels have seen, they use time as a termination of liability.

Other manufacturers duck the issue by claiming that their wheels are designed to be only used on a race track where there are few road imperfections. This allows the wheel designer to minimize the thickness of the rim portion which has the greatest effect on reducing the wheel's rotational inertia, but as a result, it will also be less resistant to pothole damage.

Here's the position taken by Marchesini:

"Although magnesium wheels are stronger then most aluminum wheels, Marchesini wheels, like other magnesium wheels, are for racing applications ONLY and are not intended for street use."

They mean it. You get into trouble when the attempt to save weight results in thinner, and consequently weaker, cross sections.

So think twice about buying the lightest wheels available. For the street, the lightest wheels offer the greatest handling improvement but are not the best choice in terms of survivability.

That said, magnesium alloys also require more maintenance. Without a durable protective coating, they'll corrode in damp environments — unlike aluminum which naturally forms a protective oxide coating. The thin protective layer applied to magnesium is a chromate coating which is then painted. The paint on most magnesium wheels are somewhat fragile. Some are powder coated and have a tough clear coat, but they still get stone chipped and need paint touch-ups regularly when used on the street.

You should always be cautious when buying used alloy wheels. Damage from potholes cause cracks that are difficult to detect and need nondestructive testing to reveal.

Wheels that need refurbishment require special methods.

How to Refurish Magnesium Wheels. - Ducati.ms - The Ultimate Ducati Forum

 

[Bullitt]

Interesting.

I recently placed an order for a set of M7R Genesi wheels from Marchesini (they wouldn't make the alu version for me as they only make blanks in large numbers, whereas the mag wheels have a different manufacturing process so single units can be produced - so I was told).

I was very wary about Mag wheels for a road bike, given the potential of stone chipping, pothole thumping and general wear and tear of road use. An interesting reply from the supplier pointed me toward the fact that they use the same method for manufacture for the Superleggera, being homologated for OE applications. Interestingly, the Marchesini website also mentions road use on their website for the wheels.

AFAIK, Ducati (Marchesini) do not given any limited life restrictions for the Desmo or SL wheels.

I had looked at PVM and OZ also, but pricewise there was little in it, so plummed for the wheels closest to oem as possible..

Will be interesting to hear the results from ND testing if you get it done. Great thread on the race bike build too!

 

[///Malcontent]

Thanks Shazaam! and Bullitt. I figured the warning was a CYA and I'm not all that worried because the wheels are essentially brand new. I don't think they've even had tires mounted.

The point about Superleggera wheels being the same construction and being perfectly suitable for road duty long term makes it more obvious PVM is just being cautious. Which I don't fault them for. The new Yamaha R1 has cast magnesium wheels too, for whatever that's worth.

 

[cbr6]

I'm not sure if Dymag is even around anymore, but in 2001 got a set for an RC51. 7 spoke mag wheels and they were street use approved .

 

[///Malcontent]

Final follow up from PVM. I asked the following questions and received these replies:

1. You are telling me that these wheels are useless and should be thrown away?
2. Does the three year life span still true if they were never used?
3. If I undertake non-destructive testing on a regular basis to monitor the wheel's condition, will that mitigate the life span concern?
4. Is this practice for just PVM wheels or all forged magnesium wheels? I ask because the Desmosedici was delivered with forged magnesium wheels and there are no such owner instructions provided.

1. the wheels are not useless, but we can’t guarantee that they are still secure if they are older than three years.
2. Magnesium wheels contain manganese, which is responsible for the decomposition of the wheel itself.
3. The decomposition goes on if you use the wheel or not, because it is a chemical process and you can’t stop or slow this process. Also there is no reliable method to check the wheel without destroying it.
4. This is guilty for all wheels out of magnesium, not only PVM wheels.

Dye penetrant crack testing requires the wheel to be stripped of all paint. Then it will have to be refinished after testing. I've decided to give them a ring test (whack 'em with a mallet and see if they ring) and just run them.

 

[Shazaam!]

Their answers don't pass the smell test.

Manganese is primarily added to magnesium alloys to improve their corrosion resistance. This is achieved by reducing the harmful effects of impurities. It has been shown that when Mn is added to Mg, the corrosion contribution from the impurity of Fe is rendered inactive because Mn atoms surround the Fe atoms and act as local cathodes.

More:

Magnesium alloy - Wikipedia, the free encyclopedia

 

[rubbish]

I'm not sure I believe their answer to #3. There are some NDT methods which should detect any small voids inside the metal, even if it all looks fine on the outside. Ultrasound and x-rays come to mind...perhaps others would work as well, like Eddy Current, but I'm not too familiar with that.

I agree with Shazaam that it's probably all "legal-talk" to avoid being liable for when things go bad, but like you said, other Mag wheels don't come with such warnings, and I've seen people use Mag wheels for many years without any issues.

 

[Motobee]

Interesting.

I recently placed an order for a set of M7R Genesi wheels from Marchesini (they wouldn't make the alu version for me as they only make blanks in large numbers, whereas the mag wheels have a different manufacturing process so single units can be produced - so I was told).

How long ago did you order your Marchesini wheels? I ordered just a rear as it looks to be a fairly close match to the stock front and was told there would be an 8-10 week wait for it to be made. Were you told the same thing?

Thanks,
Brian

 

[Bullitt]

Brian,

I ordered my wheels in mid Nov, told also that time scale, however I still don't have them...

I've dealt with Italian manufacturers like Marchesini (small, very specialised) in the past - I'll take that time scale with a pinch of slat, or maybe even a handful...

Where did you order from?

Cheers!

 

[Motobee]

Through MotoWheels in the USA. Hopefully now that the 16" Bridgestone tires are no longer being manufactured, there will multiple orders for 17" Marchesini D16RR wheels and they will make a run of them.

 

[Bullitt]

Through MotoWheels in the USA. Hopefully now that the 16" Bridgestone tires are no longer being manufactured, there will multiple orders for 17" Marchesini D16RR wheels and they will make a run of them.

I sure hope not. I asked and asked and asked if they'd make them in ALU, but told they need an order of around 300 wheels (not pairs) to make it cost effective... much much cheap than mag wheels for us, the end user though..

Anyways, looking forward to getting mine.

 

[Motobee]

No, what I was saying it that Marchesini does not keep any MR7 Genesi wheels in stock for the Desmosedici. They make them all to special order. But I think that they may wait until they have multiple orders and then make a small batch of them (10-20) wheels. They could make them one at a time, who knows?
I just know that you have to wait "Some days" as the Italians say for your wheels to arrive.

 

[///Malcontent]

When I spoke to the US importer, TAW Performance, about buying the Marchesini 17" rear, I was told delivery times depend upon Marchesini's race supply work load since they are manufactured in the same facility. When you look at Marchesini forged magnesium race wheels the resemblance is apparent.

 

[Smitty]

I have had the 17" BST wheels on order for over 6 weeks now with no firm commit when they will be delivered. I was thinking of going to the 17" Marchesini but that may be even worse.

What's the deal with these exotic race wheel companies?

If I ran my business like this there would be no business!

 

[Bullitt]

I have had the 17" BST wheels on order for over 6 weeks now with no firm commit when they will be delivered. I was thinking of going to the 17" Marchesini but that may be even worse.

What's the deal with these exotic race wheel companies?

If I ran my business like this there would be no business!

We're just little fish in a big big ocean...

 

[Smitty]

Well I did get an update today that my wheels shipped from South Africa.

So maybe my wait will be over soon.

 

[Kenny832]

So from what I'm understanding is that the OEM wheels on my D16RR needs to be swapped out to aluminum? I have plans to swap the rear to 17" mags, but it sounds like I need Alum?

 

[Apollo2]

NEED to be aluminum? Probably not.

I went with aluminum because I ride my Desmo a lot (comparatively) and ride mostly on the street. If you go through a lot of tires you have risk-exposure to scratching the rims during tire changes. Scratching the finish is a Bad Thing for magnesium wheels.

 

[Bullitt]

So from what I'm understanding is that the OEM wheels on my D16RR needs to be swapped out to aluminum? I have plans to swap the rear to 17" mags, but it sounds like I need Alum?

Absolutely not a requirement.

You can fit any type of wheel you wish, be that Aluminium, Magnesium, Carbon, even wood if you can get someone to mak them. ;-)

It's just a matter of cost and usage.

If you're going to use the bike a lot, almost as a daily rider, then mag is not going to be the best option. As mentioned, removing tyres often will expose the wheels to possible scratches and in doing so, "may" cause you problems in the future from exposed material to the elements. The biggest risk really is cracking from hitting potholes, raised surfaces etc on the road. You wont see the cracks, but you'll only find out when you have them x-rayed every few years...

Worth noting however, Marchesini have homologated their forged mag alloy wheels on the SL for road use... Good enough approval for me.

Not that I'm making assumptions, maybe your supplier only has alu wheels that he can source for the bike - which as you know, is a nightmare to get stuff for. There are plenty suppliers, worldwide that have excellent contacts with the manufacturers and they can arrange worldwide delivery.