Best and durable Omega movement now?

The 8' and 9' series coaxials are very nice to look at.

That has to count for something!

No, when I am referring to changes in parts, I'm talking about the differences in the design of the two movements. When existing calibers were changed from the Siss lever escapement to the co-axial, the amount of parts that were changed varied. So on the 1120 to 2500, not only did they add the co-axial escapement, but they changed the design of the balance spring from being one with regulating pins, to being free sprung. So comparing those two for performance due to the co-axial is difficult because they changed more than one thing.

On the 3303 to 3313, it was already a free sprung balance on the 3303, so the only change made there was to add the co-axial. The regulation didn't change, the beat rate didn't change - so these two movements are the best example to compare what performance gains might have happened just adding the co-axial made. In my experience in servicing both, there was no difference.


I don't know who "they" is, but again when I was trained by Omega, they clearly stated that the co-axial escapement was not for accuracy, but for extended service intervals.


The rest of the movements are no different, so the only question really is, does the co-axial escapement wear out faster than a Swiss lever escapement. In my experience, the answer is yes. It's rather uncommon for me to have to change an escape wheel or pallet fork in a Swiss lever escapement. It happens sometimes, but it's not common. When I do see wear on something like the escape wheel teeth, it's usually from some sort of abnormal condition rather than normal wear and tear. For example, here's what a normal escape wheel tooth looks like in an ETA 2824-2:



Here's one with very strange wear:



Looking at the pallet fork jewels, you can see why the escape wheel teeth look like they do - the jewels is chipped and was chewing up the escape wheel teeth:



Here's another - from an Omega with a Cal. 3303 - note the "line" down the left hand side of the escape wheel tooth:



Every tooth had a bit of the tooth shaved off - the reason is again a chip in the pallet fork jewel:



But again this is very rare - these are the only 2 watches I've had in with this sort of issue in the last 3 years.

The shape of the co-axial teeth means that they come to a very fine point, and that can wear. Although co-axial is touted as having less friction (which is true) that doesn't mean it has zero friction. If you look at the interaction of the pallet fork jewels and co-axial wheel teeth slowed down, you can see a very sharp tooth going over a very sharp pallet fork jewel. I took this video using my microscope with a co-axial movement in the control holder, and you can see it clearly.


If you set the play back speed of the video down to 0.25X, it becomes clear why these teeth wear. Here's an example of that very fine tip that has worn:



Here's the upper teeth on a 2500C co-axial wheel - you can see the wear:



Since my business has shifted a lot towards servicing vintage watches, I don't service as many co-axials as I used to. However when I see people post photos of the parts they get back from Omega when a service is done, I see a lot of co-axial wheels and pallet forks returned, meaning they have been replaced for wear. This doesn't happen with nearly the same frequency with a Swiss lever escapement.

Now is that a problem? I guess it really depends on how you think about watches and how they are serviced. It's normal practice to replace certain parts at every service, like the mainspring. I also know that on certain movements, I'm very likely to have to replace a specific part, because it seems to be worn on just about every movement I get in. I don't personally believe that makes it a bad movement or design - all movements have weak spots and are a series of design compromises. So is replacing these co-axial parts at every service any different, or a cause for concern? I'm not going to tell you one way or another - it's something you would have to decide for yourself if it bothers you or not.

These aren't parts that have been updated typically...

The issue was fixed with new bushings as of May 2021.


It sounds reasonable...

Not sure where you are getting this information from, but you need to find a better source - the source you have is a bit unprofessional...

The 9900 co-axial wheel is not used in either the 8500 or 8900.

All 8500 and 8900 models use the co-axial wheel from the 8500G version of the movement, which was the first 15,000 Gauss movement.

This has nothing to do with the 2500...

"Look the same" and "are the same" are two different things.


Again, all 8500/8900 get the co-axial wheel from the 8508G, which is the fully anti-magnetic co-axial wheel.

This is from the parts listing for the 8900:

7228508G30040 | CO-AXIAL WHEEL


Omega certainly did, which is why they made the wheel and the pallet fork from anti-magnetic materials.

Balance spring and balance staff.

Yes.


2500's are not updated with new designed escapements.