My 1861 Speedmaster Pro (311.30.42.30.01.005) is ~12 months old. Since I bought it, it had pretty consistently been running fast +3-4s/day. Sometime in the last week, it shifted to running a touch slow: -2-3s/day. Also, the chronograph hand now seems to reset 1 degree to the left of zero (-359°).

I am pretty sure that these are acute changes. I will admit that I am just eyeballing things - however, I am still in an extended honeymoon phase with this watch, so I do somewhat obsessively check how fast/slow it is each night when I take it off. I have not changed any of my standard wear patterns: I still wear it daily 5days/week and rest it crown down overnight.

This watch is still under warranty and I was already planning to take it in in March to get the seals/gaskets checked. I was just wondering, however, is there some easy explanation that would tie these changes together?

Appreciate any thoughts.

 

I am not sure about centring of the chrono seconds. It's not like a quartz chrono that comes with tools to adjust the chrono hands. So either the registration mechanism is off, or the hand has moved on the pinion slightly. I am not sure which is most likely - the former probably.

With regard to timing I think anywhere between -3 and plus 4 is really good. That's chronometer standard. I expect you are in the top percentiles with those figures.

 

As much as people say they don't change their wearing patterns, given the amount of positional variation that these watches can have and still be in tolerance, there can be fairly significant timing changes if you don't replicate exactly from one day to the next how much time the watch stays in each position.

On top of that if you are using the chronograph that will affect timekeeping, so again another variable if you are using it for different lengths of time each day. In addition, if you type of movements you make include sort of rapid flicking of the wrist, this can cause momentary disturbances in the balance oscillations that will take time to recover, so the number of those in a given day can change timing as well.

So for best timekeeping, wind the watch every day, around the same time of day.

On the position of the chronograph seconds recording hand, if it is not 100% centered, it was most likely that way from the start. A brand new hand being pressed on is quite tight, so it is unlikely that it would move on the post - that's usually more of a problem with vintage watches where the hands have been removed and installed several times.

Cheers, Al

 

Thank you for the reply and the reassurance. While I am not really concerned about the accuracy, I was more worried about the change. That being said, as you point out, this is certainly still well within spec.

 

I appreciate the insight. Once I found that my watch would run the least fast when resting crown down, I got used to seeing it slowly tick up +3s, +6s, +9s each night when compared to a reference. I hadn't given thought to the number of minor variations over the course of a day/week that could change the timekeeping.

You are probably right about the chrono seconds hand. I spent a lot of time before posting squinting at my watch, asking myself, "Has this always been this way?" It really does feel like it has changed - but, given that I am now focused on a minor change in timekeeping, this minor change in the chronograph may well be placebo/projection/confirmation bias/etc.

Thank you for the thoughts.

 

Hi Al, can you explain why using the chronograph affects timekeeping? Thanks in advance for sharing your knowledge.

 

What do you mean, crown down? Do you mean resting on the crown?

 

“if you type of movements you make include sort of rapid flicking of the wrist, this can cause momentary disturbances”

I think there’s your answer, dude.

 

Rate can be affected by the amplitude of the balance, so when the chronograph is used, the balance amplitude will lower, and the rate can change.

 

Yes.