how are the asian 21j movts in the Gmt's?

[Prsist]

when it fails just swap it out? are they problematic?

[JoeyB]

I've had a couple, none ever failed. The GMT hand seems to track slower and needs re-setting about once a week or so, but that's my only complaint. 

[Prsist]

i love the look of them but not enough to sink big money into. same as the exp II. Good to hear it jusr kept running.

[TeeJay]

I've never had a problem with them (other than self-inflicted damage )

[Ronin]

Never had a problem with them either. Especially the "fixed" 2x reduction GMT hand versions. The non-settable ones. These work great for the basic GMTs with rotatable bezels.

[Prsist]

Never had a problem with them either. Especially the "fixed" 2x reduction GMT hand versions. The non-settable ones. These work great for the basic GMTs with rotatable bezels.

fixed 2x reduction?

[Ronin]

Yes, as in non-settable. The 24 hour is actually rotating at half the speed of the hour hand.

[Prsist]

Yes, as in non-settable. The 24 hour is actually rotating at half the speed of the hour hand.

Pretty reliable until it dies? Once it does i assume I could buy another and swap mvts. Is it a special 21j? Or are they all the same.

Thinking of opening a new thread specifically for the 21j Rolex Exp. II white dial. See how many have and how well they like.

[JoeyB]

There are several different 21j GMT movements just as there are several 21j regular movements. The 21j GMT movement is designed to be a GMT from the start, not an adaption or mod like the ETA/Asian 2836-2. The biggest problem in using them for a build is the GMT pinion size. It's bigger than the gen Rolex and ETA 2893-2, and usually bigger that the modified ETA/Asian 2836-2. Finding a GMT hand to fit it can be a problem.

[Ronin]

There are several different 21j GMT movements just as there are several 21j regular movements. The 21j GMT movement is designed to be a GMT from the start, not an adaption or mod like the ETA/Asian 2836-2. The biggest problem in using them for a build is the GMT pinion size. It's bigger than the gen Rolex and ETA 2893-2, and usually bigger that the modified ETA/Asian 2836-2. Finding a GMT hand to fit it can be a problem.

On the flip side a bigger pinion is better than a small one. Given enough material on the GMT Hand, it can be broached.

[JoeyB]

The gen is 1.7mm. I opened one up to fit a 1.8mm. The one I'm using in a build right now is 2.0mm, and the gen hand won't open up that far, or better  said, I'm not knowledgeable enough to do it! As I recall, freddy talked about this on his 1st 6542 build which led him to piece together his GMT hand.  

[Prsist]

On the flip side a bigger pinion is better than a small one. Given enough material on the GMT Hand, it can be broached.

Is it just like every other 21j, when it dies, swap it or trash it?

[Prsist]

The gen is 1.7mm. I opened one up to fit a 1.8mm. The one I'm using in a build right now is 2.0mm, and the gen hand won't open up that far, or better said, I'm not knowledgeable enough to do it! As I recall, freddy talked about this on his 1st 6542 build which led him to piece together his GMT hand.

You are talkin over my head

[Rolexaddict]

I use myself the Chinese GMT movement DG3804B, 11,5 lines, 21600bph. Its a true settable 4th hand movement and very reliable. The 4th hand is not slow at all.

Sold 26,60 US$ from Otto Frei

http://www.ofrei.com/page1119.html

Sounds like the GMT movements found in Explorer/gmt reps are the Asian 2813 with a 4th hand adapted like makers did with the eta2836-2, may be that's why the 4th hand fonction could have flaws

[Dizzy]

I have an old ExpII rep with Asian movement in it from at least 10 years ago.. its get the non settable GMT hand that takes 24hrs to go around. It still keeps perfect time and is more accurate than some of my ETA 2836 movements. Ive transplanted this movement into a number of watches including submariners, a couple datejusts and a daydate and now its sitting in my parts box ready for the next temp home. Im really shocked it still runs as well as it does.

dizz

[JoeyB]

You are talkin over my head

The pinion is where the hand mounts and moves the hand. Because there are a few different movements we all call "21j" that pinion size can vary by who made it, so fitting the hand to it can be problematic. 

The movement from Otto Frei that Rolexaddict uses is a good and reliable movement, designed as a GMT from the start, not a conversion. The GMT hand pinion is 2.00mm. 

[JoeyB]

I use myself the Chinese GMT movement DG3804B, 11,5 lines, 21600bph. Its a true settable 4th hand movement and very reliable. The 4th hand is not slow at all.

Sold 26,60 US$ from Otto Frei

http://www.ofrei.com/page1119.html

Sounds like the GMT movements found in Explorer/gmt reps are the Asian 2813 with a 4th hand adapted like makers did with the eta2836-2, may be that's why the 4th hand fonction could have flaws

RA, where to you source the GMT/4th hand from? 

[Prsist]

The pinion is where the hand mounts and moves the hand. Because there are a few different movements we all call "21j" that pinion size can vary by who made it, so fitting the hand to it can be problematic.

The movement from Otto Frei that Rolexaddict uses is a good and reliable movement, designed as a GMT from the start, not a conversion. The GMT hand pinion is 2.00mm.

Are the 21j GMT movt's used by the factories modified movts? So an Otto Frei gmt movt has been design as a GMT and hence more reliable?

[JoeyB]

Are the 21j GMT movt's used by the factories modified movts? So an Otto Frei gmt movt has been design as a GMT and hence more reliable?

To my knowledge of the ones I've seen and read about on the forums, all the 21j GMT movements are designed to be GMT. Frei gets his from more than one source in China too, so they are likely all the same quality. Of course Frei has a guarantee. And of course there is the mounting of the dial that can vary from one 21j to another.  Dial dots are your friend.