Modding a noob GMT

[bklm1234]

Introduction

This GMT II is the incorrect hand stack version. With its brother, the correct hand stack version being out of production, it is the best GMT II rep currently available, IMHO. The dial markings, date font, date mag, date window position, rehaut depth and thickness, crystal height and beveling, case, bracelet are most accurate. It's no surprise because it comes from the same factory as the noobmariner. This factory makes some of the best rollie reps including YM, Explorer II, GMT II correct hand stack and incorrect hand stack, and of course the noobmariner.

The Weaknesses

This watch has a few flaws, all of them fixable:

- wrong crown. It's a little oversized and has the wrong shape. But the teeth definition is excellent. I'm not going to change it. I'll leave it to the eventual owner (By-Tor) to take care of it if he wants to.

- wrong CG shape, I'll trim the inside. That's all is needed. There's no need to reshape the outside

- the bezel insert has the wrong font and colors for pepsi and red/black. By-Tor already bought the inserts. I will provide the mod instruction here.

- the bezel teeth are OK. But I like to see longer and sharper teeth. I'll replace the stock bezel with one from a cn sub. The side-effect is the bezel can be easily popped off by hand. You can change the bezel insert easily. I call it the "Transformer GMT". It's like having 2 or 3 GMT II in one watch. What you give up is the clicking when you turn the bezel.

The Process

The watch before modding:

Removing the bezel. This is the scariest part.

Masking-tape the bezel and the case to protect them from getting scratched

Pry a utility razor between the bezel and the case. Be really slow and careful. It is basically a noobmariner bezel and case. Many know how hard it is to pop the bezel. I almost lost a finger trying one time. We want to separate the bezel from the case a little at a time.

Finally I got the bezel out, couldn't help bending it though. In the process I used a flat head screw driver to help pry the bezel off once I got a good gap from the razor blade. Use some wooden stick to cushion the prying so you don't scratch the case.

Reshaping the CGs.

Prepare to remove the tube. First take out the tube gasket before sticking the rat's tail file in

Remove the tube with a rat's tail file

File the inside of the CGs with a flat needle file

Basically done.

Cyclop wasn't level with date window. Popped the crystal, re-aligned and re-installed the crystal. Now the cyclop is level with the date window.

Prep'ping the replacement bezel.

Compare the stock bezel with cn sub bezel. The stock bezel has shorter and pointier teeth.

Look at the longer and sharper teeth on the cn sub bezel.

The gear teeth on the bottom have to go

File them off with a large flat file

Gear teeth gone

Get a replacement insert from JeweleryOut for $10 + $5 shipping. Mill off the ridge on the back like this

Don't mill off too much otherwise the insert can't snap in to the bezel and you have to glue it. Mill this much and that's enough

and it will snap in and fit perfectly

To fit the bezel on, bend the retaining wire to a pentagon.

Make the wire look like this from the side. It helps to pull the bezel close to the case

Fit the bezel on without the insert.

Check if there's any gap between the case and the bezel. If yes, file the bottom of the bezel some more.

Ladies and Gentlemen, the transformer "GMT II"

Pepsi insert on

Switching bezel. Just pop the bezel off by hand.

Red/Black insert on

Bracelet back on, showtime.

I'm happy how it turned out. I had a lot of fun and some scare in the process. I hope you enjoy this post.

-bk

[Stephane]

Wow, very nice post BK.

I love to see these nude pics and the work.

Hmmm, I'd love to have a transformer and quickly change the bezels.

I'll try to take mine out tonight or tomorrow

Thanks for sharing,

Stephane

[By-Tor]

I'm getting the 2 (different) best GMT Master reps, and make a complete and updated GMT buying guide for the members. Interesting to see how these two beauties compare against eachother. Big thanks to bk for modding this for me.

@bk: Thanks for posting this here. You could post your amazing Submariner Guides here, too.

[Stephane]

@bk: Thanks for posting this here. You could post your amazing Submariner Guides here, too.

Yes, BK.

I finished reading them out there and they are 100% helpful for the community.

Cheers

Stephane

[stac]

Great post

Outstanding photography

[Cats]

Great story BKLM1234,

i think i will have to try this at home beacause the wat you tell and picture it makes it so simple.

Regards,

Cats

[alligoat]

Great job bk. Interesting how the factory uses the noob serial number. Thank goodness they use the correct modlel #.

BTW, what you call a rat tail file, I call an ease-out. Like for backing out broke screws, etc. But it works just the same, if fact it might be better than jamming a file in there- if you want to reuse the case tube. Excellent write up and pics.

[By-Tor]

Here's a quick rep vs. gen comparison.

bk is absolutely correct. The installed "sharp" bezel makes a difference. The crown is the only apparent flaw (Pugs can probably replace it eventually). The hand stack is only visible with a loupe, and when the hour hand and GMT hand "meet". I'd rather take a bullet proof movement than risk it with the correct stack modification. The gmt hand rim is a bit thicker on the rep, about the same thickness as the gmt hand on Master I.

[elprimerozen]

Great!!!!

[Guest Carl]

Thanks for a great article.

I think I hear the call of a GMT....

[thedudeabides]

great info, one thing, what is a CN sub bezel?

thanks

[bklm1234]

great info, one thing, what is a CN sub bezel?

thanks

CN sub is Chinese submariner, means not a TWB/MBW. In my context, it's not even a noobmariner. The VIPmariner is a good example of a CN sub. They are cheap subs that usually people pick up in Asian for $20, 30, 40.

-bk

[docblackrock]

Nice pictorial.

Couple of things to clarify though...

So I'm clear, you switched the bezels because the CN Sub bezel is better quality (teeth) than this 'noob' assembly? Ok got that. But did you file off the ratchet teeth simply because the 'noob' uses a different click-spring mechanism (the unidirectional Tag Heuer-like ring type unlike the old CN and TW little clicker/sping)? Or because the Sub bezel has unidirectional ratchet teeth, whereas the GMT needs to be bidirectional. i.e. how does your GMT bezel rotate now? Clicks or freely?

Also, AFAIK the correct hand stack version is not discontinued just expensive and not on inventory.

I have had both modded TW and CN GMTIIs and the only thing that still bothers me (hand stack aside) is that they still can't make a halfway decent 24hr hand for the standard 2836 GMT-adjustable movt. Stem too short, too thick and too dark in colour. Triangle pointer too large and not equilateral.

[By-Tor]

Also, AFAIK the correct hand stack version is not discontinued just expensive and not on inventory.

The problem with the correct hand stack version is the dial, which is really bad. Well, the coronet and ROLEX text are from Explorer II.

They produced with the same specs as the watch bklm reviewed here VERY BRIEFLY. I'm quite sure that particular (visually best) version is out of stock.

The correct stack version isn't good mechanically. Some members have been lucky and got a working watch. I have owned 2 correct stack Explorers, and the other one developed 2 fatal problems in just 2 days. The other one I traded almost right away. I recall both bk's correct stack versions were problematic too. The dial is loose, hour hand setup breaks (mine broke in 24 hours), the hands get stuck with eachother, etc. Maybe you'll get lucky... but 1 bad watch out of 2 was enough "experimenting" for me.

Personally, after owning many rep GMT Rolexes I'll always choose the wrong stack version from now on. The small visual flaw is a small price to pay for reliability. I understand how the hand stack is a major visual issue for some, but not for me.

[Dizzy]

very nice!! I'm gunna have to build a GMT soon. I think its the one rolex rep that i"ve never had. I would like to go vintage but they are just so darn small. I'll have to pick a year that i like and go from there.

Excellent work!

Lonnie

[Tribal]

Great Job

Looks fantastic

Nice idea to change the Bezel...

[docblackrock]

The problem with the correct hand stack version is the dial, which is really bad. Well, the coronet and ROLEX text are from Explorer II.

They produced with the same specs as the watch bklm reviewed here VERY BRIEFLY. I'm quite sure that particular (visually best) version is out of stock.

The correct stack version isn't good mechanically. Some members have been lucky and got a working watch. I have owned 2 correct stack Explorers, and the other one developed 2 fatal problems in just 2 days. The other one I traded almost right away. I recall both bk's correct stack versions were problematic too. The dial is loose, hour hand setup breaks (mine broke in 24 hours), the hands get stuck with eachother, etc. Maybe you'll get lucky... but 1 bad watch out of 2 was enough "experimenting" for me.

Personally, after owning many rep GMT Rolexes I'll always choose the wrong stack version from now on. The small visual flaw is a small price to pay for reliability. I understand how the hand stack is a major visual issue for some, but not for me.

Since I planned on making a hybrid (using correct stack movt only, the rest being built using TW, CN and gen parts), the crappy dial is not an issue.

But the mechanical reliability is, and it's what I'm more wary of. As I said, if only it weren't for the crappy GMT hand then I would like you be happy and content with the more reliable bastardized 2836 movt with 1675-type hand stack. It's THAT horrible stubby GMT hand that bothers me visually much more than the stack itself. Maybe I just need to get me a 2893 to fit my 2893 (with excellent 24hr hand) hand set?

[bklm1234]

the correct hand stack, besides reliability issue, has an annoying feature: the date change follows the GMT hand. Normally when you travel, you set the hour hand to the local time. On the gen and probably other GMT movements, the hour hand effects the date change. So the date is not necessarily your local's date, a problem for long travel. The Zigmeister pointed that out in his review of this bastardized movement. It's something you have to get used to.

-bk

[brook0]

Wonderful Tutorial!

Great sources of knowledge here.

Thanks to all!

[docblackrock]

the correct hand stack, besides reliability issue, has an annoying feature: the date change follows the GMT hand. Normally when you travel, you set the hour hand to the local time. On the gen and probably other GMT movements, the hour hand effects the date change. So the date is not necessarily your local's date, a problem for long travel. The Zigmeister pointed that out in his review of this bastardized movement. It's something you have to get used to.

Unless of course you use the 24 hr hand as your local time maybe?

[$tingray]

Nice post bk

Hmmmm. Maybe it

[yt74]

Get a replacement insert from JeweleryOut for $10 + $5 shipping. Mill off the ridge on the back like this

[

-bk

First off, great post, secondly I tried this mill to snap in mod with a sub insert and I couldn't even get close. At one point it got kind of close to snapping in, but then nothing. I was very careful about trying after every single filing rotation. I am beginning to think you guys saying this can be done are pulling out chains!

[bklm1234]

@docblackrock: of course no problem using the GMT for local time. It's not so natural for a supposedly GMT watch.

@$tingray: that's the same watch as the one modded in this post. At least do the CGs. Have fun.

@yt74: is your sub a noobmariner? The insert mod works for MBW and cn subs. The noob has a slightly smaller diameter, ~.996" vs. ~1.001" on the cn sub. You probably need to sand the perimeter a little.

-bk

[Star69]

if anybody would point me in the right direction :

where can i get the Noob GMT ?

thanks

Frank

[yt74]

yt74: is your sub a noobmariner? The insert mod works for MBW and cn subs. The noob has a slightly smaller diameter, ~.996" vs. ~1.001" on the cn sub. You probably need to sand the perimeter a little.

-bk

Nope, MBW 16610...

Edited September 19, 2007 by yt74