I haven’t. I’ll have to try those on the next build.
So this establishes 55 G as the known minimum weight for U4-type stems in the Boba housing.
Even then, people here often seem to prefer 57 G, even 57 G Long. That’s what I recommend people try first when going to lower weights.
I have only used Bobas in hotswap, haven’t felt the need to create a board since they are fairly heavy tactiles.
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To anyone that got in on the limited edition black U4’s, did they have the longer (16mm+) separately purchasable Gazzew springs?
Looks like 14mm. (Factory donut-dipped; guess they started that earlier than I thought!)
3Dkeebs.com has restocked the U4T Blacks - they are currently available in 55g and 65g versions, but I’m not sure if those have the same spring type as the first run or not,
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I like how the measuring tool matches the switch. 
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Sold out at the moment, but it’s Wuque’s FR4 ruler:
I think it looks really cool, and it’s super useful.
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So they are 55 G switches with pre-lubed springs?
So basically these are usable directly out-of-the-box?
55g or 65g; there’s an option for this run / batch / whatnot.
Pretty much, yeah. There’s definitely still some tuning headroom, but these don’t ping like some older stock U4 / U4T I’ve used. I actually lubed a batch of each not too long ago, and both had pretty significant ping before lubing - these don’t. It’s there, but minor.
You might still hear some amount of spring wiggle depending on your setup and typing style, but I’d say its faint and probably well within most people’s tolerances for an enjoyable switch.
I think all stock Gazzew switches sold from vendors at this point have the same lubing treatment; a little thin grease / thick oil dip on the bottom of the spring - which goes a long way - and just the lightest thin oil sheen on the legs to mitigate friction.
Tuning from there would involve coating the spring in oil or possibly donut-dipping the top of the spring in grease to mitigate the minor wiggle, and lubing the stem & housing rails to increase smoothness.
Lubing the legs will reduce tactility, but still leave plenty intact since it’s such a high-tactility switch anyway - this might be worth it for some because it further increases the smoothness and gets rid of the “dry” feeling I think the switches otherwise have.
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After hearing about the 14mm 55g springs in these, I wonder if they’ll have issues returning larger keys like the spacebar. This thread has indicated that 55-57G Long 16mm+ springs seem to be the sensible minimum. 14mm places these firmly as “short” springs.
Good analysis, and agrees with my experience as well.
U4 are okay in factory condition, esp. if they’ve been donut-dipped and some stem lube. But I find them better with 3204 on stem + rails, they do feel “dry” otherwise.
@Winters_Mute 55-57 G Long is more reliable, in my experience, but I was comparing that to 55 G 15mm(?) Spirit.
The OUTEMU premium-line springs tend to be heavier than they should be. At least, the 52 and 62 G springs are. I think 62 G U4 Boba, which some think is the ‘standard’ ‘light’ weight, is a little heavier than it should be. Unfortunately, 55 G Bobas were not available in many locations.
So the 55 G OUTEMU springs may be enough, if they function as heavier than most other 14mm springs somehow. 55 G is usually enough for the 1-1.5U keys, I’m a little dubious about it for large modifiers like shift keys and spacebar. If I were to do a 55 G build, I would consider 62 G for the spacebar.
I’m about to test 2 U4 Boba with 55 G OUTEMU springs that have been through a polishing machine. Wonder how they’ll do.
I ordered some U4s, they probably will arrive next month. I have a pack of TX long 55g with me already. Do you think it will work normally with that spring weight? I read above that 57g long, or even 60g long, might be necessary for that normal, snappy return.
It’s been a while since I tested springs with U4.
I will be getting some stock OUTEMU U4 Boba 55G samples next week, so I can see how 55 functions.
If 55 G OUTEMU is slightly overpowered like their 52 and 62 G springs are, then it could be okay. 55 G Long should honestly be good enough. The improvements from 57 and 60 G Long springs over 55 OUTEMU might be … subtle.
I recently assembled 2 U4 Boba switches using stock parts.
White Boba housing, U4 stem, OUTEMU 55 G spring. No lube of any kind, anywhere
They were run through a polisher machine for 400,000 iterations.
That got rid of some of the stock mushiness. Not so much of that now. But man do they feel dry. So I’ll have to lube them and see how that goes.
In terms of responsiveness, they type okay. Like a rubber-dome keyboard.
Buttttttt… if you type slowly, you can feel the tactile bump ‘catch’ on the upstroke. It’s more pronounced than you would find in the 62 G.
Normal typing is pretty okay, but you will notice on slow, individual keypresses.
Lube would presumably help with this. But, again, this makes a case for 57 or 60 G Long springs. Honestly, 57 G should be fine with most keycaps, especially if you are polishing and then lubing according to Gazzew’s instructions.
Little leery about stock OUTEMU 55 G springs, at least without lube.
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I just lubed 1 of the 2 polished, 55 G U4 Boba switches.
It’s much better now. ‘Wetter’ instead of dry. Sound is much improved, and the operation is noticeably improved.
These 55 G U4 should be okay for normal typing if at least the spring and guide rails are lubed (not sure if Gazzew recommends the latter). Fine for Cherry profile.
It wasn’t so great completely dry. But if you’re willing to do a little work on the switches, the 55 G OUTEMU become normal enough for my usage. Might keep some 57 or 60 G L springs for any larger keys that give you trouble.
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This is very informative, thank you!
I was planning on lubing those U4 anyway, so I guess it’s not an issue for me then haha.
Did you try out the Pewter stems in Boba housings?
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Yeah, the 55 G work fine for me with modest lubing.
I can’t remember the details of my experiment with Pewter stems in the Boba housing.
I seem to recall that the stem may have been stuck or sticky.
This is likely a result of the standard OUTEMU tight-tops I use with Boba housings. The tight-tops seem to work well with non-OUTEMU stems that aren’t made with too-fine tolerances, ie stems that are kind of loose. So they work okay with Cherry, Kailh Pro, Gateron budget, and Cherry-like stems. But ones that have a tighter fit to their housing, like Pewter, are problematic for me.
The tight-tops I received are REALLY tight, so they have given me issues with Durock, and to an extent AKKO and Everglide Jade Green stems. I have to use powerful springs to get the latter two to operate, and that was probably the case with Pewter. Couldn’t make a light tactile with it.
My successful Pewter experiment involved putting the stock Pewter stem into a lubed Taro Ball housing, with a 57 G 14 or 15mm TX spring. The Taro Ball housing was lubed much better than my stock Pewter housing, and it was a smooth and tight switch that had okay sound.
I find that I haven’t taken a liking to any stem based off the Durock Light Tactile. It’s actually heavier than Naevy 1.5 according to Youtube, although Naevy is supposed to be an Ergo Clear. [I still have to try Naevy.]
You might consider using the Boba linear housing, like the LT or Bobagum housing, for your Pewter experiments. The Herculean Boba tactile leaf tends to turn even Gateron Browns into an Ergo Clear, and any mid-range Brown into a heavy Ergo Clear.
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I will try out the Pewter stem in both Bobagum and Boba U4 housings and will post my thoughts here.
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In the spirit of transparency, I haven’t read through this entire thread, so forgive me if what I say has been rehashed ad nauseam. I tried the U4s for the first time (thanks @Deadeye!), and I really like them.
They are whisper quiet, feel great on a brass plate, and have really shifted my preference when it comes to silent switches toward silent tactiles. (I’m still linear gang for non-silent though 
).
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I’m missing my Topre switches but I’m only in MX space at the moment. Has anyone played with springs to get these close to silenced Topre? I feel like the U4 bump is more intense and the keystroke is heavier than 45g Topre, less sure about 55g Topre. I’m wondering if playing with lighter and longer/shorter springs might help smooth out the bump a little.
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Did we ever get a full resolution on the proposed issue of the u4/t cruciform thickness from a while back? I remember allegations that they were stressing if not cracking GMK stems. I have noticed that caps are harder to take off of them then other switches (actually why I’ve never put my u4t’s in a board). I would appreciate any official info (I know Gazzew said made a statement that he would look into or something), or even anecdotal evidence that could speak to the wear on caps, if any, long-term. @Deadeye, I figured you may have something, lol.