T47 bottom bracket standard

Discuss light weight issues concerning road bikes & parts.
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Stendhal
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by Stendhal

pdlpsher1 wrote:
Sat May 04, 2019 8:57 pm
And lastly, T47 BBs are heavier because they are made of aluminum. My Chris King T47 BB weighs 103g, which is perhaps even lighter than some of the PF30 thread-together adaptor BBs.

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This is good news as I have just ordered a Chris King T47 BB (for a 30mm crank), which I weight-budgeted at a relatively svelte 106 grams. This is for a frame by a mass market bike company that anticipated Trek by specing T47 on at least one carbon frame (any idea who, it’s not as large as Trek but it is also not a custom builder)
Specialized S-Works Tarmac SL6 (6.39 kg), Cervelo Aspero (7.87)
Retired: LOW// mki, Pinarello Dogma F10 \ F8, Lapierre Pulsium, TIME Fluidity, Wilier Cento1 SR, Ridley Noah, Cyfac Cadence, Cervelo S2, R3, R5, Felt Z25, Klein Quantum, Cannondale 2.0

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Stendhal
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by Stendhal

deleted double post :oops:
Specialized S-Works Tarmac SL6 (6.39 kg), Cervelo Aspero (7.87)
Retired: LOW// mki, Pinarello Dogma F10 \ F8, Lapierre Pulsium, TIME Fluidity, Wilier Cento1 SR, Ridley Noah, Cyfac Cadence, Cervelo S2, R3, R5, Felt Z25, Klein Quantum, Cannondale 2.0

by Weenie


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pdlpsher1
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by pdlpsher1

My CK BB is also for a 30mm crank. So your BB should be at 103g. If you haven't done so I highly recommend the CK grease injection tool. I use the cheap green marine grease and I refresh the grease a couple times a year. When you inject the new grease don't pull on the grease gun trigger too hard. Go slowly. If you try to inject too much grease in all at once you will pop out the seal. This happened to me. Just go slow and easy. It's so much fun watching the old black grease come out of the bearing.

I have a thread-together PF30 adaptor by Praxis. This is for a GXP spindle and it weighs a ton (154g.) Hambini BBs are even heavier as they are machined from a solid billet.

I can't really think of any manufacturer using a T47 BB on a carbon frame. You have me stumped.

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Calnago
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by Calnago

pdlpsher1 wrote:
Sat May 04, 2019 8:57 pm
Calnago wrote:
Sat May 04, 2019 7:08 pm
Thread pitch is just the distance between the threads... it could be fine, coarse, whatever. It is independent of the bore
Not really. A lot of thought actually went to deciding on the 1mm thread pitch. It was a compromised decision based on the following variables- easy of manually tapping into existing PF30 BB shells made of titanium (a finer thread makes it a lot easier compared to a coarser thread like 24tpi used in the English BSA), preserving the structural integrity of the existing PF30 shells since a finer thread will result in less materials removed, and the availability of the M47x1 taps. Ultemately the former two variables won out.
Let's try this again.... you said earlier that the 1mm thread pitch was chosen so that existing PF30 metal BB shells can be tapped and turned into a T47. All I was saying was that the 47 was chosen, not because of any thread pitch, but because they were dealing with a PF30 nominal bore of 46mm. Obviously they couldn't go less than that, so to enable the cutting of threads that would remove the least amount of material.... too much and that could weaken the shell, they ended up with 47. Remember... T47 was an afterthought to fix the issues of PF30 in metal frames, so the shell wasn't really designed to have much or any material removed from it's bore afterwards. But I hear ya on not knowing too many folks (zero in my case) who have actaully had this done to their existing steel or ti PF30 frames. But it makes for a great BB to use for any new builds.

And saying that a finer thread makes tapping into exisintg PF30 ti shells a lot easier compared to a coarser thread like 24tpi is uh, do you know how much coarser that really is? Well, it's like the same, or pretty much the closest equivalent metric thread pitch you can get. It's 1.0mm versus 1.058mm (metric equivalent threadpitch of 24tpi). So, if you think that is functionally coarser, then well, ok... I'd say it's functionally the same, essentially the same as the English and Italian thread pitches we've been used to forever, just finally getting around to not mixing two differnt measurement systems in the same measure, (36mm x 24tpi for example).

I'll look forward to aquiring a new set of 47x1 taps... if Trek actually goes ahead with this, and I hope they do. It's all good.
:beerchug:
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

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pdlpsher1
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by pdlpsher1

Well, apparently there's enough of a difference for the T47 founding fathers to choose the 1mm thread pitch vs 24tpi :D They just didn't pull that spec. out of the thin air. Anyways the finer thread does require extra care when installing the cups as one can easily cross-thread. I know it doesn't sound like a lot of difference (25.4tpi vs. 24tpi) but this is something to watch out for.

On my tandem I do have FP30 BBs and would like to tap them into T47 BBs. But I probably should leave this to the professionals...

TobinHatesYou
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by TobinHatesYou

When I say I want a coarse thread, I mean more like 1.5mm or possibly even 1.75mm, not the ridiculously small difference between 1mm and 24 TPI. I see no reason to choose a metric thread that is close, but not equal to 24 TPI just because. There’s basically no downside in going coarser on a new standard...as pdlpsher1 mentioned, it was selected only to make it easier to tap threads into existing PF alloy sleeves/rings.

talltales
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by talltales

1 mm thread pitch is close to BSA that is 24 tpi = 25,4/24 = 1.058 mm. 1 mm is a fine pitch, but im sure its fine, as long as some care is taken during manufaturing. Shouldnt be a problem, Imo.

Edit: I see this was already mentioned several times :)
Last edited by talltales on Sun May 05, 2019 5:09 am, edited 1 time in total.

AJS914
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by AJS914

pdlpsher1 wrote:
Sun May 05, 2019 3:22 am
Well, apparently there's enough of a difference for the T47 founding fathers to choose the 1mm thread pitch vs 24tpi :D They just didn't pull that spec. out of the thin air.
I'm pretty sure I read back when this was first announced that one of the reasons they chose this thread pitch was because someone was already making taps. This made the project much easier to execute. If they had to find a tool maker to make special the T47 taps, it would have been cost prohibitive.

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Calnago
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by Calnago

You both (Tobin and PdlPsher1) don't get it and one's arguing for fine thread pitch, which has already been decided upon for good reason, which we have always had, we're just simply changing to an essentially equivalent metric pitch and nomenclature. And now Tobin, who's arguing for coarser, which we have never had, but he seems to think it's better for some reason. You only want to remove as little material as possible from the PF30 bore of 46mm. Coarser threads mean greater depth as well, and hence, more material gets removed. But still... please explain why you think coarser threads are better. Up to this point, you've been like a child, claiming "Threads should be coarser" and when asked why, at least so far, your answer seems to be "just cuz". That may work when you’re 4 years old, but a bit more of an explanation might be nice. The fine pitch has seemed to work for many many years in both English and Italian bb shells... why would a coarser pitch be better.
While you ponder your answer, I will tell you why a fine pitch is good for this application... one, already discussed, the threads don't have to be too deep so the walls of the shell can be thinner, but really I think the more valid reason is this... At some point the cups will thread down to the shell face and the finer the pitch the more gradual and uniform that interface between the cups and the faced shell face will be, and that's a good thing. And yes, the shells will need to be properly faced. With the fine pitch, they will settle in on that perfectly faced shell nice and solid and straight and aligned. End of story and all is well.

And when we're all talking metric these days... don't you think it makes sense to have the complete measurement in one measurement system... metric. Hence, 47mm x 1mm. Taps are available, I've already checked. It's easy to understand, well, for most. For some reason Pdlpsher1 seemed to think there was quite a difference betweeen a pitch of 1.0 and 1.058 (24tpi converted to metric). There really isn't. But it's clearly confusing to some. That's all. I'm all for calling it 47mm x 1mm over 47mm x 25.4tpi any day. When you refer to your height, I'm going to assume you're short... do you call yoursefl 5'ft 15cm... or do you say 5'6", or 168cm? Because the 5ft 15cm thing is analagous to the 47mm x 24tpi thing.

I'm out, you can figure it out yourselves. For now I'm going to just wait to see what Trek actually does before thinking about it too much more.

Night you two, have fun.
Last edited by Calnago on Sun May 05, 2019 5:27 am, edited 1 time in total.
Colnago C64 - The Naked Build; Colnago C60 - PR99; Trek Koppenberg - Where Emonda and Domane Meet;
Unlinked Builds (searchable): Colnago C59 - 5 Years Later; Trek Emonda SL Campagnolo SR; Special Colnago EPQ

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pdlpsher1
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by pdlpsher1

Sheesh....a long dissertation just to prove that my statement of "The 1mm thread pitch was chosen so that existing PF30 metal BB shells can be tapped and turned into a T47" is wrong?

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Stendhal
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by Stendhal

pdlpsher1 wrote:
Sun May 05, 2019 2:39 am
My CK BB is also for a 30mm crank. So your BB should be at 103g. If you haven't done so I highly recommend the CK grease injection tool. I use the cheap green marine grease and I refresh the grease a couple times a year. When you inject the new grease don't pull on the grease gun trigger too hard. Go slowly. If you try to inject too much grease in all at once you will pop out the seal. This happened to me. Just go slow and easy. It's so much fun watching the old black grease come out of the bearing.

I have a thread-together PF30 adaptor by Praxis. This is for a GXP spindle and it weighs a ton (154g.) Hambini BBs are even heavier as they are machined from a solid billet.

I can't really think of any manufacturer using a T47 BB on a carbon frame. You have me stumped.
The new-ish Ibis Hakka MX all-rounder bike (like the Open U.P.) is carbon \ T47. It was designed by former pro racer \ Berkeley engineer \ ex-Specialized Andy Jacques-Maynes, who posted a PDF listing the different bottom brackets compatible with different cranksets. My frame is scheduled to ship June 15.
Specialized S-Works Tarmac SL6 (6.39 kg), Cervelo Aspero (7.87)
Retired: LOW// mki, Pinarello Dogma F10 \ F8, Lapierre Pulsium, TIME Fluidity, Wilier Cento1 SR, Ridley Noah, Cyfac Cadence, Cervelo S2, R3, R5, Felt Z25, Klein Quantum, Cannondale 2.0

TobinHatesYou
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by TobinHatesYou

Just going to add that Chris King himself thinks they should have gone coarser for the sake of durability.

Nefarious86
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by Nefarious86

SWorks crank in a Trek.. Sacralicious :)Image

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silvalis
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by silvalis

TobinHatesYou wrote:
Fri May 03, 2019 11:15 pm
And there it is. Anyone capable of reading tea leaves knew this was coming in the immediate future. I figured they would just go press fit with 90.5x42mm dimensions, but T47 (86.5x46mm threaded) is quite flexible too. The only reservation I have with T47 is the 1mm thread pitch. The only other real option is BB386EVO...they want to keep the wide shell for obvious benefits like stiffness and tire clearance.

Don’t be surprised if the reason for the 2020 Domane’s delay was a last minute change of heart WRT BB standard.
Did I miss something? T47 is 68mm width no?

ps: no need for T47. We're all going dub :D
Chasse patate

by Weenie


TobinHatesYou
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by TobinHatesYou

silvalis wrote:
Sun May 05, 2019 1:11 pm

Did I miss something? T47 is 68mm width no?
Yeah it is. I was half thinking of what my ideal wide-only version would be there by accident.

DUB AND T47 aren’t mutually exclusive. One is effectively a spindle standard vs a BB shell standard.

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