T47 bottom bracket standard

[AJS914]

Cycling tips is reporting a "rumor" that Trek may switch to T47. That would be awesome to see a major manufactuer adopt this standard.

https://cyclingtips.com/2019/05/trek-ru ... -brackets/

[TobinHatesYou]

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.

[pdlpsher1]

This news won't affect me directly as I already have T47, but it's nice to hear that T47 might become a widely adopted standard. Does this also mean Trek will add an aluminum insert with threads into the carbon shell?

The 1mm thread pitch was chosen so that existing PF30 metal BB shells can be tapped and turned into a T47. However I'm not aware of anyone who has actually done it other than seeing one frame being done in a Youtube video tutorial.

[TobinHatesYou]

This news won't affect me directly as I already have T47, but it's nice to hear that T47 might become a widely adopted standard. Does this also mean Trek will add an aluminum insert with threads into the carbon shell?

The 1mm thread pitch was chosen so that existing PF30 metal BB shells can be tapped and turned into a T47. However I'm not aware of anyone who has actually done it other than seeing one frame being done in a Youtube video tutorial.

I just wish they had moved on from BB90 a year earlier. :p

And yeah presumably two threaded rings will be bonded into the shell though a full length sleeve is also possible to further reduce the chance of play.

[1415chris]

Since the weight is no longer in high demand as it was in the past, I think we'll see full length sleeve, especially it seems to be easier from manufacturing perspective.

[TobinHatesYou]

Since the weight is no longer in high demand as it was in the past, I think we'll see full length sleeve, especially it seems to be easier from manufacturing perspective.

May depend on the frame. Specialized uses a full length sleeve on the Venge, but on the "lighter" Tarmac, it's two separate rings, I think?

[morrisond]

Fantastic news! I have T47 on my fast Steel bike - works great - zero noise - easy install.

My PF86 Carbon Gravel Bike and other Carbon frames before it - not so great.

I'll never buy another frame that isn't threaded in the BB - I have had too many issues with Pressfit that have cost me thousands trying to get around (I ended up selling frames and taking baths on them).

I'm really glad Trek is going this way - they have some really nice bikes but I won't buy one unless threaded.

All my Favourite Carbon Superbikes from Trek/C-Dale (I won't do BB30 either anymore been there done that), BMC, Storck are all some sort of non-threaded solution.

Hopefully this is an Industry trend.

[wheelsONfire]

Anyone that knows the extra weight going from a press-fit to T47?

[Calnago]

Ok, T47 being adopted by a major manufacturer, now that's something I can get behind. I like threaded BB's, who doesn't. They're simple and they work, and they don't require some expert installation with fancy presses and retaining compounds in order for it not to creak. So, if Trek does adopt T47 on a large scale, then kudos to them. The added production costs, and there are some, will of course be passsed on to the consumer, but that's ok by me. Of course, reduction in production costs never get passed on to the consumer, unless there is heavy competitive pressure to do so. Such is life.

But some early comments in this thread puzzle me or just need clarification.

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.

What would going to a pressfit 42mm bore have solved, other than making the hole bigger? That would get us right back to square one with all the problems inherent when BB30 was first introduced and then subsequently trying to incoporate it into a carbon shell. It would make using a standard Shimano 24mm spindle more problematic than the current BB90 since you'd have to use reducers the same way as you would now with BB30, which just adds more layers without addressing the issues caused by the bearing/shell interface in the first plae. No, that would really be a dumb step backwards, even if you were just wanting to only consider space for the larger spindle.

And what pray tell, are your reservations with a 1mm thread pitch? It is essentially what has been used in both English and Italian threads all along. The pitch is for all practical purposes no different at 1.0mm versus 1.058mm (24tpi converted). It's just really standardizing on a uniform metric number instead of continuing to use the tpi convention of 24TPI. But since it will never be and doesn't have to be compatible with any existing BB's out there, it makes sense to go with a standard 47 x 1.0, and keep everything in the same measurement system. I've got no problem with that. But would love to hear yours.

This news won't affect me directly as I already have T47, but it's nice to hear that T47 might become a widely adopted standard. Does this also mean Trek will add an aluminum insert with threads into the carbon shell?

The 1mm thread pitch was chosen so that existing PF30 metal BB shells can be tapped and turned into a T47. However I'm not aware of anyone who has actually done it other than seeing one frame being done in a Youtube video tutorial.

You are confusing pitch with bore, as the main reason the 47mm dimension was chosen. T47 came into being largely to address the inherent problems with PF30 in metal shells, namely... creaking etc. The nominal bore for PF30 is 46mm. But with all the creaking and what not, wouldn't it be great if we could just run a tap through that bore and voila, create some threads and then create a bottom bracket to screw into it. Hence the 47mm. Great idea, for independent frame makers. Thread pitch is just the distance between the threads... it could be fine, coarse, whatever. It is independent of the bore, and in the case of English and Italian shells the thread pitch is the same, even though the bore is different between the two.

Since the weight is no longer in high demand as it was in the past, I think we'll see full length sleeve, especially it seems to be easier from manufacturing perspective.

I think it could go either way. While a one piece sleeve certainly would ensure that both halves are aligned, and probably be easier to bond into the shell... , the one piece affair does kind of block things up a bit in an area where various Di2 or EPS wires need to pass. I think that's why Colnago may have split there's up in the latest C60's and carried it over into the C64, as opposed to it being simply just a weight saving measure, although it does save a bit of weight.

Speaking of Colnago, they have been using this design in their Threadfit BB since the introduction of the C60. Call it T45 if you like, the concept is the same. In a world of pressfit BB's, they had to make the best of a bad situation and provide a shell that would accept pressfit BB's; they had little choice really. But rather than just do their best to bore out a perfectly concentric hole in a carbon shell like everyone else was trying to do with widely varying degrees of success/failure, they opted to bond a threaded alloy sleeve into the shell, which protects and preserves the frame, and then just screw some easily replaceable alloy threadfit cups in that would be nice and concentric and accept the current crop of pressfit BB's. It is by far the best solution to maintain the integrity of the frame over time while still allowing for the pressfit bottom brackets of today. In Trek's case, since they're pretty good about honoring their lifetime warranties, if there BB shells get enlarged or worn from poorly fitting or installed bearings over time, they've been on the hook to either replace the frame or you have to send it back for what I presume is a fairly labor intensive build up of the shell.

I think it might be informative for those still scratching their heads over what T47 is etc., to include an excerpt below where I explained why I consider Colnago's Bottom Bracket the crown jewel of bottom brackets these days. Consider it T45...

Excerpts from a post in Colnago C64 - Inside and Out
Ok... so before I start wrapping things up, I want to do one more post on the "Crown Jewel" of the C64. That would be the bottom bracket lug and the Threadfit solution that Colnago has implemented, beginning with the C60. In reading some of the magazine reviews... calling out the Bike Radar article in particular, I came away with the perception that some of these reviewers really didn't understand what was going on down there, and were mostly just trying to regurgitate what they were told at the briefings in order to meet their review deadlines.

So, if you were confused by some of what they were writing, let me try to make it a bit clearer, and far more accurate...
First of all... Threadfit 82.5 is not a brand new BB "standard" at all, as the article was implying. It's just Colnago's answer to the Pressfit BB solutions which have been become so prevalent today. Colnago has always tried to build bikes which last. Pressfit Bottom Brackets pressed into raw carbon shells are about as contrary to that philosophy as you can get. If they aren't a perfect pressfit, they can move around within the shell tiny amounts, causing that annoying creaking that has become all too common these days and futhermore, that movement also causes wear on the shell. If it wears enough, you've got a nice throwaway frame. Realizing that... Colnago decided to bond in a threaded alloy sleeve into the BB shell of the C60. That sleeve is permanent and part of the BB lug, exactly the same as a threaded BSA bb would be. But, at the time of the C60 launch, there were no threaded solutions to just screw in there in order to accommodate the pressfit bb's that did exist (I'll talk about Wishbone and Ceramic Speed momentarily). So they developed their own Threadfit 82.5 cups that threads into the bonded sleeve. The threadfit cups conform to the BB86 standard (hence not a "brand new" standard) of 41mm inner diameter and an 86.5mm wide shell. Shimano and Campy spindles/cranks fit nicely into this standard. So, with the Threadfit cups now threaded into the BB shell sleeve, you are ready to install whatever Pressfit solution you want to go with. I'm a Campy guy so I use their 86.5 x 41mm cups, same as most of the review bikes that were installed with Campagnolo cranks had. With me so far?... I'm seeing some glazed over eyes out there. Oh well, I will press on.

Let's have a quick look at the C60... it's the same as the C64 with one exception which I'll get to...

My C60, as it came from the factory, Threadfit cups installed... note the alloy sleeve going all the way through...



Here's the Threadfit cups which I removed from my C60 during building just to have a look at the details of the BB...



And the shell with the bonded threaded sleeve, but Threadfit cups removed...

Ok, with me so far? Good. Now we have the C64. The only difference is that instead of a once piece bonded sleeve going all the way through the BB shell, they now have two pieces bonded in separate collars, threaded, and thus the middle part of that alloy shell has been eliminated. Nicely molded cable guides have taken it's place. But operationaly, it is EXACTLY the same as the C60. In fact, the later C60's were incorporating the two collars instead of the single sleeve already. So, nothing "new" as far as that goes for the C64.

Below is the C64... as it comes from the factory. Same 86.5mm shell. Same threaded portions for the Threadfit cups. And same, exact Threadfit cups get threaded in. But the middle section of the bonded in sleeve is now gone... Here's the C64 BB shell... focusing on the inner portion of the non drive side Threadfit cups (and bonded in collar)...



And a little closer... you can't really see the edges of the bonded in collar becasue of the overspray from paint and likely some of the bonding agent oozing around the edges. The threadfit cups get screwed in afterwards, once all the appropraite cleanup and facing of the outer shell is done...



And one more drilldown to the lower edge...

I was going to show you the same stuff as I showed of my C60, with the Threadfit cups removed, so you could see that it is all exactly the same as my C60, but once I showed up for our date with large tools in hand... that's when the parents got involved, and said... "Whoa... unless you're going to marry our daughter... you're not going to violate her with those things!". So... you'll just have to to take my word for it that it's the same, with the exception of two threaded collars instead of a continuous sleeve, threaded at each end. I suppose I could have told the parents not to worry, that I've done all this before... but what parent really wants to hear that either.

So, I just kept the tools below to myself... and sulked away slowly...


Ok... so now that you've got some visual context for it all... there's nothing really new over the C60 except that the one piece sleeve is now two pieces, and even that had already been incorporated into the latest C60 production. So, what is the Bike Radar article blathering on about... got me. They ponder why Colnago didn't adopt the "pre-existing" T47 "standard". Well, for one thing, the T47 standard wasn't out when Colnago went with their own Threadfit solution in the C60. T47 is no better than Threadfit; it's actually trying to do the same thing. So for manufacturers that haven't taken the initiative to do something better, then that might be a way to go (to date there hasn’t been much success getting manufacturers on board). But Colnago took that initiative before T47 was even introduced, with the C60. Aaach... anyway, it was pretty clear to me that the Bike Radar article really did not convey a good grasp on what they were even talking about, and seemed to confuse a lot of people in the process.

The Colnago bottom bracket lug is good. Very good. Leave it at that.

So, enter Ceramic Speed, which kind of confused the issue even more, and it shouldn't have. All Ceramic Speed have done is produce a BB that replaces the Threadfit cups and screws directly into the bonded in sleeves, just like the Threadfit cups do. It alleviates the need to press in whichever bb you were going to use afterwards, eliminating the go between if you will. But wait, what Ceramic Speed is doing has already been done, by a company called Wishbone. So... no big deal... it's not some huge "Oh no, another bb standard" moment at all. And if you're using Campagnolo, then the Ceramic Speed option, at least for the Ultratorque cranks, would probably just consist of some threaded cups, which accept the CULT bearings which are pressed onto the Utlratorque cranks.

Currently with my C60 and a Campy install, and this is still the case with the C64 if you prefer, you would just press in two Campy cups to the Threadfit cups. Then install the crank with it's awesome CULT bearings. I happen to think Campy's CULT bearings are second to none and I wouldn't use any others. But if you're using another crankset, perhpas you would like to have a look at Ceramic Speed's offerings, but it's not necessary. It's just another option. The threadfit cups plus whatever BB works with your cranks is just fine as well.

So, where does that leave us... the same as before really, and it's a good place to be. Why? Because unlike with almost all other carbon frame manufacturers, if in the event your BB shell wears (and in Colnago's case that would be the alloy Threadfit cups), then all you have to do is simply replace the Threadfit cups... a super simple 5 minute job. Versus a worn and chewed up carbon shell from a bad fitting BB... well good luck with that. Oh, and those Threadfit cups are made of finely machined alloy, nice and smooth and concentric and round, which is more or less a crapshoot when dealing with raw carbon bb shells these days.

I hope that maybe clears up a bit of confusion caused by journalists with a deadline and some vague recollection of what they were told at a briefing surrounding the "new" bottom bracket. It's not that different, but I do like the molded in cable guides... a lot. It really is a Crown Jewel among bottom brackets.


End of excerpt, back to a potential adoption of T47 by Trek:
Ok, so in conclusion, if Trek does adopt T47 on a wide scale, then that would certainly be a big move and I whole heartedly approve. At least much bigger than wave cell technology in helmets . Expecting it to become a widespread standard overnight is very wishful thinking however, as many manufacturers are probably just fine with the cost savings they've cultivated and many mechanics such as myself have learned to install pressfit BB's first time trouble free so that they stay that way. So, there's not a huge incentive for other large frame manufacturers to follow suit at this point. But it is a good start, and a long overdue admission that pressfit BB's maybe weren't the great advance in technology that they were purported to be for way too long. While it's not a slam dunk that Trek will adopt it fully just yet, given they seem to be talking to the media about it, it's at a minimum a very good sign. I'm optimistic. Here's to Trek... do it!

[Karvalo]

What would going to a pressfit 42mm bore have solved, other than making the hole bigger?

There would be relatively standard BBs available to fit all spindle types.

[Calnago]

^ huh? Which you would have with T47, but with the added benefit of threads, the gold standard of BB fit. With T47 you’d get a direct fit for whatever crank you want to use, versus a 42mm bore with a pressfit bearing (lest we forget the BB30 nightmares, they’re the reason PF30 was developed), and then, if you want to use a Shimano crank for example, you’d be using reducers etc (not a direct fit). But essentially, you’d be solving no problem and just perpetuating the old in a bigger hole. T47 actually does something to make things better from a long term functional aspect, so I’m all for it. I’m just surprised, but happy, that Trek is even considering it.

[mrlobber]

Finally a real reason to consider Trek again (quite like their bikes, and ride one too, but never have really got around the fact that only Shimano cranks are essentially accepted, well, GXP too)

[pdlpsher1]

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.

Somebody asked what the expected weight increase to the frame might be. The aluminum insert itself doesn't weigh a ton. For example, this T47 aluminum insert from Paragon Machine Works weighs 26g. But of course you also have to account the weight of carbon and bonding epoxy added to the frame. 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.

[Karvalo]

^ huh? Which you would have with T47, but with the added benefit of threads, the gold standard of BB fit.

^ Huh? You asked what problem 42mm PF would have solved compared to BB90. I'm not recommending it, or comparing it with T47, I'm simply answering the specific question you asked. Not sure where I lost you, to be honest

[robertbb]

@Calnago: Surely that red goop/overspray in the C64's BB is just inexcusable on a "prestige" frame of that price. I'd want perfection in side and out.