T47 bottom bracket standard

Discuss light weight issues concerning road bikes & parts.
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silvalis
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Location: Aus

by silvalis

Yep, but I believe both AXS groups are only DUB?, so None of the major groupset players are 30mm anymore. T47 is a patch fix for 30mm cranks and if you believe sram's claims about dub durability in small BB formats, then IMO it's a poor solution for carbon bikes.



Oh I see. There’s a narrow and a wide format t47. Confusing
Chasse patate

talltales
Posts: 93
Joined: Mon Mar 11, 2019 10:43 pm

by talltales

T47 appear to have the same axle-bearing metal to metal contact, that was the reason my crank was creaking and the reason some crank axles get severely worn over time. I would have liked to see a sleeve like on hollowtech II that is creak free and doesnt abrade the axle. Other than that I believe its a solid step away from the annoying press fit BBs that at best belong on a Walmart bike.

by Weenie


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pdlpsher1
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Location: CO

by pdlpsher1

T47 is a BB shell standard. Whether the BB has plastic sleeves or not it’s up to the BB manufacturer. My CK BB has plastic sleeves so the 30mm spindle has no metal to metal contact with the bearing. Where did you get the impression that T47 BBs don’t use sleeves?


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kdawg
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Joined: Wed Nov 20, 2013 9:10 pm

by kdawg

pdlpsher1 wrote:
Mon May 06, 2019 8:06 am
T47 is a BB shell standard. Whether the BB has plastic sleeves or not it’s up to the BB manufacturer. My CK BB has plastic sleeves so the 30mm spindle has no metal to metal contact with the bearing. Where did you get the impression that T47 BBs don’t use sleeves?


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My White Industries BB doesn’t have a sleeve - but I thought that the sleeve only prevented water etc getting in from the seat tube - it only goes between the inside edges of the cups rather than between the axle and bearings.
I'm left handed, if that matters.

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petert123
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Joined: Tue Nov 13, 2018 1:02 pm
Location: London, UK

by petert123

Just reading though this post with interest - getting a titanium frame with a T47 and want to run SRAM AXS (Force or Red), guessing I need the narrow format BB? Looked at the C-Bear and Chris King models so far, worth the extra money?

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kytyree
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Location: US

by kytyree

kdawg wrote:
Wed Jun 19, 2019 9:29 pm
My White Industries BB doesn’t have a sleeve - but I thought that the sleeve only prevented water etc getting in from the seat tube - it only goes between the inside edges of the cups rather than between the axle and bearings.
I use a sleeve with mine because I've got a brake line and a Di2 wire running through there and don't need them rubbing against a spinning shaft.

Hexsense
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Joined: Wed Dec 30, 2015 12:41 am

by Hexsense

talltales wrote:
Mon May 06, 2019 6:20 am
T47 appear to have the same axle-bearing metal to metal contact, that was the reason my crank was creaking and the reason some crank axles get severely worn over time. I would have liked to see a sleeve like on hollowtech II that is creak free and doesnt abrade the axle. Other than that I believe its a solid step away from the annoying press fit BBs that at best belong on a Walmart bike.
Just a tale to let you see the picture:
Once upon a time Shimano etc. deliberately select their axle to be 24mm while the popular bearing size has 25mm ID, so that they can fit plastic hat between bearing and axle. This reduce abreasion and a lot of potential fitting issues. Some company see the plastic hat as an adapter that is not required, so they custom made bearing with 24mm internal diameter. It'd work fine because axle are steel and all tolerances in the system (including threaded-bb) are pretty good.

The hell break loose when BB30 enter the market. 30mm crank axle, direct fit to standard 6806 bearing which has 30mm ID. 30mm diameter axle are stiffer so the axle can be made with aluminum instead of steel to save weight (along with press-fit bb to the frame to save even more weight). And now you have the modern day pressfit bb controversy. PF30, BB386, T47 etc. can cure bearing to frame fitting but make no chance to axle to bearing fitting since almost everyone (except Chrisking) will stick with standard bearing size, which has 30mm inner diameter so no space for plastic hat.

Now, DUB at least switching the axle to 28.99mm, leaving 1.01mm for plastic hat if the bb is plenty large. Or use that extra 1.01mm for bigger balls in the custom made bearing when try to fit into small bb holes. Since T47 is pretty large, most brands should be using that 1.01mm space for the plastic hat for DUB crank.

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pdlpsher1
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Joined: Thu Jul 19, 2012 6:09 pm
Location: CO

by pdlpsher1

I have the Chris King Threadfit T47i. It has a plastic spindle sleeve (pic. below doesn't show it) and angular contact bearings. I'm using it with a Quarq PM with 30mm spindle. I also have the Chris King grease injector. The injector allows you to replace the grease within the bearing in five minutes. Awesome BB and highly recommended. CK sells a spindle sleeve kit for DUB should you desire to use this BB along with a DUB crank.

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