Custom carbon frame - which bottom bracket?

Discuss light weight issues concerning road bikes & parts.
jever98
Posts: 812
Joined: Wed Feb 18, 2009 12:02 pm

by jever98

My custom carbon frame is being built over the winter and I can't make up my mind which BB shell I should choose.

Currently, the plan is to go with a PF30 and to install Specialized S-Works cranks with a power meter. The S-Works need to be modded slightly to fit on a PF30.
Weight: Crank + P2M (no rings): ~511g
Bottom bracket (wheels MFG): 114g (or SRAM at around 89g)
Total: around 600g to 625g

An alternative would be to go for a BSA shell:
Frame weight increase: ~50g
Quarq dZero carbon with: 559g (from site)
GXP BB: ~100g
Total: ~710g

Seems like I'm looking at about 100g weight penalty if I go for BSA. My concern is that the PF30 does have more creaking tendencies, even when built well (which I trust will be the case)

Does anybody have brilliant ideas how I can improve on the two options above?

...Maybe with a T47 shell, using a CK BB to fit the Specialized cranks?

Thanks
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No longer in the industry

Marin
Posts: 2754
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

BSA. Unless this is a total weight weenie project I'd focus on hasslefreeness :D

That said, I'm running BSA but I'm modding Shimano BBs for GXP for 30g savings...

Marin
Posts: 2754
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

So, who's building your frame and what's it gonna be like?

jever98
Posts: 812
Joined: Wed Feb 18, 2009 12:02 pm

by jever98

Hi Marin,

Rich Craddock from Filament. And it will be awesome, tremendous ;-P.

My aim is to be sub 7kg in a completely rideable clincher setup, which is not easy with my size and weight (2m / 88kg). So every gram counts :)

It's the disc carbon frame I posted a drawing of elsewhere: viewtopic.php?f=10&t=146699
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No longer in the industry

physeter
Posts: 33
Joined: Mon Jul 11, 2011 10:35 pm

by physeter

Another vote for BSA

Two custom bikes, both with BSA

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havana
Posts: 352
Joined: Tue Jan 09, 2007 5:04 pm

by havana

That would be a total no brainer for me. BSA.

Press-shit is the ultimate example of a solution for a non-existing problem.
Most "innovations" in cycling are solutions for non-existing problems.

Marin
Posts: 2754
Joined: Wed Jan 22, 2014 11:48 am
Location: Vienna Austria

by Marin

Thanks, I remember now! Sub 7 with disc is hard, but BSA still makes sense IMO.

jever98
Posts: 812
Joined: Wed Feb 18, 2009 12:02 pm

by jever98

Marin wrote:Thanks, I remember now! Sub 7 with disc is hard, but BSA still makes sense IMO.


Yes, my bank account won't like me I fear...

Current thinking is:
- Schmolke TLO bars and post, Extralite stem
- Schmolke TLO disc clincher or Bike Ahead Bituro road (both around the 1200g)
- Probably ETAP HRD - I like Shimano, but the clean-ness of SRAM is attractive
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No longer in the industry

Broady
Posts: 270
Joined: Thu Jan 03, 2013 5:02 pm

by Broady

BSA or maybe T47.

JackRussellRacing
Posts: 221
Joined: Thu Nov 03, 2016 4:32 pm
Location: North Carolina, USA

by JackRussellRacing

.

Lieblingsleguan
Posts: 152
Joined: Mon Mar 23, 2015 9:47 pm

by Lieblingsleguan

A creaking PF30 can be remedied with a threaded Wheels Mfg PF30 bottom bracket if necessary. There is no such solution for BB30, but I wouldn't worry about PF30.

Agree with the others that BSA is perfectly fine but if you want to hunt for grams, go PF30.

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kkibbler
Posts: 829
Joined: Tue Sep 09, 2014 9:30 am

by kkibbler

My heart says BSA but it does rule out the odd crankset choice.

PF30 with a thread-together BB for the best compatibility.

hambini
Posts: 131
Joined: Tue Nov 15, 2016 8:13 am

by hambini

BB386 would be my choice - and I make bottom brackets!

Almost all bottom brackets are press fit because the final interface between the bearing and the cup or frame is an interference fit. The reason why most people pick BSA is because it forces bike manufacturers to be accurate with their machining, also any inaccuracy is external of the bike frame, so you don't have a compound tolerance stack up.

Press fit allows bike manufacturers to have half caked tolerances. If they got the tolerances correct, then press fit would not be a problem. Cannondale, Boardman and Cervelo all take the mick with their tolerances. Look and Time are at the other end of the spectrum.

Have a watch of this

https://youtu.be/zryhuHkbb-o

jever98
Posts: 812
Joined: Wed Feb 18, 2009 12:02 pm

by jever98

Thanks Hambini, I saw your vids :-).

Richard makes a one-piece shell, which should keep tolerances in check. The attraction of PF30, for me, is that you can have the shorter axle cranks like S-Works and Hollowgram.

Would you consider making a PF30 / BB30 version of your BB?

Best
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No longer in the industry

hambini
Posts: 131
Joined: Tue Nov 15, 2016 8:13 am

by hambini

jever98 wrote:Thanks Hambini, I saw your vids :-).

Richard makes a one-piece shell, which should keep tolerances in check. The attraction of PF30, for me, is that you can have the shorter axle cranks like S-Works and Hollowgram.

Would you consider making a PF30 / BB30 version of your BB?

Best


Hi,

For BB30, I can't make a bb30 bottom bracket. I've seen some people that make them one piece but they have frigged the bearings and will compromise life.

For PF30 to fit a BB30 crankset, that is doable but there is a general trend now towards BB30 (90mm) cranks. so they aren't 68mm anymore. So I can make them as a special but I don't keep them as a stock item.

Hope that helps

Hambini

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