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Bottom Bracket help

3K views 29 replies 12 participants last post by  Notvintage 
#1 ·
I'm completely lost here, hopefully someone can help.

Building a Chinese carbon frame for a friend, and I can't find a bottom bracket that will work. It currently has a BB30, which the OD is correct, but it wont accommodate the 24mm shimano crank shaft. I ordered a set of BB30 adapters and they make the total width too wide for to have enough crank shaft exposed to mount the left crank arm. The shell is 90mm with the plastic cups in place.

Aside from using a SRAM crankset, what are my options? He's already bought a 6800 groupset.
 
#2 ·
90mm is exactly how wide it should be. A normal english threaded frame is 68mm, the cups are 11mm each. 90mm. A Trek carbon road bike is...BB90...90mm. If your friends bike is 90mm w/ the adapters installed and you can't get the left arm on you're doing something wrong. I can't say what w/o seeing the bike.
 
#5 ·
it's not BB30 then, is it.

BB30 = 42 mm x 68 mm.

If you don't know what you have, how can we help?

Suggest you try again with the description.
 
#4 ·
The shell is 90mm with the plastic cups in place.
Its 90mm before the adapter are installed. Sorry if I wasn't clear.
Still not clear.

I'm going to throw out a guess here:

Grab a rubber deadblow mallet.
Hit the driveside crank arm/spider firm.
Presto.
Now you have enough room to install the left arm.
Sometimes it takes a man's touch.
 
#13 ·
You could beat on this thing all day long and it's not going to budge unless you smash the carbon. The right side crank arm and chainrings are snug against the frame and I still don't have enough spindle on the other side to mount the left crank arm with the adapters in place.
 
#10 ·
#8 ·
a couple of pictures will help but if you can insert the long spindle into the BB from both sides of the adapter to check bearing clearances try the rubber mallet taps on the drive side crank to drive it through the non drive side bearing. If in the check you can't insert the spindle through the non drive side bearing you may have a SRAM GXP BB adapter which has 24mm bearings on the right and 22mm on the non-drive side. Pics please.
 
#16 ·
Just a student of BB standards trying to help.

I'm not aware of any standard that meets what you say you have there. BB386EVO is closest but that would have the BB30 bearings in cups pressed into a 46 mm dia shell. The adapters for Shimano look like this for that 386EVO Adapter for 24mm Spindle Cranks (Shimano, FSA, etc.)
 
#22 ·
don't think so.

BB90 is 90.5 mm wide with 37 mm moulded in bearing seats, taking a 37 mm od x 24 mm id bearing. Trek standard designed specifically for Shimano cranks.

OP has insisted that it's 90 mm wide with BB30 size bearings, and we have pointed out that there's no such thing. Assuming he's correct about bearings the closest would be 86.5 mm wide BB386evo. Hence my advice.
 
#20 ·
Cannondale should be f'n boycotted until they go bankrupt for all of the trouble they caused by sparking these new BB standards - absolutely none of which have been shown to offer any benefit whatsoever over the tried and true English threaded BB that has served us flawlessly for decades.
 
#25 ·
What does Cannondale have anything to do with any of this?? Do you know how many different headset standards there are? People always want lighter, stiffer, faster bikes & the manufacturers complied. You cant't offer the public those things without breaking some eggs.

Bigger bottom bracket shells = greater stiffness & allows larger tube shapes for aerodynamics. The same thing happened with the headtube area. All this stuff was going to happen regardless. But I do understand your intent if somewhat misguided.
 
#27 ·
Since the OP has picked up the toys he threw out of the pram and toddled off into the distance, I'm going to give my $0.02 to this drift.

I agree at least mostly with waspy:

I don't have a single "wide BB" bike and they are plenty stiff.

Cannondale had stiff, fat tube frames that were English BB. The shell width is the same on BB30 and BSA after all.

BB30 was a flawed standard that never really took off. For about the first 12 years of it's existence, nobody else in the frame and components business was interested.

The big lie was "lower Q factor" which if repeated enough gets believed.

If you want a villain it would be SRAM who came up with PF30 and all of a sudden the frames were easier and cheaper to make, and BB30 all of a sudden had a new life.
 
#29 ·
As a 2014 Cannondale Synapse Carbon with a BB30 owner, I can say that the bike definitely feels stiffer than my older Trek Pilot OCLV with a standard threaded BB (Shimano Hollowtech II). However, I do not believe the stiffer feeling is a result of BB30, nor have I ever had a problem with the BB. I upgraded the Cannondale to full Shimano Ultegra 6800 at 3500 miles which required a simple Wheels Manufacturing adapter - no problem. At 7000 miles, still no problems with the BB.

I just bought a new 2017 Jamis Renegade Exploit with a standard threaded BB (Hollowtech II). It feels no less stiff in the BB area than my BB30 Cannondale.

Just a few observations.
 
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