scplus5

So I'm attempting to put a new crank in a 2016 synapse carbon 105. The bike is marked bb30, not bb30a. The crank I'm installing is an FSA SLK light bb30 crank.
When I push the spindle through the bb, there is not enough spindle sticking out of the non drive side for me to be able to tighten the NDS arm to the point where it bottoms out on the end of the spindle. It's like the spindle is not long enough or the bb shell is too wide. When I measure the difference in the amount the spindle is sticking out and the depth of the pocket in the arm (that the spindle inserts into) it's about 3-4 mm different. It's physically impossible to tighten it to the point of bottom out.

What's going on? Help please!

Slash5

2016 Cannondale catalog says the Carbon is BB30a. Easy to tell - measure the frame. Will be 68 for BB30 and 73 for BB30a.

scplus5

The bike is clearly marked bb30. I looked at a few websites that said it's bb30.
I'm seriously confused

Slash5

2015 catalog says BB30a as well. What was the old crank like? What did it measure?

https://issuu.com/cannondale_usa/docs...912505/8937095

scplus5

So apparently the frame is bb30a after all. Pure BS that the bike frame is NOT marked as such.

Now for the solution...the crank was a great deal, so I'd like to use it if possible.
Provided the bearing surface lines up and there is sufficient thread engagement (I can measure all this), what would be the harm in making a 5mm spacer to go into the "pocket" of the crank arm, therefore taking up the extra space and allowing it to be fully tightened?
Fwiw, i am a machinist and could easily make a perfectly fitting spacer.

DeadGrandpa

I recently had my LBS replace the BB on my carbon Jamis, which I believe I heard them say was a BB30, not sure if it's an "A" model or not. The LBS guys said there were two slightly different bb's that were available, and they weren't sure which one
was correct, so they ordered both. One cost $20 and the other cost $200. Guess which one was the one that fit.

Slash5

If I understand what you are proposing, I would think all 5 mm will be on the drive side making your chainline way off. Also less engagement in the splines and in the retaining bolt. Probably better to sell your crank and get one that fits.

stevoo

You are correct.
Your Synapse is a BB30A even though Cannondale proudly silkscreens the frame BB30.
Maybe the marketing folks were not talking to the tech guys. Who knows. Is what it is.
I have had good results fitting standard 24mm style cranks using Wheels Mfg adapters. You need BBRight/BB30A adapters not BB30 as you now know.
Also allows you to adjust the chainline to a more normal dimension as the Synapse I fixed had an unusual/challenged chainline as OEM.
Good luck.

scplus5

I admittedly do not understand chainline, but I'll be reading up on it today.
You are correct about what I'm proposing. However if my understanding on bb30a is correct, then the extra 5mm is added on the NDS only, meaning I would not be affecting anything on the DS by doing this.
Of course I have considered the decrease in spline adjustment, but I haven't yet measured to see just how much it would be left with.

scplus5

I'm not really interested in using a 24mm crank/shimano etc. I'd like to stay with SLK if possible. If some of the reading I've been doing is correct, then a bb386 crank can be used with adapters.
Any experience with this?

scplus5

Nevermind on the spacer. In theory I think it's a great idea.
I measured just now and there would be only 6mm of spline engagement. I believe there's plenty of thread engagement to be secure, but not the splines.
My engineering and machining background would love for this solution to work, but I just don't think it can.

So now it's about what cranks I can adapt to the frame.

cpach

Yeah, 386 EVO cranks will work, as will cranks like Praxis (will require a Praxis M30 BB) or Raceface, many SRAM cranks.