Hello, I bought a Cannondale Synapse, mi first serious road bike. The bika came with a FSA 50/34 crank, since the rest of the group is 105 and I wanted bigger rings, the LBS installed a Shimano 105 crank with bb30 adapters

I did not have a clue about the need of adapters if I wanted to install a Shimano crankset.

is the use of adapters going to affect the performance of the bike? is better to use a BB30 crankset?

A different LBS is telling me a BB30 bracket is going to perform better with a BB30 crank, since its going to keep the original stiffness

I have used both BB30 specific cranks and Shimano cranks on BB30 frame. The Shimano crank performed fine in the frame with adapters. I never had issues with the adapters.

At first I was more concerned about increased drag in the BB bearings due to the plastic adapter but I didn't notice any and the Shimano crank was plenty stiff for me.

No problem.

In theory the bb30 will be stiffer because of the diameter of the spindle but most riders will never need that extra stiffness. Bb30 adapters also aren't all the same. Praxis adapters work great. I had a cheaper fsa adapter that started creaking after a while

so do you think the LBS is lying in order to sell me a BB30 crank?


If I finally buy a Sram Rival crank, would this crank work well with the Shimano 105 group? or the 105 crank will work better?

I wouldn't say they are lying but I would say that unless you are putting down pro level power or you are 250lbs + and standing out of the saddle and pedaling that you probably aren't going to notice a difference in stiffness.

The 5800 105 cranks are awesome even if a little heavy. The stiffness of the rings probably evens out any stiffness lost from the smaller spindle size. I would get one of these adapters eventually

https://www.praxiscycles.com/conversion-bb/

But if LBS already installed the cranks and adapter and everything is working I wouldn't worry about it right now

I have adapters so I can use my Quarq (GXP) in a BB30 frame (Tarmac). Works fine.

You should be fine. Yes, BB30 bottom brackets are designed to work best with BB30 cranks, but there are several really good work-arounds.

I suspect the adapters you have are the plastic spacers that reduce the bearing diameter from 30mm to 24mm and take up the spindle length. Most people have no issues with them.

If you are unhappy with that, your next step should be to consider a conversion bottom bracket. These bottom brackets press into the frame, replacing the BB30 bearings and fit your crankset.

If you are hell-bent on going with a BB30 crankset, then yes, the Rival will work. BUT, you may still be using spacers. Sram made many of its BB30 cranks with extra long spindles so they also work in BB386 and BBRight bottom brackets.

I just did this on my CAAD 10 - no perceivable difference.

You installed Shimano on your CAAD you mean?

Shimano cranks on BB30 frames, via adapters works well - did for my 2 x CAAD10s and the Jamis Xenith anyway!

cheers

Yes...well, I didn't. But the shop mechanic did. Put on 105 cranks/rings on my bb30 CAAD 10 via adapter.

A surprisingly large number of bikes are sold in this configuration: BB30 with plastic adapters and a Shimano crank.

From experience, I would say that you're better off with a BB30->Shimano Bottom Bracket solution like those sold by PraxisWorks and WheelsMFG, because the plastic shims tend to lead to creaking. But the shims are cheaper.