The Pros and Cons of the Outboard vs Inboard Euro Bottom Bracket.
This is a questions we get quite a bit: Which is better, the Inboard or Outboard BB?
Well, as you will find below, there are Pros and Cons to each.
We asked two experts to give their opinions…see their answers below…
“The euro bottom bracket is a huge upgrade from the old style pound-in with a hammer American bottom bracket. With a thread in BB, it allows for a more free-spinning bottom bracket which will make it spin smoother! The regular euro bottom bracket is a huge upgrade to bmx race frames. The small bearing keeps everything close and tight into your frame.
The outboard bottom bracket still works with the euro bottom bracket shell, but now uses a larger bearing that sits outside the frame. The larger bearing puts less stress on the bottom bracket bearings which, in turn, lets it spin smoother and faster. The outboard bottom bracket doesn’t work too well with imperial style sprockets: it sets the sprocket out a little bit further so it is harder to get the chain line straight. With that being said, the ultimate set up would be the outboard bottom bracket with the spline driven 4-bolt spider and the profile elite chainring (which has off set teeth to help the chain line even more).
I always suggest chasing the bottom bracket on any frame before installing ether style bottom bracket.”
-Chad Powers (Powers Bike Shop)
“Pros on the Outboard BB: Easy to thread in if you prep correctly & thread it in straight, there is no pressing involved and I love that aspect with outboard bottom brackets.
Cons on the Outboard BB: I haven’t proven it, but I definitely go through many more outboard BBs than mid bottom brackets. You would think the mid BB on a freestyle bike would be damaged and would be done first? But no, it’s always my outboard. I feel like because the bearings are positioned so much wider, there is a much larger force put on them.
Pros on the Inboard BB: As to the basic old euro BB’s, I feel they last FOREVER if you find the right one. It is still compacted and inside the frame, but threads in as well. But, unlike the Outboard, the Inboard euro isn’t an extra inch wider on each side so there may be less force put on the bearings?”
-Tony Larson (Mudslinger’s Bike Shop)
More general info here on each Bottom Bracket: