jitenshaman

I'm thinking to upgrade my Dahon Jetstream EX and I'm investigating about the orginal

part dimensions and a replacement.


What I'm sure :

Brand : American Classic

- bottom frame width : 68mm
- bottom frame width + chrome overtaking : 74mm
- bottom frame width + chrome overtaking + tightening screw : 82mm
- axe : 118mm

But didn't know if I need to change for a 68 x 118mm or other bottom bracket ?

What would be your recommendation ?

Abu Mahendra

A Shimano Road Hollowtech II should do, no? What crankset do you intend to use?

jitenshaman

I bought recently a carbon FSA crank set but I realized that it was not ISIS but ISIS octalink v1.
Then I considered first a Shimano 105 5500 68x118. But this model seems to me heavy (250g).
But I don't know if I need choose 68 or 73/74mm. Bottom frame width is 68 but the original bottom bracket seems exceed 3mm on both sides.

Is Hollowtech II exists for octalink ?

Abu Mahendra

ok...Dahon BB, and folding bikes generally, are Road BB, that is, 68mm BSA. The crankset spindle type needs to mate with the BB type. You need to go, in the first instance with the bike BB shell width, not the width of the BB installed on it.

Now, there are many BB types, and I don't know them all with precision. No, Hollowtech is Hollowtech, and Octalink is Octalink. They are physically different, the latter being an earlier move away from Square Taper. Octalink has the spindle in the BB while Hollowtech is a hollow BB that takes the spindle integrated in the crankset. Hollowtech is the Shimano standard on both Road and MTB nowadays so I would try to go with that.

jitenshaman

Thank you very much for this precision ! Then I assume the visible chrome part visible on both sides of the BB is a part of the BB itself, isn't it ? Not a part of the BB/frame ? (I'll post photo).

Abu Mahendra

yes, those are likely the BB cups (black with writing) which screw onto the bike's BB shell (white). Hollowtech BB are essentially two cups containing the bearings and rotating mechanism that screw on, one on each side, to the BB shell. Like so...

jitenshaman

Thank you !
Here is the pic :


Jetstream EX BB

L Arnold

Dahon Mu SL11 BB


Mu SL11 Side view (likely FSA)
That is a similar BB to the one on this MU SL11. It threads into a standard BB thread and fits the 68mm span. This is not quite the same as the Jetstream EX but it is an interesting approach.
The matching spindle will be important to make a good chainline still (always the sum of the parts).
FSA 4000 BB

This is the MU SL11

jitenshaman

Thank you for your feedback. Finally I ordered a Shimano 5500 68/118. I hope there is no mistake in my choice. The bottom bracket seems to me heavy but choice is very limited.

Dockhead

So did it work?

The BB is knackered on my Jetstream EX and it would be great to be able to order a new one in advance.

Dockhead

OK, I guess not. He's got different cranks with Octolink; I have the original FSA Gossamer ISIS crankset. The knackered BB is an American Classic.

So can I replace the BB and leave the old spindle? Or do they come all together? Anyone have a recommendation about the best replacement?

Joe Remi

You need a new ISIS bottom bracket, the spindle is integrated into it.

Dockhead

Thanks!