Atlantis FD clamp size?

[Stephen Merelman]

I am assuming it is 31.8mm, since it is clearly not 28.6mm. Can anyone confirm?

On a related note, anyone have a 31.8mm FD they want to unload? 

smm

[Kim H.]

I have a stock Shimano front derailleur from my Clem with a clamp diameter of 31.9mm that I am not using. It worked well for a 2x crankset with 34/24 rings. 

I can find out specifically what model it is and take pictures of it, if you like.

Email me, if you are interested.

Kim Hetzel.

[Nick A.]

Hey there,

I'm running a 46/30 with a shimano tricolor FD and a 28.6 braze-on adapter on my 2022 Atlantis.

Hope it's helpful.

Nick in Falls Church VA

[Stephen Merelman]

Alas, my 28.6 units definitively don't fit. 

This frame is the last iteration of the Atlantis. Riv says this about it, which is a little inscrutable: "an ovalized seat tube bottom, from a round 28.6, to a lateral 31.8 x 25.4 oval (starts as inch-and-an-eighth, gets squished to an inch by inch and a quarter)."

This seems to imply a 31.8 is the right size,  but I can't find that written down anywhere official. 

[Gene B]

I just built up my 2022 Atlantis. I'm running a 35mm Campagnolo 'Racing Triple' with a 34.9 - to - 28.6 shim

[Garth]

The first and obvious thing to do is measure the tube, be it with calipers or a measuring tape for the circumference, divided by 3.14 for the diameter.  Even a string and a ruler will do.

The way I understand the seat tube is it's only ovalized at the very bottom where it joins the bottom bracket, for rigidity. Where the FD goes it's round it should still be the round 28.6 as Riv states. I have certain vintage Campy 28.6 clamp on FD's that don't fit my Bombadil perfectly, even though they're both 28.6. Who 'ya gonna call ? Ghost-busters ! ((((((  :-)  )))))

All the Riv Atlantis photos of the last model shows a shim being used for the FD.

[Bill Lindsay]

I am assuming it is 31.8mm, since it is clearly not 28.6mm. Can anyone confirm?

I can confirm that IF you have a Rivendell single bicycle and a 28.6mm front derailleur is too small for your seat tube, then it's 31.8mm.  I've owned several Rivendell single bikes and the only one that comes to mind that had a "baseball bat seat tube" that grew to 31.8mm at the bottom was my Leo Roadini.  It's reasonable that they'd make the Atlantis with the same baseball bat seat tube.  

The right way to do this is own a bin full of nice front derailleurs in all possible configurations so you can just grab one and use the one that fits.  If you don't want to carry that kind of inventory, then measuring is the next best thing.  

Bill Lindsay

El Cerrito, CA

On Saturday, August 31, 2024 at 3:14:44 PM UTC-7 smer...@gmail.com wrote: