Adjusting Toyo Atlantis geometry
Jay P
I do a lot of trail riding + loaded bike picnicking with a 58cm Toyo Atlantis (72.0 degree head tube and seat tube).
And I have noticed those angles slacken a bit on Rivendell production frames over the last 10-15 years
I also saw that in addition to the regular 1mm baseplate for the fork crown the Chris King website also lists a thicker 5mm baseplate that they no longer produce, sell, or are willing to manufacture.
At some point I realized a thicker baseplate would slacken the Atlantis head and seat tubes and started to wonder how that would change the nature of the bike.
And figured a thicker baseplate would be fine on my Atlantis as it has ~15mm of extra steerer tube, a very low bottom bracket, and is a little undersized for my 91cm pbh. And as Chris King uses base plates rather than crown races (ie, it does not serve as a bearing race), I figured a custom fabricated piece would likely work fine.
So eventually I asked Jim Merz (via the Classic Rendezvous list) to fabricate an 8mm thick baseplate – that is pictured next to the original baseplate (he made it out of 10-2-3 Ti alloy) -- which I believe will slacken the Atlantis angles by ~0.43 degrees. I was aiming for somewhere between too much change and too subtle to notice.
I’ll try the thicker baseplate with no other changes to the bike, and then will swap the current 46cm noodle bars + 10cm dirt drop stem with a 135mm face plate stem + wavie bars + lugged seat post (to experiment with further slackening the effective seat tube angle) to get a still relaxed and upright but more assertive and stretched riding position for trails (and maybe a little better for a wider range of handlebars).
I won’t be able to install until the end of March but thought to share the idea with the group in case this is novel or interesting – it’s been fun to think through and will be an easy experiment to undo.
Jay P.
Marin, CA
