RockShox AXS Dropper Post Sizing

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I'm thinking about spending the money to get the fancy wireless Rockshox Reverb AXS dropper post. I'm not understanding Rockshox's sizing instructions, though.

In particular, the "Minimum Exposed Seatpost" measurement. That's really the "Maximum Exposed Seatpost" measurement needed, right? That is, one can drop the seat so that the "D" measurement is just about zero, and can extend it all the way up to the "A" value in those charts. And if one doesn't insert the post all the way into the frame (at least 80mm needs to be inserted), then that Maximum gets larger, but the true lowest drop position also gets larger.

Am I wrong here? What's confusing me is the "Make sure the exposed seatpost is not higher than the rider seat height." They claim the longer seatposts won't work, but surely that's set by the "What is the longest seatpost I can use" section.

I'm really confused. I don't know why they just don't give us the length of the Body (which would be C-D+the height of the top ferrule) and then we could figure out the rest from the travel. The top ferrule is just under 65mm (D-Travel) for all versions, call it 55mm with 10mm from the top of the post to the middle of the seat rail clamp.

Help!

 

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OK, I found this chart at JensonUSA:

And "C" answers my question.

I've concluded that the "Make sure the exposed seatpost is not higher than the rider seat height" criteria only matters if you want the maximum seat height to not be higher than your normal riding position. However, doing this often means giving up some travel. I'd rather let the seat go higher if I wanted - basically I'll put my butt where I want the seat height to be, and if needed, can tweak from there. Which I think means I go with the largest travel such that "C" still fits in my frame, which is the 170 travel - so that's what I ordered.

 

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And... it fits!

Interestingly, our bikes have SQ Lab saddles. They are different models. My wife's model is the SQlab 602 M-D Active Saddle, which has a big elastomer rear connection for the rails, which actually gets in the way of the Reverb's battery if you try to move the seat as far forward as possible, or tilt the front up more. I think she'll be OK with the position that gets the seat horizontal and just misses the elastomer, but we'll see on the first rides.

It actually snowed today, so no test rides.

The button action is pretty nice - post unlocks/locks as instantly as I could tell, no perceptible difference compared to a cable. The post was little sticky at first (documented), but a few up and down actions seems to have smoothed it out. Because we have thumb throttles on the left, I mounted the controller button above the bar on the right side. That seems convenient sitting on the bike in the garage, but we'll see out on the trail/road.

I used the SRAM AXS app to connect to the post and controller, which turns out is the way to get firmware updates. So, yeah, my seat post has a little computer and gets OTA updates, just like my Tesla.

Biggest problem remaining is mounting my Cygolite rear tail light. I could mount lift the seat post enough to clear a clamp, but I'm actually looking at some larger post clamps to go around the top ferrule instead to keep the saddle low position as low as possible.

BTW, a few web sites are now discounting this seatpost. I got mine for $600 each and just saw a place for $530, as well as a few for $660 or so (depending on post size and travel). Don't know if this is in reaction to competition (Magura recently updated their Vyron wireless seatpost), or a sorting out of supply chain, or perhaps the introduction of a new model from SRAM (although it was just updated not that long ago). At any rate, while expensive, the $260 price cut was enough to get me to pull the trigger. With our EBikes, getting rid of another cable that threads through the cramped space above the Ultra motor is very worthwhile, not to mention removal of a cable to the handlebars. And the easy controller button action is nice on the thumbs, too.

I would consider upgrading the the GX wireless derailleur as well, but then I'd lose the GearShift automatic temporary motor suspension while shifting, which is a nice feature to prolong drivetrain life.