Cannondale Scalpel Team Carbon 2010 XC 26" wheel bike with Lefty Speed Carbon SL and Mavic Crossmax Axle cap is part number KH124 (maybe)

Twenty years go when I wrote a post title like this one I was pretty sure at least one person who needed help would find through Google and have a better day.

Now? It's like tossing a bottle in the ocean.

If you happen to have come across this bottle here's what you need to know about this weird bike that I picked used when I didn't know any better and have an odd affection for. Even though it's the bike equivalent of a 20yo Porsche -- albeit with much better engineering than a Porsche.

1. If you have a Cannondale dealer or good local bike shop just use them.
2. The Cannondale Lefty suspension is a cult within the XC singletrack world and Cannondale did whatever weird/fun thing came to mind.
3. With this single (Left!) side suspension comes a proprietary hub that has been through at least 3 revisions. The version I have is forgotten by most (Cannondale very kindly sent me a free replacement when I asked -- but it was the wrong version!) The weird hub has a proprietary hub retention system made up of a fancy bolt with rubber O-ring that does most of the work along with a reverse threaded "axle cap" that engages with the O-ring, keeps water and dirt out of the moving parts, and also helps with bolt retention (bolt loosens but runs into the reverse threaded cap and they kind of jam together). Cannondale tweaked this design often because that's what they do (and why some love them and some fear them). Some models tightened with a Shimano freewheel tool, others used a pin-type chainring tool (but at least they aren't super exotic tools).
4. These caps tend need replacing. Probably because most don't expect the reverse threading and strip it the first time they change a tire. Or they fall off.
5. My 2010 Lefty Crossmax hub uses the Cannondale Lefty SuperMax Axle Cap and Bolt - Black - KH124. After my model came the Lefty 50 Hub Axle Cap And Bolt - Black - QC117. This 50mm standard width part is much too shallow for my bike, even though it's described as  fitting "vintage Lefty hubs, Lefty SL hubs, and Lefty 50 hubs including Lefty Oliver. Will not correctly fit SuperMax, Lefty 2.0, Lefty 60, or Lefty Olaf hubs."
6. There are other versions I think for later boost and fat bike hubs.

UPDATE 7/12/2024: It fits better than the QC117 but it screws deeply into the hub and might kind of float in there? Sort of weird.