Biking To-Do List: November 2020

First, yes, I still owe you all 2 posts on the theory and practice of half-step gearing, which is slow going at the moment, but I'm working on it. 

Second, I decided to repack an old set of Shimano Ultegra 6700 carbon pedals and was shocked to find there is no main bearing, and the "needle bearing" isn't a needle bearing at all, it's a home-brew dual ball bearing where the cups are ground into the ends of a ~ 12mm steel barrel, and those balls are teeny tiny, like something out of a Swiss watch. We're talking flat-sided toothpicks for handling all 36 of these 3/32 little devils. The PD-R8000 is made exactly the same way.

Third, I'm still trying to figure out a way to salvage my old bike's headset by using a thicker grease meant to resist being hammered out of the contact area (pound-out). Turns out there's a grease sold by AmsOil made specifically for this purpose used in heavy duty off-road earth-moving equipment - Synthetic Polymeric Off-Road Grease, NLGI #2

Think articulated joint in the center of a bucket loader rolling over rough ground with a bucket load of ore and a huge weight stack at the extreme other end of the machine. (these guys couldn't get laid in a mattress factory, but watch the video anyway) You'd want the thicker NLGI #2 grease for headsets retrofitted with sealed bearings with much smaller engagement areas than the original press-in ball bearing cups.

This, and repacking my Ultegra pedals led me to a lengthy investigation of grease, and especially, compatibility of greases with different bases (they're not), because I bought some of Park Tool's PPL-1 Polylube poly-urea grease, and I wanted to be sure it would play nice with other (primarily lithium-based) greases. Park Tool says it does. My research says NO. 

BTW, the base isn't the lubricating agent. The base is the stuff that gels and suspends an oil, and slowly weeps the oil onto a bearing over time, but it's NOT the primary lubricant (some additives like moly or graphite provide lubrication as well). That is to say, the base is what makes something a grease instead of an oil. There's a fairly wide window of bearing speeds and loads where grease works, and bicycle bearings are way, way inside that window. Easy-peasy. 

10% ball bearing failure @ 45,000hrs

By way of contrast, high speeds, high loads, and high heat make active lubrication under pressure with oil absolutely necessary for ICE engine main "bearings", which aren't bearings at all, but bushings with oil galleys cut into them, while hypoid gears' very high pressure loads in manual transmissions require very thick oil that can stand up to molecular shearing, but no active, pressurized lubrication system is needed there.

At any rate, I leaned a ton of interesting and important information about grease, when it's used, and how to select it. There's a really brilliant blog post in this if I'm up to the challenge. I do want to assure you all though that I'm very happy with all the RX-es I've made on this blog, and in particular, I still think for ball bearings running at the speeds (50-250 rpms) and pressure loads of bicycle hubs, BBs, headsets (my special need notwithstanding) and pedals, pure Teflon grease directly on the balls, cups & cones, and Teflon fortified grease to displace dust, water, etc in the rest of the grease cavity, makes the best possible lubrication. 

 If this changes I'll shout it from the rooftops, but I don't see that happening for decades. FinishLine makes both the pure Teflon grease and the Teflon fortified grease. I bought some Krytox GPL 205 10yrs ago and paid $65, but it's gotten cheaper. I still have about 1/4 left, so yes, I use it sparingly, but it will never leave you metal to metal and is chemically inert, so it won't react to metal, plastic, paint, etc. If you're riding disk brakes and the hub is soaking up a lot of heat, PTFE grease is about as good as it gets.

With COVID-19 running rampant everywhere again, as predicted, please do take care to stay safe at all times - 90% of the time will get you killed with this remorseless executioner.