Tuesday, March 12, 2013

Ultegra 6700 Hub: Near Death Experience

Last fall my back wheel, the expensive, custom built one, developed an annoying creak. It's an Open Pro Mavic Rim attached to an Ultegra 6700 rear hub via 14/15 butted DT spokes on the drive side, and 14/17 super-butted spokes on the NDS.

After spending hours trying to relieve the spokes, and generally driving myself nuts trying to remedy the creak, I gave up and put my nearly identical spare on, and have ridden that the last 8 months. A couple of months ago though, I realized it was time to get ready to replace my "winter" wheel with my summer wheel, and decided to repack the bearings on both in the process of swapping them out.
Parts replace were 5,6,8,9, and 10,11,12,13. Photos are of #10's cup surface
I was shocked to find both cups and cones on the drive side pitted and spalled on my spare wheel, (purchased from PBS at a huge discount). I realized that since it was my spare, and having few miles on it, I had NOT repacked it in 2 years, as it still had factory grease in it. This was either an appalling factory lubrication failure, and/or, a serious QA problem for Shimano. I really have no idea where the blame lies, but you will note there is micro-pitting and a bit of rust all over the cups.

Pitting and spalling of an Ultegra 6700 rear hub
It's important to understand that normally for loose ball bearings, a pitted cup has no remedy, and the hub is ruined - garbage to be hurled into the trash can in disgust. For Shimano hubs (and many others), there is one exception though, and that's the drive-side cup in back, as the cup is actually part of the free-hub body, and is NOT pressed into the hub as all the other cups are, both with front and rear hubs. (the other side of the cup is a cone for the internal free-hub bearing - pretty clever)

I took the good free-hub body off my creaky, custom wheel, the axle with 2 good cones, and was able to put together one good wheel by cannibalizing two bad ones. There's definite advantages in having two identical, or in my case, nearly identical wheels (the PBS wheel uses 14/15 double butted Wheelsmith spokes on both sides). Since rear wheels are much more likely to break than front ones, having two identical rear wheels is much more important. Think about relative tire wear in the front and back, and double or triple that. 

 I ordered a new free-hub body from Amazon, and a new cone from Performance Bike Shop, who happen to remember they're a LBS, and should provide this service. They did so after a complete failure the first time (they lost all record and recollection of the order, until I jogged their memory, and then they just shrugged), 6 weeks of waiting, and then a week waiting for the re-order. When I went to pick the drive-side cone up, they informed me they couldn't sell just one - in clear contradiction to the two cones, each with their own part number, plastic bag, and price. I HATE being lied to!!!

$20, plus tax for the two cones, and $45 for the free-hub body. I'd RX getting the 2 cones along with the axle in a rebuild kit for $30 - a better deal IMHO. $65 is a lot of money to put into rebuilding a hub that didn't cost much more than that when I bought it, but the alternative was to toss the entire wheel. Nasty thing, having a nice wheel wrapped around a bad hub. In fairness to PBS, the 2nd mechanic I dealt with was very professional.

I'll see you on the dark side of the moon. Very hard to photograph. These are the best of 100+ attempts.
When the parts came I mounted them on the custom wheel, resigned to having an expensive creaky wheel for all my trouble, but still a spare. I'm not sure if it was the new free-hub, the RnR process, the new cones, new balls, or Teflon grease, but the creak is GONE!

 I now have 2 good wheels, assuming I don't find anymore nasty surprises when I repack my winter wheel, and I have replaced the stock bearings, which have G20 balls, with G10 balls I bought in bulk from Amazon.com. Btw, balls are rated according to their tolerances, so the smaller the number, the tighter the tolerances, and therefore, the better the balls. G10 is as good as steel bearings get. You can get G5 ceramic balls, and that is an advantage in having loose ball hubs. Generally though, my enthusiasm for loose balls has dissipated significantly. ;)

This looks like a spectacular grease failure. I think this was factory grease. I packed the new bearing with pure Teflon grease spread on the cups and cones, and then packed full with Finish Line grease with "some" Teflon in it. I assumed since it contained Teflon, it would be compatible with pure Teflon grease. It's usually a bad idea to mix greases.
 This brings me to an important point. If you have cartridge/sealed bearings, (a misnomer, as all bearings have seals) you don't have to worry about the cups getting pitted or spalled. You replace the cups, cones, balls, and seals whenever you replace the cartridge bearing. The downside is, you're paying a lot of extra money for parts that aren't usually needed, so for any given price point, you get better quality bearings in a loose ball hub, AND, you can get them. Chris King, for example uses his own in-house mfg-ed sealed bearings - which he doesn't sell to the public.

Close to what I've been using, which I purchased at $120 an oz from an aerospace contractor, so it's MIL-Spec. This should work just as well for 1/6th the cost. Spread in zig-zag pattern across the ball path on the cups and cones before packing with the grease below to hold the balls in place while placing them in the cup. The very best grease for preventing spalling is 100% Teflon grease. Hard to find.
Good, basic bearing grease for bikes. Basically, I use it as a filler to displace water and dirt, and let the pure Teflon do the work of keeping the bearings rolling.

There's nothing very hard about replacing or repacking ball bearings, nor free-hub bodies. It pays to swap your wheels out at least once a year, and at least repack them. The G10 balls are going for a dime a piece at Amazon. There are 18 in back and 22 in front. Well worth the trivial expense in my view.
Morningstar Ball Tweezers
Highly recommended is a constant tension ball tweezers. They hold the ball with a constant force, which you relieve when you want to release the ball. This guarantees you don't scratch the ball by squeezing it too hard. It also makes holding the slippery little devils much, much easier, and allows you to press the balls into a cup's grease pack, which will hold the balls in place until you can place the axle and cone to keep them from falling out. 

This one has a brass ball holder, which makes scratching a ball impossible. These are tools mechanics treasure. A source of bragging rights for those who know how easily balls can get scratched. When working with bearings, every attempt should be made to maintain a surgically clean environment. A human hair mixed in the grease, speck of dirt, metal fleck, or bit of rubber seal will degrade and/or ruin a bearing. It is absolutely essential that your tools, hands, rags, and general work area be absolutely CLEAN!

I am happy to report that the creak is gone, so almost worth the $65 bucks. Now I can focus on building up a new speed wheel in back, based on my old Alex wheel hub, DT Swiss bladed spokes, and a DT Swiss R585 30mm deep rim. With 24 spokes, and the 30mm profile, it should be slippery, and since the Alex hub is pretty light, a reasonable weight as well.

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