Technical FAQ: Switching derailleur cages, brake pads, cranks, and forks

Dear Lennard,
I am interested in converting my Ultegra 6870 rear derailleur from a short cage to medium cage. In the parts diagram, it shows that the three differences are the outer plate, inner plate, and plate axle assembly. I have read that it may not be possible to convert the plate axle assembly but would like your advice. Is it possible to convert the plate axle assembly from SS to GS? Also, is there anything else I should consider when trying to convert?
— Kelly

Dear Kelly,
Yes, it is possible to convert your Ultegra SS rear derailleur to a GS rear derailleur.

We have done this switch in my shop to get a wider gear range on a new Dura-Ace Di2-equipped bicycle, by switching parts between Ultegra and Dura-Ace Di2 rear derailleurs. We would just buy two rear derailleurs — a Dura-Ace Di2 SS (short cage) rear derailleur and an Ultegra GS (long cage) rear derailleur. We would remove the lower knuckle assemblies from both and interchange them. It always worked fine. We then had a Dura-Ace Di2 GS rear derailleur to put on the customer’s bike with the wide-range cassette they wanted, and we sold the resulting cable-actuated Ultegra SS rear derailleur that now had a Dura-Ace cage on it.

I have never obtained these items as individual parts and done this switch. Here is the exploded drawing of the two options. As you alluded to, there is a different part number (Y5YD98020 vs. Y5YD98030) for the lower knuckle’s shaft, spring, seal, and washers (dubbed “plate axle assembly”) depending on if it is SS or GS. I find it surprising that there would be a difference and am dubious whether there actually is one. Since our experience is that Shimano made these parts compatible between Ultegra and Dura-Ace and cable-actuated and Di2 electronic models, it is hard for me to imagine that this part would not be interchangeable between Ultegra SS and GS models. Toggle back and forth between this page and this page and see if you don’t agree. If it were me, I would not buy that part; I would just get the inner and outer plate, which are much cheaper parts to boot. I really can’t imagine that your existing lower knuckle bolt won’t work with a GS cage. And the downside if I’m wrong is low anyway — lower than what that part would cost you. If it doesn’t work, the worst thing that happens is that you put it back together the way it was, order the GS plate axle assembly, and do the disassembly and reassembly again when that assembly comes in.
― Lennard

Dear Lennard,
I have several wheelsets I like to use and switch around. When switching between carbon and aluminum wheels, I change the brake pads out for the specific ones for each wheelset, but when switching from one carbon rim to another, do you really need to switch the pads? Pretty annoying to have to remember. I have a pair of Reynolds tubulars I use with Reynolds blue pads, then some Rolf carbons that I use the Rolf pads for and some Enves with the Enve pads. Can I just use the same pads for any carbon wheel or should I keep switching them out every time I change wheels? This is when discs sure have an advantage for sure.
— Jonas

Dear Jonas,
I’m sure if you were to ask the rim manufacturers, they would likely tell you to stick to their pads. That said, my experience has been that many carbon pads work with a wide range of carbon rims. And, as you are certainly aware, there are aftermarket pads available from companies like SwissStop and Kool-Stop that are made for carbon rims and are not specific to any brand or model of rim.

My primary test has always been squealing. If they squeal, I keep trying other carbon pads until I find some that don’t squeal. If you can find a set that work on both of your wheelsets without squealing, I think you might as well give them a try.

I would also watch the rate of pad wear, and if you find your pads being ground down like an eraser, then that’s probably not a good choice for your rims. It goes without saying that you try them out on roads with low consequences before flying down a mountainside with your life depending on them.
― Lennard

Dear Lennard,
I got a great deal on a time trial frame that I am about to start a build on. My current road bike has all Ultegra 6700 components. I do have a Stages power meter (left crank arm) that I am using with this set-up.

From my browsing, the newer 5800 and 6800 series of components are more readily available and cheaper that what I can find 6700 components for. I am on a tight budget for my build and do not want to purchase another crankset and power meter. My time trial bike will more than likely be my primary ride. Can I use my Ultegra 6700 crankset with the 5800 or 6800 series chain and components? If not, would my 6700 crankarm with my Stages power meter be compatible with a 6800 crankset since they both have a 24mm spindle?

The difference between 10- and 11-speed is not critical for me. I just want the best bike I can build with a small budget. I have an extra 10-speed crankset that can go on my road bike so it would always be ready to ride.
— Dan

Dear Dan,
All of Shimano’s Hollowtech II non-drive arms are cross-compatible. So if you were to use that 6700 left arm with a 5800 or 6800 crankset, it would work; you’d of course want to make sure both are the same length!

While I’m surprised that you can find current 11-speed components cheaper than old-model 10-speed ones, you can certainly use that Ultegra 6700 10-speed crankset with a 105 5800 or Ultegra 6800 11-speed drivetrain without problems. It will shift just fine.
― Lennard

Dear Lennard,
I’m considering a fork swap on my gravel bike (a Fuji Tread). The fork I’m considering has a different offset. The stock fork has 50mm of offset. The head tube is 72 degrees and the trail is listed at 60mm. The new fork has 45mm of offset. Assuming all other factors are equal (fork length, etc.), what will change on my bike and will I notice a difference in handling? From some reading I’ve done, I understand the trail will actually increase. I get some minor toe overlap currently, will that get worse? The advantage of the new fork is that it has mounts for water bottles on the fork legs. I’m preparing for the Almanzo 100 next spring, and additional bottle mounts could come in handy. I don’t like anything on my seat post, so that eliminates some of the options out there.
— Kevin

Dear Kevin,
The bike will become a bit more stable and will want to hold its line more than your existing setup. Yes, the trail will increase if you install a fork with less rake, and stability increases with increasing trail. Yes, your toe overlap with the front wheel will increase if you install a fork with less rake. The effects will be subtle; I wouldn’t be surprised if you didn’t even notice the handling difference.
― Lennard