When Campagnolo went 11 speed what seems ages ago, it was seen as one too many cogs, but when Shimano moved the all range of their road group sets to 11 speed last autumn, that basically meant the days of 10 speed drivetrains are over. So, what to do? Stay on 9 speed, like I do! Jokes aside, these days in Europe it is cheaper to purchase a whole 5800 group set than it is to buy a pair of shifters and a couple of spare cassettes for 5700. So my advice is: embrace 11 speed. For the first time in nearly 20 years, the tracks of Shimano and Campagnolo run parallel again, meaning there is some form of cross compatibility between the brands. The two manufacturers will never admit to this, but it is well documented that as long as you don’t mix and match shifters and derailleurs between brands, you can run a Shimano 11 cassette with a Campagnolo drivetrain and vice versa. Basically, the pitch between the 11 sprockets in a cassette is close enough between brands to make it practically interchangeable. However, the amount of lateral movement your rear derailleur operates per click is a function of the cable pull and the derailleur geometry. Although the net result is the same, Campagnolo and Shimano obtain the same result using different cable pull and different conversion ratios, hence the importance of NOT mixing these.
11 speed also demands a wider free hub in the case of Shimano, which means your old 9/10 speed wheels are no longer compatible. Time to throw them in a skip and invest in a new set? Sure, if you like to throw money at the problem, that is indeed one solution. Conversely, if you are a bit of a Scrooge like myself, you can perform one of the following modifications:
1) Swap the free hub for an 11 speed compatible one, where one compatible exists
2) Swap the free hub for a Campagnolo one, that will accept 11 speed Campagnolo cassettes, if that option exists (it does not for Shimano branded wheels)
3) File the protruding edges of the free hub splines to create some extra room. The 11 speed cassette requires some 1.8 mm extra room, but you should be able to get away with filing 1.5 mm in most cases. You just have to make sure that the removal of the edges won’t result in the cassette binding with the hub shell and that your derailleur can accommodate a couple of mm extra movement without hitting the spokes.
One of the spline edges has been filed on a Novatec free hub… now to the others!
And half an hour later… job done… a 10 speed freehub is now 11 speed!
What else can you do with 11 speed? Well, quite a few interesting things, in fact. I have always liked Campagnolo Ergo levers and recently purchased a set of scratched 11 speed Record shifters for a few pennies. However, I do run disc brakes and I prefer a Shimano drivetrain. It turns out the pull ratio of Campagnolo 11 speed is 2.6 mm, close enough to Shimano 9 speed 2.5 mm, which means my Record shifters can be paired with a 9 speed XT derailleur to smoothly shift a 9 speed MTB cassette on my cyclocross bike. It works amazingly well. For convenience I left the two spare clicks at the bottom end of the cassette, just after the useless 11 teeth sprocket, and I have limited the rear derailleur to make sure any accidental extra click won’t result in chain derailment. It’s a lot of words, but really a 30 minutes conversion that allows me to take advantage of the best of both worlds. Campagnolo awesome ergo levers and Shimano’s mountain bike sturdy and well-engineered components, with an increased range of gear ratios for those steep banks.
In conclusion: move on! 11 speed is good not because of the extra sprocket which you will never know you have, but because it allows you to do things you could not do before without using pulleys or expensive Shimano splined-Campagnolo spaced cassettes.