I like metzler tubes and use them on my LS - they are somewhat heavy, but the thicker rubber seems to last well, and the metal valves seem to be a little bit longer than some other brands, which is handy with that narrow, deep well and tall central rib in the LS wheels. I use the ME E18 tube on the front, and the ME F18 tube on the rear, though the ME E18 tube is rated to fit tires from 3.25 up to 4.1 or more inches, so I just carry one of these as a spare tube under the seat as it can do dual duty front or rear if I get a flat. I am sure other brands will work too.
If you don't already know - one thing about motorcycle tire sizing - metric tire sizing anyway - is that the numbers don't actually give the exact dimensions of the tires height and width - the actual dimensions may vary significantly from the value of the number and vary depending on the rim width, but the RATIO of height/width WILL match the ratio of the numbers specified. For example, Vendor A tire in 120/90 x 18 metric size may actually be 116mm when mounted on a specifc rim, while Vendor B tire in 120/90 x18 might be 122mm when mounted on the same rim and inflated to the same PSI. But, the RATIO of height to width for each tire will both come out to the same 120/90 fraction. So, getting that out of the way, be aware that some brand's sizes may not be the exact same physical size as a different brand's sizes.
That said, I like the performance of the Bridgestone Battlax BT45 bias ply tires on my LS. The rubber is quite sticky and rides smooth and resists following rain grooves and metal decking. While you can still get some tires in the original imperial english sizes that came on the bikes (3.25x18 front, 4.0 x 18 rear), I am running the aforementioned BT45 tires in 100/90x18 (front) and 110/90x18 (rear). I could also have run the 90/90x18 front tire instead, but it was harder to obtain, and the slightly larger front tire I am using has only made the straight line stability of the bike slightly better, IMO. The snowflake front rim wheel on the non-LS models is narrower than the LS wheel's rim, and it should ideally use the 90/90 tire for that application, if choosing theis metric size tire model.
The Spitfire S11 tires are also good and used by many airhead riders. There are some other brands and models out there to consider as well, but I've settled on the BT45 for my LS.
Some people ride the LS wheels without tubes - the rims do have an internal shoulder "bump" that many claim is appropriate for bead retention with tubeless tire mounting. Some have told me that the bump isn't quite the proper size, but is quite close. BMW shipped the LS fromt he factory with tubes installed (some will argue that this is simply the traditional German reluctance to change) but I feel if they shipped them out with tubes, I'm going to continue to use them with tubes. Others choose to run tubeless and haven't reported issues - or simply haven't had a flat yet at speed to report whether the bead was retained in position or not. I'm going to err on my own personal side of caution in this case and use tubes, but you will definitely find others here who go without and are happy to do so. Your mileage may vary, etc.
