Fat Tires and Front Derailleurs, Ad nauseam.
Earlier last year I was experimenting with wide rims + big tires on my Karate Monkey and had the joy of dealing with tire rub on my front derailleur cage. I was using an early proto of what led to the Rabbit Hole rim and a Maxxis Ardent 2.4” tire. Thankfully we make [and supply with our frames] a nice little fitting, the “Monkey Nut V2” [MNV2].
Several Surly frames, starting with the Karate Monkey, have come equipped with our horizontal dropout with a derailleur hanger. This little frame bit is appropriately referred to as the “Karate Monkey Dropout.” Clever marketing, I know. The reason for this combination is it allows for single speed use, multi geared drive trains with derailleurs, or internally geared hubs. All executed quite simply.
On many of our frames, if you opt for the geared configuration you can run your wheel fully forward in the dropout with a front derailleur and have no issues. This is true for our complete bikes, as we pick tires and front derailleurs that play nice together. For a while, many of the front derailleurs being produced by 2 of the major derailleur manufactures came in a “multi pull” version. This was a great innovation for shops and consumers, though maybe not for the Karate Monkey. Shops only needed to stock 1 model of derailleur which came with seat tube shims to cover what used to take 6 different versions. Easier inventory management, and consumers were more likely to be able to walk into a shop and buy a front derailleur on the spot, versus having to special order something. One side effect, evident on our frames, was that all that adjustability encroached on tire clearance. At the same time, tire manufactures were realizing that bigger 29’er tires were a good thing and tires up to and bigger than 2.3” started to be available. This was a great, but didn’t help with the clearance issue that was developing. It was when these became available that we realized we had some issues with certain tires on the Karate Monkey. As a result, after some revision of the original, the Monkey Nut version 2 [MNV2] came about [there is that clever marketing again]. We could have simply made the chainstays on our frames longer, but this would penalize those who ride single speeds, or 2.1” tires, or didn’t use the multi-pull derailleur. Those people [including Surly employees] still wanted the shorter rear center if possible.
What this little piece does is give you, the consumer/owner/mechanic of a Surly frame, a nice dead stop for wheel installation. This deadstop is 14mm rearward from full forward. If you are using a front derailleur that has a large cage and a big volume tire, you may have some clearance issues. The MNV2 positions your wheel away from the derailleur, which you could do without the MNV2, but it gives you a consistent spot to position your wheel, so your brakes [disc or rim] always stay in adjustment [considerably harder without using the MNV2]. It will also prevent your wheel from pulling forward, in the event that your wheel was insufficiently tightened [it happens to all of us once, admit it], which isn’t a super big deal on a single speed, but if there is potential tire and front derailleur interference, it could damage the derailleur.
We supply Monkey Nuts with all of our frames that use the KM dropout and/or our Troll dropout, and they are a handy little piece. On the Krampus for example, you can run the frame in a 1x__ set up without the MNV2 and have a shorter rear center. If you need the added gear range of a front derailleur; you could outfit your frame with one of our offset double cranks [Mr. Whirly MWOD or OD Crank], a front derailleur and slip the MNV2 into your dropout. Plenty of front shifting clearance.