Hi Lewis!
Unfortunately, when the Forum upgraded to new software, the old links broke. I have found the links relevant to your question and have repaired the cross-references so they should work as you click them. The old thumbnail files for attached photos did not make the trip to new software, so the thumbnails have been replaced by generic icons. Click on them to open the photos. Most have some corruption, but should be clear enough to see what they portray.
Basically, the Sherpa fit boiled down to this:
1) Unlike the Nomad, the Sherpa (like the RavenTour and later Raven) has seatstays small in diameter than those on the Nomad and they are closer together. This alone solves many of the fit problems I ran into putting the AXA Defender on the Nomad.
2) I found tire clearance adequate with 2.0 Duremes, but that is the maximum. The opening of the Defender is 50mm. The part near the tire sidewalls is 63mm. 63-50=13/2-6.5mm maximum clearance per side, provided the ring-lock is fitted in height to mirror the tire profile. This proved fine in my usual use with 2.0 tires, but could become problematic in heavy mud (as I sometimes encounter with wet desert dry lake playa). For reference, the Trelock RS 450 Balloon model offers 14mm clearance per side in the same location. Mud clearance should not be a problem in any ordinary use. If you are running 1.75in tires, you'll have no clearance problems running an AXA Defender.
3) Mounting options vary for frames (like Thorns) lacking the M5x0.8mm bosses for direct mounting...
a) The little "Spam can" metal straps and worm drive option...I found fiddly to fit and insecure and not worth the bother. Heaven help you if you need to remove the lock and refit it. This kit was sometimes included with the locks, but now seems less common than even a year ago.
b) I had really good luck with the AXA "ATB" mounting kit. It consists of two shaped plastic blocks, a couple of nuts and externally toothed washers, and two vinyl coated end-threaded "cup hooks" that wrap around the seatstays and grasp it. With this kit, mounting was a breeze and removal and reinstallation is easy if you need to. All that is needed is an 8mm socket wrench or Y-wrench. The kits come in two sizes, so you just need to choose the one appropriate to your seatstay diameter. My Sherpa Mk2 and the Raven Tours both used 16mm seatstays so the larger kit was ideal. Here is a link to the ATB kit in two sizes:
http://www.dutchbikebits.com/index.php?route=product/product&product_id=52c) AXA offer a new kit, each side has two metal worm-drives and two plastic straps. The new kit was introduced with the new Victory lock and will also fit the Defender. It looks both logical and secure, and a couple of sets are on their way to me in the mail now. I have not yet seen them in person but on the face of it, I favor these new mounts over all others for the AXA Defender or later Victory model ring-locks. All that is needed for installation is a screwdriver to make it a fast and straightforward operation. There may be a problem with missing the canti bosses or seatstay bridge, but I'll find out when mine arrive.
d) AXA (and others, including ABUS) offer mounts to place the ring-lock on your canti- or v-brake mounts. I don't favor this because the lock is outside the rear triangle and so vulnerable to some removal exploits that do not apply when the lock is trapped inside the seatstays. Trelock also offers a plastic mount that clamps the seat tube. That is considerably more secure against theft than a canti-mount but won't always work on bikes where there is a lot of space between the seat tube and rear tire due to long chainstays (Thorn). A special note for RavenTour and Raven owners: The canti mounts are unlikely to be compatible with the Rohloff cable stop used on the internal shifter on those two bikes. This does not apply to the Sherpa, which has a derailleur drivetrain.
To install one of these ring-locks on a Sherpa or RavenTour/Raven is pretty straightforward:
Depending on mudguard width, you may only need to drop the lock over the 'guard, fit the mounting straps loosely 'round the stays, bolt the lock to the straps, then tighten the straps, checking to make sure the lock is mounted evenly away from each sidewall and the lock hasp clears the bottom the rim. Done.
In more extreme cases, you might need to deflate the rear tire or even remove and reinstall the wheel a couple of times to initially fit the lock. If the mudguard is wider than the *opening* of the lock, you will need to remove the rear wheel and approach the 'guard with the lock sideways, rotating it upright into the wider opening for installation. That's a one-time thing when fitting or removing.
Trying to mount the AXA Defender on the *Nomad's* larger diameter, more widely spaced stays required considerable modification to the AXA ATB mounts and the end result ultimately did not meet my standards for a secure fit -- it was fine in practice, but the minute "clocking" around the mounts bugged me and I feared it could pull free if a thief really pushed a loaded bike with the lock shut. That -- along with concerns over extreme mud clearance with 2.0 tires is what led me to the Trelock RS 450 Balloon model, which was just introduced late last year, along with the AXA Victory. It *just* fits my size 590M frame provided I reversed and inverted the Trelock ZR20 mounts. It is secure and there's no "clocking". These ZR20 mounts will also fir the AXA Defender and other ring-locks and are holding my old AXA Defender to one of my rando frames now. The use threaded brass inserts embedded in glass-filled nylon and are very secure.
Okay, here are the relevant links, Lewis...
Original topic asking of anyone had fitted an AXA Defender to a Sherpa:
http://thorncyclesforum.co.uk/index.php?topic=1944.msg9015#msg9015My description of what I fitted to my own Sherpa and how:
http://thorncyclesforum.co.uk/index.php?topic=1944.msg19634#msg19634My followup here with detailed photos showing the ATB "cup hook" mount:
http://thorncyclesforum.co.uk/index.php?topic=1944.msg19741#msg19741A query I answered on how to mount the AXA Defender to a Nomad:
http://thorncyclesforum.co.uk/index.php?topic=6301.msg37831#msg37831My cautions about Nomad fitting here:
http://thorncyclesforum.co.uk/index.php?topic=6301.msg37831#msg37831My fully detailed procedure for fitting an AXA Defender to a Nomad's larger 19mm diameter, more widely spaced seatstays:
http://www.thorncyclesforum.co.uk/index.php?topic=4987.0For balance, some Forum members have had good luck fitting ABUS Amparo 4850 ring-locks to their bikes. I did not care for some of the Amparo's features (and it is difficult to find this model with a captive key) and found the mount tended to "clock" 'round the stays a bit over time on my size 590M frame -- stay width where the lock actually mounts does vary a bit across frame sizes due to geometry. Hence my choice of either the AXA Defender/Victory for bikes with smaller seatstays and the Trelock RS 450 Balloon for my Nomad's large diameter, widely spaced stays.
JimK's treatise on his ABUS Amparo 4850:
http://www.thorncyclesforum.co.uk/index.php?topic=4148.msg18856#msg18856My Sherpa Gallery with photos of the lock in place can be found here:
http://thorncyclesforum.co.uk/index.php?topic=3896.msg17095#msg17095Hope this helps.
All the best,
Dan.