Hi Mark!
Good to hear your Sherpa is moving forward...exciting, isn't it?
I can't wait to see photos as it progresses; I'll bet it will be a corker!
As to your question regarding components, I can offer some opinions based on my own experience. Keep in mind, others will likely have their own very valid views and preferences based on the lens of their own experience. There's no one right answer for all.
In my opinion, the real beauty of Shimano's products is in their second- and third-tier lines, where the buyer/user receives most of the function of the top-end stuff at the tiniest penalties in weight and finish. Good, solid value for the money and remarkable service life for most components at the above-entry level (sometimes longer, in the case of LX vs XT(R) wrt to hubs for long-distance touring...according to some posts and opinions on various touring forums). As far back as the late 1970s, my Shimano hubs worked at about 98+% the function of Dura-Ace and about 50% in finish, addressed quickly with some metal polish.
Having looked closely at user experiences/reviews and the parts themselves, I believe I would go with either Deore or LX or a mix of the two.
For Sherpa, I chose plain-vanilla Shimano Deore for the crankset, rear hub, cassette, derailleurs, and brakes. Because I used bar-end shifters on drop 'bars, I went with Dura-Ace there and was very pleased with it as well. Later, I decided I preferred the single-spring/hard-stop and low profile of the Deore
Shadow-series rear derailleur, so I switched to that (and liked it very much, but the Shadow series require a higher minimum chain tension than the double-sprung mechs to work really well. Shadows are especially nice for shipping 'cos if stored in a lower-than-top gear, the mech is actually *inside* the hub q/r, safe from impact damage). The Tektro brake levers Thorn offered worked very nicely with the v-brakes, and abounded with thoughtful detals like a lever-mounted q/r and cranked blades for comfort. I have pics of the lot posted in my Gallery entry here:
http://www.thorncycles.co.uk/forums/index.php?topic=3896.0Your requirements are actually the same as mine: "...durability, minimal service requirements and, when it comes to transmission the ability to climb hills nicely. 22t granny of for me". I stayed with the same crankset combination (44/32/22) and rotated through several cassettes in my own quest for "just right" gearing. I started with the 11-32 and found it was not low enough. I replaced it with an 11-34 and liked that much better, but the real winner for me was the 12-36, which had a more realistic high, a much better low, and a better progression throughout the available range, which really helped. Do be warned and aware, however --
Shimano intends that cassette for the "29er" market, and in that application also warns that enough excess torque can be produced so as to damage the freehub/hub connection and pawls unless it is used with a hub designed specifically for it. I did the maths and concluded that for seated climbing, my low-torque/high-RPM/low-surge/pedaled-circles riding style, 170mm vs 175mm+ crankarms and 26" wheels, I would be well within the safety margin whe using the 36T, and that proved to be true. Second Gear is a 32T, so there are no precautions needed there or higher on the cassette. That might not hold for everyone, so if you go this route, be sure to use some caution. It would be Really, Really Bad to shear a drive pawl or strip the hollow freehub bolt from its anchor in the hub midway up a hill in the Middle of Nowhere. You'd be left with a very expensive and cumbersome wheelbarrow, and touring bikes make lousy wheelbarrows (the same-side pedal whacks one's shins repeatedly as you try to push the lot. Such unforeseen events are why I pack a couple tubes of my favorite etching polyamine-polyamide epoxy resin. It can get one out of the wilderness and back to the road in the event of an extreme failure).
All the above is in no way meant to disparage the higher-end Shimano offerings. The parallel-push mechanism of the upper-end v-brakes really does help the pads hit the rim squarely to even-out wear, and the finish on the higher-end components is really exquisite. It is just that for me, those little increments in refinement were not enough to offset the price difference and I found the lower-tier plain Deore to offer great value that fully met my needs.
An additional thing to consider is theft. High-zoot components are almost like waving a flag at a thief. Unlike bikes, components are easily removed from a locked bike and are virtually untraceable; few are serially-numbered (Rohloff hubs excepted), and all can be moved transparently on eBay. I figured that kind of resale market just isn't as lucrative for the lower-end stuff, and I breathed a little easier when I had to leave the bike for a few moments (securely locked, of course). I have known people who have lost numerous bits of their XTR componentry simply because it was XTR...and irresistible.
As for the bottom bracket/crankset design...that's a tougher call. Numerous touring and MTB forums (including the Dutch Weraldfietser site), many users, and myself all agree the external-bearing cranks just don't have the service life of an internal-bearing/square taper designs, which is proven and still readily available for replacement in the remotest of places. The trouble with the external designs is -- despite the seemingly oversized bearing cases -- the bearings themselves are of too-small diameter and too-few number to really bear the load properly withou undue wear. Add in the problems caused by poor bearing seals and sometimes inadequate factory greasing, and the bearings have a pretty poor lifespan compared to internal BB/square-taper designs. When (not "if") the bearings seize, they tend to carve divots in the spindle, which is captive/part of the right crankarm, and things go bad quickly from there (the spindle rotates *in* the bearings rather than *with* the bearings when that happens...the result is not pretty). A friend had to use a some extraordinary means just to remove his for replacement with a square-taper design BB and crank.
That said -- and fully understanding the limitations -- I selected to again go with a Deore external-bearing crank for the Nomad that is replacing my Sherpa. Why? Has Dan lost his mind? No...it was for some very carefully-researched reasons:
1) In compact cranks, four-arms are replacing five-arms, and the bolt circles differ. Where I live, it has been difficult to get replacement 110/74 BCD chainrings, but the selection of 104mm chainrings is limited to Shimano-compatible 'rings with contouring, pins, and ramps. It is a bit of a Hobson's choice either way, but my best guess is for 104mm to go forward a bit longer from today. We'll see; I'm probably wrong!
2) Square-taper cranks are going away, slowly but surely. As Andy Blance has noted in his brochures, really good-quality square-taper BBs used to be readily available at very good prices. Now...the quality has generally declined for the cost and availability. There's really high-end offerings like Phil Wood and SKF (though there have been problems reported with the latter)...and then there's a gap in the market till you get down to the lower levels in quality and service life (plastic retainer cups are a bit of a giveaway). In recent years, I've had good luck buying my square-taper BBs on eBay, looking for the NOS/current offerings from Tange, who at one time made the 105+ levels of BBs under contract to Shimano...and I think the Tange-direct versions are a little higher-quality yet. The last one I bought in 2010 cost about USD$34 + postage, and there are still some out there. Otherwise, I'd suggest going with a Phil Wood (no relation to me, despite the surname) as soon as needed and call it done. I have over 35,000mi/56,000km on a square-taper version, and it still feels as-new but with less friction. I'm hoping that will translate into long service life in an external-bearing BB as well.
3) I love, love, love the ability to remove the *entire* crank in the field using only a 5mm allen key. Also, there are none of the problems that can occur with a square-taper, such as seating the crank, matching the taper angles exactly and such, and the splined design with
stainless HollowTech spindle reduces the possibility of galling at the interface (but do continue to use anti-seize compound and recheck the torque at intervals, as before).
4) For me -- even with my hummingbird style of fast/light pedaling, I *thought* (placebo effect is wonderful) the cranks/BB were much stiffer under load. There is far less chainring deflection at the front mech for me, and the basic Hollowtech design is sound and simple...except for the bearings execution.
5) That leaves the Achilles heel of the HollowTech system -- the bearings. Having carefully researched the market, there's three options I would consider:
a) Replacement bearings in the original cups
b) Chris King
c) Phil Wood
My plan is to use the Shimano bearings for about 2,000mi/3,200km, inspecting periodically, then switch to a Phil unit and call it done for a good long while. Looking at the reviews on MTBR (I suggest you check them out for the components you are considering...see: http://www.mtbr.com/reviewscrx.aspx ), the Phil Wood unit looks most reliable in field use. I have carefully considered the Chris King unit and -- despite being able to re-inject it with grease -- have found it wanting
for my needs. There are a number of replacement bearings that will fit in the original Shimano cups after you knock out the OEM bearings, but most tend to be of fairly poor quality when you check them against any bearings-company catalog of offerings. And, you're still stuck with the original cups, which IMHO have some sealing flaws themselves. Shopping carefully, the Phil unit can be found for about USD$120, and this actually seems reasonable given the service life people are getting from them. Unlike some of the MTBR reviewers, I won't ever submerge the BB, preferring to remove my touring bags and portage the bike and bags separately across flooded areas and creeks and smaller streams, rather than riding through such. This alone makes a pretty big difference in bearing service life, and the SON28 dynohub and pedals will also thank me for keeping them dry.
Hope this helps. I wish I could offer some firsthand comparison with Acera, but I have never had occasion to use it. Check out those MTBR reviews and see what others think there.
All the best,
Dan.
