Michael Lanchester said:I recently read an article in Australian Cyclist about the Trek
7400. It includes a 7 speed Shimano Nexus Hub and roller
brake. I believe that this will be shortly upgraded to 8
speed.
I have a 24 speed GT mountain bike with Rock Shox Judys and
slicks. Mostly Deore Lx components and xt derailer. I have
been commuting to work on and off for around 7 years. Recently
I have gotten totally sick of it due to the distance (16km each
way) and the maintenance of the gears and chain required.
I switched from a derailleur system to an internal hub for the
same sorts of reasons. I bought a bike with a Shimano Nexus
4-speed automatic hub (because it was half-price) with a view to
quickly changing hat to a conventional 7-speed internal. I soon
imported and fitted a Sram/Sachs Spectro S7. So I can comment on
some of your questions.
Quoted message said:My derailer shift cable has never been right (professionally
adjusted) and shimano chainrings and spockets wear out far too
fast etc. Not to mention a slight buckled rear wheel rubbing on
the V-Brakes. And maintenance required for the Rock Shox to
keep them flowing nicely.
I figured that if maintenance could be reduced I would be
happier.
I am considering selling the GT and buying a Trek 6045 (the 26"
wheel version of the 7400). It includes the nexus 7or 8 speed
hub.
I need some advice from the experts formalise my decision :-
Will the hub it significant reduce maintenance ?
These hubs are maintenance-free to quite high mileages. I've now
got about 6,000 km up on mine, and I hope to get at least 10
times that before I need to service it.
I recently disassembled and re-greased an old Shimano internal
3-speed hub that had done 3 of my kids on a BMX. It had no signs
of wear. It's ready for any grand-kids now.
Quoted message said:Is chain and sprocket wear reduced ?
The sprockets aren't showing signs of wear, but I've replaced the
chain (and will need to do so again soon). I'm sure the chain
would last much longer if I cleaned it - but I've been simply
re-oiling it, ignoring the dirt.
Occasional chain adjustment is required, to accommodate wear.
In any case, most bike shops sell the generic 3-splined rear
sprockets that fit these internal hubs (Shimano and Sachs
included) for something like $10.
Quoted message said:Do nexus hubs shift as well as an XT/LX derailer (when
perfectly adjusted) ?
The Sachs hub changes very reliably if you stop peddling for a
fraction of a second. When stationary, a touch of back-peddling
does the same job. The Shimano 4-speed would change even under
peddling pressure (but made the occasional protesting noise).
Does the hub incur significant resistance ?
Not that I can detect, but Sachs is reputed to have slightly less
drag than Shimano. I think a pair of gunked-up rear derailleur
jockey wheels would induce more drag than one of these hubs.
Quoted message said:What does the roller brake compare to ? (canti's with shimano
pads, V-brakes with koolstop pads, Magura disks etc)
The Shimano Nexus roller brake would lock up the back wheel very
easily. That's much more difficult to do with the Sachs internal
drum brake (unless the front brake's applied as well, throwing
the weight forwards). However, the Shimano brake quickly
suffered brake-fade on any prolonged steep descent - soon fading
out to nearly nothing if no front brake was used, presumably due
to heat build-up. I haven't been able to induce brake fade on
the Sachs unit - it's absolutely consistent.
Quoted message said:Does the hub give you enough gear range ?
Almost enough for me. The Sachs 7-speed has about the same total
range as the new Shimano 8-speed. The Shimano 7-speed has less.
In terms of gear-inches, I've got the Sachs set up with a range
from 30.6 to 93.3. Within my acceptable cadence range, this
gives me road speeds from about 8 km/h to 45 km/h.
One advantage of the Shimano units is that they (and their
replacement parts) are available in Australia. For that reason,
I think I'd have chosen the Shimano 8-speed if it was available
at the time.
John
