Cycling UK Forum

As I contemplate my latest bike-build, I wonder which kind of rear wheel dropout to choose. I'm using an Alfine SG700 and wonder what the respective advantages are for using i) the original drop-out fitted to the frame, ie one suitable for a derailleur transmssion, or ii) change it for an Alfine-specific dropout. I imagine that a fixed postion dropout would need a way to tension the chain... I will be adopting a disk brake, too.
I'd like to take all factors into consideration, but would need advice to do so.

I've run Shimano and Rohloff hub gears in purpose made drop outs, horizontal and standard derailleur type. Purpose built with an EBB or where the disc brake slides with the hub would be my first choice. Horizontal is OK, you need to adjust the brake and chain tension at the same time, but it isn't a big deal or very frequent Stopping the hub from moving while riding can be an issue, but not insurmountable. A vertical dropout with a tensioner just works pretty much like a deraileur, adds a bit of inefficiency and collects muck, but the wheel and BB in fixed positions have their advantages. The inefficiency is I'm sure measurable, but not by my legs. Most tensioners will of course lower the chain to the ground, more a disadvantage on a small wheel bike than a large.

Rear facing horizontal with tugs is most secure but fiddlier to set up. Sloping forwards ones are easier to work with and drop the wheel out but it's only axle nut torque holding the wheel in place. I don't know if any disk brakes come with sliding mounts but I doubt sloping dropouts is an option.

I would suggest that -if you can do- you perhaps should fit and use the hub (in rim brake format) to start with to see that you like it before having major modifications made to the frame. If you are fitting it to a moulton, there is something to be said for modifying a spare swingarm in the way you want for similar reasons.

The debate as to 'what is best for IGH installation' is almost as old as cycling itself. IGH fitments tend to be based on singlespeed arrangements or derailleur arrangements simply because IGHs are commonly fitting (by the bicycle manufacturer or by the bike's owner) to framesets designed for other gearing systems. As PH mentions the best IGH setups are quite different from those used for other transmissions; at least with sliding dropouts they can be changed for ones of different type if needs be.

The main reasons for wanting a tensioner with an IGH are freedom from having to retension the chain (not a major concern IME) or wanting to run more than one chainring or sprocket (which makes it mandatory more or less). Even with a moulton the chain tension variations with rear suspension movement are small and don't really influence this choice. There are of course plenty or reasons for not wanting a tensioner.

In theory adding weight near the hub (IGH, disc brake etc) is adding to the unsprung weight and ought to interfere with the suspension action. In practice the rear suspension action on a moulton is short and stiff, so is less noticeable. However you can see if this is really the case and/or if you like the IGH by fitting/using it in rim brake form before committing to major changes to the bike.

cheers

If you're going to the trouble of having new dropouts or even a whole new triangle, why not future-proof yourself a bit further with a set of sliding Rohloff dropouts?

http://www.bobjacksoncycles.co.uk/rohloff-hubs/

https://kitesurfbikerambling.wordpress.com/2009/12/14/tensioning-chains-eccentric-bb-vs-sliding-dropouts/

The slide removes the necessity for a tensioner or EBB and the disk mount moves with the dropout, so no misalignment issues, and preserves the advantages of a vertical dropout. There are probably better engineering solutions but these are quite pragmatic. Not as elegant as the TSR/SST dropouts though!

I have these on my Battleship commuter/tourer and they work fine, though the fixing screws have a tendency to seize if not kept lubricated and loosened occasionally. The Battleship in its quotidian rigging runs an Alfine 8 with the green anti-turn washers, but can borrow the Rohloff wheel from our tandem for solo cycle camping.

mjr wrote:Rear facing horizontal with tugs is most secure but fiddlier to set up. Sloping forwards ones are easier to work with and drop the wheel out but it's only axle nut torque holding the wheel in place. I don't know if any disk brakes come with sliding mounts but I doubt sloping dropouts is an option.

One considerable snag with rear-facing dropouts is that you can't get the wheel off because the mudguards are in the way - unless I'm missing something

profpointy wrote:One considerable snag with rear-facing dropouts is that you can't get the wheel off because the mudguards are in the way - unless I'm missing something

Yes. You undo the rear stays of the mudguard first and then it flexes back far enough to allow the wheel to drop down and out. In practice, I find derailling the chain a far bigger nuisance with rear-facing dropouts, to the extent that I sometimes undo the quick link rather than wrestle with it.

profpointy wrote:

mjr wrote:One considerable snag with rear-facing dropouts is that you can't get the wheel off because the mudguards are in the way - unless I'm missing something

On my Surly Troll (rear facing dropouts) I fitted the rear muguard with SKS Secu-Clips - the sort of things that are usually used on front mudguards. The mudguard stays just pull out of the clips and makes rear wheel removal a doddle.

Five years, no problems.

Oooh - how exciting - all these varialables... I'm gonna try out the bike first with the existing one-size-fits-all dropout first, as suggested. Likeing the idea of the snug and repeatable fit of a dedicated drop-out but will mull over the pluses and minuses and not rush into anything!

profpointy wrote:One considerable snag with rear-facing dropouts is that you can't get the wheel off because the mudguards are in the way - unless I'm missing something

It's can be issue but not insurmountable, for a start there's the size of the tire, flatten that and you have that much leeway. I've also seen some tug nuts that have the mounting for guards, so once you've released the wheel you also have the flex of the guard (EDIT - Same principal as above). You'll also have had to set your guards a bit further from the tyre than you might like to account for the wheel moving when you tension the chain, though you'll get that with any method that moves the wheel. So doable, but yes it isn't something you have to contend with on some other methods. It helps if you've chosen a chainring/sprocket combination where the wheel is always either side of central, it's a long way to slide if you start with it all the way forward.

Tiberius wrote:

profpointy wrote:

mjr wrote:One considerable snag with rear-facing dropouts is that you can't get the wheel off because the mudguards are in the way - unless I'm missing something

On my Surly Troll (rear facing dropouts) I fitted the rear muguard with SKS Secu-Clips - the sort of things that are usually used on front mudguards. The mudguard stays just pull out of the clips and makes rear wheel removal a doddle.

Five years, no problems.

I stand corrected ! On my purpose built Condor fixie it has traditional forward facing drop outs and you can't get the wheel in when the tyre's pumped up as it clashes with the mudguard

simonineaston wrote:Oooh - how exciting - all these varialables... I'm gonna try out the bike first with the existing one-size-fits-all dropout first, as suggested. Likeing the idea of the snug and repeatable fit of a dedicated drop-out but will mull over the pluses and minuses and not rush into anything!

TBH, it's something I'd think about when choosing a new frame but not so big a difference that I'd consider having one modified, unless maybe I was having it painted or some other work done anyway.
You might note that the Round the World record has been held at least twice by riders using hub gears and a tensioner.

having it painted or some other work done anyway.

Zactly that - my last build project came in an excellent colour (BRG) and I popped a Campy groupset on it, really just to see if I'd been missing anything over the years as I've favoured hub gears since my first TSR - and a chap has got to have a Campy-equipped bike once in a life-time! Nice tho' it is, I recall all the things I didn't like about disraeli gears, which I won't go into now... So, one more build project to go! I get to choose the hub I want, the brakes I want - and of course, most important of all, the colour I want! Then I'll stop - honest...

You might note that the Round the World record has been held at least twice by riders using hub gears and a tensioner.

Well, well - I'll be in good comapny then! Bet they're i) younger than me and ii) have steely firm thighs in a way that I do not...

PH wrote:

simonineaston wrote:You might note that the Round the World record has been held at least twice by riders using hub gears and a tensioner.

I've used my Rohloff hub in two frames - one with sliding dropouts and the current one where I use a chain tensioner. Both work fine but I much prefer the latter.

profpointy wrote:I stand corrected ! On my purpose built Condor fixie it has traditional forward facing drop outs and you can't get the wheel in when the tyre's pumped up as it clashes with the mudguard

And the front of the mudguard can't flex because it's fixed to the chainstay bridge? My road bike is like that if it's actually run with the 32mm tyres it was designed for - so as a result, I tend to use 28s on it.