Hub gear - which sort of drop-out is best?

[PH]

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.

Lots of variables, lets start with that, not least the guards. The common SKS chromos will easily flex 15mm without damage, even if attached at the seatstay bridge, let's cautiously call 10mm, I can set the guards an extra 10mm off the tyre and also get at least another 10mm with a deflated tyre. 30mm is enough to clear any horizontal dropout I've had, though again there''s variables. Above is an example of it working for someone and there's plenty of others, and the tyre size is only relevant while it's inflated.

[simonineaston]

where I use a chain tensioner. Both work fine but I much prefer the latter.

I built up a Moulton Safari-a-like which had a Sturmey Archer 8 speed hub gear. I popped it into an original series 1 rear fork, which readers will need no reminding, was designed to accomodate SA's FW (amongst others...), so there was no issue with fitting in washers designed to eliminate rotation. I added my own threaded chain tensioners, which worked well enough, but I can see that a chain tensioner based on an idler wheel might be an alternative solution. The threaded jobbies seems slightly old school. I can also see that fixing the postion of the hub by popping it into a dropout with no adjustment will suit a brake disk setup, there being less wiggle room, literally.

[simonineaston]

All is going well with my intention to fit an Al-fee-nay 11-speed into vertical drop-outs - I am feeling very cheerful about it all. Has anyone ever used an existing and clearly, redundant, mech hanger to fit a chain tensioner to? In my case it will be the single jockey wheel Al-fee-nay branded ct-s510...

[gazza_d]

That's exactly what I did with my Moulton APB Simon.
Triangle has vertical dropouts with a mech hanger.
I fitted the 2 wheel alfine tensioner and it works just fine although I needed to tweak the chaInline with a couple of washers. Been ok for 3 years now.

[simonineaston]

Excellent!

[Brucey]

IIRC the twin pulley tensioner (CT-S500, spring loaded) fits to a gear hanger (much as a derailleur would) but the single pulley one (CT-S510, not spring loaded I think) fits to the axle and also replaces one of the NTWs.

This means that there is only one angle possible between the dropout slot and the cassette joint arm when CT-S510 is used; if this matches well with your frame, great, but if it doesn't, you are a bit stuffed.

So this photo shows what happens if you try and use CT-S510 with vertical dropouts and seatstay gear cable routing; it simply won't work with standard parts;



However it is clearly possible to modify CT-S510 to fit a gear hanger instead;



but I don't know how easy it is to do this exactly.

cheers

[simonineaston]

this means that there is only one angle possible between the dropout slot and the cassette joint arm when CT-S510 is used; if this matches well with your frame, great, but if it doesn't, you are a bit stuffed.

This is exactly the case. Assembling the hub, using anti-turn washers 7L / 7R means the cassette joint lies neatly along the line of the chain stay. Swapping 7R for CT-S510 rotates the axle through lots of degrees so I'm planning to keep to the 7 pair and simply move the tensioner, taking the opportunity to ditch its heavy anti-turn bracket, to the old disraeli gear hanger, which'll look quite neat.

bracket weighs almost...

...as much as the tensioner!

[simonineaston]

PS, both your piccies, Brucey, show the chain routed under the tensioner jockey wheel, whereas my inclination would be for the chain to go over the wheel - would I be grabbing hold of the wrong end of an important stick, if I followed my instinct to push the chain up??

[Brucey]

I think the chances of the tensioner moving (eg over a bump) may be increased when the chain is pushed upwards; there is also less adjustment available in total, I think (*) , and taking the wheel out always means disturbing the tensioner (whereas this isn't always necessary with a hanger mounted tensioner). However the chain wrap is also greater (could be useful on a small sprocket) and the chain is further out of the way of all the grot on a small-wheeler too. So swings and roundabouts...?

(*) when a tensioner is hanger mounted , it is usually further back than normal; I think this brings the pulley closer to the sprocket.

cheers