Dingle Speed Thinkering

[Adam Alphabet]

A little help/clarification on the whole dinglespeed front.

I have a bike set up in mind for a specific trip. Lot's of pushing and HAB, some off trail riding, some perfect single track and some dirt roads to access it all.

I've bikepacked out in this area before on a 3x10 drivetrain and really only needed a hand full of gears. I want to keep my bike simple this time around but too simple, ie single speed on a really really spinny gear would be well, bluntly, dumb.

So I'm thinking the following.....and please correct, explain, chime in, etc...

Up front on 64/104 bcd crank: 30T on middle 26T granny.
Cassette hub with SS cogs and spacers: 21T and 25T.

*Will this work?
*Is it as simple as keeping the tooth total the same? (30+21=51) (26+25=51)
*Could you theoretically further increase the 'tooth differential' as long as the totals are the same (and fit within your cranks bcd)?

I've read about chain length and have even found a chain length calculator online. Chain line would be another potential issue?

My frame has paragon sliding dropouts but I don't want to be messing with the drop outs every change. Ideally I'd be able to ride the 30/21 for parts of the trip and then the 26/25 by loosening the QR moving the chain over and continuing on. Limited futzing is necessary to make it worth it.

Thanks in advance everyone!
Adam.

[mbeardsl]

In short, the answer is yes, yes, and yes.  Chain length won't matter if you keep to same tooth count. Chain line won't matter if everything is spaced properly. Nowhere near what you see on 3x10 setup.  If you go huge tooth differences you may need to space everything further apart so as to not rub on the larger cog/ring.

I would say those two gearings are a bit spinny? I'd opt for more of a 32x24/36x20 but depends on terrain you're travelling.

[Adam Alphabet]

Thanks for the reply. I was hoping someone could back up my assumptions and internet reading.

I'm curious if something as extreme as say 22F/25R and 30F/17R would work.  I haven't been able to find any good info on people using large gear spreads.

I need a really crawly gear and one that is tolerable enough to pedal on some dirt roads and easy single track. Not your typical bikepack terrain. Lot's of hiking involved, some river fords, pushing and pushing and pushing with some pedaling thrown in on occasion and wonderful descents. It borders on adventuring and single track touring. Great fun!

[gdillon]

I've asked this question on here before and in practice the chain length DOES change because of the angle difference between the chainring and cog. If your frame has track ends and you are using a bolt on or chain tensioner, you can make those small adjustments when changing gears.

When I had a dingle setup using sliding dropouts I could make one ratio perfect, but the other would be off.

The 26/25 ratio sounds pretty nice for climbing and singletrack, but I agree that the 30/21 is not a suitable "road" gear unless the roads are also steep with little amount of flats. 32/19 or taller might be better.

[mbeardsl]

Thanks for the reply. I was hoping someone could back up my assumptions and internet reading.

I'm curious if something as extreme as say 22F/25R and 30F/17R would work.  I haven't been able to find any good info on people using large gear spreads.

I need a really crawly gear and one that is tolerable enough to pedal on some dirt roads and easy single track. Not your typical bikepack terrain. Lot's of hiking involved, some river fords, pushing and pushing and pushing with some pedaling thrown in on occasion and wonderful descents. It borders on adventuring and single track touring. Great fun!

I don't think you'll find anything written on that wide of a gear choice just because most people opt for a closer one e.g. riding 36x18 to the trail at ~15mph, then 32x22 on the trails at ~9mph.

I don't know what Dean means re trouble with the QR and how that relates to a chain tensioner.  I'm 230# and have never had a QR slip (even held when I stripped an I9 drivering in the hubshell) but YMMV I suppose.  Just have to make sure it's tightened down well.

As for a chain tensioner, are you running sliders or EBB or have some other way to tension the chain?  If not, gear selection will be pretty important but I'm sure you can find something that works well enough.

[mbeardsl]

I've asked this question on here before and in practice the chain length DOES change because of the angle difference between the chainring and cog. If your frame has track ends and you are using a bolt on or chain tensioner, you can make those small adjustments when changing gears.

When I had a dingle setup using sliding dropouts I could make one ratio perfect, but the other would be off.

Curious what your ratios were?  Mine have always been fairly close and while the chain length changes slightly, it was SO small for me that it didn't matter in practice.  It wasn't enough that I felt like changing the sliders was worth the effort.  I guess I could see that being more significant with a very wide spread but not sure by how much.

I've used this chain calculator with success in the past (http://www.machinehead-software.co.uk/bike/chain_length/chainlengthcalc.html), and plugging in the 22/25 and 30/17 gives a difference in chain lengths of <1.5mm (or 0.12% longer).  That sounds about right in my experience.

[gdillon]

I run 32/23 and 36/19. I agree that the difference wasn't much, but enough to not have a perfect chain tension. In hindsight, my chainring was probably off center as well, which would compound the chain difference of 1.5 mm (which sounds low to me, but probably correct), so look out for that, too.

There are probably some tricks I don't know about regarding chain tensioning. Sliders and EBBs haven't worked for me... But not the topic here.

Good luck making a simplified drivetrain. Go with the wide swing in gear ratios, especially if your trip has big stretches of flat terrain.

[Adam Alphabet]

This is the type of info/discussion I was looking for. People's experiences are always the best teacher.

I think I'm settled on trying 22/25 and 30/17.

Chain angle aside (not chain line). If I really need to I'll just pull the sliding dropout outs back in the frame to tension/slack the chain if need be. The gear changes won't be frequent enough, but simplicity, reliability and lack of futzing around are the goal for this.

Thanks again guys.