BicycleBicycle

Hello Everyone.
I have a bianchi san jose single speed (I think it's between the 2008 and 2010 model).
Sometimes, when I go on long rides or even in the city when I am in a particularly hilly area for a long period of time, it would be nice to drop down a gear.
It would also be especially fun to be able to climb up some technical sections of the local singletrack rather than have to walk up some of the hills.
Most of the time one speed is fine though.
I have therefore concluded that I want 2 speeds.

I am running a 42/16 right now, and I was considering two options:
1. get 20/22t freewheel on the other side of the rear.
2. Since I have a sugino xd crankset (it accepts a second chainring), I was thinking about doing a dingle set up.

The dingle sounds more attractive as it would be less weight, and when "switching speeds" I would simply have to stop, loosen the wheel, move the chain, and then tighten again.
With the flip/flop set up, I would have to flip the wheel around which is more labor (I also have a unidirectional tire back there).

My question is, what do you guys consider a good ratio?
is 42/22 overkill?
how about up front?
Will 36/16 feel the same as 42/20?
Is 32/16 too small? (2.0 ratio).

I want a pretty significant drop (I would only change speeds when it's so steep that I literally cannot pedal, or when the length would require full bore stand up pedalling the entire time).

I know that you have to consider many factors (strength, size of bike, etc.).
However, I know that there is a general sentiment of "how much smaller" and "how much bigger" a 4-6 tooth difference up front and in the back would feel.

It's really the extended climbs at 10%+ gradient that get me as the short ones (small block length) I can either power through or they are just too steep and long for me to consider them seriously right now (think 15%+ for like an 1/8th-1/4 of a mile), or at least until I train more.

Whaddya guys think?
Thanks.

phobus

I think this will help you answer your questions:

BikeCalc.com - Speed at all Cadences for any Gear and Wheel

robsta

I had a similar issue and needed a smaller gear for longer hills.
In the end I went for a Sturmey Archer S2 kick shift. With a 39 tooth chain ring and ( I think) 18 cog it gives me about 75 and 55 gear inches.
This works fine for me although for touring around Japan I might stick on a bigger cog to get the gear inches around 40 and 60 ish.

The way I read your post at the moment (assuming 700c wheels and 28mm tyres)
currently
42/16 = 70 gear inches
with the flip flop options
42/22 =56
42/20 = 51

With smaller chainring
36/16 = 60
32/16 = 53

Ive never tried a dingle but if it works without fouling the chainline too much I`d start with the 36 chain ring. Would a 32 mean pushing the wheel back too far for chain tension?
A 32 would definitely be much easier on those long climbs.

With a 75-55 set up and some planning I rarely have to get off and push, but then with a lower gearing I wouldn't have to avoid so many passes.

Would be interesting to see what options you choose and how it works out.

Seeing how this is a single speed and fixed gear forum maybe the purists might not mind us intruding a little seeing as there is no twin speed / dingle forum.
All the best
Rob

bwilli88 

I have a 73 Raleigh SuperCourse set up as a dingle speed. It has a 17-21 2 speed freewheel with 46x42 chain rings. while it is in 46-17 it has a GI of 75.3 and in 42-21 it has GI of 55.7. It is easy to change the gears, release the QR, move the wheel front and swap chainrings and cog, pull back and center the wheel and tighten the QR.

IMG_20180717_114219125 by Bwilli88, on Flickr

Here are closeups of the drive train on another bike with a 52x48 chainring set

IMG_20161021_144452736 by Bwilli88, on Flickr


IMG_20161021_144447945 by Bwilli88, on Flickr

bmwjoe

I have a 16/18 dingle that I usually run with a 42t chain ring. This gives me ~70 gear inches with the 16 tooth in the back. I have run the 42/18 (63 gear inches) a few times on a hilly century or to have parity with my friend who also runs 63 gear inches and it was fine. My track drop outs let me just move the wheel to accommodate the extra 2 teeth in the back, but I have never needed to do this on the road. When I have a flat century or I am feeling fit I run 52/18 with a longer chain. It is only a 73 gear inch but I can hang with a pace line w/o spinning to much.

I am a fan of the dingle. It does give the geared bikes something to talk about... " So, how do you shift?"

Ride Safe,

Joe

BicycleBicycle

Just to remind everyone, I have a sugino XD crankset that accepts a compact road double.
I still have a single freewheel.

I recently tried putting both a 42 and a 34 up front (I have a 16t rear cog).
I had to shorten my chain and it got to the point where the wheel was practically falling off the dropout but the axle was juuuuust at the edge.
I wasn't going to risk f-ing up my frame so I just took it off and luckily the store I got it from gave me store credit (I'll probably use it to buy some kind of accessory someday).

For the record, I even tried to buy a halflink and it this time the chain was too small for the 42t sprocket up front.

I assume that most horizontal dropouts are similar in length so an 8 tooth difference up front is too much!

I am now going to purchase a 36t sprocket and see if that works better (6t difference).

If this gives me problems, I will try an even/odd gear combination (has something to do with the way the chain links up).

However, i'm fairly certain that a 42/36 up front will work.

I'm hoping to put the rear brake in a "sweet spot" that still makes contact with the rear wheel when I move it without having to adjust the pads (My current option is to just unhook the rear brakes after the gear change for a climb, then re-hook them after i'm done).

I hope to carry a 15mm in my pocket and just do a quick draw to change gears (less than 20 seconds of effort).
Update coming soon.

robsta

Make a video of the quick draw.

Also, if you can't find a rear brake sweet spot you could just leave the brake open (as in when removing a wheel) as this is for going up a steep hill.
When you summit you can move the wheel to the higher gear position and close the brake then. Assuming no clearance issues.

Still prefer my set up though

Cheers
Rob

hairnet

Have you looked into getting a White Industries DOS freewheel? 2 speed freewheels in 16/18, 17/19, and 20/22. You can also use a cassette wheel with single speed cogs and cassette spacers. Pair that up with chainrings that have two tooth difference and you have a true dingle drive. Having the two tooth difference in the front and rear in theory allows you to change your gearing without repositioning the rear wheel. I tried it a few years ago on my mountain bike and it worked nicely because it allowed me to have to have a low gear for the trails (which are almost all climbing here) and a tall gear for the road.

Broctoon

bwilli88 

here is a 2 speed freewheel that is 16-20, set this up with a 44x48 and it will be sweet.
https://www.ebay.com/itm/SUNTOUR-FRE...5mE7:rk:8:pf:0

Surly also makes a dingle speed fixed gear.