Phil_gretz

You know, the OP never gave his bike or front chainring setup. What is the application? Some kind of specialty bike or hand crank? 23 posts engineering a solution for which there may be a different problem. Maybe a triple up front would do the trick?

Reynolds 

What is the practical limit for low gears? I haven't too much experience about it, but I found 22/28 enough for all hills, mostly because lower than that would've been too slow to keep upright.

ksisler

531; That brings up a good point as it is really two separate and distinct aspects;
-- The 'practical limits' of gearing for a bicycle and 'Practical' is in the mind of the needer; Probably a 10-42T 11-speed cogset with a 14/60T quad chainring crankset, although I am not at all sure what one would do with it or how one would really shift it. Can Google on SRAM and Mountain Tamer for a thread to pull on those.
-- Now as to what folks feel they need or even perhaps really do need for some bit of riding they do or might want to do (or maybe for tree climbing???) who knows. But I doubt that any extreme capability that could be assembled would not find a friend in need somewhere.

/K

fietsbob

Practical limit for low gears on a 2 wheel bike is so low you fall over ..
or lose all the momentum starting up, in half a crank rotation.

I have a Mountain Tamer Quad , 16t, if any one wants to try , Ill Sell It..

a Tadpole trike it can be quite low, to tow heavy loads slowly up a hill ..

ThermionicScott 

7.5" or so?

john0

Given that casual bikes have none of the need of racing bikes for fine gear changes, but do benefit greatly from both simplicity and big gearing range, I was investigating the possibility of achieving approximately the range of a 21-speed triple with a single chainring.

Reynolds 

That would be like a 12/40. Just a little faster than trackstanding.

jyl

Big jumps between gears at the higher end of the range are painful, whether you're a racer or just a regular guy trying to maintain a 20 mph cruise in variable conditions. If 20 mph is a speed you would only hit in bursts or downhill, them you don't need the big chainring on a triple.

fietsbob

Tried a 16 : 28 in a mtb, that is a gear more suitable to recumbent trikes , being so Low, 0.57:1..

ThermionicScott 

Unless the triple in question used a 13-21T freewheel/cassette, it's really tough to replicate that range with a single chainring. But, there is a great appeal to simplifying down to one chainring and eliminating front shifts.

There are a lot more options for wide-range cassettes (like 11-34) in 8-speed and up -- to make this dream work, you may need to upgrade...

Reynolds 

SRAM XX1 11 speed-single chainring uses 10-12-14-16-18-21-24-28-32-36-42 and a 28, 30, 32, 34, 36 or 38 chainring. With the 28, development is 1.4 - 5.9m (17.5 -73.6 G.I.), with the 38 1.9 to 8.0m (23.8-99.9 G.I.).

jyl

That is funny. Literally a slow walking speed. I doubt I have the balance to keep it upright at that "speed".

fietsbob

Put the Schlumpf planetary crank on my Brompton. the cranks are not connected to the chainring,
but instead power passes through a planetary gear. So Its one chain ring but acts like 2 ,
as if say; a 50t. 20t combination
the gear in low is a 2,5:1 reduction gear.. Then, the cranks turn faster than the chainring.

No Cable or levers, Tap a shuttle button running between center caps, with your heel, to shift. .

the reduction gear allows a 3 speed hub to be used twice, for 6 distinctly different gears...

offered in 110 and 130 chainring types. then , Sturmey Archer hubs can climb the Swiss Alpine roads.

cherokeeronin

Thats something new for me. So you can use a 48-36-22 without any proboems with the FD? Ive read somewhere from Shimano that you the max gear difference is 10-12T, for example 40-32-22 or 48-36-26. If that's possible, I'll try working that out.

hokiefyd 

I know this is a super old thread, but for those who are tracking stuff like this, Rivendell is selling cassettes made by S-ride that meet the description. 11-36, 13-34, and 13-42...all 7-speed. I think these are relatively new in terms of availability, so many may not know about them.

https://www.rivbike.com/products/cassettes-7

Hondo6

Old thread, but I'll address cherokeeronin's question anyway.

Shimano derailleur specs are reputedly fairly conservative. A 20-22T max difference is common spec for newer Shimano triple FDs as I recall, so a 26T difference may well be do-able if the proverbial stars align.

I've never pushed a FD beyond spec, so I can't address that from personal experience. But I have used a Shimano RD a bit past its specs without issues.