saddlesores

was wandering around the eastern suburbs of bangkok this morning, stopped in a small non-chain bike shop, mostly chinese mid-range mtb's and some crabon racers.

what caught my eye was a $500 mtb.....the gear cluster was bigger than the brake disk.

turns out it was a 33-spd....22 small ring in front, with an 11-spd 11-46 cluster, using a deore rear derailler.

i didn't know, but now i do. perfect gears for laotian mountains! 22:46 with 26" wheels ----> 12.4 GI
(or 13.7 with 700c)

daddy's goin' shoppin'!

indyfabz

SRAM offers at least one cassette with a 50t cog.

Colnago Mixte

Picture assist for crabon racers:

MrJames67 

I don't think you can pedal uphill at 12.4 gear inches and stay upright on a bicycle, without tipping over, or doing a slow motion track stand, can you? Unless you're coasting downhill . Am I mistaken? Did you ride this bike uphill?

saddlesores

i've been riding a 26" with 22:34 and a 700 with 22:36 up long (20km+) hills at 50-60 rpm with a moderate 20kg load. according to my calculator that would be approximatefully 2.5-3 mph or 4-4.5 kmh.

no problems up to 12% grade, 14% can't go more'n half a kilometer, over 14% maybe a hunnert meters. (no standing)

i thought 36 was the absolute limit for regular touring type deraillers, and those 40T+ clusters required really expensive low-production models or some weird hanger attachment.

also thought it only worked on 2x systems, not enough take up capacity for a small inner ring. i dinna wanna lose the range and spacing. but this seemed to be a reg'lar 3x crank. think it was 22-30-40.

this appeared to be an ordinary long cage deore on a cheap-ish chinese bike. no time today to try it out, and anyway, bangkok is completely flat.

planning on returning to china next month, will have the time and money to try it out. just checked taobao and can get a 9spd 40T with some hanger extender thingy around $15. easy switch, can still use existing shifters. will have to see if i can find 9spd bigger'n 40T, and maybe a higher smaller cog than 11T.

i know i can do it, shirley i can!

Trevtassie

Sunrace do a 9 speed 11-40 cassette that works fine with an SGS Deore Derailleur. Stick a 20T front chainring on (you need to attack the bolts and spider with a file) and you get 12.9 on a 26" bike. With a 20-30-40 triple you get 725% spread.

saddlesores

interesting. seems no real need to get the 50T.
20:40=12.78 20:50=10.22
22:40=14.05 22:50=11.24

the 22:40 is ridable. 20:40 maybe. the 50's prolly not.

so deore sgs RD-M592 will set me back $30, and the sunrace 9spd 11-40 will be $15. i can use my microshift indexed shifters, and the current crank maybe. it's 22-32-44...will have to check if the 44 big ring will exceed capacity. maybe switch that to a 40.

bikenh

Gee, the smallest gear I've ridden was something like a 30x23 and that was on a 22-25% grade climb just on the west side of the state house in Frankfort, KY. I had 30 pounds of gear on me at the time and I was still riding along at 3-4 mph. I couldn't imagine riding such a small gear. The rpm at 3-4mph would be incredibly fast. Talking about getting nowhere fast.

saddlesores

fast rpm's? nah, just sit comfy and toodle up at 55-60 rpm. i timed myself on a 30km 8-10% climb, averaging 6.0 km/h, or 3.7 mph.

anyhoo, i'll be getting this bike i built a couple years ago. former owner moved, left it in china. built from taobao stuff and leftovers, and a schwinn frame from the seconds/rejected pile.

cyccommute 

Yes, it would be slow but not all that slow. Here's the gearing system assuming a normal mountain bike crank. At 90 rpm, the speed is about 3.5 mph which is still fast enough to keep the bike upright without too much skill.

According to the gear calculator above, a 30x23 gear at 60 rpm is going to move along at about 6 mph. That's hardly a fast cadence. To get to 3 to 4 mph, the rpm are going to be much slower.

I've ridden 16 inch gears at 3 to 4 mph and it's a pretty slow cadence. It's a lot easier than 30x23, however.

I've been wondering if this was possible. It's a stupid low gear but I like stupid lows. (Currently use a 20x11 or 15.5 inch gear)

edthesped

Yeah but it's only single front ring compatible no? I'm putting together a new bike and, as usual, want brifters and it looks like double cranks are my only options at this point and best I can find is that only a 34T max rear cassette is recommended with any of the new group sets. I have an 48/32 crank sitting in the garage and need to figure out how to pair it with at least a 36T cassette and preferably a 40T cassette.

saddlesores

https://www.wolftoothcomponents.com/products/roadlink

so this little doohickey moves the derailleur out to accommodate larger cogs up to 40T. does it affect the total capacity? suppose i could set the limit screws to not access the smallest two cogs.

indyfabz

I believe so. But haven't you heard? 1x drivetrains are the future of all bikes.

saddlesores

the mid-range chinese mtb that started this off had a triple with 11-spd 46T....

(now combine that with a 5-speed rear hub and a 3-speed internal bottom bracket......)

fietsbob

Unless in a recumbent trike at a certain gear development ,
you can gear so low you fall over..

or if you stop, get so short a distance up a hill ,
you cannot get your other foot on the pedal, before your momentum
is back to zero... or losing gained distance

I found this true when I put a mountain tamer quad, on an MTB..
16t chain ring and 'just' a 28t low gear cassette cog [0.57:1]

a 16:32 is 0.5:1 (1 pedal stroke, top to bottom, wheel turns a quarter rotation )




...

fietsbob

In Short, My bail out lowest climbing gear, touring, is 2 feet..

saddlesores

waitaminnit! the gear charts don't do 16T, but if you take any numerator and denominator and double them both, you get the same GI. right???

which means a 16:28 should be the same as a 32:56, which for a 45mm 26" tire would be 14.56 GI.

20:35=14.56
22:38=14.81

certainly beats your 24" low gear!

****

14-15" gear is rideable given a sufficient incline and ability to balance. i think the problem will be not torquing the rear so much you strip the grooves on the aluminium freehub body.

fietsbob

Ratio X wheel diameter. in inches.. gear inch (penny farthing big wheel)
wheel circumference says how far you go every time that wheel rotates

Development is as if that penny farthing wheel turns once ,
though the chain drive that is as if that size... unicycle..

4:1 52:13, 48:12, 44:11..





....

u235

I do rooted trail hills at 2-3 mph with 26/40 on my MTB. Traction is the limiting factor, not balance. Would a loaded touring bike be much different on a smooth surface that slow? I've never had to try. Maybe maintaining that speed on a loaded bike requires more coordination but the think the higher cadence should help.

CliffordK

One of the issues with those super sized rear cassettes plus a triple is a lack of chain wrap with the derailleur.



I think I'm running an 11/40 or 42 on the rear, and a 30/39/53 on the front. With an M8000 RD, I think.

I can get all but one gear combination, which I left off the Big/Big combo. I realize some people suggest a potential danger of hitting Big/Big, but I decided that would be more rare than other combos based on my cycling, and it turns out with the Shadow that the rear derailleur may not be damaged from over-stretching.

cyccommute 

Bull! Maybe you fall over but not everyone would. It takes only moderate skill to ride at very slow speeds without falling over and the more you practice, the easier it is to ride. I've ridden behind someone walking on a bike path while waiting for on-coming traffic to clear. They weren't walking fast either.

​​​​​​​
Again, it's not impossible to start at a low speed and still get your foot on a pedal. I've started on many a steep, unpaved hill on a mountain bike and continued up hill without falling over. It takes a little bit of timing and a bit more skill than riding slowly but it doesn't require superhuman abilities.

Perhaps you found it to be true but, again, that's you. I've had a quad with the 16 tooth chainring and a 34 tooth cog. That's in the 12" range that saddlesores is talking about. It takes more finesse than a 20x34 but not much more.

CliffordK

I've wondered about that.

Riding behind a person walking on the level, however, is very different from riding on a steep hill.

I do a fair amount of cargo hauling, and hills and heavy loads are a pain. I've realized that there are places&loads where walking is too fast... and I'd like to have the gearing to be able to ride slower than walking pace.

My next project will be a cargo/tow trike.

However, the power for an upright seems to be just somewhat greater than a recumbent, so I'll likely go with an upright.

Trevtassie

20 x 40 is easily rideable. I don't think 20/22-50 would be worth it. I'm a big one for low gears, means you can get up almost any hill at walking pace without grinding, I want my knees intact when I'm 80! SPD helps with restarting on steep hills, you can easily pull up on the clipped in pedal, because the gearing is low enough not to pull your foot out.
You might have a problem with the 44 front though, if you accidentally cross chain. The 592 will just do 20 to 40, the chain is pretty slack on 20-11 and pretty tight on 40-40.

saddlesores

riding at walking pace on a flat sidewalk with no baggage is pretty easy. ever walk past 90-yo retirees riding on a boardwalk?

much more difficult on the flats when loaded. strangely, riding at the same speed with the same load on an incline is much easier. if only we had a super-scientist who could explain the physics!

yes, starting on a steep hill is more difficult. i've never tried it clipped in.....imagine that would be almost impossible. but not that hard with platforms. if using toeclips, just ride on the "bottom" of the pedal, wait until you've built up some speed to try and flip it over.....or wait until you crest the hill.

saddlesores

looks like the 50 with tiny front rings won't make that much of a difference, or will be unridable.

exellent! now i've got a plan. i'll buy an 11:40 that includes the adapter thingy, and a 592 derailler.

then replace the rings (or buy a new cheap crank) with 20-30-38 (or 39).
that'll give me a sub-13 wall crawling gear, and still have a 96 (38:11) or 83 (39:13) top end. otherwise no use for the 11 and 13 cogs if 40T or higher.

suppose i could keep the 22-xx-40, but 14 GI won't be low enough.....will always be regretting i'd not gone with the 12.8!