Yet Another Cycling Forum
General Category => The Knowledge => Topic started by: Domestique on 13 October, 2011, 09:03:29 pm
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I have been looking at using an Alfine 11 build in a future touring bike but lowest gear is going to be 25.8"
Thats using a 38x20 set up om 26x50mm wheel/tyre set up.
My Aravis has a lowest gear of 22.1"
I can not ever remember being in the lowest gear other than to make sure the gears worked.
Just wondered what evryone else was using and if the thought is its not low enough for fully loaded touring.
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I've read that for loaded touring it's advisable to have at least a 1:1 drive, and ideally 2 or 3 lower. I've no idea how this translates to gears-inna-can though ???
Edit: actually I'm being dumb, isn't a 26" wheel with 1:1 drive give a 26" gear? so you're not far off.
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My set up is 44/32/22 and 11/34, with rather big and fat tyres so I would say 28". That should give me a 18" gear as my lowest, with that I have managed a few 1/4 hills fully loaded.
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My Alfine-11 rig has a bottom gear of 24.6" (36x20, 26" wheels) which can get me up pretty much anything, loaded or not and, so far, the rear hub still contains cogs and sprockets rather than mangled swarf. The 1st gear on the Alfine is intended as a 'bailout' anyway, as the gap between 1st and 2nd is rather larger than the gaps between the other gears.
Back in the days when I was riding silly mileages, one of my bikes had a bottom gear of 20x32 (16.7") but in all honesty if I had to engage it I was probably better off walking anyway.
I'd say that a bottom gear of sub-26" is sufficient.
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How to tell a London commuter: he chooses a cog that gives his 8 speed Alfine a 45" bottom gear, and 118 top. And then never runs out of gears. Don't think I'll take it touring, though.
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My Thorn Raven tour is running 44 x 16 on a Rohloff and 26"x2" tyres which gives a range of about 20" - 105". It goes up most hills but this double chevron (http://www.bing.com/maps/?v=2&cp=51.13391953630505~-0.7584131298385488&lvl=15&dir=0&sty=s&eo=0&form=LMLTCC) managed to beat me a couple of weeks ago, though! Fortunately it's not a long walk, just a very abrupt one that's hard to take a run at despite the opposing single chevron, due to bends, trees, and consequent lack of visibility.
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There's nothing you can't do with a 19" gear, if you lie back and think of Wowbagger...
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There's nothing you can't do with a 19" gear, if you lie back and think of Wowbagger...
;D :thumbsup:
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I'm currently deciding whether to fit the smaller chainset - which would give a 19" bottom gear, or whether I'll be ok fully loaded in Scotland with a 24" ???
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I have a 22t chaining and a 32t sprocket driving a 26x1.5 shod rear wheel. Fully laden I have resorted to the occasional walk. :-\ ;D
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I'm currently deciding whether to fit the smaller chainset - which would give a 19" bottom gear, or whether I'll be ok fully loaded in Scotland with a 24" ???
I remember 20% grades in Scotland, and being quite glad to have a 16" bottom gear. I guess it depends on how fit you are and how heavy "fully loaded" is.
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Rohloff 18".
I've used it on a camping trip, trying to get up some Devon & Dorset hills with full panniers.
However, it gets to the point where you are trying not to wheelie so you'd need front panniers to get any benefit of anything lower. Pedalling a low gear still beats walking and, as I found out, it can actually be harder to push a loaded bike up a very steep hill in cleats.
When my chainring wears out I'll gear it up a bit since I think I've only used 1st gear a couple of times in 10,000 miles.
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Rohloff 18".
I've used it on a camping trip, trying to get up some Devon & Dorset hills with full panniers.
However, it gets to the point where you are trying not to wheelie so you'd need front panniers to get any benefit of anything lower. Pedalling a low gear still beats walking and, as I found out, it can actually be harder to push a loaded bike up a very steep hill in cleats.
When my chainring wears out I'll gear it up a bit since I think I've only used 1st gear a couple of times in 10,000 miles.
You just need to do some more touring ;)
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Personally I wouldn't want a bottom gear higher than 24" on a loaded tourer. But each to his/her own.
Swap the chainset/chainring/sprocket to lower the gears if the bike doesn't come with what you want. Customise!
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Gone for 20 -105 on the Moulton tandem with a Rohloff. Don't think I could keep my balance on a gear any lower! On a solo the front wheel lifting becomes a problem.
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I think I'd always want a gear at around the 20" for hard alpine passes and stupid steep.
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Regarding hub gear manufacturer quoted low-gear limits, to prevent damage from excessive torque:
I reckon these can be taken with a pinch of salt. For instance, why does it matter if you have a gear lower than the "limit" if you only ever pedal smoothly with it, never honk with it, applying no more force than you do with higher gears?
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Regarding hub gear manufacturer quoted low-gear limits, to prevent damage from excessive torque:
I reckon these can be taken with a pinch of salt. For instance, why does it matter if you have a gear lower than the "limit" if you only ever pedal smoothly with it, never honk with it, applying no more force than you do with higher gears?
Because the lower the gear the higher the internal torques given the same input force.
Think of a really really low gear (i.e. equivalent to 1"). You can still put in the same pedal force but the torques inside the hub gear would be so large they could rip the metal teeth off the hub/planet gears or twist the axle itself.
Somewhere between a 40" gear and 1" gear you'd get to a point where the internal torques could be too much for the weakest part of the hub gear, so they set a lower limit on the gear. Obviously they'll have some leeway in there, but not as much as you'd think.
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Ah, ok. That's fair enough. It still would be possible though to pedal softly enough* for there not to be too much torque inside the hub - though of course this would have limited use in practice.
* More softly than what is designed for with the usual gears.
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On a solo the front wheel lifting becomes a problem.
Unless you're lying down on the job. Then the problem becomes getting moving again if you ever stop, especially if the surface is slippery. In the absence of a brake lever on the rear rack to facilitate pushing, my preferred technique is to slow right down but to only stop for badgers ;D
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Sometimes the only thing that gets me up a hill is the certain knowledge that if I stop I won't be able to start again. And sometimes what prevents me getting up a hill is the feeling that I'm going so slowly and wobbling so much I'm about to topple over. A pinch of balance is worth a pound of gears in my case, or would be if I had it. Now I suppose I should go and measure my gears.
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They're linked though - it's much easier to balance if you're pedalling more evenly (which usually equates to a higher cadence and lower gear), especially if your bike is arranged such that pedalling reaction force is delivered through the steering controls.
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Personally I wouldn't want a bottom gear higher than 24" on a loaded tourer. But each to his/her own.
Swap the chainset/chainring/sprocket to lower the gears if the bike doesn't come with what you want. Customise!
Indeed. I'll run anything for a lowest gear on my tourer between 26x28 and 30x25. Just depending on the terrain. But don't forget to change the middle ring if you drastically change your small ring. Just to make the steps a bet evener. I either run 50/40/30 or 50/39/26. Should I want to run a 24 small ring I'd probably change to 50/38/24. But that would need a swap from Campag to Shimano compatible cranks.
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My choices are between 48-38-28 and 42-32-22 (Paired with an 11-32 cassette). I'll probably fit the latter if I get round to it this weekend. I'm just not sure how happy the front mech is going to be with a 22t ring, and I can see this being fiddly.
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My choices are between 48-38-28 and 42-32-22 (Paired with an 11-32 cassette). I'll probably fit the latter if I get round to it this weekend. I'm just not sure how happy the front mech is going to be with a 22t ring, and I can see this being fiddly.
If it's a braze-on mech, it could be a bit iffy. With a clamp on I see no big problems, the difference between smallest and largest stays 20 teeth.
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I use 50-36-24 with an 11-30. But the 11t sprocket isn't usable, so it's effectively a 13-30 7-speed. Works well for all my purposes.
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Definitely 20" or less if loaded and in hilly places. I use my 17" every weekend with only a light load, I am a spinner though.
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Looks like some fettling may be on order then :)
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Just checked with Sheldon. My gear range is 21.4-102.9"
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All you need to remember to work out gear inches is: chainring divided by sprocket, times tyre size. Hard wire that in your grey matter.
Some popular tyre sizes:
700x20C = 26.1" = (622 + 20 + 20) / 2.54
700x23C = 26.3"
700x25C = 26.5"
700x28C = 26.7"
700x32C = 27"
700x35C = 27.2"
26x1.3" = 24.6" = (559 / 2.54) + 1.3 + 1.3
26x1.5" = 25"
26x1.75" = 25.5"
26x2.1" = 26.2"
26x2.5" = 27"
(Not accounting for real-world variations and squashage, but near enough for general comparison purposes)
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All you need to remember to work out gear inches is:
here: Clicky (https://market.android.com/details?id=org.bikecalgary.fixedgears&hl=en)
Biggsy's sums are hard.
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It's dead easy with a calculator, and if you approximate the tyre size. 27" will do for 700C.
What about when you wake up in the middle of the nght with a gear customisation idea, but no computer?
Oh, just me, is it? :-[ :D
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It's easiest of all with Sheldon Brown's gear calculator (http://www.sheldonbrown.com/gears/) :D
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It's dead easy with a calculator, and if you approximate the tyre size. 27" will do for 700C.
What about when you wake up in the middle of the nght with a gear customisation idea, but no computer?
Oh, just me, is it? :-[ :D
It's just you. I'd never go to bed without at least a smartphone handy.
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I do gear calculations in my head as I ride along sometimes. And yeah, Biggsy, sometimes when I lie in bed awake. You're not alone.
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You people relying on the internet for simple sums. ::-)
What are you going to when World War III starts and all the interwebs are down? :D
I just got a smartphone today, by ze way. :thumbsup:
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My link's for an android app. It's not online.
only you can tell us what it's like without t'interweb, you're the one with the BlackBerry, Biggsy
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Replying from BB now. :P
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I do gear calculations in my head as I ride along sometimes. And yeah, Biggsy, sometimes when I lie in bed awake. You're not alone.
So do I. It distracts me from thinking about the gradient.
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Lowest gear on my tourer is 18.5"
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thank god for this thread, i thought i was going soft cos I was struggling last time out with panniers. Turns out my lowest gear is 27", I might need to fit a triple :)
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Kim seems to think I pack a solid 19". Rohloff, 42--->16, 26" * 1.5". She might be flattering me a little.
Having said that, Mrs. Wow and I once rode up this hill:-
http://www.streetmap.co.uk/map.srf?X=271037&Y=68730&A=Y&Z=120
on the tandem, which would have been 46--->16, 26" * 1.75", which must be slightly bigger - perhaps 22"?
This just goes to show that I'm more impressive with Mrs. Wow's help than I am on my own. This particular performance was witnessed by a car-full of children who applauded roundly when we climaxed.
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Actually about 20"
Oddly, Sheldon's calculator doesn't have a 26x1.75 option, but 1.9 gives 20.9" and 1.5 gives 19.9" Still bigger than you have by yourself.
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Edit: actually I'm being dumb, isn't a 26" wheel with 1:1 drive give a 26" gear? so you're not far off.
Not sure if it right or not, but isnt it the circumfrance of the wheel rather than the diameter
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No, the diameter of the wheel (or tyre rather) dictates the gear. That's why penny farthings have such a large main wheel - to get a usefully large "gear" when there's not the usual chain and sprockets.
The circumference is used by a cycle computer to calculate distance. I guess this is what you're thinking of.
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No, the diameter of the wheel (or tyre rather) dictates the gear. That's why penny farthings have such a large main wheel - to get a usefully large gear when there's not the usual chain and sprockets.
The circumference is used by a cycle computer. I guess this is what you're thinking of.
Thank you Biggsy :thumbsup:
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Thinking about it..... Since circumference is of course directly related to diameter, you could use circumference inches as units for comparing gears if you like. We just commonly use diameter inches because it's easier to visualise, and because it gives nice short chunky numbers (when rounded to the nearest 0.1", which is good enough).
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Diameter is used purely to give your brain an easy reference (when compared to a direct-drive wheel, like a Penny Farthing).
An 18" "granny gear" is like pedalling a Penny Farthing with an 18" diameter front wheel (getting close to the radius of your cranks)
You can use circumference as a comparison if you like but it's harder to visualise.
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And of course the problem with gear inches is they don't take into account the crank length. My 19" bottom gear gives a gain ratio closer to 20" with a 170mm crank.
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A 5mm difference in crank length makes a such a small difference to the gear that I forget about it unless being particularly fussy. But I would switch to gain ratio units when comparing gears with more crank difference than 5mm. YMMV.
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Fair point. I was coming at it from the perspective of a 155mm crank user, which is different enough to be worth calculating for.
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A 5mm difference in crank length makes a such a small difference to the gear that I forget about it unless being particularly fussy. But I would switch to gain ratio units when comparing gears with more crank difference than 5mm. YMMV.
... and most people ride with the same crank length across bikes.
Somewhat OT:
Apparently it's a big issue on the track, and in gear-limited formulae such as junior races. IIRC the "inches" figure is usually what is limited, so for fast riders their spin-fu is the limiting factor, not fitness. So (I think) shorter cranks help them ride faster, cos their feet travel less far.
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That is really dumb for track race organisers not to take crank length into account, because details are important in the competitive world.
Shorter cranks make the gear higher, and may be more ergonomical for riders with shorter legs, and provide greater ground clearance.
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Thinking about it..... Since circumference is of course directly related to diameter, you could use circumference inches as units for comparing gears if you like. We just commonly use diameter inches because it's easier to visualise, and because it gives nice short chunky numbers (when rounded to the nearest 0.1", which is good enough).
That'll be gear development, in metres, as used on the continent. It's the distance travelled in one pedal rev.
Re crank length, isn't that a gear ratio never takes crank length into account coz for a given ring x sprocket and wheel size, it's always the same gear regardless of crank length.
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Re crank length, isn't that a gear ratio never takes crank length into account coz for a given ring x sprocket and wheel size, it's always the same gear regardless of crank length.
Yes. It's just that a gear is no use without a crank to drive it, hence the desire to account for crank length as well.
I suppose it's technically incorrect to say that crank length affects the gear, but I can't think of another one or two-word term that everyone will understand
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Re crank length, isn't that a gear ratio never takes crank length into account coz for a given ring x sprocket and wheel size, it's always the same gear regardless of crank length.
Yes. It's just that a gear is no use without a crank to drive it, hence the desire to account for crank length as well.
I suppose it's technically incorrect to say that crank length affects the gear, but I can't think of another one or two-word term that everyone will understand
Mechanical advantage ?
Long cranks are long lever arms, move further at a lower instentaneous reather than short cranks move less distance at a greater load. However as mentioned above a short crank enables the feet to travel less distance and therefore the posibility of a higher cadence.
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Mechanical advantage ?
Good, except by itself may be confused with the mechanical advantage of brakes and other things.
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Mechanical advantage ?
Good, except by itself may be confused with the mechanical advantage of brakes and other things.
Where's the confusion? It's the same thing!
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The context could be confused, without an introduction that I'm talking about gears and cranks, etc. Suddenly mentioning "mechanical advantage", you might think I'm talking about brakes or something else.
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In other words, it's not specific enough. Nor is "gear" when it may or may not be including the crank length factor.
I can't think of a brief term that is not-too-techy but also not-too-technically-wrong that people with only a moderate amount of bike knowledge would understand.
I appreciate that the majority of YACFers have more knowledge than that, but I like to include the minority as well - to make as many posts as possible unstandable by as many people as possible, within reason, and within what doesn't seem too boring or patronising. It's not easy.
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My lowest is about 18.5" (22 chainring /32 sprocket *700x28) [edit: with 175mm cranks] There have been several times I wished I had lower gears, but fitting a 34t sprocket is about as low as it can go I think!
As previous posts though, it depends how quickly you like to spin the cranks.
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(with apologies to Kim and her ilk,) the 170mm crank has such dominance that this isn't really an issue, at least not worth introducing more jargon for, anyway.
(Riders that have gone to the trouble of using much shorter cranks are probably quite used to correcting for the sloppy terminology of the masses.)
Whether 170mm should be so dominant is a different debate ...
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Same goes for wheel size, one number is used for 700c/27in and 20-35mm.
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(Riders that have gone to the trouble of using much shorter cranks are probably quite used to correcting for the sloppy terminology of the masses.)
Agreed. I'd also suggest that by the time you're nerding about gear ratios, learning about the different ways of expressing them comes naturally.
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(with apologies to Kim and her ilk,) the 170mm crank has such dominance that this isn't really an issue, at least not worth introducing more jargon for, anyway.
I would agree for the bike-owning population altogether, but not quite for YACFers. I'm beginning to wish I hadn't mentioned the jargon thing though. A new term is bound not to stick, even if we come up with a good one. :(
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Same goes for wheel size, one number is used for 700c/27in and 20-35mm.
Not by everyone, but yes this is another source of confusion and inacuracy.
There's a 1.1" difference between 700x35 and 700x20, for example. (See table on page 2 of this thread).
ps. Apologies for being so geeky today on the forum. I've taken a bit too much of my medication!
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I'm always amazed at the height of the bottom gears people use! My Trice TNT (20" wheel, 152 mm cranks) has a bottom gear of 12 inches and I find this a great comfort on our Cornish hills. Perhaps if I was a big strong, young rider........... but I'm not!
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We don't all have three wheels to assist with balancing at the speed you go at. ;)
Welcome to the forum, by the way, Jobro. :thumbsup:
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I'm always amazed at the height of the bottom gears people use! My Trice TNT (20" wheel, 152 mm cranks) has a bottom gear of 12 inches and I find this a great comfort on our Cornish hills. Perhaps if I was a big strong, young rider........... but I'm not!
marj's ICE trike has a bottom gear of 14" which has seen action in the Peak District
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I'm always amazed at the height of the bottom gears people use! My Trice TNT (20" wheel, 152 mm cranks) has a bottom gear of 12 inches and I find this a great comfort on our Cornish hills. Perhaps if I was a big strong, young rider........... but I'm not!
marj's ICE trike has a bottom gear of 14" which has seen action in the Peak District
Surprised nobody's mentioned the Schlumpf Mountain Drive yet O:-)
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It's dead easy with a calculator, and if you approximate the tyre size. 27" will do for 700C.
What about when you wake up in the middle of the nght with a gear customisation idea, but no computer?
Oh, just me, is it? :-[ :D
It's just you. I'd never go to bed without at least a smartphone handy.
I keep a sliderule by the bed just in case. It's better for the environment, less trees to cut down and no power consumption.
By the way my 23 section tyres come out at 26.35", I always calculate with 26.4". I can't remember what I use for the 26"x1.5s and I never bother to calculate for mtb tyres, whatever the gear is it's never the right one!
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With a 20kg load I accomplished the touring raid Pyrenean with 20" bottom gear on 26*1.75 slicks and 175mm cranks. I had a cycle computer that gives gradients and the steepest encountered was 22% with 11% being fairly typical. After a day or two I reached the point when a 7% climb was when it got easy.
In 2010 I did the 4 day version unloaded with quite a low gear, say 25" on a 700c wheel and 170mm cranks. I thought it'd be easier but it wasn't! (possibly because it rained every day with snow showers on the Col du Tourmalet. My shoes were wet through most of the time.)
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12" gear on my ice adventure too :thumbsup:.
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How low can the Schlumpf Mountain Drive go?
Frere
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How low can the Schlumpf Mountain Drive go?
Frere
It reduces the gearing by 2.5x when engaged - how low do you want it to go? ;)
http://schlumpf.ch/hp/md/md_engl.htm
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Just had a look - seems it can be used with a Rohloff, am getting my mind around that combination.....
As forumers might advise, cold shower time? :P
Frere
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Following the last post (phone doesn't do quotes) - is this becomming a gear limbo competition?
I've currently got an 18.7" gear on my bike, and I've got more use out of it than I expected so far. I'm glad I didn't try this with the bigger chanrings.
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Just had a look - seems it can be used with a Rohloff, am getting my mind around that combination.....
As forumers might advise, cold shower time? :P
Frere
The clutch on the new versions is fixed-friendly too .... S3X + mountain drive? ;D
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I've got 18 at the front and 32 at the back on a 26" wheel, so that's about 14 and a half inches, but it is on this (http://www.tandem-club.org.uk/nf2002/2005-07/post/p050731z.jpg).
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I'm seriously considering a range of 12.3" to 133.3 on my new bike.
My excuse is that I can't get off and push up any hills, because I'd need both hands for the crutches, and wouldn't have one free to push the bike with.
I still need to find out if I can actually balance at 1.5mph uphill on a 'bent bike.
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Just had a look - seems it can be used with a Rohloff, am getting my mind around that combination.....
As forumers might advise, cold shower time? :P
Paging Tigerbiten. Tigerbiten to the ridiculously low-geared courtesy phone please...
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I'm currently debating whether or not to email Florian Schlumpf and ask him if the Mountain Drive is Pugsley-friendly - I suspect not, since the Pug has a 100mm BB shell, but the only harm in asking is potentially to my bank balance ;)
The current prize for Most Utterly Ridiculous Low Gear probably goes to a fellow of my acquaintance who has (or had, not seen him in ages) a Greenspeed trike fitted with, amongst other things, an SRAM 3x7 and a Mountain Drive. His lowest gear, with the MD engaged, was 7" ...
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7" is awesome, that should get a trike up 45% inclines?
Frere
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I've got 18 at the front and 32 at the back on a 26" wheel, so that's about 14 and a half inches, but it is on this (http://www.tandem-club.org.uk/nf2002/2005-07/post/p050731z.jpg).
That's an impressive rig! I thought at first glance it was tandem + tagalong + trailer, rather than triplet + trailer, but either way it's heavy haulage of the cycle world. And it looks so gloriously happy. :thumbsup:
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at first glance it was tandem + tagalong + trailer, rather than triplet + trailer
Tried that when sprog number two came along. It's not to be recommended as the trailer tries to overtake the bike when going down hill. The only way out is to accelerate!
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CamPhil, I think you are being a bit pessimistic to think you will be climbing at 1.5 mph! A brief seance with my calculator shows 12" gear produces 3.5 mph at 100rpm - a result the more convincing 'cos thats what I see in practice. I get Steep hill: 4mph, Very Steep hill: 3.5 mph, Very Steep long hill 3.5 mph with frequent stops for gasping....
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I had this thread in mind last weekend when I was in a hilly place with my Rohloff lowest gear 17". I was spinning doing about 5.5Km/hr in the lowest gear, I rarely honk. I get off & walk if my speed drops to 5 Km/hr and looks like staying there.
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I'm waiting for someone to say they've got a reverse gear.
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According to http://www.kreuzotter.de/english/espeed.htm (http://www.kreuzotter.de/english/espeed.htm), on a 33% gradient (the steepest you'll ever see on-road, you would need to output about 400watts to got 3mph. It drops to 320W for a 25% slope.
For ordinary mortals like me, that's anaerobic sprinting output. So regardless of the gear, you are going to struggle to keep up 3mph up a really really steep hill. Zig-zagging to reduce the effective gradient can help.
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CamPhil, I think you are being a bit pessimistic to think you will be climbing at 1.5 mph! A brief seance with my calculator shows 12" gear produces 3.5 mph at 100rpm - a result the more convincing 'cos thats what I see in practice. I get Steep hill: 4mph, Very Steep hill: 3.5 mph, Very Steep long hill 3.5 mph with frequent stops for gasping....
That 1.5mph is with 155mm cranks, and based on cadence falling to 40rpm.
Obviously, if I can keep up >60rpm, I will, but power output may be the limiting factor, as noted by mrcharly.
Both the bike (Barcchetta Cafe, needing modification for me) and the dual-drive are on order, so we'll see.
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I'm waiting for someone to say they've got a reverse gear.
;D
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That'd be everyone riding fixed, surely? ;D
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The gear range on the new Trike goes from ~10" to ~130".
I was thinking of useing a Mountain Drive on the new trike but ended up useing the the High Speed Drive at it made the build a lot easier to get that range useing standard parts.
The bottom 3 gears are really below the Rolhoff min spec of 14", so I try not to use them .......... ;D