Author Topic: Touring gears - lowest inch's  (Read 8830 times)

Kim

  • Timelord
    • Fediverse
Re: Touring gears - lowest inch's
« Reply #50 on: 20 October, 2011, 12:29:02 pm »
Fair point.  I was coming at it from the perspective of a 155mm crank user, which is different enough to be worth calculating for.

mattc

  • n.b. have grown beard since photo taken
    • Didcot Audaxes
Re: Touring gears - lowest inch's
« Reply #51 on: 20 October, 2011, 12:35:15 pm »
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.
Has never ridden RAAM
---------
No.11  Because of the great host of those who dislike the least appearance of "swank " when they travel the roads and lanes. - From Kuklos' 39 Articles

Biggsy

  • A bodge too far
  • Twit @iceblinker
    • My stuff on eBay
Re: Touring gears - lowest inch's
« Reply #52 on: 20 October, 2011, 12:41:43 pm »
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.
●●●  My eBay items  ●●●  Twitter  ●●●

Re: Touring gears - lowest inch's
« Reply #53 on: 20 October, 2011, 01:16:38 pm »
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.

Biggsy

  • A bodge too far
  • Twit @iceblinker
    • My stuff on eBay
Re: Touring gears - lowest inch's
« Reply #54 on: 20 October, 2011, 01:20:00 pm »
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
●●●  My eBay items  ●●●  Twitter  ●●●

Re: Touring gears - lowest inch's
« Reply #55 on: 20 October, 2011, 01:27:30 pm »
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.

Biggsy

  • A bodge too far
  • Twit @iceblinker
    • My stuff on eBay
Re: Touring gears - lowest inch's
« Reply #56 on: 20 October, 2011, 01:32:32 pm »
Mechanical advantage ?

Good, except by itself may be confused with the mechanical advantage of brakes and other things.
●●●  My eBay items  ●●●  Twitter  ●●●

Kim

  • Timelord
    • Fediverse
Re: Touring gears - lowest inch's
« Reply #57 on: 20 October, 2011, 01:35:54 pm »
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!

Biggsy

  • A bodge too far
  • Twit @iceblinker
    • My stuff on eBay
Re: Touring gears - lowest inch's
« Reply #58 on: 20 October, 2011, 01:50:35 pm »
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.
●●●  My eBay items  ●●●  Twitter  ●●●

Biggsy

  • A bodge too far
  • Twit @iceblinker
    • My stuff on eBay
Re: Touring gears - lowest inch's
« Reply #59 on: 20 October, 2011, 01:57:39 pm »
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.
●●●  My eBay items  ●●●  Twitter  ●●●

Re: Touring gears - lowest inch's
« Reply #60 on: 20 October, 2011, 02:00:51 pm »
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.

mattc

  • n.b. have grown beard since photo taken
    • Didcot Audaxes
Re: Touring gears - lowest inch's
« Reply #61 on: 20 October, 2011, 02:03:13 pm »
(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 ...
Has never ridden RAAM
---------
No.11  Because of the great host of those who dislike the least appearance of "swank " when they travel the roads and lanes. - From Kuklos' 39 Articles

Re: Touring gears - lowest inch's
« Reply #62 on: 20 October, 2011, 02:07:04 pm »
Same goes for wheel size, one number is used for 700c/27in and 20-35mm.

Kim

  • Timelord
    • Fediverse
Re: Touring gears - lowest inch's
« Reply #63 on: 20 October, 2011, 02:07:43 pm »
(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.

Biggsy

  • A bodge too far
  • Twit @iceblinker
    • My stuff on eBay
Re: Touring gears - lowest inch's
« Reply #64 on: 20 October, 2011, 02:09:26 pm »
(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.  :(
●●●  My eBay items  ●●●  Twitter  ●●●

Biggsy

  • A bodge too far
  • Twit @iceblinker
    • My stuff on eBay
Re: Touring gears - lowest inch's
« Reply #65 on: 20 October, 2011, 02:16:08 pm »
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!
●●●  My eBay items  ●●●  Twitter  ●●●

Jobro

  • Trice TNT
Re: Touring gears - lowest inch's
« Reply #66 on: 20 October, 2011, 06:33:11 pm »
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!

Biggsy

  • A bodge too far
  • Twit @iceblinker
    • My stuff on eBay
Re: Touring gears - lowest inch's
« Reply #67 on: 20 October, 2011, 06:35:33 pm »
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:
●●●  My eBay items  ●●●  Twitter  ●●●

jogler

  • mojo operandi
Re: Touring gears - lowest inch's
« Reply #68 on: 20 October, 2011, 06:37:43 pm »
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

interzen

  • Venture Altruist
  • Agent Orange
    • interzen.homeunix.org
Re: Touring gears - lowest inch's
« Reply #69 on: 20 October, 2011, 06:44:18 pm »
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:-)

Re: Touring gears - lowest inch's
« Reply #70 on: 20 October, 2011, 10:58:27 pm »
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!

Re: Touring gears - lowest inch's
« Reply #71 on: 21 October, 2011, 01:45:52 pm »
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.)
Move Faster and Bake Things

Re: Touring gears - lowest inch's
« Reply #72 on: 21 October, 2011, 08:44:09 pm »
12" gear on my ice adventure too  :thumbsup:.
the slower you go the more you see

Re: Touring gears - lowest inch's
« Reply #73 on: 21 October, 2011, 10:44:11 pm »
How low can the Schlumpf Mountain Drive go?

Frere

interzen

  • Venture Altruist
  • Agent Orange
    • interzen.homeunix.org
Re: Touring gears - lowest inch's
« Reply #74 on: 21 October, 2011, 10:45:46 pm »
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