Author Topic: Graphing gear inches from speed & cadence...  (Read 1390 times)

Graphing gear inches from speed & cadence...
« on: March 25, 2013, 07:53:40 am »
This may be way too geeky, but might interest some:  :facepalm:

I just posted a step-by-step guide to graphing gear inches by time or distance on my blog. It comes out with stuff like this (for a 200km brevet):



For instance, it shows I shouldn't worry much about gearing over 90" on a future brevet bike (but want to get the range from 60-85" on a single chainring if possible).  :thumbsup:

Manotea

  • Where there is doubt...
Re: Graphing gear inches from speed & cadence...
« Reply #1 on: March 25, 2013, 09:13:52 am »
Sorry EF, I Must have my thick head on today. This looks like it should be interesting but can you explain why it is, and how to read the graph?

Re: Graphing gear inches from speed & cadence...
« Reply #2 on: March 25, 2013, 09:21:50 am »
Sorry, I just realised there's no y-axis on that screen grab. Curses!

The graph shows the time (in seconds) spent riding at any given gear size during a 200km brevet. In this case you can see I spent about 4x as long riding at ~70" as ~90".

In fact, I hardly needed gearing higher than 90" (or smaller than 40") at all.

Although it looks semi-continuous if I could remember the block size and chainset on that bike, I suspect the peaks would correspond to gear combinations. If you're using a widely spaced cassette you could probably find the point(s) at which you change at the front and look at whether you're spending a lot of time on either side (i.e. more shifting than would be ideal).

Because there is quite a respectable efficiency gain from having a straight chain, there is some value in working out where you are actually riding in the block (although you could just take a look between your legs from time to time ;-)

LEE

Re: Graphing gear inches from speed & cadence...
« Reply #3 on: March 25, 2013, 10:38:21 am »
So there's a reason why people just say "go with a 72" gear" for fixed and SS then?

Re: Graphing gear inches from speed & cadence...
« Reply #4 on: March 25, 2013, 11:24:58 am »
72 inch seems to work for me about 90% of the time.I like EFs idea of a single chainring and say a 7 speed cassete.I think 40 inch would get me up most of the hills I encounter and unless you are racing or trying to keep up with your mates,you don't really need to go much above 90 inch either.I think bikes have become far too complicated.Just free wheel down the hills and relax with the tailwinds.

The next bike I buy may well be a hub gear,if someone could convince me of the reliability.

Kim

  • Timelord
Re: Graphing gear inches from speed & cadence...
« Reply #5 on: March 25, 2013, 12:42:47 pm »
That's quite interesting.  I don't have a cadence sensor (well, not for my Garmin), but I wonder how it would reflect my tendency to use low gears to accelerate from a standstill.  In the absence of bastard hills, I don't spend much time or distance in them, but they get used very frequently...
Careful, Kim. Your sarcasm's showing...

Re: Graphing gear inches from speed & cadence...
« Reply #6 on: March 25, 2013, 01:19:40 pm »
You could use a filter to trim out all the data points where you were in a gear higher than X", then do an x-y scatter of distance and gear size to see at which points of the ride you were in a low gear.

You could, obviously, then plotting distance against gradient on the same axes to superimpose the terrain profile.

LEE

Re: Graphing gear inches from speed & cadence...
« Reply #7 on: March 25, 2013, 02:12:24 pm »
72 inch seems to work for me about 90% of the time.I like EFs idea of a single chainring and say a 7 speed cassete.I think 40 inch would get me up most of the hills I encounter and unless you are racing or trying to keep up with your mates,you don't really need to go much above 90 inch either.I think bikes have become far too complicated.Just free wheel down the hills and relax with the tailwinds.

The next bike I buy may well be a hub gear,if someone could convince me of the reliability.

The hills I can't manage on 72" are what I'd deem "silly hills".  I'd happily have a "KISS" bike (Keep It Simple Stupid) with single chainring and 7/8 sprockets at the back.  A thumb shifter for reliability would make it pretty bomb-proof and dirt cheap.

a 42T chainring married to a 12-28 rear would give you around 95"-40" with 72" right in the middle somewhere.  Nice winter commuter setup

zigzag

  • unfuckwithable
Re: Graphing gear inches from speed & cadence...
« Reply #8 on: March 25, 2013, 02:27:17 pm »
i've been using 1x7 setup for pbp, lel, 1001miglia and many other long rides - not a single issue :thumbsup:

LEE

Re: Graphing gear inches from speed & cadence...
« Reply #9 on: March 25, 2013, 04:16:15 pm »
i've been using 1x7 setup for pbp, lel, 1001miglia and many other long rides - not a single issue :thumbsup:

I like that setup.  I have the parts to turn my Single-Speed Orbit into something similar, a 9-speed equivalent.

Re: Graphing gear inches from speed & cadence...
« Reply #10 on: March 25, 2013, 08:21:50 pm »
72 inch seems to work for me about 90% of the time.I like EFs idea of a single chainring and say a 7 speed cassete.I think 40 inch would get me up most of the hills I encounter and unless you are racing or trying to keep up with your mates,you don't really need to go much above 90 inch either.I think bikes have become far too complicated.Just free wheel down the hills and relax with the tailwinds.

The next bike I buy may well be a hub gear,if someone could convince me of the reliability.

The hills I can't manage on 72" are what I'd deem "silly hills".  I'd happily have a "KISS" bike (Keep It Simple Stupid) with single chainring and 7/8 sprockets at the back.  A thumb shifter for reliability would make it pretty bomb-proof and dirt cheap.

a 42T chainring married to a 12-28 rear would give you around 95"-40" with 72" right in the middle somewhere.  Nice winter commuter setup

Many decades ago when boys were boys and only the nobs (and flash racer types) had two chainrings the norm for a lot of us poor schoolboys was a 46T ring with 14-24 on the back (5 sprockets in those days). One of us who was keen on loaded saddlebag type stuff might have had a 14-28 (or a girl, like my sister who was also posh enough to have 2 rings, 46-49). 46/24 was sufficient to get up most hills and I found the 45" bottom on my sister's bike really low! How have I become such a wimp that in my old age I can need a 22T ring on a bike for touring!
I have run a mtb with a single 32T ring and a 7 speed 13-30 cassette which worked really well but really needed guides on the ring  because the chain jumped off from time to time on the 30 sprocket. Chain line wasn't too far out either. The gear range was fine for most off-road stuff.

Re: Graphing gear inches from speed & cadence...
« Reply #11 on: March 25, 2013, 11:30:11 pm »

Because there is quite a respectable efficiency gain from having a straight chain,
I'm a bit out of date on this one. The last lot of experiments I'm aware of (funded by HPVA, but I've mislaid the link to the report. It's about 10 years old) showed that chainline had no effect on efficiency, but small sprockets were inefficient. Do you have a reference for that assertion?

Apologies that I started with a negative reaction. Your graph was both intriguing and informative. Thanks for sharing it. It does make me wish I was 40 years younger ;).

simonp

  • Omnomnomnipotent.
Re: Graphing gear inches from speed & cadence...
« Reply #12 on: March 28, 2013, 12:21:05 am »
There is a reason people tend to mostly ride high 60s - low 70s fixed gears, it seems :)


citoyen

  • Cat 6 Racer
Re: Graphing gear inches from speed & cadence...
« Reply #13 on: March 28, 2013, 04:34:25 pm »
In fact, I hardly needed gearing higher than 90" (or smaller than 40") at all.

Thank you for this. I've often questioned why road bikes are geared as high as they are and usually get short shrift from people who think they actually have a use for a 120" top gear. I suspect most of them would find similar results to you if they actually measured their gear choices. Even proper racers have very limited need for gears that high.

citoyen

  • Cat 6 Racer
Re: Graphing gear inches from speed & cadence...
« Reply #14 on: March 28, 2013, 04:36:52 pm »
The hills I can't manage on 72" are what I'd deem "silly hills".  I'd happily have a "KISS" bike (Keep It Simple Stupid) with single chainring and 7/8 sprockets at the back.  A thumb shifter for reliability would make it pretty bomb-proof and dirt cheap.

Something like this really should be the default set-up for off-the-shelf hybrids.

Re: Graphing gear inches from speed & cadence...
« Reply #15 on: March 28, 2013, 04:50:55 pm »
I think zigzag uses this exact "quiche gears" setup for his long rides.
"Yes please" said Squirrel "biscuits are our favourite things."

fboab

  • It's a fecking serious business, riding a bike
Re: Graphing gear inches from speed & cadence...
« Reply #16 on: March 28, 2013, 05:16:35 pm »
In fact, I hardly needed gearing higher than 90" (or smaller than 40") at all.

Thank you for this. I've often questioned why road bikes are geared as high as they are and usually get short shrift from people who think they actually have a use for a 120" top gear. I suspect most of them would find similar results to you if they actually measured their gear choices. Even proper racers have very limited need for gears that high.
Two words: masher and flatlander.
I'd be very curious to see what our graph looks like. marcusjb said somewhere that he audaxes almost entirely in the middle ring. We ride almost entirely in the big, which currently is 50 (I prefer 52 on a solo). And mostly down towards the 11 tooth end, at that.
TSS is not Total Sex Score, Chris!

LEE

Re: Graphing gear inches from speed & cadence...
« Reply #17 on: March 28, 2013, 05:18:09 pm »
I think zigzag uses this exact "quiche gears" setup for his long rides.

See upthread about 7 posts

Re: Graphing gear inches from speed & cadence...
« Reply #18 on: March 29, 2013, 12:34:28 am »
On my way back.

I'm slow.

I'm not keeping up at the back.

Ta.
"Yes please" said Squirrel "biscuits are our favourite things."

Re: Graphing gear inches from speed & cadence...
« Reply #19 on: March 29, 2013, 06:52:32 am »
All this talk of 72 makes me feel well wussy. 67 in the summer 63 in the winter here, even when I lived in Cambridge. In fact I'm not convinced I'll move from 63 if summer comes. Span up to 55kph down hill yesterday, so don't feel completely hamstrung, and there are a few hills where I have to properly honk to get over the top.

citoyen

  • Cat 6 Racer
Re: Graphing gear inches from speed & cadence...
« Reply #20 on: March 29, 2013, 10:34:24 am »
Two words: masher and flatlander.

There are always going to be exceptions - I did say "most" rather than "all".

Personally, if I lived where you did, I would find a gear that gave me 32km/h @ 100rpm pretty much optimal. Assuming you're doing around the same speed in a 50x11 or 12 gear...  you must be doing less than 60rpm? Yikes. That is mashy.

Anyway, if that suits you, fine, but I really do think the vast majority of people ride bikes that are over-geared for their needs. Which is largely because that's how road bikes are sold.

simonp

  • Omnomnomnipotent.
Re: Graphing gear inches from speed & cadence...
« Reply #21 on: March 29, 2013, 04:29:13 pm »
All this talk of 72 makes me feel well wussy. 67 in the summer 63 in the winter here, even when I lived in Cambridge. In fact I'm not convinced I'll move from 63 if summer comes. Span up to 55kph down hill yesterday, so don't feel completely hamstrung, and there are a few hills where I have to properly honk to get over the top.

I started on 64" in 2008, then 67", then 71" (on which I rode the Bryan Chapman in 2011) then 75" on my Pompino. Now I’ve moved to Somerset and am commuting into Bristol, I find 67" about right again.

The 67" gear gets me up 1:6 gradients, but not much more. I have done 64kph on 67" and 67kph on 71"; both just shy of 200rpm. I don’t see speeds above 55kph on my commute generally.

I would not ride long distance above 70" again unless very flat. I ended up hurting my wrist on the Bryan Chapman, and I can spin reasonably well.

mattc

  • n.b. have grown beard since photo taken
    • Didcot Audaxes
Re: Graphing gear inches from speed & cadence...
« Reply #22 on: March 29, 2013, 05:32:22 pm »
Two words: masher and flatlander.

There are always going to be exceptions - I did say "most" rather than "all".

Personally, if I lived where you did, I would find a gear that gave me 32km/h @ 100rpm pretty much optimal. Assuming you're doing around the same speed in a 50x11 or 12 gear...  you must be doing less than 60rpm? Yikes. That is mashy.

Anyway, if that suits you, fine, but I really do think the vast majority of people ride bikes that are over-geared for their needs. Which is largely because that's how road bikes are sold.
I agree with Citoyen on this.

The 'more powerful' minority to which boab belongs could simply buy their cog of choice, while the other 95% of riders (especially those new to the sport, buying a bike off the shelf) would be better served.
Has never ridden RAAM
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