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Gear inches? Good and Bad

DonDaddyDDonDaddyD Posts: 12,689
edited September 2009 in Commuting chat
OK another silly question but with bike repairs and the purchasing of intricate parts comes a desire to understand.

So, I recently got a new cassette a 8speed 12 - 23. My big chain ring is a 53.

What is the average (so not Lit's) gear inch a person would normally commute in.

Right now:
I push off in my second cog a 53-21t (66.3inch),
Move up to the 3rd to cruise a 53-19t (73.3)
Then start my sprinting/riding fast in my 53-17t (81.9inch) - I certainly ain't spinning is this gear.

Is around 80inches the norm or the 'expected inch' for the average commuter on a roadbike?

Personally I think I need to go by MPH, but the holding thingy for my computer broke during transit of bike to the bike shop prior to repair :x
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A true scalp is not only overtaking someone but leaving them stopped at a set of lights. As you, who have clearly beaten the lights, pummels nothing but the open air ahead. ~ 'DondaddyD'. Player of the Unspoken Game

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  • Is this for getting yourself a fixie, or just out for knowledge?
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  • DonDaddyDDonDaddyD Posts: 12,689
    Just out for knowledge
    Food Chain number = 4

    A true scalp is not only overtaking someone but leaving them stopped at a set of lights. As you, who have clearly beaten the lights, pummels nothing but the open air ahead. ~ 'DondaddyD'. Player of the Unspoken Game
  • _Brun__Brun_ Posts: 1,740
    You should be riding in a gear which gives you a comfortable cadence. What particular gear that is is irrelevant.
  • Hi,
    It Depends.

    The gear you're in links your cadence to your road speed. Cadence is an individual thing, though it's sometimes claimed or observed that experienced riders tend to pedal faster.

    eg: POBSO riding Shopper 50-60rpm, leisure cyclist 60-70rpm, tourist/commuter 80-90rpm, fast roadie 100+ rpm.
    This is the sort of rough rule of thumb that doesn't bear close scrutiny!!

    Obviously road speed varies, too- that's why we have gears (well, some of us).

    So, if you like to spin, say, 90rpm and commute on flattish roads at, say, 18mph, you'd typically want a gear of about 67" . A less spinny rider, cruising downhill at 20mph might prefer 75rpm, and would then want a gear a little over 90".

    Is 80" the norm? I dunno. How normal are you, anyway :-). It seems a bit high to me, but bikes are often geared high- inexperienced riders like a low cadence and experienced riders like to go fast... Maybe I'm a bit wierd, cos I prefer to cruise at a fairly high cadence but I'm not fit enough to sustain 20+ mph.

    Cheers,
    W.
  • rolf_frolf_f Posts: 16,015
    DonDaddyD wrote:
    So, I recently got a new cassette a 8speed 12 - 23. My big chain ring is a 53.


    I push off in my second cog a 53-21t (66.3inch),
    Move up to the 3rd to cruise a 53-19t (73.3)
    Then start my sprinting/riding fast in my 53-17t (81.9inch) - I certainly ain't spinning is this gear.

    Hang on a mo - are you saying you start on your big chainwheel on your second biggest cassette sprocket? Surely that's going to be a pretty bad chainline which might explain some of your wear problems. What do you use the smaller chainwheel for?

    I'm not familiar with bikes with 2 chainwheels as my tourer and mtb both have three - normally I start in the middle cog and middle sprocket so expect to move between middle and big chainwheels as a matter of course. I'd assume the same would apply on a bike with 2 chainwheels.
    Faster than a tent.......
  • I might be being monstrously stupid here... but if you are in the big ring on the front and only the second/third on the back, does that not mean your chain is running quite skew?
  • DonDaddyDDonDaddyD Posts: 12,689
    Rolf F wrote:
    DonDaddyD wrote:
    So, I recently got a new cassette a 8speed 12 - 23. My big chain ring is a 53.


    I push off in my second cog a 53-21t (66.3inch),
    Move up to the 3rd to cruise a 53-19t (73.3)
    Then start my sprinting/riding fast in my 53-17t (81.9inch) - I certainly ain't spinning is this gear.

    Hang on a mo - are you saying you start on your big chainwheel on your second biggest cassette sprocket? Surely that's going to be a pretty bad chainline which might explain some of your wear problems. What do you use the smaller chainwheel for?

    When you say chainwheel I take it you mean chain-ring. In that case yes, yes and yes. I recently got a new 8speed cassette a 12-23 (I didn't have it before) my big ring is a 53. I didn't realise that my gear inches would be so high before I've even gotten into my fourth cog. With hindsight I probably would have gone with a 12 - 25.

    I'm running a triple and though loathe as I am to do so, I may use the middle ring.
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    A true scalp is not only overtaking someone but leaving them stopped at a set of lights. As you, who have clearly beaten the lights, pummels nothing but the open air ahead. ~ 'DondaddyD'. Player of the Unspoken Game
  • Rich158Rich158 Posts: 2,348
    I generally commute with about 81 gear inches, which does lead to a cadence on the slow side, generally about 70rpm. When I had a geared bike I would spin at a far higher cadence, typically about 100rpm.

    My philosophy towards the fixie and the GI I run is I want a hard gear on hills etc, to build leg strength, and something I can spin out downhill to work on leg speed, and a bit of resistance on the flat to encourage me to try and spin. 80 GI works for me at the moment, but I suspect that will change given time.

    Ultimately whatever works for you is fine, there's no hard and fast rule
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  • DonDaddyD wrote:
    I'm running a triple and though loathe as I am to do so, I may use the middle ring.

    Why are you reluctant to use the middle ring?

    There's no point having a 21 speed powertrain and restricting yourself to six gears, especially if the lower ones are inefficient and causing increased wear.

    There are various ways to set up your gear ratios, but with modern multi-speed setups, I think it's normal to have less overlap than in the past. You should be able to set up a close-ratio cassette and triple so that you can do most of your riding on the middle ring, instead of having to double-shift frequently. Move to the big ring for descending/tailwinds/SCR-sprints and use the small one for climbing & headwinds.

    You should find you can build up to a "better" cadence, get a quieter, more efficient chainline and reduce wear by doing so.

    If you prefer not to be seen without the chain on the biggest ring you have, then get a double, use a shorter BB axle and get your chainline sorted. If you bring the outer ring into line with the middle of your cluster you can use the whole range of sprockets with the big ring in normal riding, and just use the inner 'ring as a bail out gear with the largest few sprockets for hills....

    Cheers,
    W.
  • rolf_frolf_f Posts: 16,015
    DonDaddyD wrote:
    When you say chainwheel I take it you mean chain-ring. In that case yes, yes and yes. I recently got a new 8speed cassette a 12-23 (I didn't have it before) my big ring is a 53. I didn't realise that my gear inches would be so high before I've even gotten into my fourth cog. With hindsight I probably would have gone with a 12 - 25.

    I'm running a triple and though loathe as I am to do so, I may use the middle ring.

    Worse with a triple then - I remember when I got my Dawes (about 1990 - if you can remember that far back :lol: ) returning it for its 50 mile service and being told off by the mechanic for having run crossed chainlines - presume it must have distorted the derailleur slightly though it always seemed a bit hard to believe.

    I think if you have gears, you should use them. I can't imagine your small chain ring is much use in London but the others should be. I tend to regard the middle ring as flat cruise default and the big ring as downhill and fast cruise default. I have no objection to using the middle on the flat or slight uphills - especially if there are headwinds. If you only use the big one, you might as well ditch the front mech entirely!
    Faster than a tent.......
  • DonDaddyD wrote:
    I'm running a triple and though loathe as I am to do so, I may use the middle ring.

    Why are you reluctant to use the middle ring?

    There's no point having a 21 speed powertrain and restricting yourself to six gears, especially if the lower ones are inefficient and causing increased wear.

    There are various ways to set up your gear ratios, but with modern multi-speed setups, I think it's normal to have less overlap than in the past. You should be able to set up a close-ratio cassette and triple so that you can do most of your riding on the middle ring, instead of having to double-shift frequently. Move to the big ring for descending/tailwinds/SCR-sprints and use the small one for climbing & headwinds.

    You should find you can build up to a "better" cadence, get a quieter, more efficient chainline and reduce wear by doing so.

    If you prefer not to be seen without the chain on the biggest ring you have, then get a double, use a shorter BB axle and get your chainline sorted. If you bring the outer ring into line with the middle of your cluster you can use the whole range of sprockets with the big ring in normal riding, and just use the inner 'ring as a bail out gear with the largest few sprockets for hills....

    Cheers,
    W.

    In traffic I tend to stick to the 50T there is little point flicking between chainrings in traffic and london at least central, flicking between the chainrings I find is bit pointless.

    once out of town yes use those rings. in traffic I tend not to or you spend your life clicking though gears.
  • biondinobiondino Posts: 5,990
    For regular, neutral cruising I'd go for something in the mid-70s. My fixie is 72 and it's fine though a wee bit frustrating on slight downhills or with a tailwind. 50/18 would be about perfect.
  • What is the average (so not Lit's) gear inch a person would normally commute in.

    Sorry DDD but you're asking impossible questions today. As your last one boiled down to numerous factors including quality/cost/maintenance, so this boils down to preference adn to some extent, terrain. I run a 50x16 on my SS. My boss runs a 48x18. Run what ever gear feels right to you. If my commute involved hills i wouldn't run 50x16...
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  • CiBCiB Posts: 6,098
    Is it me? I thought having 20 gears [but not 20 ratios, we've done that] means that I can use whatever gear suits at any point on the journey. In 20+ miles going up & down and cruising on a billiard table of a road for some of the way pretty much all 20 of mine are used at various points, including occasionally dropping from the 53 to the 39 front ring whilst going up a couple of gears at the back to get a similar but slightly softer ratio.

    The answer to the question 'what's the average?' would be 'the middle one'. Cadence though is usually between 80 & 95.

    It took some time to convince my boys that they should change gear when they want to - there are no rules about what ratio suits any specific road condition - too many variables, including the boys themselves.

    <facetious mode>What gear do I commute in? Warm top now and a Ron Hill leggings from tomorrow...</facetious mode>

  • Sorry DDD but you're asking impossible questions today. As your last one boiled down to numerous factors including quality/cost/maintenance, so this boils down to preference adn to some extent, terrain. I run a 50x16 on my SS. My boss runs a 48x18. Run what ever gear feels right to you. If my commute involved hills i wouldn't run 50x16...

    Correct me if I'm wrong, but surely gear inches are a whole lot more then saying 48x16 etc... You and your boss could be running the same gear inches despite one being 50x16 and the other 48x18. But I do know what you mean :)

    My SS MTB runs about 56", I calculated 56" on my 27 geared MTB, but they both felt very different. Possibly lower weight, straight chainline and crank lengths might have had a big factor in that :wink:
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  • Eau RougeEau Rouge Posts: 1,118
    I'm the same as Chris, I tend to use all the gears, and often use the 50T with the 23T (largest) at the back without any problems, though I do go for a slightly lower 75-90 rpm cadence range. I'm not overly in love with changing the front gearing. I do change it if I need to, but if I can avoid it, I do.
  • Correct me if I'm wrong, but surely gear inches are a whole lot more then saying 48x16 etc...

    Hmm, only a little bit more: crank length makes a little difference and wheel size (including tyre) a bit more...
    You and your boss could be running the same gear inches despite one being 50x16 and the other 48x18. But I do know what you mean :)

    50x16 is around 84" whereas 48x18 is nearer 72... That's a pretty big difference.
    My SS MTB runs about 56", I calculated 56" on my 27 geared MTB, but they both felt very different. Possibly lower weight, straight chainline and crank lengths might have had a big factor in that :wink:

    Well, yes... that's part of the point of an SS/FG, isn't it? But the gear ratio is the same, even if it feels different because of the differences between the bikes.

    It's easier to push a 70" gear on my fixie than on my tourer, but it's still a 70" gear... and my cadence will be the same, if I'm doing the same speed.

    Cheers,
    W.
  • redddraggonredddraggon Posts: 10,862
    You and your boss could be running the same gear inches despite one being 50x16 and the other 48x18. But I do know what you mean :)

    50x16 is around 84" whereas 48x18 is nearer 72... That's a pretty big difference.

    You made a large assumption there though. You assumed the same wheel size and tyre width, which isn't necessarily true.
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  • rolf_frolf_f Posts: 16,015
    Why would you want to run big front, big rear though? It is surely less efficient and it isn't as though it is any harder to change gear with left than right. Doesn't bother me on my Dawes with downtube shifters even though only the rear is indexed.

    Yes, sometimes there is a need to change to middle and then drop down on the rear to compensate but that is only inconvenient on downtubes.
    Faster than a tent.......
  • redddraggonredddraggon Posts: 10,862
    Personally I've never found an issue with using Big-Big, although I only use it for short climbs. The chainline isn't that bad with a double (although it is with a Triple).

    However if you need big-big on the flat you aren't strong enough to be in the big ring.
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  • RoastieRoastie Posts: 1,968
    I find the aversion to shifting at the front interesting. I flick between the front rings quite a bit. When I rode with a 52/42, I actually used the 42 a great deal in London. Now with the MTB triple ( :oops: ) on The Pig, although I use the middle ring a lot less - it still gets in on the action a fair bit.
  • You and your boss could be running the same gear inches despite one being 50x16 and the other 48x18. But I do know what you mean :)

    50x16 is around 84" whereas 48x18 is nearer 72... That's a pretty big difference.

    You made a large assumption there though. You assumed the same wheel size and tyre width, which isn't necessarily true.

    I think Buns just assumed I'd taken that into account, which I had.

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  • KiblamsKiblams Posts: 2,423
    Surely gear ratio is a much better way of discussing the cadence relating to your chainring/sprocket size? For example on a MTB you can gave 22T:32T or 32T:22T; same inches but vastly different cadence.

    I run my commuter with a gear ratio of 44:16 (2.75) which is not far off your 53:19 (2.78)
  • redddraggonredddraggon Posts: 10,862
    Kiblams wrote:
    Surely gear ratio is a much better way of discussing the cadence relating to your chainring/sprocket size? For example on a MTB you can gave 22T:32T or 32T:22T; same inches but vastly different cadence.

    I run my commuter with a gear ratio of 44:16 (2.75) which is not far off your 53:19 (2.78)

    Have you taken into account wheel and tyre size difference between road and MTBs?
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  • You and your boss could be running the same gear inches despite one being 50x16 and the other 48x18. But I do know what you mean :)

    50x16 is around 84" whereas 48x18 is nearer 72... That's a pretty big difference.

    You made a large assumption there though. You assumed the same wheel size and tyre width, which isn't necessarily true.

    Hah! pedant!
    [ patronising tone ]
    Yes, I did. Well spotted. Did you notice which wheel size I'd assumed?

    Now, is it a reasonable (or large?) assumption?
    Let's assume that the boss has a 29er with 1.9" tyres (I think this is unlikely). His 48x18 will then give him a 74.3" gear. Let's further assume that BuckledRims is running Inch & a quarter slicks on 26" rims (more plausible), he'd then have a 76.5" gear.

    The difference would then be quite a bit smaller, and if they had radically different crank lengths, then the effective ratio might get pretty close.... but they still wouldn't be running the same "gear inches"....

    [/patronising tone]

    I think the point is sound, though I'll happily concede that if each of them happened to have the most extreme wheel+tyre sizes available, it's conceivable that they might end up with the same gear.... :-)

    Cheers,
    W.
  • KiblamsKiblams Posts: 2,423
    Apologies, I have just looked up gear inches and my post was most ignorant. Had not considered that it might take size of wheels into consideration. (is the MTBer in me using our simple ways :P )
  • Kiblams wrote:
    Surely gear ratio is a much better way of discussing the cadence relating to your chainring/sprocket size? For example on a MTB you can gave 22T:32T or 32T:22T; same inches but vastly different cadence.

    Umm, no: sorry: Assuming a nominal 26" wheel, the 22:32 would be 22/32 * 26 = 18" (eek!) whereas the 32:22 would be 32/22 * 26 = 38".
    I run my commuter with a gear ratio of 44:16 (2.75) which is not far off your 53:19 (2.78)

    Yes, not far off, assuming the same wheel size.

    Cheers,
    W.
  • Stuey01Stuey01 Posts: 1,273
    Kiblams wrote:
    For example on a MTB you can gave 22T:32T or 32T:22T; same inches but vastly different cadence.

    err, no.

    22:32 = 36.2 inches

    32:22 = 17.1 inches

    assuming a 26" wheel with 1.5" tyre, and 170mm cranks for both calculations

    EDIT: beaten to it by poster above.
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