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Thread: Cranks

  1. #1
    Grumpy Old Bugga europa's Avatar
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    Cranks

    I see a lot of talk about shorter cranks and the benefits that some people get.

    Here in Oz, they only stock the 'normal' sizes ie, 170 and upwards.

    Any suggestions on brand names and where to get the things?

    Then the eternal argument about what length. Any suggestions?

    I'm really only changing the cranks because I need new cranks on the commuter and there's a sort of manic sense in taking the 172.5mm cranks off the bent, putting them on the commuter and getting the bent some shorter cranks. Money is a problem so premium solutions aren't an option.

    Richard
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    Senior Member Timmi's Avatar
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    I believe I've seen a Shimano Sora available in 165mm and 167.5 - these are relatively inexpensive.

    Personally, I found some Shimano Ultegra (WAY nicer and lighter) on eBay, that are 167.5 and which I have received for my recumbent. I believe I paid $75 for them. You'll need to change your bottom bracket however. I ordered a Shimano 5500... it's an entry level bottom bracket, but has sealed cartridge ball bearings, plus extra needle bearings on the drive side. (needle bearings can withstand hundreds of times more pressure than ball bearings, and thus the crank lasts much longer).

    Also look under the brands Truvativ and FSA... they may make some.

    I'm assuming you don't want singlespeed cranks, which are easy to find in 165 but not compatible with narrow chains.

    Here is an eBay search tip:
    When you find any crankset on ebay, within the listing, at the top, you'll see what category it is under, such as:
    Listed in category: Sporting Goods > Outdoor Sports > Cycling > Bicycle Parts > Road Bike Parts > Cranksets & Bottom Brackets
    Here's the link for you:
    http://sporting-goods.shop.ebay.com/...QQ_sacatZ56195
    Click on it, and enter your search words.
    Enter only the terms 165 and double (or triple, but you'd be crazy to go with a triple instead of a compact double, because a triple sends your right foot out so much farther than the left, messing with the Q-factor), and check the box to search titles and description.
    It's important that you go to the sub-category first, or you'll get thousands of unrelated products. This way, you find what you want.
    You probably have a square taper, so make sure the crank you get has that as well. Beware, because there are cranksets for square taper (most common in used parts, and some new parts), ISIS (truvativ, fsa), Octalink (v1) and Octalink v2, and with external bearings (probably not compatible with an older frame).
    Unless you want to swap the bottom bracket. In which case, get a 108-110 for a double, 113, for triple, crankset, and make sure it matches your frame's threading and bottom bracket shell width, and make sure the interface matches your crankset (splined ISIS, splined Octalink, splined Octalink v2, square japanese, square).

  3. #3
    Senior Member BlazingPedals's Avatar
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    How in the world did this thread get sucked into the recumbent forum? The OP is not a bent rider and the subject of short cranks is not bent-specific.

    I use 155mm cranks on my latest lowracer. Not that I'm a convert, it's just that I need the short cranks because otherwise I can't adjust the bike short enough to reach the pedals. Short cranks give up a little bit in torque but the advantage is that you don't need to bend your knees as much at the top of the pedal stroke, meaning less strain and higher output in the first 1/4 of the circle. To compensate for the torque, you have to spin better, which may mean lower gears.

    My 155s are made by Thorn. Current searches don't show any made by them that are that short. Whereas 165 are easy to find, 160 are a bit harder and 155 are very hard. Well, maybe that's an exaggeration - you can always get cheap short cranks that are made for kids' bikes. You may be able to get your current set shortened, depending on what you've got.
    http://bikesmithdesign.com/Short_Cranks/shorten.html

  4. #4
    Grumpy Old Bugga europa's Avatar
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    Quote Originally Posted by BlazingPedals View Post
    How in the world did this thread get sucked into the recumbent forum? The OP is not a bent rider and the subject of short cranks is not bent-specific.
    This got 'sucked into the recumbent forum' because, as you know from reading and replying to my posts in the 50+ forum, I AM A BENT RIDER and I am buying these cranks for my bent ... as stated in the last paragraph of the post.

    Thanks for your input and I'll look it up, but once again, the bent community turns on someone who finds that bents aren't super wonderful for him. Note to all people considering buying a bent, don't ever criticise the things, the bent community doesn't like it. Jeez, I ask a question with the aim of improving things with my bent in the hope that I might learn to like the thing (and, I admit, trying to save a bit of money) and I get jumped on. I'm sorry that I don't find my bent wonderful like you find yours. I really wanted to, but it hasn't bloody worked out that way.

    Richard
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  5. #5
    Bikepath
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    This person is an expert on short cranks. He has some for sale and will also shorten your present cranks if they meet certain criteria. Give him a call or email. http://bikesmithdesign.com/

  6. #6
    Senior Member BlazingPedals's Avatar
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    Sorry europa. I didn't mean it as a complaint about you but about the mods moving another thread for reasons unknown except that the word 'bent' was buried in the text. I wasn't real clear on what you were proposing, and tigrrrtamer must not have been either or he wouldn't have recommended a compact for a 'bent.

    My Thorn set cost 75 pounds, which at the time was at least 50% more than a 105 set would have cost. And chainrings were extra. I'm wracking my brain trying to remember what cranks Brian Harnett used on his homebuilts a few years back at one of the BROL rallies. I think they were Bullet brand. At the time, he said the advantage was they were cheap.

  7. #7
    Senior Member Timmi's Avatar
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    Quote Originally Posted by BlazingPedals View Post
    or he wouldn't have recommended a compact for a 'bent
    Could you please explain to me what is the matter with using a compact crankset on a recumbent?

    I want to keep my Q-factor in check, and keep the pedal offset on left and right as equal as possible, to prevent back problems brought about by the right pedal commonly being too far outwards.
    Last edited by Timmi; 10-15-08 at 10:43 PM.

  8. #8
    Grumpy Old Bugga europa's Avatar
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    Quote Originally Posted by BlazingPedals View Post
    Sorry europa. I didn't mean it as a complaint about you
    That's cool mate. Take it as an over reaction from an old phart over stressed by his load who's had a few too many disappointments from something he'd lusted after since a teenager. A bit of thought from me would have told me you weren't taking a shot at me. Sorry about that.

    Looks like most of you are talking about modified cranks - funny, the impression you get from Bentrider is that you can buy them over the counter. I've got a mate who'd probably do that for me (he builds model engines from scrap as a recreation).

    I hate trying to sort out this bent in isolation, there are things that can realistically only be tackled in person, but that's not my lot I'm afraid.

    I'll have another chat with my lbs and see what he can source though he's already intimated that the aussie suppliers only bring in 'normal' df stuff, which in this country means 'roadie'. I wouldn't even be looking at this if I had road gearing on the commuter - the commuter has an mtb crankset and the gearing is such that I'm constantly swapping between the big and middle ring which is annoying at best. Having seen so many positive reports about short cranks on bents, the thought was to put the bent's cranks (currently 172.5 long with road type gearing, I forget the tooth count but it's a good selection for my riding) on the commuter and put short cranks on the bent (again with road type gearing) in the hope that I'd gain even a marginal improvement.

    That won't fix the main problems which are a seat that doesn't allow me to stretch my legs out (I slide forward unless I have a boom length that doesn't allow my leg to fully extend), a bottom bracket height that requires really fit abs (and hence reduces my breathing) and the flying hamster handle bar position that leaves me cramped for breath. There's probably a good bent in there somewhere trying to get out but I lack the money or the expertise to stuff around with the sodding thing much more than I already have. If you can't get a bike to work for you within 1000km you're probably well served giving up.

    I'm ranting again aren't I. Probably reacting to too much study (uni) and with the end of the semester coming up, it's only going to get worse. I'll return to the bent over the long break at the end of the year, but don't hold a lot of hope for the thing.

    Richard
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  9. #9
    Senior Member geebee's Avatar
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    Trisled.com.au sell them in any length you are likely to want and then some.
    I found 155's nice and I am 5'8'', I was immediatley faster on the flats but the hills took some cario adjustment.
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  10. #10
    Grumpy Old Bugga europa's Avatar
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    Quote Originally Posted by geebee View Post
    Trisled.com.au sell them in any length you are likely to want and then some.
    I found 155's nice and I am 5'8'', I was immediatley faster on the flats but the hills took some cario adjustment.
    Would it be rude to electronically kiss your feet?
    The cranks they offer sound spot on and at the price, I can afford to exeriment.

    I'd forgotten about the local racing scene. For those of you unlucky enough to live out of Australia, we have a very active human powered racing scene. Cripes, I even forgot that I have a cousin who runs the racing program for his school. The emphasis is on trikes with full fairings belting around a race track as opposed to road riding - when I last spoke to him, that same cousin expressed the same sort of wonderment about riding a two wheeled bent on the roads as most people do

    Richard
    I had a good bike ... so I FIXED it

  11. #11
    Senior Member BlazingPedals's Avatar
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    All other things being equal, you give up your two lowest gears when you go from a triple to a compact. Most recumbent riders aren't willing to do that. Maybe you are?

  12. #12
    Senior Member Hank244's Avatar
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    My tricycle has a Schlumpf (mountain drive) BB. I currently have 152mm cranks that work nicely (able to "spin" much better than when using 170mm). As an experiment, I have a 127mm set coming in the mail.

  13. #13
    Grumpy Old Bugga europa's Avatar
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    Quote Originally Posted by Hank244 View Post
    My tricycle has a Schlumpf (mountain drive) BB. I currently have 152mm cranks that work nicely (able to "spin" much better than when using 170mm). As an experiment, I have a 127mm set coming in the mail.
    127mm

    Are the pedals welded to the spindle or something?

    Richard
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  14. #14
    Senior Member Timmi's Avatar
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    Quote Originally Posted by BlazingPedals View Post
    All other things being equal, you give up your two lowest gears when you go from a triple to a compact. Most recumbent riders aren't willing to do that. Maybe you are?
    Why yes I am! LOL and I don't see the point in going so slow I would no longer be able to balance and would just fall over. (isn't that the point of recumbents anyways? going fast? (comfort too, but speed is the fun part) after all, I think almost all recumbent owners also own other bikes, that are probably already well geared for the hills)

    I have NEVER used the internal chainring - I could remove it from my 1997 mountainbike or off of my 2006 recumbent and sell them as parts removed from new bikes if I wanted to. I didn't use it while climbing Rougemont and Mt-Tremblant on my mountainbike (a heavy 1997 Specialized aluminum RockHopper), I haven't needed one to climb that 18% grade in St-Hyppolite with my racing bike in a 42x(26?) gear, the front wheel lifted off the ground on some pedal strokes if I didn't lean forward, so that's pretty much as steep as you'll go I suppose... it's never been a problem for me.

    So I don't have a use for a granny gear... and for those who need one nothing stops you from gearing the rear cassette differently... instead of having 11-26 or 11-28 with a triple front, you could have 11-32 or 11-36 with a double front compact crankset instead and have a similar lowest gear... I'd much rather have a better Q-factor with symmetrically placed pedals (in relation to centerline), instead of an extra chainring I'll never use with lowest gears I never use. Swapping a couple of cassette chainrings pales in comparison to messing up your Qfactor with a triple in order to get lower gearing.

    As a matter of fact, if you changed from a triple, with a small chainring of 34 and a rear sprocket of 28, to a compact double, with a small chainring of 36 and a rear sprocket of 32, you'd get a smaller gear with the new compact crankset (and even smaller with 36x36). Of course, it all depends on what you're comparing, my point is that with some very standard cassette combinations you can still get the same low gear as you had with a triple. My belief is that the benefits strongly outweigh any counter-arguments, when it comes to a double compact versus a triple.

    BlazingPedals, if you are the guy in your avatar, you certainly don't look like the kind of man who needs a granny-gear either!
    Last edited by Timmi; 10-16-08 at 03:33 PM.

  15. #15
    Grumpy Old Bugga europa's Avatar
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    Quote Originally Posted by tigrrrtamer View Post
    As a matter of fact, if you changed from a triple, with a small chainring of 34 and a rear sprocket of 28, to a compact double, with a small chainring of 36 and a rear sprocket of 32,
    Hmm. My large chainring is a 52 and my smallest rear cog is 11 ... on both bent and upright.
    My granny is 26 on the df though still 30 on the bent with a rear cog of 32. That granny gets used around here. I like to spin at a cadence of 90 up a hill and I have a couple of regularly tackled hills that require that gearing. So not only does your compact not have the range I need, it has that huge hole between the rings requiring a multi gear change on the rear when you change on the front - that would annoy me intensely.

    One of the nice things about bents is the fact that the long chainline reduces the effects of cross chaining so, provided your front dr allows it, you can work the full rear cassette from whatever chainring you're on.

    Compact gearing - I've never been able to understand why people choose such a compromise but then again, people tend not to understand why I have a 26 tooth front granny mated to my 32 tooth rear.

    Richard
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  16. #16
    Senior Member Timmi's Avatar
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    Quote Originally Posted by europa View Post
    Hmm. My large chainring is a 52 and my smallest rear cog is 11 ... on both bent and upright.
    My granny is 26 on the df though still 30 on the bent with a rear cog of 32. That granny gets used around here. I like to spin at a cadence of 90 up a hill and I have a couple of regularly tackled hills that require that gearing. So not only does your compact not have the range I need, it has that huge hole between the rings requiring a multi gear change on the rear when you change on the front - that would annoy me intensely.

    One of the nice things about bents is the fact that the long chainline reduces the effects of cross chaining so, provided your front dr allows it, you can work the full rear cassette from whatever chainring you're on.

    Compact gearing - I've never been able to understand why people choose such a compromise but then again, people tend not to understand why I have a 26 tooth front granny mated to my 32 tooth rear.

    Richard
    Richard, you have LOTS of overlap in terms of duplicate gears. LOTS. Sit down and make the calculation yourself. You can have your cassette spaced wider apart and when you switch from the large to the small on the front you won't have to switch way over on the rear - in fact, if at the bottom of a hill, chances are, this time you might even fall into the correct gear the first time, with just one shift (at the front). On a triple, the chainrings are too close in gearing and you end up having to switch on the rear soon after you've switched on the front. You're just displacing the problem. And when you're coming to a downhill, one front shift and you're in high gear to sprint down - no messing around. I think compacts are more no-nonsense, in addition to less weight and improved ergonomics over a triple.

    If you are strong enough to push a 52x11, you don't need a granny gear period: But maybe you are geared incorrectly to begin with. Do you really need that x11? Or even a x12? Back in the days I was racing, us strong racers didn't even have access to 12t! The smallest made up to a certain time was 13t, and when the 12 became available mainstream it wasn't allowed in race regulations anyways. I'm sure you could find a way to make your range on a double optimal and just as good as with a triple, by simply thinking out your gears on the rear cassette.

    You're no young spring chicken... how's your back? Mine is terrible. Don't ergonomics count for anything in your book? Q-Factor hasn't been talked about back in the day, and pedal offset is a discrepancy still overlooked or voluntarily ignored today, yet such a cause of back problems for cyclists... I mean, just imagine if you were forced to walk with your right leg stretched out to the side... ALL of the time. If bad shoes can ruin a back, imagine the damage this can do.

    I encourage you to re-think your position on this. Annoyance is a personal decision, as to what course of action one adopts in the face of something... in other words, it's more a question of personal attitude towards a phenomena than the phenomena itself.
    Cheers! Timm
    Last edited by Timmi; 10-16-08 at 06:02 PM.

  17. #17
    Grumpy Old Bugga europa's Avatar
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    Quote Originally Posted by tigrrrtamer View Post
    Richard, you have LOTS of overlap in terms of duplicate gears. LOTS. Sit down and make the calculation yourself.
    Yep, lots of overlap, no need to do any calculations, it's obvious on the ride. However, with the gearing I have, I can sit on the large ring for fast work, the middle ring for slow or uphill work and, of course, the granny for the monser hills and there are lots of them in my area - if I ride more than 10kms, I will need that granny to get home (why are the big climbs always on the home leg?).

    I like my configuration because I can go from one chain ring to the other without excessive messing about with the rear gears - widen that seperation and every change on the front will necessitate changes on the rear. Further, reducing the middle ring will just make it less useful on the roads I use - I can say that without fear as my commuter has a middle ring similar to a compact setup.

    Note: I monitor my cadence pretty well and like to stay in the mid to high eighties - slowing that cadence down or spinning frantically is foolishness I save for my fixed gear bike.

    Nope, for me and my riding, compact cranksets are just a recipe for inefficient gearing, but you do need to remember that I have a rather wide range on the back and genuinely need that granny gear.

    If you are strong enough to push a 52x11, you don't need a granny gear period: But maybe you are geared incorrectly to begin with. Do you really need that x11? Or even a x12?
    With all the hills around here, the 11 gets used quite a bit. I can't pull it on the flat but tilt the earth the right way and it gets a workout. In fact, I use my entire range of gears. I like to climb with a cadence in the 90's and don't like having to stand to climb - it does horrible things to my heart rate.

    Of course, standing's not an option on the bent and I'm selective of my hills with her - mind you, with the twist grip gear change, I wouldn't want the mucking about that a compact crank set woould entail (if I ever get a bent to work for me, twist grip shifters WILL be replaced with something that works). If I rode it more, I wouldn't have to worry about hills as I'd be able to spin up them, but I'm not riding it much and hence am not bent strong.

    I'm sure you could find a way to make your range on a double optimal and just as good as with a triple, by simply thinking out your gears on the rear cassette.
    Sorry mate, the gearing on my df sportster is optimal already ... for my purposes. Based on my previous ride, I did a lot of thinking when I built the sportster and chose my gearing accordingly (she was built up from a bare frame).

    You're no young spring chicken... how's your back? Mine is terrible. Don't ergonomics count for anything in your book?
    My df sportster causes me no back problems at all because the bars are at saddle level, the saddle is far enough back to give me a balanced sitting position, the reach has been tinkered to suit me and the cleats have been set back as discussed by Steve Hogg (aussie fitting expert). Add to that a Brooks saddle (so I don't need padded pants and, in fact, never use them) and I've got a very comfortable bike ... along with its optimised gearing (sorry, couldn't resist a tease).

    Teasing aside, Steve Hogg talks a lot about back issues and, unless you're carrying an injury (like my dicky shoulder), back problems are usually associated with a poorly fitted bike - using KOPS and similar, old school fitting methods cause me no end of trouble and pain. Steve's methods remove pain.

    The bent, on the other hand, has a seat that doesn't support my back properly because it's hard and the wrong shape for me, the pad is slightly too wide for my shoulder blades and causes trouble, the head rest fouls my helmet (compulsory here) which leads to neck pain and I slide forward everytime I hit a bump ... hence I find a shorter than optimal leg reach is needed to keep me on the thing. It's not major but it's bloody annoying. It's probably sortable too but I've yet to find a solution that doesn't involve making new bits for the bike.

    I encourage you to re-think your position on this. Annoyance is a personal decision, as to what course of action one adopts in the face of something... in other words, it's more a question of personal attitude towards a phenomena than the phenomena itself.
    Cheers! Timm
    You won't convince me on compact cranks. I have considered them but for me and my riding, my triple setup is optimal.

    The bent? If I had someone here who knew what to look for and what he was talking about, AND I had spare money to spend on the thing, I could probably get it right or at least a lot better. But I don't have either the support or the money. It doesn't help that my sportster is sooo darned comfortable and well set up nor that my commuter is much better suited to the commuting I do than the bent. The thing's has been relegated to 'toy' status ... which is not what I envisaged when I bought it.

    Richard
    I had a good bike ... so I FIXED it

  18. #18
    Senior Member Timmi's Avatar
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    Quote Originally Posted by europa View Post
    Nope, for me and my riding, compact cranksets are just a recipe for inefficient gearing, but you do need to remember that I have a rather wide range on the back and genuinely need that granny gear.

    Teasing aside, Steve Hogg talks a lot about back issues and, unless you're carrying an injury (like my dicky shoulder), back problems are usually associated with a poorly fitted bike - using KOPS and similar, old school fitting methods cause me no end of trouble and pain. Steve's methods remove pain.

    The bent, on the other hand, has a seat that doesn't support my back properly because it's hard and the wrong shape for me, the pad is slightly too wide for my shoulder blades and causes trouble, the head rest fouls my helmet (compulsory here) which leads to neck pain and I slide forward everytime I hit a bump ... hence I find a shorter than optimal leg reach is needed to keep me on the thing. It's not major but it's bloody annoying. It's probably sortable too but I've yet to find a solution that doesn't involve making new bits for the bike.

    The bent? If I had someone here who knew what to look for and what he was talking about, AND I had spare money to spend on the thing, I could probably get it right or at least a lot better. But I don't have either the support or the money. It doesn't help that my sportster is sooo darned comfortable and well set up nor that my commuter is much better suited to the commuting I do than the bent. The thing's has been relegated to 'toy' status ... which is not what I envisaged when I bought it.
    Richard
    There is no "inneficiency" there. On a normal double you often have one quarter to one third of the gears that is duplicated. Most people, when they hit a hill, they have to shift both front and back, with a double, they actually ahve less shifting. No need to argue, we get the message that you are happy with your triple and will stick with it.

    If you're not stubbornly closed-minded however, you get my point, and understood that the reason I was making it was because someone here said that a double on a bent is plain wrong. And I disagreed. Then you jumped in and I felt obligated to defend my opinion, because of where it all originated.
    Last edited by Timmi; 10-19-08 at 02:53 AM.

  19. #19
    Senior Member Timmi's Avatar
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    Quote Originally Posted by europa View Post
    Yep, lots of overlap, no need to do any calculations, it's obvious on the ride. However, with the gearing I have, I can sit on the large ring for fast work, the middle ring for slow or uphill work and, of course, the granny for the monser hills and there are lots of them in my area - if I ride more than 10kms, I will need that granny to get home (why are the big climbs always on the home leg?).
    I like my configuration because I can go from one chain ring to the other without excessive messing about with the rear gears - widen that seperation and every change on the front will necessitate changes on the rear. Further, reducing the middle ring will just make it less useful on the roads I use - I can say that without fear as my commuter has a middle ring similar to a compact setup.
    Nope, for me and my riding, compact cranksets are just a recipe for inefficient gearing, but you do need to remember that I have a rather wide range on the back and genuinely need that granny gear.
    Richard,
    By the sounds of it, you put a lot of thought into your gearing.
    I'm curious, what IS your gearing anyways?
    Timm
    Last edited by Timmi; 10-19-08 at 03:04 AM.

  20. #20
    Grumpy Old Bugga europa's Avatar
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    Gears.

    My bent wears what it came with but it's not a lot different to my Jamis except that it has 26x1 wheels ie, 26" diameter with 28mm tyres as opposed to the 700c on the Jamis.

    My Jamis (df) which has darned near perfect gearing for me has a 50, 39, 26 crankset mated to a one of the SRAM 11-32 rear cassettes which is arranged 11-12-14-16-18-21-24-28-32
    The shifters are Ultegra, the front dr is a 105 and the rear dr is DeoreLX (for the long cage).


    That gearing allows me to work either on the large ring or the middle ring depending on whether it's a bit hilly or flat. I can only pull top gear going down hill but there isn't a ride I can do from home that doesn't have me pulling top gear at some point and there are other hills that have me not bothering to try to keep up.
    The Ultegra shifters and 105 front dr allow me to use the full range on the rear cassette though obviously, I only go on the smaller cogs for shortish periods or if anattentive - I still subscribe to the theories against cross chaining. I can spin quite happily up most hills on the middle ring and for those that demand the granny, I NEED the thing.

    I've got one hill that I do regularly that is 3km on the granny with a cadence of around 90. There's another brute that is shorter but steeper. Maybe nothing for you young blokes but hard on this old wombat. I've yet to get up that first hill in one hit on the bent but I'm happy to put that down to lack of bent fitness - as I've said elsewhere, if I'm not riding the bent every day I loose that fitness very quickly and seeing I'm not climbing hills every day on the thing, I don't expect to be able to. Different with the Jamis, she climbs like a cat up a tree no matter how long I've been off the bike.

    If lazy, I can live on the middle ring but the Jamis is so much fun to ride the big ring gets used a lot.

    Coming up to a climb, I'll flick onto the middle ring, and the jump between top and middle is such that that rarely requires a change at the back. I'll work my way down the rear cassette until in bottom then, if needed, will drop onto the granny which gives me an extra three gears (the equaliser between the two is the fourth cog). Sometimes I'll go up a cog or two on the back, but usually if I need the granny, I stay on it to conserve my heart rate. Coming over the top of a hill, I'll work my way up on the rear cogs, then change onto the middle at some point - it's a jump but I've deliberately chosen a big jump from granny to middle to give me that stupid bottom gear.

    There are roughly 2 gears between the big and the middle (it's not a clean split, the cross over gears are slightly different). When going from middle to big, you need to be spinning in the 90's to make the change cleanly but if you aren't, why would you bother going onto the big ring? Similarly, I'll drop onto the middle from the big when slowing where again, the gear difference isn't really a problem.

    However, were I to have a larger jump between the big and middle rings, I would have to muck about with the rear cogs and I can't see the point in that. That's especially pertinent in that I've all the top speed I'm brave enough to use and when the middle ring is too high for a hill, I've got my granny set up - I do not need to expand the range of gears available to me on those two rings in normal riding.

    For me, expanding that jump between big and middle rings would be inefficient because I would no longer enjoy a clean change. Further, lowering the middle ring, would force me into more changes on the front as the middle ring span out or I cross chained more while trying to use the smallest cogs.

    Interestingly, my commuter has a smaller middle ring - a 34 courtesy of an mtb cranket - and that's bloody useless, get it rolling and get it onto the big ring. Maybe it's not interesting, maybe I'm just pissed off with it.

    The Ultegra shifters handle the triple crankset with ease - I really don't know why people complain about them. Further, the relatively small jump between middle and big ring is also handled quickly and with ease. The leap from granny to middle is slow but it's also well outside the range recommended by Shimano, and it's not done often enough to be a problem.

    So, for me, changing to a compact setup would mean:
    1/ getting rid of changing between granny and middle ring ... which isn't a problem on any of my bikes (except the fixie where I get upset if the chain comes off the ring)
    2/ widening the gap between middle and large ring which isn't desirable
    3/ lowering my middle ring which would take it out of the sweet zone it's in now, result in more cross chaining and probably more shifting between big and middle
    4/ result in me having a higher bottom gear which is undesirable because I use the bottom gear I have now - no, I'm not going to stand and grind up hills because that spikes my heart rate and it already runs close to my maximum (yes, I hit and maintained my max for 10 mins one day and have no desire to do it again, my REAL max, not some calculated number).

    The only positive I see in going to a compact (for me, YMMV), is that it'd be 'trendy' - I ride a steel framed bike, with a frame that is oversized to modern eyes so I can get the bars up at saddle height, using a Brooks saddle wearing kakhi shorts and t-shirts. Come summer, there's a bandana or cycling cap under my peaked helmet to protect my scalp from sunburn (bald where the hair isn't thin and I've already got skin cancers up there) There ain't nuffin trendy about me, though I do use clipless pedals on the Jamis (SPDs) and the bent while the commuter wears toe clips.

    All of which is a bit weird on a bent forum, so I'll go back to my original question. I like the gearing I have on the bent which is similar to the Jamis. It does wear a higher granny (still the stock 30) but the wheels are 26", not 700c which seems to compensate. I can't ride the bent up the big hills but come close enough to know that if I was riding the bent all the time, I'd be able to ... or I could just put a 26 on the granny and go even slower, possible now that my balance is a lot better.

    The commuter has this dreadful mtb setup with the useless middle ring and a large ring that's okay because when you stick this fat old wombat on top, in a non-aerodynamic riding position, with over 10kg of text books in the pannier (I weighed them one day and nearly died with shock), in traffic, top speed isn't a problem. That middle ring is.

    The bent has 172mm cranks.
    Sooooooo, seeing so many people have found short cranks a positive experience, I thought I'd swipe the cranks from the bent to give the commuter half reasonable gearing and put short cranks on the bent, killing two birds with the one stone so to speak, but only if I can do it at a reasonable price - if it's going to be expensive I'll just keep swearing at the gearing on the commuter (which stops me swearing at cars I guess).

    But yeah, compact cranksets? I can't see the point ... but maybe you aren't in your fifties, shaped like a wombat and having to muck about with some pretty decent hills.

    Richard
    I had a good bike ... so I FIXED it

  21. #21
    Grumpy Old Bugga europa's Avatar
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    I've just repeated myself a lot haven't I. Sorry about that. I'm supposed to be doing an assignment for uni so am probably in procrastination mode.

    Richard
    I had a good bike ... so I FIXED it

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    Senior Member Timmi's Avatar
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    Wow, yes, that is long! I thought I was the world-champion in procrastination, but I guess, I, finally met my match.

    Now, just to find a big enough timeslot in my schedule to read that novel of yours...

  23. #23
    Senior Member Timmi's Avatar
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    Allright... I made some verifications... I went out and sat in the sun with a calculator, pen and paper. (I ended up plunking it all into my spreadsheet anyways, but it was too nice outside, I couldn't resist).

    Now just a note so you know I'm not trying to start a war here! So everyone, please, stay calm, as this may shock you! If you have a heart condition or are easily offended by alternate points of view, please change the channel now! ;-)

    The purpose of this is to examine the feasability of replacing a triple with a double-compact. And because Richard gave us an example of a triple that works really good for him, he gave us the opportunity to do some analysis with a good triple as our baseline.

    Some of our criteria shall be to minimize chain flex (crossover), unecessary sifts, and too wide gear gaps when changing from one chainring to the other. (if I read everyone correctly, I think that pretty much encompasses the discussion here).

    Please take note that one thing I don't want to get a retort on, is that these are not actual gears. I know! So let's just call it a "multiplication factor", which inserts (in bold) into the gearing as follows:
    (Chainring/Sprocket)*wheel circumference=development
    It doesn't matter whether you're looking at just PART or the total formula, because it's all multiplication and division... so proportionally it stays the same. So lets reduce things to their simplest form, shall we? That way it applies as much to 20", 24", 26", 700C wheels.

    As a side note, since we're on the topic of cranks, I may as well mention the entire formula we would concern ourselves with, if we calculated what this all means to us ERGONOMICALLY. Thus, the formula gets a little bit longer:
    PedalStrokeCircumference*ChainRingT/SprocketT*WheelCircumference
    (where PedalStrokeCircumference = (CrankarmLength*2*pi) ...I don't substitute "wheelcircumference" with a formula because you SHOULD measure it right with marks on the ground and rider weight reducing the radius at the crush point with the ground - or contact patch if you prefer).
    That last formula is to compare SPEED (NOT RPM) your feet are going in relation to the wheel's linear displacement on the ground. Speed as in muscle-twitch speed - important. This is useful when changing from a 170 to a 165mm crankarms for example... you'll feel like you're pushing bigger gears, so watch out. For this reason, you can use smaller gears, and because of reduced circumference, it's easier to spin, and with the increased RPM bring the speed back up to where it was.

    The below table has 3 sections, as you can see.
    First, is Richard's gearing - this will be our baseline, our starting point.
    Second, Compact with an actual SRAM cassette configuration that can be bought in all good bike stores (and on eBay if you like to shop there).
    Third, is a proposed configuration, for which not all derailleurs will work. However, I've seen some new rear derailleurs come out in the past year that can handle a gap of 6 teeth quite comfortably.

    Triple Crankset, our baseline:
    11 - 12 - 14 - 16 - 18 - 21 - 24 - 28 - 32
    50T
    4.55 4.17 3.57 3.13 2.78 2.38 2.08 1.79 1.56
    39T
    3.55 3.25 2.79 2.44 2.17 1.86 1.63 1.39 1.22
    26T
    2.36 2.17 1.86 1.63 1.44 1.24 1.08 0.93 0.81

    Compact Double, with standard/stock SRAM cassette:
    11 - 13 - 15 - 17 - 20 - 23 - 26 - 30 - 34
    50T
    4.55 3.85 3.33 2.94 2.50 2.17 1.92 1.67 1.47
    34T
    3.09 2.62 2.27 2.00 1.70 1.48 1.31 1.13 1.00

    Compact Double, with more aggressive spacing in the smaller gears:
    11 - 13 - 15 - 17 - 20 - 24 - 28 - 33 - 39
    50T
    4.55 3.85 3.33 2.94 2.50 2.08 1.79 1.52 1.28
    34T
    3.09 2.62 2.27 2.00 1.70 1.42 1.21 1.03 0.87

    And btw, if your brand of compact is a 50/36 rather than a 50/34, the numbers aren't that far off the above.

    Now, looking at Richard's table, it is easy to see why he likes his gearing. When he shifts on the Front, from the Large Chainring, to the Middle Chainring, he is only skipping One Gear. So, instead of landing in the next sequential gear (as if he'd stayed on the same chainring), he is skipping one, thus shifting by two. Not a bad thing when you're meeting up with a hill. Great!

    Things get less optimal though, when Richard goes from the Middle Chainring to the Small Chainring. He skips Two Gears (downshifts by three gears). And most of us at that point would certainly shift the back at least one higher to bring that back in line before shifting down again as the ascent continues.
    At a glance his largest gap seems between 50x12 and 50x14 at around 0.6 - there is a big sudden jump in percentages, higher than the difference between x11 and x12. Not perfect, but not dramatic either, except we may have one high gear too many, a slot that could be put to better use in the lower gears.

    Now, I don't know how many of you are like me, but I just HATE shifting gears in a hill, and the less the better.

    In the middle, you see a Stock Compact Double setup (some compacts will be 50-36, others 50-34, so depends on which brand you have - I chose 50-34 for the example because I thought it might be better for the granny-gear).

    The gap between 2 gears in this setup goes gradually from 0.7, in the highest gears, to .5, .4 in the middle gears, and .3, .2 in the smallest gears... this is probably a nice progression in percentages. This is good... when Richard is going downhill, he wants wide shifting swings, because he's got gravity helping him out, and he's resting anyways (compared to going uphill), and just having fun... and in the small gears, the gap gets smaller to allow to better fine-tune for those climbs where it's more important.

    Now when you shift from, say, 50x23 to 34x23/34x24, you can see that you're also just 2 gears lower. We're coming to a hill and we just shifted down 2 gears a single front shift.

    So as you can see, we have about the same gaps. Percentage difference is only slightly higher between gears. We're doing less shifting and landing closer to an ideal gap when shifting on the front.
    Last edited by Timmi; 10-19-08 at 05:36 PM.

  24. #24
    Grumpy Old Bugga europa's Avatar
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    Quote Originally Posted by tigrrrtamer View Post
    Compact Double, with more aggressive spacing in the smaller gears:
    11 - 13 - 15 - 17 - 20 - 24 - 28 - 33 - 39
    50T
    4.55 3.85 3.33 2.94 2.50 2.08 1.79 1.52 1.28
    34T
    3.09 2.62 2.27 2.00 1.70 1.42 1.21 1.03 0.87

    And btw, if your brand of compact is a 50/36 rather than a 50/34, the numbers aren't that far off the above.
    Oh dear, I knew you'd run into trouble as soon as you tried to make the numbers work for you
    (oh I do so love it when other people justify my own misconceptions )

    My much maligned commuter, the brute that spawned this thread, wears an mtb crankset. The rear cassette is actually the same as my Jamis (btw, I really like SRAM cassettes, but that's beside the point).

    That bike gets ridden mainly on the flats. Adelaide is a large, flat city surrounded by hills. I live in the hills but when commuting, park at the bottom of the hills and ride in from there. Yes, I know it's lazy but it's still a 10km commute and to go all the way home requires negotiating a very dangerous bit of multil lane road with a 70km/hr speed limit, then a sharp climb that hits 10% for a sizeable slab of it and which usually takes me a good 20mins followed by 6kms of rolling 80km/hr road - at the end of the day, I'd rather drive that.

    So I choose the lazy option and commute on the flats. My commuter is what you'd call 'weighty' - she's a beefy touring frame with one of the heavier Brooks saddles, carrier, mudguards, thumping great big steel hitch for my wee daughter's tag-along, hefty U-lock and typically, over 10kg of text books in the panniers. Not heavy weight touring but lower gears are preferred to higher gears.

    That's to set the scene.

    She's got an mtb crankset ... because when I built her up, I was able to get a second hand crankset for not a lot of money (and the sodding thing has cost me heaps in other bits trying to work around it ).

    The middle ring on the commuter is ... wait for it ... a 34 tooth!
    Just like Tim suggests.
    And I hate the useless thing.

    You get the bike rolling, pop up a gear or two and bing, you need to be on the big ring. My big ring is nothing like the 50 you suggest, possibly a 42 but I don't know at this time.

    To make any use of a 34 on the back, I'd need to be able to run it right across onto the small cogs ... which I can't do with an mtb front dr dammit though I could with a road dr ... which then wouldn't shift with my mtb shifters (did I mention this crankset has spawned other issues?).

    The main point being that 34 is ludicrous for flat or even undulating bike path running - she's often on a narrow bike path that follows the River Torrens and is up and down the bank like a dancer's knickers. The jump between the 34 and the big ring I carry now is enough to annoy me, increasing that jump even further just justifies my choice of a triple set up.

    Tim, you are a far more forgiving man than I am ... but I'm old enough and grumpy enough to refuse to put up with too much bulldust from machinery.

    Now, if I think about the undulating territory around home, such as my favourite 20km loop where I need and use the full range of gears on my middle and big rings but not the granny, having to muck about going from big to middle would drive me nuts, especially with the extra shifts needed at the back every time you change chain ring. Maybe there's a difference in riding style. I change gears a lot and work to stay in a relatively consistent cadence zone and when you lack torque like I do, you change often.

    Richard
    (at uni ... procrastinating)
    I had a good bike ... so I FIXED it

  25. #25
    Senior Member Timmi's Avatar
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    Quote Originally Posted by europa View Post
    Now just a note so you know I'm not trying to start a war here! So everyone, please, stay calm, as this may shock you! If you have a heart condition or are easily offended by alternate points of view, please change the channel now! ;-)

    The purpose of this is to examine the feasability of replacing a triple with a double-compact. And because Richard gave us an example of a triple that works really good for him, he gave us the opportunity to do some analysis with a good triple as our baseline.
    Richard, did you read that part? This isn't about you and your choices anymore.
    I didn't want to argue with you - I was moving on to something bigger than one individual's needs... and I was using your wonderful and great works-for-you gearing as an example.

    I didn't want your long stories justifying your choices. Being closed minded is constantly feeling yourself threatened (which I was not trying to do) and having to defend yourself, even when it is being said that we are using this as an example to continue another discussion, namely, the feasability of a Compact Double instead of a Triple... not for you! But for others in general! But maybe it's my fault for making it too long and you didn't read it... just looked at the tables and then replied.

    So could you please just take it for what it is? Accept it as such? I already told you, since you keep on fighting for my approval, that I do give you my blessing with your choices (not that I ever felt you needed my permission, but you keep on coming back at me here, so I'm officially going on record that I approve and am sending you some love!). I wrote that because someone here attacked me, and pretty much told me that a sane knowledgeable person couldn't possibly want to put a Compact Double onto a recumbent. I mean, a double on a recumbent... God forbid!!!

    As I said, I'm only taking your triple as a baseline for comparison, because it seems like very good gearing to use for comparison's sake. You just gave us a wonderful example to go with is all!
    Cheers!
    PS: your condescending tone in your opening sentences wasn't cool.
    Last edited by Timmi; 10-19-08 at 07:47 PM.

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