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This question is not the same as the 36 gear post which used a combination of internal hub gears, cogs, and chainrings. This one is much simpler and much lower cost.

Part of the problem of something like a 1x15 (which doesn't exist) is chain misalignment. However what about something like this to get 15 progressive gears with good chain alignment? You have 5 cogs in the back, spanning a 1.75:1 range (28, 24, 21, 18, 16 for example). However, instead of the typical triple front, have the fronts so they are 2x of the next smaller chainring. For example, imagine something like 14, 28, and 56 front. This would be most practical on something like a roadbike. The 3 front chainrings would be aligned with the innermost, the middle, and the outmost cog. Crosschaining would be moderate at most so nothing to worry about. The idea here is you can start with the granny chainring, shift all 5 cogs, then go to the middle chainring and repeat all 5 cogs, then shift to largest chainring and shift all 5 cogs again. That would give you 15 progressive gears without having to do any fancy interleaved shifting. There is no way to get duplicate gear ratios here and the change between adjacent gear ratios is a reasonable 15%. The range (spread) between lowest and highest gear would be 7 which is quite generous (lowest is 14/28 = 0.5 and highest is 56/16 = 3.5). If someone wanted this biased more towards taller gearing that could easily be done.

So my question is why don't we see gearing like this on bikes when it makes good sense? Even a child can grasp the simple concept of shifting thru all 5 cogs then go to the next larger chainring and repeat.

This concept can be tweaked to 3x4 for someone who wants wider gaps between gears and fewer gear ratios and to 3x6 for someone who wants narrower gear spacing and more gears (18 vs 15 vs 12 gears total).

If a 56 tooth front chainring is too large, we can go with 13, 26, and 52 instead and adjust the rear cogs to 26, 23, 20, 17, 15.

I think it would be fun to make a bike like this but I think the problem is the FD wont be able to handle that much difference in tooth ranges but if that is the only limiting factor, then perhaps a 2x5 or even a 2x6 with this same concept. That would have a spread of about 4 which is good enough for a roadbike.

I actually checked this technique with my bike and if I change my granny chainring to 22 and keep my 42 large, it will work fine cuz when I shift from small/small, I don't then go to large/large cuz of the MegaRange gear I may eventually have. I am actually temped to try it. It would give me 13 progressive gears which beats a 1x11 in several ways. 1x11 has its advantages but well chosen sprockets in a 2x7 setup can beat it in other ways. Changing my $100 bike to a 2x7 is much more cost effective than going to a 1x11 and I will have more range too. Actually there is $0 cost if I just shift over the middle chainring (skipping it entirely but just using it as a "ramp" between the smallest and largest chainrings.

Criggie
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David
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  • I actually think it is kinda funny my posts get downvoted (likely by the same people) cuz that shows me they are closed minded in their ways and not willing to accept alternate views. Many people do not race nor do they ride in the mountains or do anything competitive on a bike and many have very limited budgets so to me it makes much more sense to talk about practical and affordable things here rather than some $300 crankset for example being marginally better than some cheaper one. – David Jan 27 '16 at 13:06
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    Sorry to be border line rude but this is the 6th flavor of this gearing proposal. Why don't we see stuff like this when it makes sense good sense to you. Existing 2x10 - 2x11 is used on every road bike I know and seems to work for everyone else. Why would anyone want a 3x5 over a 2x11? The only variation is compact or not. Do you even road bike? What is the last pass you climbed on a road bike? What is your top speed on the flats and what gear? So you are entertained. This is a community and we can close questions with enough votes. – paparazzo Jan 27 '16 at 13:22
  • I am generously offering my solution to those out there that may already have a 3x7 (like me) and want to alter it to a 2x7 with simple progressive shifting. I have a $100 Walmart MTB as you already may know. I don't know what my top speed is and it would depend on what bike I ride and in what gear and for what duration but what does that matter for this question it is irrelevant. Yes I have many gearing concepts and even more I haven't posted but even though they are not well received here, that doesn't mean they are not good ideas. I may do the 2x7 conversion on mine cuz it makes sense. – David Jan 27 '16 at 13:26
  • I tend not to downvote "real" questions but rather try to address them (as I have here). However you do need to consider why these ideas aren't being implemented, especially the ones that would use (mostly) standard components). Like you I like a wide range of gears. I've got 4.5:1 between min and max on a 3x8 setup, and that's enough for me. I could push either end, possibly even both, by tweaking my chainset -- In practice to avoid drilling out rivets that would probably mean changing the BB and cranks as well. You may have the same restrictions. Do let us know how you get on. – Chris H Jan 27 '16 at 13:38
  • Another point is you mention every road bike you know uses 2x10 or 2x11 but who said my concept is strictly for road bikes? My 2x7 conversion from a 3x7 can be done cheaply and should work well for mild offroading (like I do when I ride thru grass). The triple chainring complicates progressive shifting so my design just eliminates it which removes the problem without sacrificing any range. Many of the gears in the middle chainring are duplicates anyway so it makes sense to get rid of it and realign the remaining 2 chainrings so that are aligned with cogs 3 and 5 for minimal crosschaining. – David Jan 27 '16 at 13:39
  • Yes, the one on my $100 Walmart 3x7 nearly doubles (24 vs 42 teeth). I never tried it but I think if I full twist the shifter I can go from the granny chainring to the largest in one feel swoop. If I got a 21 tooth new graany chainring then it would be a true 2:1 ratio. If removing the middle chainring causes issues, then maybe just shift thru it (not using it). That is free to do and is an easier shift cuz you can easily go from one stop of the shifter to the other. There is not guessing like with the middle gear. Even if it is marked on the shifter, your eyes may be on the road. – David Jan 27 '16 at 13:46
  • It is relatively easy for a professional biker to get any (physically possible) gear arrangement that he wants. If they aren't being made, they aren't useful. In fact, you could likely make your proposed setup yourself, aside from the problem of finding derailers capable of handling the ranges. It's easy enough to remove cogs from the rear and replace them with spacers. And a guy with an NC machine could craft your front sprockets, if you can't find them on the market. Have at it!! – Daniel R Hicks Jan 27 '16 at 13:48
  • My idea doesn't require any mods actually it is already there, even on my cheap $100 Walmart bike! My stock cogs are currently 28,24,22,20,18,16,and 14. My stock chainrings are currently 24,34,42. I can simply shift all 7 cogs on the granny chainring and then go back to the 2nd largest cog on the largest chainring (skipping over the middle chainring). There is a nice 1.71 to 1.75 close ratio gear when changing chainrings which is beneficial since that shift will take longer. So my point is I can do this right now with no cost at all! It is just matter of discovering this which I did. – David Jan 27 '16 at 13:54
  • 3 is not 2. What 2 ring FD on the market doubles. Don't get how taking your WallMart from 3x7 to a 2x7 is an upgrade or cheaper than just keeping what you have. And you said roadbike in the question. No kidding cheaper than a 1x11 - that would be like $500. I don't think you can even get 11 in a 26" wheel but off the shelf components does not seem to be a constraint for you. – paparazzo Jan 27 '16 at 14:03
  • My concept is simple. Take a triple chainring bike that doubles or nearly doubles (as is my case) the front gears and just skip over the middle chainring, thus giving you a doubler for free! It works! No cost, no adjustments, no new parts... NOTHING! Doing this gives me 13 progressive gears about 10% apart with a very nice 2% upshift when changing chainrings which allows for easier recovery as the bike coasts down slightly. The only gear (of the 14 possible) I wont use is large/large. – David Jan 27 '16 at 14:07
  • So in summary after reflection this revolutionary concept is no different than what you have today. And you wonder why you are down voted? – paparazzo Jan 27 '16 at 14:12
  • My point is why dont they sell 2x7s or even 2x8s, 2x9s, 2x10s, 2x11s... set up like this already? I actually think a 2x7 has an advantage over the others since it will have less lateral chain deflection which is a good thing. I think for me instead of trying to change my granny gear from 24 to 20 (which may or may not work), it might be better for me to get a new crankset and put something like 22 and a 44 on there. That way I can go from 170mm to 175mm cranks for a longer stroke. I remember as a kid I did this and had a lot of fun. I don't ride far (10 miles tops) so it should work. – David Jan 27 '16 at 14:16
  • No kidding they don't sell it already. Maybe there is a reason? Are you never surprised by how many of your revolutionary concepts are not currently available off the shelf? – paparazzo Jan 27 '16 at 14:19
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    Less talking, more wrenching. – Criggie Jan 27 '16 at 20:31
  • Comments are not for extended discussion; this conversation has been moved to chat. – jimchristie Jan 29 '16 at 20:04

1 Answers1

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Your double shift (when you change chain rings) would have to be perfect. You'd have no power until you'd shifted both front and rear. This would be especially bad changing down for a hill.

The front derailleur would have a very hard job to do. I'm not sure current designs could be extrapolated to something that could handle a 20+ tooth difference and a range of 30+. For that matter the difference in chain length between the extremes would be interesting for the rear derailleur.

Chris H
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  • For an upshift, you would have power if you shift to the larger chainring first, then adjust the rear. Your cadence would drop a lot initially but you would recover quickly. I wish twist shifters had a "lockout" to prevent it from going into the largest cog unless maybe you did something extra. That way someone could go from the smallest cog to the 2nd largest cog quickly. For me, that is exactly what I want. Another example where the bike technology has failed me. – David Jan 27 '16 at 13:17
  • For an upshift under power doubling the resistance would be nasty. I'm no pro, so I'm spinning out at around 100rpm. Drop that to 50 and I'd come up off the saddle for the same power input. Then it would take quite a while to recover to the 70rpm where I'd be happy, as I'd be in a high gear for the conditions. But upshifting generally allows more options than downshifting (stop accelerating vs. don't go up the hill). – Chris H Jan 27 '16 at 13:33
  • I agree it is not a perfect solution to progressive gears but for free it is darn good! My $100 Walmart bike can do this right now with just the stock gearing (no mods). The double shift is the only drawback but it is only a slight drawback. Yes there would be a jolt for that gear only but it wouldn't actually quite need to be 2:1 ratio if you don't shift to the largest cog with the largest chainring. It can be smaller like 42:24 like on my bike which is 1.75:1 so you would go from 100 rpms down to 57 rpms briefly but then you can recover quickly by downshifting the rear cogs. – David Jan 27 '16 at 14:01