Mysteries of shifting

Discussion in 'Cycling Equipment' started by BiggMakk, Nov 12, 2006.

  1. BiggMakk

    BiggMakk New Member

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    I have ridden for eons but I have yet to figure out shifting efficiency. I would like to hear how others deal with situations like mine.

    Here’s what I mean: Let’s say I am pushing a 50/17 gear on a flat road and suddenly I hit a hill. Obviously I will start to slow down as I start to climb but I want to maintain my cadence.

    Option 1
    If I stay on the 50 tooth chainring and keep shifting down on my rear derailleur I will eventually end up on my 23 tooth rear cog (this causes the chain to grind because it’s at an extreme angle). At a certain point I will have to shift to my 34 tooth chainring – but now I am on the lowest gear (34/23) and my legs are spinning with almost no resistance (much higher than my ideal cadence); and many times I don’t even need that low of a gear. So then I am up-shifting to find a comfortable gear – but by now I have wasted momentum.

    Option 2
    If I downshift to my 34 chainring and stay on my 17 rear cog, again, I am spinning with almost no resistance because 34/17 is too low. I again need to up-shit eventually using the 12 tooth (this too causes my chain to grind from the angle). And as I continue to slow, I need to down-shift again until I find a comfortable gear.

    Is this what everyone else deals with? Are we supposed to be constantly fidgeting with shifting and having wild fluctuations in pedaling cadence? Isn’t there a better way to increase shifting efficiency without losing momentum?

    I ride a 50/34 compact double with 12-23 8-speed rear. Some of the issues could arise from riding a compact crank – there is a 16 tooth difference vs. a 14 tooth from 53/39.

    Thanks to all in advance.
     
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  2. thomas_cho

    thomas_cho New Member

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    hi there, I ride a 10spd setup, so I am not sure if the same applies. I do not have the gear ratios handy, but I find that when I drop the front to the 36, I shift up two gears on the rear, and I have about the same resistance.

    So when I am approaching a hill, I know I cannot do with the 50 chainring, I do the above, and then change down a gear or two on the rear if that is still too hard a gear to turn over.
     
  3. mikesbytes

    mikesbytes New Member

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    Try droping to the 34 and at the same time shift up to the 15 or 14.
     
  4. gclark8

    gclark8 New Member

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    plug the whole lot into here and you can easily see where to down or up shift the front chairings and how many to shift on the rear; http://sheldonbrown.com/gears/
     
  5. bobbyOCR

    bobbyOCR New Member

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    If its short, get off the saddle and power over it :D

    That isn't the case alot of the time so I would shift to the 34 before the hill and find a gear at the back which works.
     
  6. sogood

    sogood New Member

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    Isn't that the reason why we have lots of overlapping gear ratios for the different chainrings? So that a change of chainring would not cause too much of a change in the gear ratio.
     
  7. BiggMakk

    BiggMakk New Member

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    So many responses from Down Under. But then it is Monday morning already.

    I have tried shifting at the same time. Unfortunately sometimes my chain falls off. That makes me a bit flinchy and take the cautious approach.
     
  8. BiggMakk

    BiggMakk New Member

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    Funny you should mention Sheldown Brown. I have the gear ratios printed out and taped to my stem. It only further illustrates the huge leaps shifting between the two front chainrings causes.

    I am starting to sense that this issue is the same for everyone - except they don't seem to be quite as bothered by it as I am.
     
  9. sogood

    sogood New Member

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    If it bothers you, then you might care to stay with a triple. Or you can play around with the choice of rear cassette to modify that overlap of gears b/n the two chainrings.
     
  10. BiggMakk

    BiggMakk New Member

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    I agree. I will need to select my rear cassette with care. Unfortunately the standard Shimano cassettes are what I am stuck with. Apparently there are tinkerers who can create custom cassettes but these are made from different types of cogs. I have no clue if they work properly. Thanks.
     
  11. Bro Deal

    Bro Deal New Member

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    If you know you will be using your little chainring then shift to it whenever it is convenient. This may be on the lower slopes of a climb, when the slope kicks up really steep, or when you shift down to your second to last cog while still on the big ring. Upshift a couple of cogs to keep your cadence in the desired range. It is usually a good idea to baby your pedalling when you shift down to the little ring so there is less of a chance of dropping the chain.

    Personally, I usually use Bobby's method: stand up while in the big ring. When that does not work anymore I can shift down to the little ring and the gear is about right for riding in the saddle. If you are not physically maxed out then you can generally use a gear or two higher when standing than while sitting; you can use this to lessen the effects of switching from the big to the small ring.
     
  12. mcr2c384

    mcr2c384 New Member

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    Personally, I usually use Bobby's method: stand up while in the big ring. When that does not work anymore I can shift down to the little ring and the gear is about right for riding in the saddle. If you are not physically maxed out then you can generally use a gear or two higher when standing than while sitting; you can use this to lessen the effects of switching from the big to the small ring.[/QUOTE]
    this is probably the only way to avoid losing time, energy, and wear and tear on the bike by grinding through gears on steep climbs, huh? I've tried this method with some success but on some climbs i think it is almost impossible to not lose your cadence.
     
  13. li rider

    li rider New Member

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    do the shift just before you hit the hill, not right after you hit the hill.

    use the 2 shift approach others have talked about. shift the rear first to a bigger ring and push through it, which you should still be able to do on the flat, then immediately shift the front to a smaller ring.


     
  14. carpediemracing

    carpediemracing New Member

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    As you point out, the wide ratio front rings (16T difference) means you have more usable gears (less overlap) but it also forces you to stay in a particular chainring longer than you would on a conventional setup (14T or even smaller difference).

    In order to take advantage of the wide ratio, you'll need to master the "double shift". This is where you shift both the front and rear derailleurs at the same time. Done properly you'll rarely miss a beat. However, doubleshifting requires that your front derailleur be particularly well adjusted, else, as you point out, your chain drops off the small ring.

    The 16T jump in front makes for poorer shifting. The smaller ring size makes it almost imperative to use the compact specific front derailleur, with the derailleur so low that the outer cage virtually brushes the big ring. You'll have to adjust the inner limit screw so that the derailleur barely misses the chain when in your lowest gear. You'll experience chain rub when making hard efforts in that gear though as the crank will flex.

    If using Campy, shift "slower". Shimano you should shift into the first of the two stops for the small ring, but that is tricky under duress. Regardless, take up all extra cable slack as the slack allows the derailleur to "slam" into the inner stop, rather than bumping into it (if the cable still has slight tension on it at that point).

    Use a chain "guard" which mounts on your seat tube and prevents the chain from going past the inner chainring. Or adjust your derailleur a little better. Or use a compact specific front derailleur. There is one that has a metal cage (third eye guard?) and one that is simply plastic. The metal one is better but may not fit on the various ovalized seat tubes out there.

    You might want to try shortening your chain a pair of links if so inclined. A shorter chain will be easier for the rear derailleur to control - especially the bouncing that occurs when shifting from the big to small ring. As I prefer a long chain for lower resistance, I would do this only as a last resort.

    An alternative to shortening your chain would be to increase the b-screw tension on the rear derailleur. Same effect, but your rear shifting performance may deteriorate a bit due to the increased distance between upper pulley and cassette cogs.

    Finally, if you rarely use your lowest gear, try moving to a 36T. This will help front derailleur performance and give you more overlapping ratios.

    Hope this helps
    cdr

    *edit* three more things:
    1. doubleshifting is possible under all but the most intense uphill efforts if your derailleurs are properly adjusted.
    2. ease up on your pedals when you double shift. This is possible even under duress and should become a habit.
    3. shift at the top of the pedal stroke so there is less pressure on the chain.
    The above steps basically replicate the scenario where the bike is on the repair stand and shifts fine. By reducing the pedal pressure as much as possible, you get closer to that "lab" environment of the mechanic pedaling while someone shifts both derailleurs and everything works.
     
  15. alfeng

    alfeng Well-Known Member

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    The most pleasant surprise of my Campagnolo ERGO shifters was accidentally finding out that they can EASILY downshift to a larger cog when ALREADY going uphill ... the first time I thought it was a fluke ... OR, that the chain had not actually moved (at all) even though I didn't hear/feel the grinding as it tried to shift onto a larger cog while already going uphill. A couple of more test shifts on the subsequent uphills, and sure enough ... the shifts onto the larger cogs were all-but-effortless.

    Previously, with Shimano Ultegra 6500 shifters, I had to go through the machinations of ensuring my chain began on the large ring before heading uphill. I briefly installed a triple so I would have a granny to bail-out onto as a way of avoiding a balky downshift. I was just on the verge (literally, days away ... the XTR Rapid Rise rear derailleur was in hand and "ready") of installing a RAPID RISE rear derailleur to facilitate downshifts before ascertaining that the Campagnolo ERGO shifters were capable of smooth downshifts when going uphill.

    I guess a previously unasked, so unanswered, question is:

    How do the new SRAM shifters handle downshifting when under load?
     
  16. CAMPYBOB

    CAMPYBOB Well-Known Member

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    is anyone here old enough to remember 'crossover' or 'half-step' gearing?

    my 'flat' bike was set up 47x54 and 14-21 (5-speed back then, of course!).

    my 'climbing' bike was running 49x52 and 14-26.

    needless to say we were up-and-down the chainrings as much as the rear cogs as we shifted to progressively lower ratios!

    with today's 10-speed rearends, i figure i got at least 8 or 9 useable cogs while still on the big ring. even so i try to get down onto the 39 just as i can't push the 53 any farther up the hill. if i have to, i make a quick single-gear fine tune shift with the rear at that point, depending on how the legs feel and where the gradiant put me in my rev range...or how hard the guys up front are making me work!
     
  17. BornInZion

    BornInZion New Member

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    In all the years I have been cycling, I have never come across a hill that was so steep I couldn't walk up it!:rolleyes:
     
  18. Blademun

    Blademun New Member

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    Uhmm..you might want to go see a doctor about that...:p

    As far as Gear Ratios; I firmly believe in the triple myself. After moving to a double on my road bike, I feel myself longing for my old gear rations I had with my 53/42/34(6?) 105 crank. Unfortunately I ruined that cranks finish, and the crank I replaced it with is too nice to switch out again.(and I don't have the cash) I love the 42t ring, its perfect for hilly or urban stop-and-go riding.
     
  19. alfeng

    alfeng Well-Known Member

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    I actually do remember half-step + granny gearing, but only had it on my bike for the briefest period of time ...

    I originally had the more pedestrian (and, at the time disdained) Alpine gearing (52/36) on my bike which I reflexively replaced with a 50/34 when I got new cranks (Sugino AT ... originally set up as approximately a half-step + granny triple BUT I couldn't get the front derailleur [the "original" soft-as-a-noodle Shimano Deore] to manage the gap between the granny and the middle, efficiently ... two disappointing shake-down rides, and I reverted to the Alpine gearing with which I was familiar) for my Gitane about 25 years ago -- my legs were stronger and I didn't know any better than to use the 34t inner (a 36t was probably out-of stock at that moment in time, so I ended up needing to buy two new chainrings instead of just one) as part of my bail-out sequence when I ran out of gearing on the rear [14-24] ... double-shifting, of course, in a less efficient way to simply get the chain onto a smaller cog while the chain was dropped to the inner chainring.
     
  20. BiggMakk

    BiggMakk New Member

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    I was the original question poster. I rewarded myself with a new bike with a 53/39 front and 12/25 rear. My old bike had a 50/34 compact crank and 12/23 rear. I was hesitant about the new, larger crank but the bike came as a packaged deal (a very good one).

    Overall, I think this more 'traditional' set-up is much better. The 14 difference between the 53 and 39 teeth makes for a smoother downshifting compared to a 16 for a 50/34 compact. I am sacrificing a bit on low-end for climbing, but the 39/25 is near the same as 34/23. The smoother shifting and less drastic change is cadence is worth it.

    Mystery solved. Thanks to everyone for their comments.
     
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