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Old 12-29-12, 02:16 PM   #1
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Front and Rear Gearing

The major vendors seemed to moving towards increasing the number of cogs at the cassette. i am thinking wouldn't it be better to spend more effort on increasing the speed at the front, with cranksets like Schlumpf and HammerSchmidt? That way, even using a 8-speed cassette with 3 speed crankset, we can have more speed than say 2x11?
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Old 12-29-12, 02:32 PM   #2
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I've wondered this as well, but the entire industry uses a 68mmx1.375" (or 73mm) bottom bracket shell, and there's only so much in the way of mechanicals you can get in there and still maintain strength.
Another issue is that the BB gears have a pretty big jump from low to high; IMO this makes chainring choices quite complicated, often requiring a person to commit arithmetic.

On the other hand, using fewer cogs in back with a double chainset and a Schlumpf drive gets you to some interesting places. With 14/17/20 cogs, and 39/52 rings, you get a massive 565% range with 12 discrete gear ratios and no overlap.

Last edited by Captain Blight; 12-29-12 at 02:41 PM.
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Old 12-29-12, 02:33 PM   #3
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You have to evaluate the whole application.

The first issue is "how many gear combinations make sense?" Your highest useful gear is determined by the point that you can continue to turn the crank. Your lowest useful gear is determined by how slowly you can go and still keep your bicycle upright. At some point the steps in between becomes silly especially at the low gear end of the range.

The second issue is that a bicycle has a comparatively wimpy power plant. With a limited power supply, you don't want to waste any power with a low efficiency gear-to-gear transmission. The nice thing about derailleur gear systems is their mechanical efficiency.
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Old 12-29-12, 08:26 PM   #4
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I quit around 7 in the back, maybe 8. It is less expensive to keep adding cogs to the rear than it would be to use a Schulmph or similar drive. I much prefer an IGH setup I suppose if I needed more gears than the 8 that come in my Nexus hub I would spring for the Schlumph drive. FWIW the efficiency of most IG hubs is right up there with a derailleur drive train, especially as they ad more and more gears to them. One thing that people forget about is the wear on parts, chains on a 2x11 drive train wears a lot faster than one on a IGH with a nice straight chain line. I would wager the IGH chain will out last the 2x11 by a factor of at least 5, not to mention having to replace cogs and chain rings. You do lose the advantage of being able to fine tune the ratios with an IGH, but for a sizable share of the market that shouldn't make that much of a difference. There is always the Rolhoff hub with it's 14 speeds. That is the gold standard for IGH.

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Old 12-29-12, 11:04 PM   #5
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With what is available at present, planetary gearing systems may not be attractive to consumers, in terms of efficiency, component weight, compatibility and price. If improvements can be made, maybe the demand would be higher?

i think the biggest difficulty is how to squeeze such a complex system into a limited BB space as Captain Blight mentioned. Unless there are obvious benefits to their bottom line, i doubt SRAM, Campy or Shimano would push another new BB standard
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Old 12-30-12, 04:41 AM   #6
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3-speed hubs exist with splines for a standard cassette, allowing you to have hybrid gearing. Whether you'd actually get any benefit vs the increase in complexity and having to juggle three shifters is debateable. You'd have a lot of duplicated gears.

The Rohlhoff 14-speed hub is basically a 7-speed with an extra gearset, so it's equivalent to having a 7-speed hub combined with a Schlumpf BB. The gear range with this is wide enough for just about any 2-wheeled application- any lower and you'd be struggling for balance and walking would be quicker, any higher and you couldn't pedal it. On something like a cargo trike, you might want something lower, but at the same time can afford to sacrifice the top end.
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Old 12-30-12, 06:12 AM   #7
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I think they should just bring back half-step gearing and be done with it.
combine it with electronic shifting so people don't have to think about the shift pattern
advertise it as doubling the effective number of speeds in the same space/weight
win
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Old 12-30-12, 08:11 AM   #8
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I think they should just bring back half-step gearing and be done with it.
combine it with electronic shifting so people don't have to think about the shift pattern
advertise it as doubling the effective number of speeds in the same space/weight
win
That's an interesting idea. The only problem that I have with half-step gearing is the number of double shifts and having to constantly think about the gear pattern. With electronic shifting and a computer that problem could be solved.

I wonder how it would cost out vs. a Rolhoff.
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Old 12-30-12, 11:06 AM   #9
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That's an interesting idea. The only problem that I have with half-step gearing is the number of double shifts and having to constantly think about the gear pattern.
I have a 2x5 half-step setup on one of my bikes. The thing to remember is that you don't have to go through every gear. I'll sometimes skip out a front shift and just use the rear, using the front shifter when I need a half-gear. If anything, the gear pattern is simpler than your typical 'overlapping ranges' setup- the rear derailleur shifts two gears, the front derailleur shifts one. It's fairly intuitive when you're actually riding.
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Old 12-30-12, 12:33 PM   #10
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The more gears at the back the weaker the wheel due to "dishing". The best compromise for wheel strength and gearing is no more than 7 speeds at the rear 6 sp would be ideal.
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Old 12-30-12, 03:35 PM   #11
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I agree. My 5-speed wheel is actually built for a 6-speed freewheel, with a spacer to centralise the 5-speed freewheel. A 7-speed will just fit in the same space, so in terms of wheel strength there's virtually no difference between a 5-speed and 7-speed setup. On my bike I used the 5-speed since that's what the bike originally came with, and it made choosing chainrings for half-step easier. A 5-speed half-step has marginally more range than a 6 or 7-speed half-step- the gear spacing at the rear is wider (most freewheels range between 14-28, with more gears giving narrower spacing) and as such the chainring size difference is larger.
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Old 12-31-12, 06:04 AM   #12
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The more gears at the back the weaker the wheel due to "dishing". The best compromise for wheel strength and gearing is no more than 7 speeds at the rear 6 sp would be ideal.
There's truth in that statement, but not enough to make it true. You have to evaluate the whole assembly.

6 & 7 speed rear wheels often use freewheels which have an inferior inboard bearing resulting in lower axle life. Many 7-speed cassette hubs have 126 OLD spacing which results in dishing similar to 8,9 & 10 speed 130mm OLD road hubs and more dish than a 135mm OLD mountain hub..
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Old 12-31-12, 11:24 AM   #13
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Schlumpf Mountain drive, is like having a 50t, 20t double..
on My Brompton I have an AW3 ...
3rd is high in low range, 4th is low in high range..
both being planetary gear types, the shifting can take place bogged down on a hill
doing that 4th to 3rd double shift.. ..

Quote:
combine it with electronic shifting so people don't have to think about the shift pattern
So far the electronic shifting for derailleur bikes, does not do that.
it just a different way to tell the derailleur when to jump, and to where.

an IGH sorts that out mechanically inside the hub, with a cable or 2.

single cable has a detent in the lever, holds against a return spring pulling back.
Di2 will not add logic, just buttons and servomotors.
and some IC saying move a certain amount.

Rohloff uses a pull-pull cable, Already, there is an Australian making a shift motor kit,
and buttons to tell it to rotate the sequencing cam mech in the hub.

Last edited by fietsbob; 12-31-12 at 11:40 AM.
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Old 12-31-12, 11:58 AM   #14
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So far the electronic shifting for derailleur bikes, does not do that.
Yet. I was just thinking about the concept.
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Old 12-31-12, 12:11 PM   #15
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I am guessing.. but the AI that you wish for may not be forthcoming, anytime soon,
since the manufacturers Gadgeteering contest, ..
between Campagnolo,SRAM and Shimano are taking place on the high profile, Pro Race Circuits,
with UCI sanctions, and rules, as the limiting agency for radical changes.
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Old 01-01-13, 07:49 AM   #16
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9 speed gear box up front:

http://www.srsuntour-cycling.com/dst...B-FR9-BAZ.html
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Old 01-01-13, 08:42 AM   #17
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Probably the biggest obstacle to seeing more units like Schlumpf and HammerSchmidt on the market is installation costs. Even if the already high initial item costs were cut in half - both of those require the BB to be faced and machined. I'd love to tell you that most BBs come at least properly faced - and unfortunately thats not true. Its a rarity even on higher end bikes, and most retail shops doen't even have the equipment to do it.
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Old 01-02-13, 06:28 AM   #18
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Quote:
Originally Posted by Monster Pete View Post
I have a 2x5 half-step setup on one of my bikes. The thing to remember is that you don't have to go through every gear. I'll sometimes skip out a front shift and just use the rear, using the front shifter when I need a half-gear. If anything, the gear pattern is simpler than your typical 'overlapping ranges' setup- the rear derailleur shifts two gears, the front derailleur shifts one. It's fairly intuitive when you're actually riding.


I agree
Half-step plus granny gives me all the range I could ask for and IMO simplifies the shifting pattern for me. I’m running a 3 X 9 with these gears 45-42-24 X 12,14,16,18,21,24,28,32,36 and I don’t follow a pattern when shifting I normally shift off the center ring like it was a 1 x 9 but once I get into the gear or the gear close to what I need then use the half step to fine tune. I have STI shifters and its very simple with a single or a double shift. Here is what it looks like.

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Old 01-02-13, 12:16 PM   #19
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Originally Posted by Retro Grouch View Post
There's truth in that statement, but not enough to make it true. You have to evaluate the whole assembly.

6 & 7 speed rear wheels often use freewheels which have an inferior inboard bearing resulting in lower axle life. Many 7-speed cassette hubs have 126 OLD spacing which results in dishing similar to 8,9 & 10 speed 130mm OLD road hubs and more dish than a 135mm OLD mountain hub..
You paint with to broad of a brush that want's to make all 6&7 speeds inferior which just isn't fair or true.
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Old 01-02-13, 10:15 PM   #20
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Reasons I've heard for having only 2 chainrings and more cogs:

-Less clunky shifting FD
-Less weight
-Smoother shifting RD

Also. There are more "duplicate" gear ratios using 3 chainrings, so usually it isn't like having more speeds.

Last edited by GT4; 01-02-13 at 11:22 PM.
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Old 01-03-13, 03:06 PM   #21
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Yes, all my 9 speed wheels are weak. 7 speeds? Really? Please time travel from 1986. Those bio pace rings were so awesome.
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Old 01-03-13, 03:22 PM   #22
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Pinion is another Frame mounted gear box.. the design is more like a Motorcycle transmission

than a bike hub, IGH.. frame made around the gear Box.


Now there is a 1 x11 Mountain cassette #1 a 10t, #11 is a 42t !!
http://www.sram.com/sram/mountain/pr...m-xx1-cassette

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Old 01-03-13, 03:53 PM   #23
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Reasons I've heard for having only 2 chainrings and more cogs:

-Less clunky shifting FD
-Less weight
-Smoother shifting RD

Also. There are more "duplicate" gear ratios using 3 chainrings, so usually it isn't like having more speeds.
There might be more duplicate gear ratios on a triple but then the triple is geared lower. Personally, I'd prefer more range than just more divisions between the rear cogs.
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Old 01-03-13, 04:23 PM   #24
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Yes, all my 9 speed wheels are weak. 7 speeds? Really? Please time travel from 1986. Those bio pace rings were so awesome.
More is not necessarily better. I manage just fine with 3 gears on one bike, and 2x5 on the other.
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Old 01-03-13, 04:29 PM   #25
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'Speeds' is a hardware count.. how many cogs and chainrings. It's the gear Ratios that turn the wheels.
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