Practical limit for number of rear cogs in the future?
 

I was thinking today, there has to be a practical limit for the number of cogs for a rear wheel to have. Today, we have up to 12 speeds, but will that trend continue? 13? 14? 15? Expanded rear dropout spacing? Even if they expand the dropout spacing, the wheel dish gets to be so bad that it'd be impossible to build a long lasting wheel.

When do you think the cog "expansion" will stop? Or what do you think will enable the next "number of speeds" revolution? Hyper efficient IGH's combined with cassettes (like SRAM dual drive)? Or will it be the bottom bracket 2 speed cranksets?

14

I would think weight will have some impact vs a 1x setup. It is tough to imagine an average cyclist needing 14 or 15 cogs unless it is a 1x and then it would make sense. The derailleur cage would have to accommodate an 11-44/50. Running a 44/46 chainring would accommodate most every situation.

John

Eventually someone in marketing will have a huge ergonomic "breakthrough". Low Q-factors for many people are both faster and better for their knees. (Well, duh!) Chains have been moving right for the past few decades to stuff more and more gears onto the cluster. But our bodies will take a few thousand years to do the same adaptation. (Maybe longer, this doesn't affect our breeding ability and therefore genetics.)

I love fix gears set up to the 120mm spaced track standard with old fashioned straight track cranks. As good or better is my Sugino double crank set up an a short Phil Wood symmetrical BB with just enough asymmetry that the inside ring doesn't quite hit the chainstay. Left crank is very close. My knees love this bike!

Ben

This is not a "more gears are better" thread. This is a "what is the mechanical limit for how far the marketing can take this ridiculousness?...thread" Go away with your single speed propaganda. :p

Continuously Variable Transmission is a reality in motor vehicles today.

How long before the idea is adapted to bicycles is anyone's guess but it is only a matter of time.


-Tim-

We already have that.

Nfinity N330/N380/N380SE - Products - nuvincicyling.com

However, it's an IGH so we lose some power.

There is a fundamental difference between people powered vehicles and motor powered vehicles. Things with motors can afford to lose a bit to inefficiencies. Let's limit this to road bikes where people want to go fast and don't want to sacrifice much if anything due to inefficient gearing or increased weight.

I'm not trying to sell single speeds, just lower Q-factors. Now that I am putting big miles on three different low Q bikes, I get reminded every time I ride my high Q bikes how much my knees dislike them, despite having far easier gears to go uphill.

Ben

I've noticed that my 2x11 setup has troubles with the chain holding onto the big ring when fully crosschained (big/big).

Cross chaining the other way (small/small) can also have issues with the chain rubbing on the large ring.

A 1x setup could use some kind of a drop stop ring which should improve the chain retention somewhat, as well as a more central location of the ring, but that will mean a worse chainline.

12x may or may not be accepted by road cyclists, but there may be reasons to stop there.

12 cogs spread over 10-50 is a pretty nice spread for general purpose riding - 20 to 100 gear inch range (or whatever 5 times range you want).

Bicycle Gear Calculator

For racing you'd want 14 cogs more tightly spaced. But now we're running into the limits of the gear-inch calculators - can't seem to put 14 cogs on that one.

I wonder if the durability of chains decreases as the width of the links' bearing surfaces decreases. Also, as the cogs get thinner will they wear faster?
Steve

Just as there was more than one way to implement a derailleur, remember that there are many ways to implement a CVT. I think Timothy is on the right track, at some point discrete cogs will give way to those conical pulleys used in CVTs so that riders don't need to think about clicking through specific gear combinations. They'll just shift one way or the other through an analog range until it feels right. And the engineers will figure out how to keep the weight penalty low. For an OP about the future of cycling, why are you so quick to rule out "what could be"? ;)

Practical limit is probably marketing ability to convince people that they need more gears.

This line of thought is getting dangerously close to the ultimate heresy: automatic transmissions for bikes.

I believe all 8/9/10/11 cogs are the same width, it's the spacing that changes.

The ultimate limitation is chain angle. With a 1x system, the chain has to swing across the full spread, resulting in large angles, especially for road bikes with short chainstays. Too wide and you'll get dropped chains, and significant efficiency losses.

Systems like SRAM Eagle and Shimano Dyna-Sys take advantage of the spoke angle, to use big rear cogs, without increasing hub width. With tighter spacing, a slight increase to ~140mm you could easily get ~15 speeds. Maybe 13-14 with the current 135mm.

The problem with IGH hubs is that they lack range. They have an infinite ratio which is great for fine tuning, but the overall range is disappointing. Nuvinci is 380%, which is equivalent to a 1x with 11-42 cassette. Good but not nearly enough for many people.

Oh fine. Although my counter argument for that would be "IGHs have been around longer than derailleurs, if there were a way to make them lighter, you would have thought they would have done it by now." :D

Nuvinci CVT? Has that one not been mentioned? The only issue with the CVT or IGH is weight... and complexity... and price. Manufacturers have yet to find the balance between weight (which lowers price) and complexity (which raises price). Sadly, I see modern bikes trying to tell (sell) people they are making progress with 1 x 350% which is probably not much better than a Sturmey-Archer 3 speed of 50 years ago. Not even sure if the setup is much lighter. A Rohloff 14sp IGH is seriously expensive. Four figures for a rear hub? I suspect the 14 speed complement informs an earlier posters comment that cassette makers will also consider that an endpoint, when and if they finally achieve it. What is really needed is a transmission that can combine the effect of a front derailleur and rear derailleur working together. To really be of value (IMO) a next generation bicycle transmission needs to offer the cyclist a wider range of gear ratios with light weight. Present offerings are stymied by the gear range so instead concentrate on selling the freedom from chain stain or the ability to shift at standstill, ability to resist mud and snow. I don't know... I'm not sold and this is why none of my several bikes are equipped with either CVT or IGH.

They said the same thing about all kinds of bicycle technology taken for granted today.

Disk brakes are too heavy, gears are for those who can't pedal hard enough and need to slow down, etc.

As I said, just a matter of time.

Yeah, I don't think they'll be in the form of an IGH. ;)

Yup, NuVinci is already infinitely variable, in "speeds"

Heretical or not: I do think automatic transmissions will come to bikes before long, but they won't look like any of the failed tries of the past. And not just for leisurely cycling -- automatic transmissions are preferred in some forms of auto racing because the shifts can happen sooner with less chance of a misshift.

I think there are a couple of people working on auto-shifting for Di2 or EPS electronic derailleurs.

It could come to cycling, but many people will be reluctant to give up control of their shifting.

I actually think it's inevitable too. There will be the usual pushback against the new technology, but eventually people will start winning races with automatic transmissions. The uncomfortable truth will be hard to deny: the computer is better at selecting gears than you are. The bike industry will love it.

I'm hoping the "enthusiast" level groups (e.g. Tiagra and Sora) won't go past 10 speeds and will keep triple cranks. With a triple crank you can really achieve an extremely wide gear range with satisfactorily tight gaps between gears with a nine speed cassette.

The "need" for more cogs is driven primarily by compact double and single ring cranksets. Selling a compact double to someone who really needs the low gearing of a triple requires a wide-range cassette. A wide range cassette enables a good marketing narrative for more cogs to achieve small gaps in the gearing. With a single ring crank wide gearing is even more necessary and so the push for more cogs is proportionately compelling.

Using a compact double with 50-34 chainrings, when the chain is on the small ring it will rub the big ring at around 2.3 degrees, which eliminates the two smallest cogs on a 10 or 11 speed cassette. Pushing out the chainline would relieve this problem a bit but it introduces problems of Q-factor. For this reason, I don't see even 2x12 catching on.

The case for 1xN is entirely different. In that case, the only limits are Q-factor and cross-chaining limits. Cross-chaining is really a matter of (1) the chainring's ability to retain the chain, (2) the cog's ability to retain the chain, and (3) the ability of the chain to tolerate the angle. The first issue is largely already solved with narrow-wide chainrings. The third issue is somewhat solved by modern chains, which are fairly flexible, and can probably be improved. The second issue is probably the limiter without some new technology. The 50T cogs appearing on some 12-speed cassettes are pretty huge and having a significant angle from the cog to the chainring has got to cause problems for a cog that is meant to release the chain smoothly on demand. I'd guess we're near that limit at 12-speed.

I predict that if we get 14-speed cassettes they're going to require a smaller pitch chain to reduce the size of the big cogs.

If someone REALLY wanted low Q and lots of gears, one could put the cassette outside the "dropout". Something like this, but do a two-sided rear triangle, make the seatstays and chainstays on the drive side very slender and have them follow the spokes inward to allow more room for the large cogs, and have the large cogs inbound from the bottom of the cassette body, like Sram ones are nowadays...

http://forums.mtbr.com/attachments/f...s_017_2945.jpg