JaccoW

I might be young with strong legs but my go-fast bike is a randonneur that doubles as a touring bike. You bet I enjoy lower gears at the end of the day, especially if I am hauling some gear up a mountain.

As for the 1x MTB guys, most only really care about getting up a hill and then bombing down one without pedalling or without their chain falling off. And that's simply a lot easier with 1x setups with narrow-wide chainrings and clutched derailleurs.

seypat

I can understand the tiny crank/pizza size sprockets on the back MTBs for added ground clearance. That's acceptable, I guess.

thook

if bikes could talk, it'd sound like merziac <<intro narration>>>

that's kinda sad he quit. i mean, sorta. maybe it was something significant that changed his mind, or maybe it was merely fleeting fancy to begin with

SurferRosa

I didn't think I was "being mean." I thought I was just asking a question. Why so sensitive?

Andy_K 

This is the thing that gets me about 1x -- everybody who likes it talks about the simplicity, but the amount of technology that goes into a clutched derailleur that can handle a 10-50 cassette kind of invalidates that in my mind. I guess as long as it keeps working it's simple for the rider. So it's simple in the way an automatic transmission in a car is simple. It's not really simple, but it usually lets you think it is.

merziac

Agreed, he decided to quit riding if he couldn't up his game another big level.

HTupolev

Those are separate issues. You can build 1x drivetrains with unclutched derailleurs, and you can build multi-chainring drivetrains with clutched derailleurs. Clutches are ubiquitous on derailleurs intended for 1x setups with 10-50 cassettes because these are used almost exclusively on mountain or sometimes gravel bikes, where most riders want the clutch regardless of how many chainrings there are. Similarly, in both their gravel and MTB lineups, Shimano derailleurs intended for 10-speed and above generally use clutches even if they're made for 2x drivetrains.

Andy_K 

Yeah, but doesn't chain drop on a wide cassette become more likely without the clutch? I know there are other ways of dealing with it (including riding on smooth surfaces). And with 10-50, I think the technology is a bit more complex even without the clutch.

nlerner

If the argument is for simplicity, then I guess we should all be riding fixed-gear bikes but then again I’m not entirely sure how gravity works. Seems like a complex system.

HTupolev

I'm not sure why chain drop as a result of bouncing would be made worse by having a wide cassette. Actually, 1x drivetrains arguably have a geometric advantage in this regard: slanted parallelograms are useful for isolating the position of the jockey wheel from front shifts, but they also make it so that vertical bouncing causes the rear derailleur to lurch laterally. Since 1x drivetrains don't need to deal with front shifts, they can reduce the parallelogram slant, and deal with chain gap by using a high offset between jockey wheel and a-pivot instead. SRAM takes this to the extreme: their 1x-specific derailleurs have no parallelogram slant at all.
Wide-range drivetrains can have greater difficulties with the drivetrain being slack in smaller sprockets, but this isn't unique to 1x. Wide-range 2x and 3x drivetrains can wrap just as much, if not more, chain. And I can say from experience with the 48-38-24 11-32 setup on my gravel bike that these sorts of drivetrains don't need a super-wide cassette to be super bouncy.

That said, there is one obvious big-cassette-specific risk: when you suddenly stop pedaling, the cassette still has its momentum from when you were pedaling. If you're on a small cog, then:
1-you were probably going fast and the cassette is spinning pretty quickly, and
2-that small cog has a lot of leverage on the chain.
And if the cassette is big, then it has a lot of momentum.
This leads to a situation where your chainring has stopped and won't let any chain through, but your cassette is still trying to push chain from the lower run of the drivetrain to the upper. This happens with all derailleur drivetrains, but is rarely severe when the cassettes are small. Having some extra resistance to chain unwrapping, like a clutch, doesn't hurt in counteracting this.

In what respect?

Andy_K 

The bigger cog means you need a longer chain, so when you're using the smaller cogs there's more slack for the derailleur to take up. They can adjust for that with extra spring tension, but at some point I would expect that to degrade shifting performance.

I should note that I don't actually know much about the details here. I'm just reasoning from my lay person's understanding of how the derailleurs work combined with some real world experience with dropping chains on a 1x10 CX bike.

Likewise, I don't know anything about the technology needed for wide range cassettes, except that when they first started showing up I read something about the R&D that went into making it work. It requires a pretty wide range of motion, and I'd imagine you need to maintain a reasonably consistent closeness to the cogs. Can you get all that with just a slanted parallelogram?

JaccoW

A clutch is quite literally a sprag clutch working on the pivot, meaning it will lock up if you move it in one direction and move freely in the other, surrounded by a metal band.
Sprag clutches are some of the most high-reliability monodirectional bearings there are. Sure you won't be making them in your garden shed but neither were those hardened ball bearings.
It's about as complex as a derailleur spring with a tension screw; barely in the back of your mind if it works, a lot of disassembly when it eventually breaks.



I consider it a positive optional improvement coming back from the 30+ years of MTB technological development. Manufacturing has changed and often improved. Old musle cars are often smoked by modern family cars and a large part of that is the enormous improvements in tyre manufaturing. The old rubber couldn't put the power down but modern ones are optimized for better handling, wear and acceleration.

As for clutches on bikes; they fit a certain type of usage that is non-existant on road bikes and most commuters. But significantly reduce a problem that was once common on mountain bikes with triples.

HTupolev

Right, but the same issue crops up in wide-range multi-ring setups with smaller cassettes.

That's why I pointed out the huge range of my gravel bike's unclutched drivetrain. That thing takes a massive 116-link chain, and even though I generally avoid the smallest couple cogs in the small ring, it still gets asked to wrap up to about 41 teeth in practical usage. It gets pretty bouncy even on the 38T middle ring, and to prevent the chain from going places on chunky descents, I'll often shift into the big ring even if I don't intend to pedal. Riding over big chunk has caused me to throw the chain off the inside all the way from the middle ring a couple times (although I haven't had it occur since I installed a Dog Fang chain catcher).

I imagine that a lot of effort went into optimizing the shift gates and derailleur geometry. But when I think "complexity" in the context of a consumer setting up a drivetrain, and holding a derailleur in the hand and seeing how it works, I think in terms of stuff like pivots and moving parts. And the wide-range 1x derailleurs are no more complex in this regard than derailleurs for smaller cassettes on multi-chainring drivetrains.

I'm not sure, but they generally don't. 1x-specific derailleurs tend to rely less on slanted parallelograms than multi-ring rear derailleurs do. SRAM 1x-specific derailleurs don't have any parallelogram slant at all. Instead, 1x derailleurs tend to use a lot of offset between the jockey wheel and the derailleur's a-pivot. So when the derailleur wraps more chain, the jockey wheel swings downward away from the cogs.

Most derailleurs have some offset between the jockey wheel and the a-pivot. But front shifting makes it hard to rely on entirely: front shifts alter the chain wrap and adjust where the jockey wheel sits relative to the cogs, which isn't something that you want.
That's why 1x-specific rear derailleurs are a poor choice for multi-ring drivetrains, and why slanted parallelograms are important: the parallelogram's trajectory is unaffected by which chainring you're in.

bulgie 

Ha! Classic. Could you also say "Why are you such a weakling, not much of a man, are you?" and then say "Hey I was just asking a question, why so sensitive? Effin' snowflake!" I mean, are there limits to the "just asking" defense?

Or are you kidding, I can't tell.

To be clear, in my post I was aiming for a breezy tone, with just a light hint of nostalgia for when I wasn't such a weakling. If that came across as "so sensitive" to you, then I suppose I should have added a smiley as insurance against being taken too literally.

For the record, I'm pretty much OK with being old and weak. Since there's no reasonable alternative to being OK with it. My philosophy now is "Any day above ground is a good day". Apologies to any coal miners, spelunkers or tunnel diggers who may read this.

Mark B

JaccoW

Learned something new here today. Cool!

SurferRosa

Good grief.

I asked why folks need lower than 36x28 on their "go fast" bike, and get all this.

bulgie 

OK OK peace! On reflection, I am probably just a tad sensitive.

But when top pros, climber specialists even (not the Laughing Group) are using a 28" gear in grand tours, mere mortals should not feel any pressure to keep low gears off their "go fast".

-mb

repechage

I fond I am reverting to my early gear limit days. a 94" gear is plenty big, a 34 inner ring really helps on the 14% grade home.

HTupolev

Because "go fast" is a purpose, not a rider or a terrain or a specific speed.

I don't think it makes sense to assign any specific ratio as a lower bound to what's needed for "go fast." In the real world, the range of ratios that people need is enormous. Preferred cadence doesn't vary that much with ability level, but top racers fly up hills several times faster than a lot of roadies in the low performance quartile. Some areas have hills that climb at 2% for half a mile at a time, some areas have hills that climb at 5% for a mile at a time, some areas have hills that average 12% for two miles at a time with stretches of 17%.
This doesn't result in a situation where some people are fine on a 39-25 and some people need to use a 36-28. The practical disparities in both ability and circumstance are far, far, far more extreme than that. It results in a situation where some people are fine on a 56-23, and others will struggle on a 26-42, even if both are on "go fast" rides.

rccardr 

Some perspective:
The 24/34 combo on the Davidson makes me fast going up the top part of Keiler Canyon and Cypress Mountain...faster that is, than those who are walking their bikes.
So, there’s that.

Reynolds 

How true. A pro going fast on a 6-8% climb is probably much faster than me going fast on the flats.

mhespenheide 

Tagging on Doc's post, above, here's the bike that I rode in two years of the Eroica California. Trek 400, with a triple. I think the low was 28x26 since the hubs were 7400 and I only ever had one cassette for them. I'm not all that fast, but it was a fun bike. It was a touch too big for me, so I converted it to a townie and sold it cheap to a co-worker's 6'6" husband. Kinda regret that now, but what can you do?

seypat

I build all of my bikes to go as fast as they can over any terrain that I see fit to ride. This special "go fast bike" idea, what is that? I build every one of them to go as fast as I can pedal them! Unfortunately, I have some big hills in the area I ride around in. Any hill is a big hill for me.

Choke 

Campy Chorus triple. It's since been replaced with a Campy MTB triple since I wanted a smaller middle ring.

SurferRosa

I took it to mean a lightweight road bike with drop bars.