Road bikes feeling the pressure of 2X10(11)?

[Grill]

I like close ratios, but I also like to climb (and live in a hilly area), so there's no way I can rock a single. If I lived somewhere quite flat then I'd think about it, but the weight penalty is less than 200g so it's really not worth it for me.

[DMF]

Highly inefficient to ride big-big up hills and I'd rather use the 39 with something in the middle of the cassette for a straight chainline. You loose A LOT of watts in drivetrain efficiency when cross chaining. Grinding big hills on big-big and talking about saving some grams for the climb elsewhere is just stupidity, plain and simple.

if you don't,use the small ring, get a smaller cassette and start using it. Or, learn to use your gears to your own advantage. Like I said, A LOT OF WATTS LOST, A LOT!!! For nothing... Insanity.

[Getter]

I went 1x10 on my MTB with a 30T RaceFace NW and OneUp 42T add on cog on the back. Alot simpler and quiet compared to my 2x10. Plus it took off around 350 gr. I don't really use the two smaller cogs very often. If I do reach the point of spinning out the 30x11...I just coast.

There is a ton more rolling resistance on a dirt road vs riding on the road. You don't have to ride up technical square rocks on a road bike.

For me...the low gearing is where it counts.

This year...I am noticing more and more road bikes equipped with 11-32 cassettes.

SRAM has their 1x11 CX group coming out.

1x drivetrain is a give or take. You can't have both. You have a low gear...but not the high... and vice versa.

1x will also accelerate chainring wear. You will have a more extreme chain line at the ends of the cassette.

On a road bike...I think I'll stick with the 2x.

Lol...I just noticed this topic id from 2012.

[Phill P]

As has been said, some terrain/riders might be ok with 1x11

crit racing for instance. You wouldn't even need the bottom few gears from an 11/23x53 for many flat crit courses.

[dgran]

You loose A LOT of watts in drivetrain efficiency when cross chaining.

I'm curious if this is something that has been quantified. It stands to reason that a straight line is more efficient, but I wouldn't hazard to say that it makes a big difference.

[DMF]

I've seen it quantified at some point, but haven't got any links handy and really can't be bothered spending half an hour digging for it. But it is easily passed the 5w mark and might even have been in the double digits... Was a long time since I saw the actual numbers mind you...

[wpccrunner]

SRAM's 1x11 CX1 Cyclocross Group. the 1x11 road group is basically here, they just need to produce some larger tooth chainrings and its done.

[WMW]

On a road bike...I think I'll stick with the 2x.

I'd want to keep my current 36/23 low gear... that means I'd need a 50/32.

So... 11,12,13,14,15,17,19,22,25,28,32 ... that is 11 gears and I could live with it.

[Dozer]

While any one of the point above make sense on their own, putting them together doesn't pass my logic test.

Here's my logic:

- As for dumped chains on mountain bikes (or road bikes), I can't remember the last time that's happened to me. I don't think that is a valid reason to go 1x. On my bikes, my front shift has worked pretty much flawlessly for years. I think that is the norm.
- Simplicity is good for mtn, cx, and road...to a point.
- Efficiency is good for mtn, cx and the road.
- The range of gearing needed for mtn bike is wider than road. A 53-39 / 11-28 road set up has a total gear range of 3.46 ((53/11)/(39/28)). That's a very wide ratio on the road, I think. A typical 2x10 mountain bike has total ratio of 4.79. 3x9 has 5.67. SRAMs 1x11 is 4.20. So, road ratio ranges are far smaller than mountain bikes. This applies no matter how big of hills are where you live.
- chain efficiency is the same for road, mtn, and cx. The chain doesn't know what kind of bike it is on. Crossed chain losses are the same. I assume a XC mtn bike racer is just a worried about driveline losses as a road racer.
- I thought running larger sprockets was more efficient due to reduced chain articulation. This is why larger derailleur pulleys are more efficient. It's also why hour records are not set using a 11t sprocket on the back. So, a 53/32 combo should have some efficiency gain over a 39/24 which could help offset chainline losses. How much for those two effects? I have no clue and haven't seen good test results for either.

So, it's not logical to me that 1x for mtn and cx is good, but is bad for the road. Conversely, it's not logical to me that 2x11 is good for the road, but not for a mtn or cx bike.

For the record, I run 2x10 on the road and 3x9 on my mtn bike. But, I'd considering changing both hence bringing this topic back up.

[Getter]

For me its all about the low gear. I'm no super cyclist...so a lot of times I depend on that low gear to get me where I need to be. There is a loop I do on my mountain bike. On the first trip up, I can make it up with my 30x36...second...third trip...I need that 42. MTB...I don't really need that high gear.

On my MTB I originally ran a 24/38 with a 11-36 cassette. Which ran fine. I went to the 1x mostly out of curiosity and was able to do it all for well under 200 dollars. The 30T in the front and 42T in the rear is equal to a 26-36. So I'm not losing too much on the low end. Only thing about running the "hack" 42T is the cranking of the b-tension screw all the way in. It slows down the shifting in the three small cogs.

I can't imagine myself running a 1x setup on a road bike. My low gear is a 36x28...I don't want to go any higher.

[Dozer]

I can't imagine myself running a 1x setup on a road bike. My low gear is a 36x28...I don't want to go any higher.

What's your highest gear?

[BeeSeeBee]

I've seen it quantified at some point, but haven't got any links handy and really can't be bothered spending half an hour digging for it. But it is easily passed the 5w mark and might even have been in the double digits... Was a long time since I saw the actual numbers mind you...

I was curious so I looked around for it, was it this James B. Spicer article (p.6, EXPERIMENTAL RESULTS AND ANALYSIS, Time variation of efficiency)? Power loss could very well be in the double digits, but it would depend on the input power (somewhere around 400W). The difference in efficiency varied (cadence/chain tension had a negative impact on efficiency), but it seems like efficiency gained from a larger cog helps offset some of the loss of cross chaining.

Code: Select all

Table 1. Drive efficiencies for different chain configurations
            50 RPM       60 RPM       70 RPM      60 RPM       60 RPM
            100W         100W         100W        150W         175W
52–11       92.5%        91.1%        88.7%       94.6%        95.5%
52–15       94.7%        92.3%        90.4%       96.2%        97.5%
52–21       95.2%        93.8%        92.0%       97.4%        98.2%

[DMF]

Can't rightly remember if that was the one, but 400w seems about reasonable for any medium non-mountain pass climb below 10min of effort, I suppose? Also suppose the positives of bigger chainrings is of little use when there is still a net loss.

400w or 390w, that's a rather significant difference in my mind to put it mildly. But let us say 5w for the sake of argument, how much rotational weight would you have to take of the rims to gain a 5w advantage on say 7% gradient climb, so we might put this in the context of grams?

I haven't seen the math but I'm absolutely certain it is out there and many of you might have read and remembered it or something close enough to make a fun equation here.

[Dozer]

5 watts out of 300W total is 1.7% if doing a slow hill climb where raising your mass up the hill is 70% the total resistance (rolling, aero and other resistance being the other 30%) would mean a 100kg bike+ride+etc combo would need to be reduce weight by 1.7kg x 70% = 1.2 kg.

All ballpark calculations, of course. but it tells me never have a 1x11 on my mtn bike if i care about time up long climbs (which i do).

As a side note, from the calculations ive done rotating mass and static mass have same effect with tolerance of significance.

[Dozer]

maybe this also means an ultra narrow 2x8 with same gear spacing with of 2x11 might be optimal do to minimized chain offset...