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chainring sizes

jonKranked

Detective Dookie
Nov 10, 2005
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one thing i've noticed on a lot of modern bikes (particularly 29ers) is the use of smaller chainrings. like 30t and smaller. i've seen dm chainrings down to 26t. is this due to wheel size? the wide range cassettes? both?
 

6thElement

Schrodinger's Immigrant
Jul 29, 2008
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Plus everyone is now riding 34lb+ long travel bikes with heavy tyres and inserts.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
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Bigger and slower-turning bikes require lower gearing...so you might need a 28t on a 29er where you'd need a 30t on a 650b, or 26t on a fat 9er FS tandem... Also, being "the guy who makes the thing" sometimes catches on in this industry, and once you make a 26t elliptical flat-top compatible non-boost spacing raceface direct mount ring, everybody else does too, because it's one more setting on the CNC...or something.

Now that we have 60t cassette cogs, I thought everybody would be on 53t chainrings, but I guess that's not the case. I like the idea of keeping everything as small (and therefore light) as reasonable.
 

Andeh

Customer Title
Mar 3, 2020
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703
For me, a 32t on a 27.5 rear feels similar in terms of power to a 30t on a 29 rear. When I first got a 29, I just threw on my old 32t ring and was like WTF is this hill so hard for a few rides, until I realized the gear-inches relationship or whatever it's called. Since then I always just adjust by 2t depending on which rear end I'm riding. (Assuming 50t cassette... that stupid 52t Eagle feels a bit too easy, but not easier enough to go up a chainring size.)

Now the other end of things, I know someone with a Norco Range, who says he can't run anything lower than a 32t on due to the low chain wrap. He says if he stomps on the pedals in a small cog while descending, it jumps off the chainring. He said that really sucks for him because he's a pretty slow climber and usually runs like a 28t on a 27.5 bike and just slowly grinds his way up the hill.
 

Jm_

sled dog's bollocks
Jan 14, 2002
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32 on my XC race 29er, but all my others are 30 and I have a 28 for the Iditarod.

IMO, people wildly overestimate the need for higher gears, when they say they are “spinning out” they are usually nowhere near 90-100rpm and it’s faster IME to spin at a higher cadence vs needing crazy high gearing. People on DH bikes are going faster and faster without 52t rings and although they tend to come with 32-34 these days, it’s a long ways from what it was and I like it.
 

StiHacka

Compensating for something
Jan 4, 2013
21,212
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In hell. Welcome!
Now the other end of things, I know someone with a Norco Range, who says he can't run anything lower than a 32t on due to the low chain wrap. He says if he stomps on the pedals in a small cog while descending, it jumps off the chainring. He said that really sucks for him because he's a pretty slow climber and usually runs like a 28t on a 27.5 bike and just slowly grinds his way up the hill.
Low chain wrap around the chainring because of the high pivot? Never thought of that. That bike must be eating chainrings like mad then. :fie:
 

Jm_

sled dog's bollocks
Jan 14, 2002
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Low chain wrap around the chainring because of the high pivot? Never thought of that. That bike must be eating chainrings like mad then. :fie:
I thought you only needed like 9t or something for wrap, seems bizarre that it would be doing that though, major design flaw.
 

6thElement

Schrodinger's Immigrant
Jul 29, 2008
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Most of the tension is only on a couple of the teeth, but it probably needs more to help retain the chain. There's some stupidly worn out high pivot idler photos in the empty beer Forbidden threads.
 

Leafy

Monkey
Sep 13, 2019
312
219
32 on my XC race 29er, but all my others are 30 and I have a 28 for the Iditarod.

IMO, people wildly overestimate the need for higher gears, when they say they are “spinning out” they are usually nowhere near 90-100rpm and it’s faster IME to spin at a higher cadence vs needing crazy high gearing. People on DH bikes are going faster and faster without 52t rings and although they tend to come with 32-34 these days, it’s a long ways from what it was and I like it.
IE literally everyone on reddit who claims 1X drivetrains aren't good. Like OK bro you're spinning out a 34-10 setup on a 29er, thats like 28mph. If you're actually able to sustain that speed not going downhill on a bike with knobbies, flat bars, wearing baggie cloths you should be ride road for a pro team because that's like sustaining 45mph with no draft on a road bike.
 

iRider

Turbo Monkey
Apr 5, 2008
5,102
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IE literally everyone on reddit who claims 1X drivetrains aren't good. Like OK bro you're spinning out a 34-10 setup on a 29er, thats like 28mph. If you're actually able to sustain that speed not going downhill on a bike with knobbies, flat bars, wearing baggie cloths you should be ride road for a pro team because that's like sustaining 45mph with no draft on a road bike.
I think it is more about having the right gears when your chainline is not totally strange. For me (26" bikes) a 32 x 42-10 (42-11) setup is good for most things offroad. But for the majority of my rides I try to take the bike out of my front door, which means spinning on pavement and gravel roads to get to the trails. If pedalling in the 32 x 10 gear the chain does not run smooth in a full power situation. So you need to shift to the 12T or even 14T to improve chainline and -wrap, which limits the range of your useable gears. Because of the wacky chain line I only use the 42T when there is really no other way to get up the hill.
While 1x drivetrains are good for many things, I still think your are limiting yourself, even with modern options. Especially on gravel bikes I do not understand how people get away with a 1x setup, the shitty chainline wastes serious Watts and the range is limited.
 
I think it is more about having the right gears when your chainline is not totally strange. For me (26" bikes) a 32 x 42-10 (42-11) setup is good for most things offroad. But for the majority of my rides I try to take the bike out of my front door, which means spinning on pavement and gravel roads to get to the trails. If pedalling in the 32 x 10 gear the chain does not run smooth in a full power situation. So you need to shift to the 12T or even 14T to improve chainline and -wrap, which limits the range of your useable gears. Because of the wacky chain line I only use the 42T when there is really no other way to get up the hill.
While 1x drivetrains are good for many things, I still think your are limiting yourself, even with modern options. Especially on gravel bikes I do not understand how people get away with a 1x setup, the shitty chainline wastes serious Watts and the range is limited.
I'd like to have 2x.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
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I think it is more about having the right gears when your chainline is not totally strange. For me (26" bikes) a 32 x 42-10 (42-11) setup is good for most things offroad. But for the majority of my rides I try to take the bike out of my front door, which means spinning on pavement and gravel roads to get to the trails. If pedalling in the 32 x 10 gear the chain does not run smooth in a full power situation. So you need to shift to the 12T or even 14T to improve chainline and -wrap, which limits the range of your useable gears. Because of the wacky chain line I only use the 42T when there is really no other way to get up the hill.
While 1x drivetrains are good for many things, I still think your are limiting yourself, even with modern options. Especially on gravel bikes I do not understand how people get away with a 1x setup, the shitty chainline wastes serious Watts and the range is limited.
I have 1x on my road bike. If a sensitive flower like me can put 1500 miles on a 1x drivetrain where efficiency matters, then I'm sure you can hurk your 36lb, tire insert wearing enduro bike down the road in the 10t cog. I only notice increased friction in the 42-33t, which is not where I want to spend much time anyways.
 

iRider

Turbo Monkey
Apr 5, 2008
5,102
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I have 1x on my road bike. If a sensitive flower like me can put 1500 miles on a 1x drivetrain where efficiency matters, then I'm sure you can hurk your 36lb, tire insert wearing enduro bike down the road in the 10t cog. I only notice increased friction in the 42-33t, which is not where I want to spend much time anyways.
Maybe you are not as sensitive of a flower as you think you are. ;)
If the bad chainline on a 1x setup doesn't bother you, good for you. But all my road and gravel bikes stay 2x because I like to have the gear range.
 

Westy

the teste
Nov 22, 2002
50,180
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Sleazattle
32 on my XC race 29er, but all my others are 30 and I have a 28 for the Iditarod.

IMO, people wildly overestimate the need for higher gears, when they say they are “spinning out” they are usually nowhere near 90-100rpm and it’s faster IME to spin at a higher cadence vs needing crazy high gearing. People on DH bikes are going faster and faster without 52t rings and although they tend to come with 32-34 these days, it’s a long ways from what it was and I like it.
Physiology has a lot to do with it. Different people have different percentages of fast and slow twitch muscle fibers. I did a genetic test that said I have little to no fast twitch. I can crank away at 60 RPM all day long and 75 when I want to put down power. I can't hold 90 RPM for more than a few seconds.

I am very happy with a 32 tooth ring with 29" wheels. There are times when I would like a lower gear but that is only when I push myself harder than my fitness can allow.
 

slimshady

¡Mira, una ardilla!
Physiology has a lot to do with it. Different people have different percentages of fast and slow twitch muscle fibers. I did a genetic test that said I have little to no fast twitch. I can crank away at 60 RPM all day long and 75 when I want to put down power. I can't hold 90 RPM for more than a few seconds.

I am very happy with a 32 tooth ring with 29" wheels. There are times when I would like a lower gear but that is only when I push myself harder than my fitness can allow.
Fast twitch muscle fibers can (and should!) be developed. I jumped on the high cadence bandwagon back in the days of the first Armstrong victory on the TdF, when a 46t XTR chainring was considered the pinnacle of performance (and a way to show your manhood without riding naked). I put a 34t mono chainring on all the (26") MTBs I had, and never looked back. Whenever I hit the gym afterwards I emphasized I wanted to develop fast twitch fibers to any instructors I got assigned. Now I can routinely spin 90-100 RPMs on long climbs, and I rarely get lactate associated cramps.

The biggest problem with 1x transmissions IMHO (as @Gary pointed out back when SRAM went balls in with them IIRC) is the teeth jump between adjacent gears. Sometimes 3-4 teeth are too much, and they impact your optimal cadence too much for you to be able to hold it for several minutes, and then you end up jumping back and forth between a couple of cogs.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
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Fast twitch muscle fibers can (and should!) be developed. I jumped on the high cadence bandwagon back in the days of the first Armstrong victory on the TdF, when a 46t XTR chainring was considered the pinnacle of performance (and a way to show your manhood without riding naked). I put a 34t mono chainring on all the (26") MTBs I had, and never looked back. Whenever I hit the gym afterwards I emphasized I wanted to develop fast twitch fibers to any instructors I got assigned. Now I can routinely spin 90-100 RPMs on long climbs, and I rarely get lactate associated cramps.

The biggest problem with 1x transmissions IMHO (as @Gary pointed out back when SRAM went balls in with them IIRC) is the teeth jump between adjacent gears. Sometimes 3-4 teeth are too much, and they impact your optimal cadence too much for you to be able to hold it for several minutes, and then you end up jumping back and forth between a couple of cogs.
After getting into road and road training, I started spinning a lot faster than I ever have on MTB. It wasn't until observing my cadence and forcing 90-100RPM that I started to learn how to do it. Now I naturally default there on the road bike. Even still, 1x has been fine there. I think if I were in more mountainous terrain, I'd like the additional range and closer cassette spacing of a 2x 11 or 12 setup vs. my 1x12.

That being said, I have often thought about going back to 2x11 on my MTB as I like close cassette spacing and the ability to drop the equivalent of 3-4 cogs with a single shifter (at the front) vs. clicking through at the rear. The reality of large changes in incline is much bigger on MTB vs. road, so the idea of shifting at the front once when you get to the bottom doesn't sound so bad. It's just a matter of getting your FD to work and nobody wants to do that. I've been tempted by the shimano side-swing front derailleurs, but just can't be bother to buy one regardless of the cost.
 

Jm_

sled dog's bollocks
Jan 14, 2002
16,683
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Fast twitch muscle fibers can (and should!) be developed. I jumped on the high cadence bandwagon back in the days of the first Armstrong victory on the TdF, when a 46t XTR chainring was considered the pinnacle of performance (and a way to show your manhood without riding naked). I put a 34t mono chainring on all the (26") MTBs I had, and never looked back. Whenever I hit the gym afterwards I emphasized I wanted to develop fast twitch fibers to any instructors I got assigned. Now I can routinely spin 90-100 RPMs on long climbs, and I rarely get lactate associated cramps.

The biggest problem with 1x transmissions IMHO (as @Gary pointed out back when SRAM went balls in with them IIRC) is the teeth jump between adjacent gears. Sometimes 3-4 teeth are too much, and they impact your optimal cadence too much for you to be able to hold it for several minutes, and then you end up jumping back and forth between a couple of cogs.
It’s not as comfortable for me to just pedal faster, but it’s also a bit more convenient at times, since it means I don’t have to be shifting all over the place as much. It tends to be a good idea for me to second guess shifting in a race if I want to go faster maybe I slowed my cadence which is more than often what happened or I can at least get more out of it first. I think the “feel” of more resistance in a higher gear makes a lot of people think they are going faster, as opposed to what is actually faster. I got faster DHing when I changed my primary gear from the hardest to the second hardest, which “seemed” too easy for everything. But pedaling faster=faster. But again, pedaling at 90-100rpm for extended periods is mentally tough, it’s not comfortable. I get “used” to it, but if I could go the same speed with the same effort in a higher gear that would be my choice. The small rear cog does eat up more in terms of friction/has more resistance, but I don’t think it’s solely that.
 

Jm_

sled dog's bollocks
Jan 14, 2002
16,683
7,609
AK
After getting into road and road training, I started spinning a lot faster than I ever have on MTB. It wasn't until observing my cadence and forcing 90-100RPM that I started to learn how to do it. Now I naturally default there on the road bike. Even still, 1x has been fine there. I think if I were in more mountainous terrain, I'd like the additional range and closer cassette spacing of a 2x 11 or 12 setup vs. my 1x12.

That being said, I have often thought about going back to 2x11 on my MTB as I like close cassette spacing and the ability to drop the equivalent of 3-4 cogs with a single shifter (at the front) vs. clicking through at the rear. The reality of large changes in incline is much bigger on MTB vs. road, so the idea of shifting at the front once when you get to the bottom doesn't sound so bad. It's just a matter of getting your FD to work and nobody wants to do that. I've been tempted by the shimano side-swing front derailleurs, but just can't be bother to buy one regardless of the cost.
The problem I always had with those 2 and 3x drops, apart from the front derailleur working right, they never left me in the right gear and I’d still have to “trim out” the rear. I hear you for the “emergency drop” like where the trail changes so suddenly or I was just in day-dream land, but on all the others it was a lot harder to taper down to the climb. With 1x almost all of the time I get to a point where I go down two gears, pause for a few seconds, and go down one more. That ends up perfect for climbing for me 95% of the time.

Of course, I did put x01 GS on both my fat bikes. Ability to dump gears instantly through the entire range is pretty cool. Not sure if it makes sense for my regular riding, but it does there.
 

boostindoubles

Nacho Libre
Mar 16, 2004
6,739
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Yakistan
I could see running a 2x drivetrain if I was bike packing but most of my rides are too short to really need a true granny.

My gravel bike is a 1x11 Shimano XT setup with 2500 miles on it - no complaints from me. 11-46 x 38t oval.

Mtb I'll run the biggest I can get away with. I often spin road to and from the trails and like to get the MPH up a little higher. Plus I can beat up on the kids in the strava wars with a tall front gear.

I spent years mashing single speeds and am used to the slow methodic slog. I like to settle in and give it the long and steady.

;)