A question about front and rear chainring teeth
#1
Junior Member
Thread Starter
Join Date: Mar 2016
Posts: 16
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
A question about front and rear chainring teeth
I have a question about front chainrings and rear cassette chainrings: What is the range in number of teeth (the count) that is normally available from the highest number of teeth to the fewest that is typically available on both the front and rear chainrings?
Thank you
Thank you
#2
Senior Member
Join Date: Feb 2004
Location: St Peters, Missouri
Posts: 30,225
Bikes: Catrike 559 I own some others but they don't get ridden very much.
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1572 Post(s)
Liked 643 Times
in
364 Posts
That's a moving target. The correct answer to that question keeps changing.
A better question might have to do with what derailleurs and shifters work with the outliers. That's a moving target too.
A better question might have to do with what derailleurs and shifters work with the outliers. That's a moving target too.
__________________
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.
#4
Industry guy
From your question, I assume you are trying to re gear a bicycle.
Derailleurs and shifters will be the limiting factor at the extremes and correct chain length will be important as well.
Rule of thumb - the closer the front chainring and rear cogs are to the same number of teeth, the lower the gear and easier to ride.
Less inches of travel per crank rotation.
If the ratio hits 1:1, (32 teeth on front chainring and 32 teeth on rear cog) the rear wheel, whatever diameter, will rotate
one time per crank rotation, traveling a distance forward equal to the circumference of the rear wheel - very easy to ride/climb.
It is possible to get below 1:1 with certain cranks and rear freewheels/cassette combinations.
The converse is equally true - a 52 tooth front ring and 13 tooth rear cog will yield 4 rotations of the rear wheel per crank rotation -
very big gear and difficult to push.
Something a very, very strong rider can push effectively and correctly without hurting themselves!
Derailleurs and shifters will be the limiting factor at the extremes and correct chain length will be important as well.
Rule of thumb - the closer the front chainring and rear cogs are to the same number of teeth, the lower the gear and easier to ride.
Less inches of travel per crank rotation.
If the ratio hits 1:1, (32 teeth on front chainring and 32 teeth on rear cog) the rear wheel, whatever diameter, will rotate
one time per crank rotation, traveling a distance forward equal to the circumference of the rear wheel - very easy to ride/climb.
It is possible to get below 1:1 with certain cranks and rear freewheels/cassette combinations.
The converse is equally true - a 52 tooth front ring and 13 tooth rear cog will yield 4 rotations of the rear wheel per crank rotation -
very big gear and difficult to push.
Something a very, very strong rider can push effectively and correctly without hurting themselves!
#5
Senior Member
The frame itself may be a limiting factor on how big a chainring (front) you can fit. A larger than originally intended chainring may touch the chainstay.
#6
Senior Member
Join Date: Mar 2006
Location: Chicago, IL, USA
Posts: 2,880
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 1461 Post(s)
Liked 1,485 Times
in
870 Posts
I have a question about front chainrings and rear cassette chainrings: What is the range in number of teeth (the count) that is normally available from the highest number of teeth to the fewest that is typically available on both the front and rear chainrings?
Thank you
Thank you
Mountain bikes have bigger ranges. I think the SRAM Eagle 1x setup uses a 10-50T rear cassette. You'll see front chainrings in the 28T-38T range on these bikes but you could go bigger or smaller if desired.
BMX bikes run rear cogs as low as 8 or 9T and as big as 16-18T, and front cogs anywhere from 20T - 44T. Bigger gearing is typically used on BMX race bikes, and smaller gearing on street/freestyle bikes.
#7
Senior Member
Join Date: Mar 2006
Location: Chicago, IL, USA
Posts: 2,880
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 1461 Post(s)
Liked 1,485 Times
in
870 Posts
Lots of other limiting factors too. Crank size, bolt diameter, number of crank arms, type of setup (geared or single speed? 1x 2x or 3x?), type of shifting, size of rear hub, etc.
#8
I am potato.
Join Date: Jun 2015
Location: Pacific Northwest
Posts: 3,116
Bikes: Only precision built, custom high performance elitist machines of the highest caliber. 🍆
Mentioned: 29 Post(s)
Tagged: 0 Thread(s)
Quoted: 1789 Post(s)
Liked 1,629 Times
in
933 Posts
It's a very, very large open question you are seeking an answer for.
What the bikes intended use is means a lot. I am going to answer in broad strokes:
It's hard to go wrong with a 34-50 crankset with an 11-32 cassette for a general purpose road bike with moderate terrain. With practice you should be able to clear mountain passes with out issue.
If your terrain is flatter or you are stronger an 11-28 would work well. More cadence friendly still would be a 12-28 cassette.
If you are super strong or ride exceptionally flat terrain an 11-25 cassette would really let you dial in any cadence you want. Mate that to a 36-52 crankset or 39-53 if you are a professional riding in pancake flat Florida with a strong wind at your back.
Going the other way: It's not uncommon to mate a 34-50 or smaller crankset (or single ring) to an 11‐34 or larger. I think cassettes go up to 50-ish now. If you have super steep climbs or are not strong this may be better. It's terrain & fitness dependent.
I had a 28-44 crankset with an 11-40 cassette. I needed an XTR mountain derailleur and a pull ratio converter from J-Tek to make it work with 11 speed road shifters. The range was from 19 to 109 gear inches...After a year or 2 I decided it was too broad. So I changed it. There just wasn't enough times I needed to carry 75 pounds of camping gear up 20% grades to justify the huge jumps between shifts.
If I were to build another city bike, I've had good experiences with an internal hub like a Nuvinci N380 and also Nexus 7 speed hubs with an 18 tooth cog mated to a 36-52 crankset.
In all cases, I find a range of about 28-32-ish gear inches at the low end to about 90-100 gear inches works for the riding I do in the terrain I tend to ride.
So grab an online gear calculator & see if you can get a feel for what will get you in that range.
If you are getting a mountain bike, anything less than 15 gear inches is beyond utility unless you are exceptionally talented with balance, power delivery, and high traction terrain. I'd call 15 gear inches the lower bound for a mountain bike. But others may disagree.
What the bikes intended use is means a lot. I am going to answer in broad strokes:
It's hard to go wrong with a 34-50 crankset with an 11-32 cassette for a general purpose road bike with moderate terrain. With practice you should be able to clear mountain passes with out issue.
If your terrain is flatter or you are stronger an 11-28 would work well. More cadence friendly still would be a 12-28 cassette.
If you are super strong or ride exceptionally flat terrain an 11-25 cassette would really let you dial in any cadence you want. Mate that to a 36-52 crankset or 39-53 if you are a professional riding in pancake flat Florida with a strong wind at your back.
Going the other way: It's not uncommon to mate a 34-50 or smaller crankset (or single ring) to an 11‐34 or larger. I think cassettes go up to 50-ish now. If you have super steep climbs or are not strong this may be better. It's terrain & fitness dependent.
I had a 28-44 crankset with an 11-40 cassette. I needed an XTR mountain derailleur and a pull ratio converter from J-Tek to make it work with 11 speed road shifters. The range was from 19 to 109 gear inches...After a year or 2 I decided it was too broad. So I changed it. There just wasn't enough times I needed to carry 75 pounds of camping gear up 20% grades to justify the huge jumps between shifts.
If I were to build another city bike, I've had good experiences with an internal hub like a Nuvinci N380 and also Nexus 7 speed hubs with an 18 tooth cog mated to a 36-52 crankset.
In all cases, I find a range of about 28-32-ish gear inches at the low end to about 90-100 gear inches works for the riding I do in the terrain I tend to ride.
So grab an online gear calculator & see if you can get a feel for what will get you in that range.
If you are getting a mountain bike, anything less than 15 gear inches is beyond utility unless you are exceptionally talented with balance, power delivery, and high traction terrain. I'd call 15 gear inches the lower bound for a mountain bike. But others may disagree.
Last edited by base2; 01-07-20 at 02:54 PM.
#9
Senior Member
Other considerations:
1. Front derailleurs are generally made for either road bikes with larger chainring diameters, or mountain bikes with smaller chainring diameters
2. FDs don't like to shift more than 14-16 teeth difference at a time. So 30/52 combinations are out.
3. Rear derailleurs are rated for total teeth difference they can take up slack for; so a 34/50 in front (16 teeth difference) and an 11-27 in back (16 teeth difference) can produce up to 32 teeth of slack. Generally the longer the arm on the derailleur the more slack it can accommodate.
4. RDs also have a maximum size of cassette they can handle. That is, it may be able to lift the jockey pulley over a 34T gear but not a 40T.
5. Like chainrings, too great a difference between adjacent cassette gears makes it shift poorly. So you're not going to find a 11-50T cassette in a 7-speed.
6. If you're changing derailleurs or shifters, be aware that SRAM ESP isn't compatible with everyone else.
1. Front derailleurs are generally made for either road bikes with larger chainring diameters, or mountain bikes with smaller chainring diameters
2. FDs don't like to shift more than 14-16 teeth difference at a time. So 30/52 combinations are out.
3. Rear derailleurs are rated for total teeth difference they can take up slack for; so a 34/50 in front (16 teeth difference) and an 11-27 in back (16 teeth difference) can produce up to 32 teeth of slack. Generally the longer the arm on the derailleur the more slack it can accommodate.
4. RDs also have a maximum size of cassette they can handle. That is, it may be able to lift the jockey pulley over a 34T gear but not a 40T.
5. Like chainrings, too great a difference between adjacent cassette gears makes it shift poorly. So you're not going to find a 11-50T cassette in a 7-speed.
6. If you're changing derailleurs or shifters, be aware that SRAM ESP isn't compatible with everyone else.
#10
Senior Member
I have a question about front chainrings and rear cassette chainrings: What is the range in number of teeth (the count) that is normally available from the highest number of teeth to the fewest that is typically available on both the front and rear chainrings?
Thank you
Thank you
1) Chainrings are only in the front
2) I've seen chainrings from about 60T down to 22T
3) Cassettes have options from 10T to 50T
4) You can't necessarily use all of these together on the same bike, definitely not with an off the shelf combo.
#11
Senior Member
Join Date: Dec 2011
Location: Layton, UT
Posts: 1,606
Bikes: 2011 Bent TW Elegance 2014 Carbon Strada Velomobile
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 626 Post(s)
Liked 701 Times
in
418 Posts
I can give you an example:
My velomobile has a triple front: 30-42-56. I've got a 26 to replace the small ring that I haven't done yet. I'm also going to bump the big ring up to 61.
The rear cassette is a 9 speed 11-34.
It weighs ~70 lbs in commuting trim (tools, spares, water, change of clothes, full electrical system), so going up hill, my cadence will drop to about 60 rpm, and my speed will only be about 4.5 mph.
On a slight downhill, I spin out around 47 mph at about 115 rpms. I want to increase my cadence a bit for the really steep hills, which is why I'm going to fit the smaller ring. The larger ring will let me pedal to about 55 mph before I spin out, maybe a bit more.
My velomobile has a triple front: 30-42-56. I've got a 26 to replace the small ring that I haven't done yet. I'm also going to bump the big ring up to 61.
The rear cassette is a 9 speed 11-34.
It weighs ~70 lbs in commuting trim (tools, spares, water, change of clothes, full electrical system), so going up hill, my cadence will drop to about 60 rpm, and my speed will only be about 4.5 mph.
On a slight downhill, I spin out around 47 mph at about 115 rpms. I want to increase my cadence a bit for the really steep hills, which is why I'm going to fit the smaller ring. The larger ring will let me pedal to about 55 mph before I spin out, maybe a bit more.
#12
Old fart
Join Date: Nov 2004
Location: Appleton WI
Posts: 24,786
Bikes: Several, mostly not name brands.
Mentioned: 153 Post(s)
Tagged: 0 Thread(s)
Quoted: 3588 Post(s)
Liked 3,400 Times
in
1,934 Posts
As others have noted, the gearing you choose depends largely on the type of riding you intend.
#13
Veteran, Pacifist
Join Date: Dec 2004
Location: Seattle area
Posts: 13,328
Bikes: Bikes??? Thought this was social media?!?
Mentioned: 284 Post(s)
Tagged: 0 Thread(s)
Quoted: 3898 Post(s)
Liked 4,833 Times
in
2,229 Posts
@Notso_fastLane - Just wondering what drivetrain components would support the gear range you are proposing? 56/11 and 26/34 Road or Mountain bike derailleurs?
__________________
Vintage, modern, e-road. It is a big cycling universe.
Vintage, modern, e-road. It is a big cycling universe.
#14
I am potato.
Join Date: Jun 2015
Location: Pacific Northwest
Posts: 3,116
Bikes: Only precision built, custom high performance elitist machines of the highest caliber. 🍆
Mentioned: 29 Post(s)
Tagged: 0 Thread(s)
Quoted: 1789 Post(s)
Liked 1,629 Times
in
933 Posts
Notso_fastLane Yeah, I too am curious what derailleur setup handles 49 chain wrap in your current state & 58 in your proposed state.
Intermediary chain tensioners somewhere? Why not a Schlumpf, paired with a Nuvinci or Rolhoff?
Curious in Seattle.
Intermediary chain tensioners somewhere? Why not a Schlumpf, paired with a Nuvinci or Rolhoff?
Curious in Seattle.
#15
Non omnino gravis
Likes For DrIsotope:
#16
Senior Member
Join Date: Dec 2011
Location: Layton, UT
Posts: 1,606
Bikes: 2011 Bent TW Elegance 2014 Carbon Strada Velomobile
Mentioned: 6 Post(s)
Tagged: 0 Thread(s)
Quoted: 626 Post(s)
Liked 701 Times
in
418 Posts
I'd have to look to which exact derailers are installed, but yes, they are stock. Most velos have a mtn bike style setup because we usually want as large a gear ratio as we can get.
And DrIsotope is correct. It's a very long chain (recumbents typically have about 3x the chain length of a DF bike). That probably helps. I've gotten some advice from other velo owners and the 61T up front is about as large as I can go with the stock chain.
I would like to try a Rohloff someday, but those are pretty pricey. I'm more inclined to probably go with a ~80T single up front, and get a Schlumpf Mtn drive.
And DrIsotope is correct. It's a very long chain (recumbents typically have about 3x the chain length of a DF bike). That probably helps. I've gotten some advice from other velo owners and the 61T up front is about as large as I can go with the stock chain.
I would like to try a Rohloff someday, but those are pretty pricey. I'm more inclined to probably go with a ~80T single up front, and get a Schlumpf Mtn drive.