Go Back  Bike Forums > Bike Forums > General Cycling Discussion
Reload this Page >

A question about front and rear chainring teeth

Notices
General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

A question about front and rear chainring teeth

Old 01-06-20, 08:03 PM
  #1  
Punchy71
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
Punchy71 is offline  
Old 01-07-20, 01:19 AM
  #2  
Retro Grouch 
Senior Member
 
Retro Grouch's Avatar
 
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 642 Times in 363 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.
__________________
My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.
Retro Grouch is offline  
Old 01-07-20, 01:27 AM
  #3  
bpcyclist
Senior Member
 
Join Date: Sep 2019
Location: Portland
Posts: 1,115
Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 451 Post(s)
Liked 364 Times in 227 Posts
Another pretty good question is, what are you planning on using the bike for?
bpcyclist is offline  
Old 01-07-20, 03:11 AM
  #4  
100bikes
Industry guy
 
Join Date: Nov 2007
Location: Minnesota
Posts: 353

Bikes: To many to name - I ride a custom built steel frame.

Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 115 Post(s)
Liked 80 Times in 48 Posts
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!
100bikes is offline  
Old 01-07-20, 10:50 AM
  #5  
subgrade
Senior Member
 
Join Date: Apr 2018
Location: Saulkrasti, Latvia
Posts: 898

Bikes: Focus Crater Lake

Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 391 Post(s)
Liked 336 Times in 204 Posts
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.
subgrade is offline  
Old 01-07-20, 02:13 PM
  #6  
msu2001la
Senior Member
 
msu2001la's Avatar
 
Join Date: Mar 2006
Location: Chicago, IL, USA
Posts: 2,870
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 1455 Post(s)
Liked 1,477 Times in 867 Posts
Originally Posted by Punchy71
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
For a typical on-road bike, a standard 2x crank would have front chainrings with 52T and 39T. A more common "compact double" would run a 50T/34T or even a 46T/36T. 1x single chainring setups usually run around 42T, but can vary widely. The smallest front chaining I've ever seen on a geared bike is 24T. On the rear, you'll find most on-road geared bikes run a range between 11-42T.

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.
msu2001la is offline  
Old 01-07-20, 02:16 PM
  #7  
msu2001la
Senior Member
 
msu2001la's Avatar
 
Join Date: Mar 2006
Location: Chicago, IL, USA
Posts: 2,870
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 1455 Post(s)
Liked 1,477 Times in 867 Posts
Originally Posted by subgrade
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.
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.
msu2001la is offline  
Old 01-07-20, 02:49 PM
  #8  
base2 
I am potato.
 
base2's Avatar
 
Join Date: Jun 2015
Location: Pacific Northwest
Posts: 3,072

Bikes: Only precision built, custom high performance elitist machines of the highest caliber. 🍆

Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 1764 Post(s)
Liked 1,577 Times in 910 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.

Last edited by base2; 01-07-20 at 02:54 PM.
base2 is offline  
Old 01-08-20, 10:13 AM
  #9  
BlazingPedals
Senior Member
 
BlazingPedals's Avatar
 
Join Date: Dec 2004
Location: Middle of da Mitten
Posts: 12,474

Bikes: Trek 7500, RANS V-Rex, Optima Baron, Velokraft NoCom, M-5 Carbon Highracer, Catrike Speed

Mentioned: 14 Post(s)
Tagged: 0 Thread(s)
Quoted: 1511 Post(s)
Liked 733 Times in 454 Posts
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.
BlazingPedals is offline  
Old 01-08-20, 12:11 PM
  #10  
Caliper
Senior Member
 
Join Date: May 2014
Location: Michigan
Posts: 990

Bikes: Many

Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 385 Post(s)
Liked 58 Times in 43 Posts
Originally Posted by Punchy71
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

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.
Caliper is offline  
Old 01-09-20, 09:03 AM
  #11  
Notso_fastLane
Senior Member
 
Notso_fastLane's Avatar
 
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.
Notso_fastLane is offline  
Old 01-09-20, 09:26 AM
  #12  
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Posts: 24,934

Bikes: Several, mostly not name brands.

Mentioned: 153 Post(s)
Tagged: 0 Thread(s)
Quoted: 3571 Post(s)
Liked 3,366 Times in 1,915 Posts
Originally Posted by subgrade
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.
Originally Posted by msu2001la
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.
If your frame has a fixed (aka "braze-on") front derailleur mount, that will also limit both the high and low range of chainring tooth counts.

As others have noted, the gearing you choose depends largely on the type of riding you intend.
JohnDThompson is offline  
Old 01-10-20, 07:58 AM
  #13  
Wildwood 
Veteran, Pacifist
 
Wildwood's Avatar
 
Join Date: Dec 2004
Location: Seattle area
Posts: 13,303

Bikes: Bikes??? Thought this was social media?!?

Mentioned: 284 Post(s)
Tagged: 0 Thread(s)
Quoted: 3874 Post(s)
Liked 4,779 Times in 2,204 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.
Wildwood is offline  
Old 01-10-20, 09:24 AM
  #14  
base2 
I am potato.
 
base2's Avatar
 
Join Date: Jun 2015
Location: Pacific Northwest
Posts: 3,072

Bikes: Only precision built, custom high performance elitist machines of the highest caliber. 🍆

Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 1764 Post(s)
Liked 1,577 Times in 910 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.
base2 is offline  
Old 01-10-20, 10:08 AM
  #15  
DrIsotope
Non omnino gravis
 
DrIsotope's Avatar
 
Join Date: Feb 2015
Location: SoCal, USA!
Posts: 8,553

Bikes: Nekobasu, Pandicorn, Lakitu

Mentioned: 119 Post(s)
Tagged: 0 Thread(s)
Quoted: 4905 Post(s)
Liked 1,731 Times in 958 Posts
Unless he's changed it out, the Strada Velo comes with SRAM X5 up front and a SRAM GX-11-A1 in the back. I'm guessing the wrap isn't an issue because the GX-11-A1 can handle a 42T cog, and the chain is (guessing here) about 12 feet long.
__________________
DrIsotope is offline  
Likes For DrIsotope:
Old 01-10-20, 10:21 AM
  #16  
Notso_fastLane
Senior Member
 
Notso_fastLane's Avatar
 
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.
Notso_fastLane is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.