The Basics of Road Bike Gearing

The Basics of Road Bike Gearing

This post examines the effects caused by the size of a bike's cassette and chainrings, as well as the number of gears on the bike.

Recently, a lot of customers have been asking about changing the gearing on their road bikes. There are a few reasons to change gearing, but most customers want to make it easier to pedal up hills in relative comfort (i.e. without pedal mashing in a low cadence). With hilly events like the Wicklow 200 and the Ring of Kerry, easier gearing is a great way to save your legs and not wear yourself out too fast.

 

This post will describe the advantages and limitations of different gearing setups including the maximum possible range for Shimano equipment. It will also discuss the effect of the number of gears on a bike. For ease of understanding, the units for a particular gear will be in km/h at 90rpm cadence on a 700x28 tyre rather than gear ratio or gear inches.

 

Standard Setup

Currently, the most common gearing setup on new road bikes is a 50/34 chainset with an 11-28 cassette. This means that the big and small chainring have 50 and 34 teeth, respectively, and the cassette’s smallest cog has 11 teeth and its largest cog has 28 teeth. This setup has a good range in which the shortest (easiest) gear combination, 34-28, has a speed of 14.1 km/h at a cadence of 90 rpm and the tallest (hardest) combination, 50-11, has a speed of 52.8 km/h.

 

Cassettes

However, what if you can’t sustain 14.1 km/h while climbing and you don’t want to drop your cadence too much? In that case, the easiest change to make is to swap your cassette to one with larger cogs. Switching the cassette to an 11-30 decreases the speed from 14.1 to 13.2 km/h and switching to an 11-34 decreases it to 11.6 km/h. These cassettes have the same 11 tooth small cog, so maximum speed is not affected.

 

The chart below shows the speeds of each gear combination using Shimano 11-28, 11-30, and 11-34 cassette with a 50-34 chainset.


As shown, the maximum speed is the same with the 11 tooth cog and the 11-28 and 11-30 cassettes share the same gearing combinations until the largest three cogs. However, the 11-34 cassette has easier gearing in every combination except while in the 11 tooth cog.

 

The largest cassette your bike can handle depends on your rear derailleur cage length. Shimano road bike rear derailleurs have two possible derailleur cage lengths: short cage (SS) or long cage (GS). Current 11 speed SS derailleurs can handle up to a 30t cog, while GS derailleurs can handle up to a 34t cog. Older systems generally have lower capacities and it’s best to check with us if you’re not sure what your derailleur can handle. You may need to change your derailleur to get the range you want.

 

Chainrings

Another factor to consider is the size of your chainrings. Shimano chainsets currently come in three chainring configurations: 50/34 (compact), 52/36 (mid compact), or 53/39 (standard). All of these sizes are compatible with the same cassette and derailleur combinations. So, for example, if your bike has a 53/39 chainset and a 11-30 cassette, your easiest gear, 39-30, has a speed of 15.0 km/h at 90 rpm compared to a speed of 13.2 km/h with a compact chainset and the same cassette.

 

The chart below compares two gearing setups using 53/39 and 50/34 chainsets with the same 11-28 cassette.

As shown, chainring size has a large effect on speed. For most people, a chainset with compact 50/34 chainrings provides a gear range that suits all their needs.

 

Most new endurance and entry level road bikes are specced with 50/34 chainsets, racing bikes with 52/36, and time trial bikes with 53/39. This is good news for most riders as the gearing corresponds to the type of riding for which the bike is intended. However, this wasn’t always the case. The compact 50/34 chainring combination only gained popularity about 10 years ago as an alternative to triple chainring chainsets and the mid compact 52/36 has only been around a few years. This means that if you have an older bike or a racing style bike that you use to train in the mountains you may have bigger chainrings than you’d like.

 

Depending on your chainset it can be easy or impossible to switch chainring sizes. Shimano 11 speed chainsets feature fully interchangeable chainrings. A few other newer chainsets have this feature, but with most other chainsets it’s not possible to change chainring sizes. In these cases the entire chainset has to be changed if different chainring sizes are desired. This is due to the mounting of the chainrings on the crank arm spider.

 

Number of Gears

The effect of the number of gears on a bike is commonly misconstrued. Depending on the spec, new road bikes will have cassettes with between 8 and 12 cogs and usually 2 chainrings. Although the number of gears differs between an 8 speed bike and an 11 speed bike, the range of gears is generally similar or the same.

 

The chart below shows gearing combinations with three cassettes, a 9-, a 10-, and an 11-speed, all with the same 11-28 range.

Comparing number of gears

As can be seen, the range of all three cassettes is exactly the same. What differs between the three is the size of the step between each gear. A 9 speed cassette has larger steps between gears than an 11 speed, which means that you may need to pedal at a faster or slower cadence to maintain your speed or pedal a bit harder or softer to maintain your cadence than you would with an 11 speed cassette.

 

Conclusion

Clearly, bicycle gearing is not a simple topic and there are many considerations to make before you make changes to your gearing. However, hopefully this post has given you a better understanding of the effects different gearing can have on your ride.

Comments

  1. Marius Judickas Marius Judickas

    Hi Mike. Max range Claris can handle is 11-34t. You would need to upgrade the derailleur to be able to use 40t cassette

  2. Mike Hughes Mike Hughes

    Hi there, great article, thanks! I've got a Specialized Diverge E5 with a Sunrace 8sp 11-34t running on Claris. I was looking at boosting that out to a 11-40t Sunrace. How can I work out if I need to change my derailleur before buying the cassette?

  3. Marius Judickas Marius Judickas

    Hello, Nurul.

    Depending on the rear derailleur capacity you may be able to increase the cassette size to 32t. You are welcome to visit our store and we will check it for you (you may also need a new chain if increasing the size of the cassette).

  4. Nurul Bachik Nurul Bachik

    Hello,
    I have a Cannondale Synapse with 9 speed (11-26T) & 53/39T when I go uphill I wanted to make it little more easier to peddle. What do you suggest?

  5. Mike Mike

    Hi Yossi,
    You do not need to change the cassette on the trainer to match your road riding wheel. I find while using zwift that any cassette is fine. If you find it a bit tougher on Zwift with the 28t then you can adjust the difficulty in the settings menu.

  6. MD MD

    Hi Mick,
    52/36 is a semi-compact. So your're probably just over geared. A compact chainset is 50/34t and changing to this would immediately open up some much easier gearing for you. If you are infact already on a 50/34t chainset then your next port of call would be to fit an 11-32 or 11-34 cassette. You will need a long cage Claris 8 speed derailleur if you have a short one. You're welcome to call the shop and we will be able to advise you further.

  7. MD MD

    Hi Raj,
    I'm afraid you seem to be at your maximum in terms of gearing. I would suggest trying to gain some efficiency elsewhere by upgrading your tyres and/or wheels. The Synapse is designed for comfort over performance so they bike will not accelerate or give as much return for your effort like it's CAAD13 or Supersix counterparts. But, if you change to a stiffer wheelset then you will get more return for your applied effort. Here is a great article that explains the benefit of changing your wheelset: https://www.icebike.org/42414-2/

  8. MD MD

    A 52/36 with 11-34 can be used but it is not recommended by Shimano. The chain will need to be longer to accommodate this and will cause a bit of chain slap when using the 36 ring on the front and the higher gears on the rear. In short yes, it will work but will work better with a 32t cassette

  9. Dave Sullivan Dave Sullivan

    Hi Walter, I trust you mean long cage. The short cage works up to 30t, so you would need a long cage for 11-34t cassette. I have a 50/34 and 11-32 set up on one bike ( Shimano 105 ) and a 50/34 and 11-34 set up on a new bike ( Ultegra ) and to be honest I prefer the 11-32 set up. The 11-34 is very clunky and I find I’m changing gear more often. The 11-32 is enough to get up most hills , even for my old legs. Just my opinion

  10. Yossi Yossi

    hi. I have on the bike 52-36 on the front and 11-30 cassete. On my tacx neo trainrt i have 11-28 cassete. Is the chainring fits both of them ? or i need to change the cassete on the trainer to 11-30 like the bike ?

  11. Mick with Thanks Mick with Thanks

    Hello,

    I have a compact 52/36 I think with an 8 speed cassette. Looking to get a bit of relief on the hills? Any recommendations or pointers, can I do anything with Chainraing of cassette? Not able to move to new bike or complete gear change af the moment

  12. Rajesh Gangadharan Rajesh Gangadharan

    Hello,
    I have a Cannondale Synapse with 10 speed (11-30T) & 50/34T, when I go uphill I wanted to make it little more easier to peddle. What do you suggest without compromising speed.
    Cheers,
    Raj

  13. James R James R

    I am using a 50/34 crank with 11-34 cassette. I am wondering if I could use a 52/34 crank with 11-34 cassette? Or should I use 52/36 with 11-32 cassette? I am in Maryland flat and hill terrain?

  14. Justin Justin

    This is my amateur status coming out, but I'm looking to upgrade my gearset. Would a 11-34 cassette work for a 50/34 chainring or should I adjust that plan? I have a fair amount of hills in my neighborhood and would like the variety of an 11/34 cassette, but if this chainring would not work, can you suggest one that will? Thanks!

  15. MD MD

    Yes, but you will need to change your groupset. Please contact us via email and we can give you more advice on pricing ETC.
    MD

  16. MD MD

    You will need to change the derailleur if it is a short cage as the maximum they will accept is a 30t cassette. If you are unsure, you can bring your bike to our store and we will let you know.
    MD

  17. Christopher Adams Christopher Adams

    I have a Cannondale Xbike can I up grade the cassette from 18 gears to 20?

  18. MD MD

    Hi Roger,
    Yes, you can fit a 34t cassette and this will be ok as long as you don't use the 34t on the rear in conjunction with the 50t on the front. Doing that will cause extra stress on the chain. You should never be in this combination anyway but it is worth pointing out.

    If there is any other questions you have, you are more than welcome to email or call us.

    MD

  19. Roger Clements Roger Clements

    hi iv been cycling for some time now but as always strugle up hills i have a cube road bike with 11/32 cassett 50/34 chainring it looks like i have a long cage derailier would it possible to change rear cassett to 11/34 to give a little better gearing for climbing or would it clash with front chain set it dishartens you when everyone else goes passed you and cant keep up my weight is 14.5 stone but fit thanks for your help roger.

  20. Dave Dave

    I have an Ultegra Di2 on a Canyon Road bike. I’m looking to change my cassette from 11-28 to 11-32 primarily to help hills. I know I’ll need to change my chain but will I also need to change the rear derailleur?

  21. Staff Staff

    Yes, a medium cage (sometimes referred to as long cage) should work fine. A short cage should only be used up to 30t as a maximum.

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