How fast were you going? The 11 is the cog that determines your fastest speed. With a 52 chainring at 110 RPM cadence, you would have been spinning out at around 40 MPH. At that speed, I typically coast. Your power usually cannot add much to what the hill is giving you. If anyone was passing you at that point, it would have been on the basis of their position, not pedaling.

The big number is your uphill gear. A 32 is super liberal, as in climb a cliff gearing.

The advantage to tighter gearing, like 11-25 or 11-23 is that the spacing between shifts is closer and affects your cadence less. So, it is easier to choose a gear to target a constant cadence and power output.

If needed add a larger front chainring. What do you have now? Do you need that 32?

To add to the last post... why 11 as the smallest rear sprocket ?
Its because up to recently, that's the smallest you can fit onto a normal free hub (shimano hyperglide design freehub).

Recent changes to a new design of freehub by SRAM and Shimano mean some can go to 10. But get your €€€ £££ or $$$ out for doing that - pricey hub, wheel rebuild, mega pricey rear cassette, etc. This design is still relatively new.

Thank you for the reply!

Yeah, all of the descents I spun out on were over 40mph (38-44mph on the declines). Yeah, this thread came out of me riding a 2:50, but never really got passed but saw a lot of people riding much faster (in the results). Was curious how I can make up that difference but it doesn’t help that I’m 6’ 200lbs, and hills just don’t like that weight. I think the 32 gearing was unnecessary, but I was concerned with what Snow Canyon was going to deliver. I was happy to have the 32, but it wasn’t needed.

Maybe I just need to get faster on the flats and maximize my position (it doesn’t suck, but I could get lower/more aggressive).

Okay...so really changing my gearing won’t do a ton for me? Maybe for a flat course it should/could be tighter.

No clue on the front on my race bike (it’s not with me at the moment), but I don’t think the 32 was necessary. Was concerned about the climb in snow canyon and my 200lbs self. But it turns out it wasn’t necessary (was nice, but not necessary).

Then there is no need to keep buying that particular cogset, maybe a 27 is fine. If you are spun out on the fast sections then you can add a larger front chainring. If you want to keep that 32 you can add a larger small chainring so you were using all your gears when you climb. if this is a big mystery then go talk to your shop they can look at your equipment and help you make some decisions none of these are hugely expensive purchases and are easy to install.

You may need a longer chain but probably not, especially if you also downsize your rear cogset and the shop will need to fiddle with the height of your front der. If you are a strong rider and currently have a "compact"front crankset, you are limited to a 52 tooth large chainring, but can go as small as 34 for the small ring. If you get a conventional crank, 38 is smallest and you can get something as large as a 60 for a large ring, which is silly. For any normal rider, a 53 is more than plenty.

If you are going to spend the time and money to do these long races, it's worth understanding the gears on your bike so you can explain things to your shop and make smart choices on the road. It takes about 5 minutes for someone to show you.

Alright, gearing.

Imagine that you're riding on a wheel, with cranks attached directly to the axle of the wheel. You might call it a unicycle. Add a second wheel and call it a bicycle if you want, it doesn't matter. The important thing is that the cranks are fixed to the wheel axle, so that one revolution of the cranks corresponds to one revolution of the wheel.



On this machine, every time you turn the cranks forward by one revolution, you move forward by a distance equal to the circumference of the wheel. If your wheel has a circumference of 168 inches, you'll move forward by 168 inches. By using a smaller wheel, you reduce the amount of resistance that you have to push against on the pedals, but you also have to spin faster for a given speed. So, the size of the wheel describes how high the gearing is.

Now, wheel circumference is kind of clunky to measure on the fly. It's easier to measure wheel diameter, so back in the 19th century when bicycles were actually built like this, people would describe the gearing by saying what their wheel diameter was. The gearing that results from a wheel with a diameter of 60 inches is called 60 gear inches.

But we quickly run into a problem: if we want a very high gear, we need to use a huge wheel. Suppose we want gearing equivalent to what Eddy Merckx used for his hour record: we would need to use a wheel with a diameter of about NINETY-EIGHT INCHES, or about two and a half meters.

That's a bicycle for giants.



So, we need a solution. Instead of using a huge wheel, we'll use a reasonably-sized wheel. In fact, we'll use a wheel where the outer diameter of the inflated tire is around 26.4 inches, which is approximately what happens when you mount a 25mm tire on a 700c wheel.

Now, if we attach the cranks directly to this wheel axle, we have a really low gear: a 26.4" gear! That's lower than the lowest gear on most road bikes. So we need to do something other than attach the cranks directly to the wheel axle. We'll use a chain drive.

So, we stick the cranks somewhere else on the bike, and we'll call this spot the bottom bracket. And we'll bolt something to the cranks: a toothed sprocket wheel that can engage with the chain. Because this is a ring-shaped object that engages with the chain, we'll call it a chainring. In our case, let's suppose that our chainring has 52 teeth: if we put a chain onto the chainring, it will pull that chain forward by 52 teeth every time the cranks make a full revolution.

Now, we need a wheel to be driven by the chain, so we stick a second toothed sprocket wheel onto the rear wheel. We'll just call this one the rear cog or rear sprocket, because why not. In our case, let's suppose that this cog has 14 teeth: this means that the rear wheel will make one revolution every time the chain gets pulled forward by 14 teeth.

We now have our complete chain drivetrain!



Okay, so what's the gearing?

Every time we turn the cranks through a complete revolution, we pull 52 teeth of chain. Every time we pull 14 links of chain, the wheel turns over. So with every crank revolution, the rear wheel spins 52/14 = 3.71 times.

So, our gearing is 3.71 times higher than what we'd previously expect for a 26.4-inch wheel. And 3.71*26.4 = 98, so our gearing is 98 gear inches. So our gearing is equivalent to that 98-inch wheel we were previously wanting to build, but we don't need to be a giant to ride the bike! Hooray!

But, having only one gear on our bike is kind of annoying. Maybe for our climbs we also want a gear that's only half as high. To accomplish this, we can simply double the size of our rear cog. So we create a cassette consisting of a 14-tooth cog and a 28-tooth cog. A 2-speed 14-28 cassette! Yay!

Errr... actually, this cassette still kind of sucks.
Maybe we're feeling fine in that 98" gear (52-14) when we're doing 30mph, and we're also feeling fine in that 49" gear (52-28) when we're doing 15mph. But what if we're going 20mph? In the 52-14 we're slowly grinding at the pedals with tons of resistance, and in the 52-28 we're having to spin the cranks at a super-fast 137 revolutions per minute.
So we really want some additional gears in between those two extremes. If this in Eddy Merckx's era and our freewheels tend to have five cogs, it's likely that the additional three cogs will be 17-teeth, 20-teeth, and 24-teeth. So this is now a 5-speed 14-28 freewheel, but a more precise description is that it's a 14-17-20-24-28 freewheel. After all, 14-16-18-22-28 would also be a 5-speed 14-28 freewheel, but our intermediate ratios are very different: they're more closely grouped in the higher gears, and more widely-spaced in the lower gears.

If we want to get really creative, we can also add a second chainring. If this is in Eddy Merckx's era and one of our chainrings has 52 teeth, it's likely that our second chainring has 42-teeth. 52-42, the standard classic double! Or at least, until people started calling 53-39 a standard classic double. Perhaps one day, 50-34 will be called a standard classic double. Oh well.
Anyway, the gearing math works out pretty much the same. 26.4*52/14 was 98, but 26.4*42/14 is 79. So if we're in our 42-tooth chainring and our 14-tooth cog, we have 79 gear inches. That's about 19% lower than the 98 gear inches that we get when we're in the 52-14 combination, because the 42-tooth chainring is about 19% smaller than the 52-tooth chainring.


I don't know.

What's a "really big hill?" If a road winds upward at a 2% gradient for 100 miles, you'll end up climbing over 10,000 feet. I'd call that a "really big hill", but it's not very steep and I don't think I'd need a super-low gear to manage it!

Also, how high of a gear the 32-tooth cog corresponds to depends on the wheel size and the chainrings. Now, most road and TT/Tri bikes have a wheel in the neighborhood of 26"-27", so there usually aren't big differences there (unless we bring stuff like 650c wheels into the picture...). But chainring choice can have a big impact. Like if you have a 53-39 crankset versus a 50-34 crankset... the 39-32 combination is 15% higher than the 34-32 combination. It's just as big as the difference between a 28-tooth cog and a 32-tooth cog!

Or, consider my gravel bike:



The lowest gears on this bike are much lower than the lowest gears on my road bikes, because the unpaved roads in the foothills can have long sections of steep gradients with loose material.
But, that cassette doesn't look like the big cog is very big! In fact, it looks suspiciously like a 28-tooth cog! And as it happens, it is a 28-tooth cog.
The subtle detail that's not clearly visible in the photo is that the smallest chainring has only 24 teeth. The lowest gear on this gravel bike is a mere 22 gear inches. Even at only 6mph, I can still be pedaling at ~90rpm if I want to.
So even though the big cog isn't that big, it creates a very low gear when paired with an itsy-bitsy chainring!

BUT ALSO

We need to consider the rider. Even if we can agree on what a "really big hill" is, and even if we're accounting for the size of the chainring, we can't say "such-and-such ratio is for such-and-such" riding if we don't know who the rider is. The variation in rider ability that exists in the real world is HUGE. Elite climbers can dance up hills well over twice as fast as weak cyclists. On a steep mountainous ascent, some average guy might be struggling to turn his pedals over in a 34-32 gear combination, but Giulio Ciccone might be totally at ease on the same hill in a 39-23 combination.

So is the 32-tooth cog for "really big hills"? I don't know. Maybe. Could be. Depends.

Thanks for this response!!! I knew some of that, but you laid it out perfect and easy to understand. Thank you!

Wow. Thank you. That was the most amazing post I have ever seen on here. Clear, linear, thorough, and illustrated. Did you previously publish this discourse somewhere? Also I did not know that about the gear inches. Chapeau, post of the year etc. etc.

No, just a forum post. Glad you liked it. :)

MSPaint FTMFW.

Good explanation.
I was going to write something covering the basics but less detailed than that - No need!

I get really irritated by the use of gear inches. It makes sense in that it takes the wheel size (and thus actual speed) into account, but I have no use for non-metric measurements. Tyres, rims, cranks, and my speed are all measured in metric, and this should be no different! ;)
However, when I'm looking at gearing I generally think in ratios since I use similar 23-25mm 700c tyres on both my bikes. Your post nicely explained WHY gears work as they do and you mentioned the ratio (chainring teeth/sprocket teeth) and for simplicity I think that's all most people need to worry about most of the time. So perhaps it would help the OP so see a few typical ratios?:

Typical compact setup for riding in the montains:
Semi-compact chainrings of 34T and 50T
Cassette with 11T smallest sprocket and 28T largest sprocket

34/28 = 1.21 (an 32T sprocket would make this 1.06)
50/11 = 4.55 (enough to get above 80km/h if you can manage a high cadence briefly)

Typical semi-compact setup for riding in the mountains:
Semi-compact chainrings of 36T and 52T
Cassette with 11T smallest sprocket and 28T largest sprocket

36/28 = 1.29 (an 32T sprocket would make this 1.13)
52/11 = 4.73

Old School double setup:
Chainrings of 39T and 53T
Cassette with 12T smallest sprocket and 23T largest sprocket

39/23 = 1.70 (too big for a smallest gear in the mountains IMO, especially if you're heavier)
53/12 = 4.42 (11T would make this 4.82)

Potential flat TT big double setup:
Chainrings of 42T and 54T
Cassette with 11T smallest sprocket and 25T largest sprocket

42/25 = 1.68
54/11 = 4.91


I'm a fairly heavy rider. Typically 82kg but currently 89kg :(
I've pedalled to over 85km/h more than once with either 50/11 on my road bike or 52/11 on my tri bike. It does take a very high cadence and wouldn't be sustainable, but at that speed you're usually better off tucking once you've accelerated anyway. Besides, you'll always lose a LOT more by having the wrong climbing gears than you'll gain by spinning out a little later. If you have to choose, prioritise the climbing gears.

Modern 11 speed groupsets give you a lot of flexibility. It's possible to have a very generous gear range without having to live with big intervals between gears. Also the silliness of wanting to emulate "pro" 53/39 setups even when much weaker than pros has subsided a lot in recent years, and I think more people ride with gears that actually suit them. I expect that's been aided by pros being seen to use compact sets and/or big sprockets in grand tours. I did the Marmotte des Alpes a couple of years ago. I wasn't sure how tough I'd find it (>5000m of climbing in 176km, much of it in the 8-11% gradient range) so I put a 11-32 cassette on my bike along with a 50/11 chainset. Things went fairly well and I'm not sure if I even used the 32T but I was glad I had it available. I left that cassette on afterwards, because it's great to be able to spin up 15% gradients in training and the down side is very minor ( this from someonbe who tends to be something of a grinder on hills).

Yes, most of the time difference will come in the uphills and flats. The downhills will not account for much time advantage. It is all watts per kg. At 200 lbs., you will need a lot of watts to get the speed on the flats and uphills.You probably need to be around 3 Watts/kg. to ride faster than 2:45. If your FTP is below 250, then you do not have enough power to ride that fast.

IMHO, tighter gearing helps you ride more efficiently. So, you only want to have the big cassette if you will need the big gears. If not, then only ride what you will need.

When I bought my bike in 1977, I didn't need no stupid low gears, I was a man! (at age 14). My lowest gear was 42/21. (Front 52,42 Rear 13,15,17,19,21). Never felt a need for a lower one.

When I resurrected the bike recently while weighing twice as much, it was pretty rough going up hills. I got a 14-28 5-speed freewheel on ebay. Better, but still would like lower up hills. Might go with a 14-32, which I can also find on ebay. But with the ratios on that, I'd only have 6 gears to choose from. Found a 39 front ring, but it's over 40 bucks, which seems like too much for a minor change.

Will probably stick with the 28 for awhile.

I find that when my speed exceeds 30-35 mph it is far more effective to tuck then try to apply power. At Ironman Lake Placid I ran a 50x11 top gear and was top 5 in several of the downhill segments on strava. I now have a 52X12 as my highest gear on my road bike. On the weekly club ride I am almost always fastest down the long steep hill and rank pretty highly in several local downhill segments.

You could find a local hill and compare times peddling vs an aero tuck.

Please do count the number of teeth on your large chainring and small chainring when you have a chance. This is an important piece of info that all racers should know.

Yup. Won't disagree.