28 Vs 32 tooth

I’m going to be doing a triathlon in an area with a lot of hills. I’ve currently got an Ultegra 11-28 cassette and was thinking of upgrading to an 11-34 but I can’t find any for sale. I have found a 105 11-32 and was wondering how much difference the four teeth would make. I’ve not changed a cassette before so don’t have any reference.

Is it worth the cash and effort?


To give you and idea of how much different it will be, on the new 32 cassette, shifting from the 28 to the 32 cog will feel pretty similar to what it’s like shifting from 25 to 28 cog on your current cassette. So that’s how big a difference it will be. It’s not huge, but it’s also not totally insignificant either. It would take a lot more info to be able to give useful advice in this situation.


The four teeth will make a reasonable difference if you’re right on the limit on the climbs. Another way of thinking about is that you’d be able to go from a cadence of 70 on the 28 tooth cog to 80 on the 32 tooth for the same speed. It would help save your legs a bit for the run.

From a mechanical perspective, you’ll need to make sure your rear derailleur has clearance for the 32 tooth cog, and also that it has the required range for the 21 tooth difference on the 11-32 tooth cassette plus the difference between your chainrings.

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I was thinking about this when I wrote the message, I’ll give that a go and try to see how it feels.

I’ve always been a grinder, even on the flat, but I’ve been working on getting the cadence up, so that would help.

And I’ve checked the mech, it will go up to a 34 so I’ve got plenty of room.


@digininja Have you seen this online calculator? It might give you some additional perspective on the differences.

Gear Calculator

I’m curious. What chainrings are you running in the front?

Related, I did not like the cog spacing on a 11-34, I found 11-32 to be more reasonable.

My dream cassette is 13-15-17-19-21-23-25-28-30-32-34. Doesn’t exist of course.

I’m considering a GRX 48-31 crankset with a 11-30 cassette to accomplish my goal.

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I’m totally sold on ultra compact chainsets, I’ve a 40t 28t XT chainset on my gravel bike paired with an 11-32 cassette. With a 28:32 bottom gear I’m still spinning when everyone else would be grinding. It’s the equivalent of having a 39t sprocket for those with a standard 34t inner ring. But is still get close ratios from an 11:32 cassette and crisp shifting that you don’t get on those dinner plate sized mtb cassettes.


I’ve got a 50-34

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I’ve just had a look and don’t really understand what I’m looking at.

That’s an interesting thought, I hadn’t considered the size of the jumps

@digininja The tool allows you to add the gears you currently have and then make changes. Just drag the gears and chain rings to match the sizes on your current setup, take a screen shot and then make the revisions to the gears to see the differences in meters of development.

Here is the description of the tool:

When buying a new bike or upgrading an old one the gear calculator can help to find the optimal gearing for it. The gear calculator displays graphically the speed and development (either in gear inches or in meters) for all gears of a given gearing system, either with derailleurs or with hub gears. Gearing system, chainrings and cogs can be chosen out of given lists or selected by moving the sprocket symbols. Not used chainwheels and cogs can be removed by moving them to the left below the graphics. The tire size can be chosen out of a list or the tire circumference can be entered in millimeters.

The gear calculator doesn’t know your riding performance, of course. Therefore it is best to start with the gearing data of one of your bikes, with gears you know or from which you know if you miss some gears at specific speeds. The gear calculator starts with a typical mountain bike 2x10 setup. The compare option allows to find a better gearing for your riding style.

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Out of interest, what sort of thing are we talking about when you say lots of hills?
Alpine climbs? Or more of a rolling course? Altitude/km?

Not TdF level climbs, but hard enough for a runner not great on a bike.

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What sort of RPM are you doing on the flat and at what power output/intensity?

Some steep climbs round that way!

I finally dragged my FTP up to 202w and my cadence is usually around 80.

My first 70.3 3 years ago it was 55, and so I put quite a bit of work in to raising it up.

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Between 80-90 RPM is a good level especially for the high intensity sustained efforts. 55 would be too low so well done on working on that and raising it up!

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I did FF and stuck to the cadence suggested which dropped my FTP from about 160 to 130, I used that for about 6 months doing mostly high cadence at the lower power. I redid FF and my FTP was up to 170 and I was fairly close to the suggested cadence while doing it.

I still have to concentrate on keeping it up otherwise I do drop back down again, but I can do it, so just have to keep focused.

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