Changing Cassette

Hi All

I own a Cannondale Supersix with 52/36 at the front and 11/30 cassette at the back.
My wife owns a Specialised Diverge with 48/32 at the front and 11/32 at the back.

My bike is quicker which means I can drop my wife fairly easily. So we are thinking of swapping bikes to close the gap slightly. However, having tried my bike, my wife doesn’t have the leg strength (yet) to get up some of the hills in our area. The hills are often short and steep, (gradients up to 20%).

I know nothing about gearing so please keep your answers really simple but if I switched to an 11/32 at the back of my Supersix, how close would that be to her gearing and would it make a noticeable difference from an 11/30?
I have DI2 and would need to buy and change to a long cage derailleur so it’s not a cheap option. But If changing derailleur and swapping cassettes makes a noticeable difference I will do that. But if it doesn’t, then I won’t waste my money.

Thanks for your help in advance.


Changing bikes isn’t going to help. Go easier.


That isn’t really helping with the question :wink:

Here is one of the many gearing calculators on the web:

In an overly simple comparison of the lowest gears suggested:

  • 36 / 30 = 1.200 input to output ratio (1 crank revolution = 1.2 wheel rotations)

  • 36 / 32 = 1.125 input to output ratio (1 crank revolution = 1.125 wheel rotations)

In reality, this is a relatively minor change and not one I think will “solve” your problem. I suspect you’d have to make a much bigger change in gearing (chainring and cassette) to get low enough gearing to fix what I think you are aiming at (being able to spin an easier gear more than being forced to muscle your taller gears which pulls you away from your wife?).

I think there may be better ways to address your issue like sag climbing by letting her roll the front at the bottom of the climb with a decent lead that you then close on your way up?

Getting an XC bike for yourself or putting Gatorskin tires on your bike is more likely to bring the gap closer.


We had a similar question one year ago with lots of ideas:

That was me asking that question lol.
I applied some of the suggestions and that’s worked great but I have put a lot of time into cycling over lockdown so was now looking at the possibility of swapping bikes

LOL, Doh! Well, why the heck haven’t you solved this yet? :stuck_out_tongue:


The hills are just part of the issue. We cycle together on the flat and small slopes and on steep or long hills, we cycle at our own pace.

However, the Supersix is more aero, it have better wheels and tyres and it transfers effort from the legs to the wheels better. In essence it is more efficient than an adventure bike.
So my question isn’t just about hills but about cycling in general.
However, my wife does need to be able to get up the steeper hills in order to be able to use the Supersix which is where my question was coming from.

But we solves a lot of the issues by always seemingly finding a bloody great headwind lol

At the moment, if you are both in your lowest gears, you will travel 1.2 times further than your wife with each pedal stroke.

If you swap to a 32 at the back you will travel 1.16 times further, so I would say it isn’t worth your money. I would let her climb at her own pace and wait at the top. I used a traditional ‘gear inch’ calculator online for the numbers.


That’s very helpful. Thank you :slight_smile:

Changing chainrings on your bike would bring it closer then the extra 2 teeth on the largest sprocket. However, I also don’t think this is worth the money. Hills will always split groups, even if the group is just two. You’d be better off going slower, or waiting. Save the money to buy her a lightweight, fast bike.

I’m a lot faster than my wife on the hills. If I try and ride with her she gets annoyed and tells me in no uncertain terms to just ride to the top and wait. :grinning:

Here’s a calculator

I understand Sheldon has moved on from this mortal coil but his website is still maintained.

There’s a much better option than swapping out the rear derailleur.

First of all, have your wife rode her own bike on these hills to determine what gearing she needs. Her setup has a easiest great ratio (chain ring teeth divided by cassette teeth) of 1.0. That’s pretty good, but honestly on 20% grades that’s still harder than many people would like. If it’s enough for her, then great, now you have your target.

Your bike (36:30) is a 1.2 gear ratio. That’s 20% harder, which is huge. You could go to a 32 cassette, but it’s still 36:32 = 1.125 ratio. To get to a 1 ratio, you need either 36:36 with your current crank or 34:34 or 34:36 (0.94) by getting smaller chainrings (like 50/34, which is common). The downside to a 11-36 cassette is bigger jumps between gears. The downside to different chain rings is a lower top speed, but in reality if you raise your cadence by just 4% you are right back to the same speed.

Now there are three limitations you have to keep in mind with changing gears. 1) If increasing chain ring size, you have to check if your frame has clearance, but that doesn’t apply here since you are decreasing size. 2) The front and rear derailleurs can only handle so much difference in tooth count between gears. 3) The rear derailleur has a max cassette limit, to an extent.

For (2), the chain wrap issue, you use the following formula to see how much chain wrap you need.

Chain Wrap = (large chainring – small chainring) + (large rear cog – small rear cog)

So for 50/34 and 11-36 that would be 41 teeth. Then you check Shimano docs for the chain wrap capacity of your derailleur. If it’s 41 or higher, you’re good.

For (3), the maximum cassette size, you also check the manual. However, in most cases you can increase the maximum size using an adapter like the road link or goat link from Wolf Tooth.

Doing this research is on you, but it’s the best way to help her get up the hills, other than getting her an e-bike

I can totally see that. I usually ride with a few mates who are much faster climbers than me (they are all tiny!) and having them around me going as slow as they can and being all chatty and chearful while I’m deep into vo2max territory and trying not too show it, is well annoying. Just go on and let me suffer in silence. :laughing:

In you heart of hearts, hidden behind The Wall of Marginal Gainz, you know this is marketing BS.

Do the swap, play with gears, carry a sack of coal, you will still be faster than your wife. But you will have learned how little aero bikes affect the outcome - and how much a lifetime of testosterone does, which is worthwhile in itself.


I would still probably have to wait at the top of hills for her even if we changed cassette.
But she isn’t sure she would even get up those steep hills right now. My thought about changing cassette was to her reach the top. Then we would cycle together on the flat.

I can’t afford a new bike as spent all my money on the Supersix lol

I know it’s marginal and we don’t cycle at 30mph enough for aero to play a massive part. But it’s just one piece of a bigger picture.

When I swapped from my Synapse, I went quicker…due to all the various elements added together, (and yes probably in art due to feeling ore excited on a better bike).
But if these elements together help bring us closer then it’s all good :slight_smile:

See my reply about that above. She has the lower gearing on her bike to see what works