Closer Ratio Cassettes

[bpsmith]

i have a new crankset to fit to bike 2 in the new year sometime. I have gone from Compact to Semi-Compact and from 172.5mm to 170mm as that is what I like on the bike 1.

Bike 1 is an aero frame with semi deep section rims. Bike 2 is more suited to climbing and have new shallow section rims ready to go on in the Spring.

When fitting the new crankset, I am toying with putting it on Bike 1, along with a new chain and a new cassette. Then sticking the used crankset on bike 2. The reason being is that I am tempted to put an 11-25 or even an 11-23 cassette on.

Just wondering if gaining the extra 1 or 2 intermediary sprockets will outweigh the loss on the climbs, or is it hardly noticeable when shifting smoothly through the gears on the flat?

 

[I like Skol]

i have a new crankset to fit to bike 2 in the new year sometime. I have gone from Compact to Semi-Compact and from 172.5mm to 170mm as that is what I like on the bike 1.

Bike 1 is an aero frame with semi deep section rims. Bike 2 is more suited to climbing and have new shallow section rims ready to go on in the Spring.

When fitting the new crankset, I am toying with putting it on Bike 1, along with a new chain and a new cassette. Then sticking the used crankset on bike 2. The reason being is that I am tempted to put an 11-25 or even an 11-23 cassette on.

Just wondering if gaining the extra 1 or 2 intermediary sprockets will outweigh the loss on the climbs, or is it hardly noticeable when shifting smoothly through the gears on the flat?

11-25 is optimal with a triple chain set for emergencies. Other than that just MTFU and get some better legs ​

 

[raleighnut]

I've got a 12-23 (10spd) on my TT bike (53-39 front) and it ain't that good going uphill.

 

[bpsmith]

I've got a 12-23 (10spd) on my TT bike (53-39 front) and it ain't that good going uphill.

Isn’t that partially due to the geometry of the TT though too?

My mate has the same gearing on a road bike and a TT and reckons he struggles a lot more climbing on the TT.

I have never ridden a TT, so have no idea.

 

[Sharky]

I always prefer close ratios, particularly either side of my "normal" riding gear. I've spent hours studying gear tables and working out where the gaps fall. But you need to work out what the lowest gear you need for the steepest hill you normally encounter. I would sacriface an 11 or 12 sprocket for closer mid ratios.

 

[Vapin' Joe]

You have to have a gear low enough to get you up the steepest climbs you are likely to encounter, and you'll want a gear that allows you to go as fast as you need to if racing or just enjoy if you're not. Those are the vital two ratios you must have and thew cassette should be built round them.

With 11 sprockets now though, unless you go to extremes at the top and bottom of the cassette there are no big jumps between gears, unlike the old days of five speed blocks when you could spend an afternoon with a gear chart giving yourself a headache trying to decide.

 

[bpsmith]

Perhaps I should rephrase the question. One bike will be used for when I intentionally set out to do some climbs. The other (aero frame) bike will be used for flatter rides, at faster speeds, but may unintentionally hit some climbs possibly. Currently both have 11-28 fitted.

What I am interested in is whether it’s worth swapping the aero bike’s cassette to an 11-23, to gain the 16 and 18 tooth sprockets by sacrificing the 25 and 28? Just interested in how the feel of the bike changes when doing more of a flatter or slightly undulating TT style route?

 

[Vapin' Joe]

What I am interested in is whether it’s worth swapping the aero bike’s cassette to an 11-23, to gain the 16 and 18 tooth sprockets by sacrificing the 25 and 28? Just interested in how the feel of the bike changes when doing more of a flatter or slightly undulating TT style route?

That's impossible to answer, really. Some riders can tolerate a bigger change in cadence than others without any effect on performance, it is very much an individual thing. The question you need to answer is how do you feel when you are shifting on the mid range of your current set up. If you feel the jumps are too big and it is slowing you down then the closer ratios would help, if you don't then I wouldn't bother.

Although you can always try and then switch back next time you renew the cassette. If you ride regularly that won't be too long.

 

[Ajax Bay]

With a semi-compact 52t large chainring, you could consider losing the 11t and going for a 12-25 - eg this one.
Do you really need to pedal at 60+kph? Flatlands will offer little scope for that.
Play with this:
http://www.gear-calculator.com/?GR=...17,18,19,21,23,25&UF=2125&TF=90&SL=2.6&UN=KMH

 

[bpsmith]

With a semi-compact 52t large chainring, you could consider losing the 11t and going for a 12-25 - eg this one.
Do you really need to pedal at 60+kph? Flatlands will offer little scope for that.
Play with this:
http://www.gear-calculator.com/?GR=...17,18,19,21,23,25&UF=2125&TF=90&SL=2.6&UN=KMH

Strangely enough, I have that page from Merlin bookmarked as it’s the cheapest price at present. Appreciate the post nonetheless.

You’re probably right on the 11. My mindset was that I love to power down the hills once I’ve climbed them, but if going to use the other bike for planned climbs then I can probably put up with the odd few occasions where I do a climb.

12-25 is a good shout, thus gaining the 16 and 18, but only losing the 28. Interesting.

I use an App on my phone for gear calculating, but that site looks good too. A quick look shows me maxing out, in the 52:12 combination, at 28mph. That’s at my natural cadence of 83. There are one or two sprints locally where I have gone for it and hit a 33mph average, albeit over 0.2 miles. Reality is that there’s only a couple of places where a few of us try and get up to those speeds.

 

[Banjo]

You can have a bigger step into your biggest cog effectively leaving you with a close ratio 10 speed plus a bigger cog in reserve for steep hills on tyred legs.