Gear ratios, cadence, speed.

[simmi]

I am a bit of a tinkerer and am at the moment tinkering with my cassette ratios to get the optimum set up for me. (43 just starting out cycling with a average speed between 15 and 16mph and lets face it am never going to get Wiggins quaking in his boots)
With a bit of maths I have worked out that with a cadence of 90 and a wheel diameter of 675mm with a ratio of 1 : 1 I will be moving at 7.12mph so to translate to my current set up in my highest gear 52/11 I would be moving at 33.7mph and my lowest 39/28 would be 9.9mph.
My thinking is why on earth do most cassettes start off with 11 or 12 teeth, even with 14 I would be doing 26.4 mph.
On the flat I can keep to about 18-20mph for some time and obviously down hills can get higher speeds but to be honest spend more time coasting than pedalling.
I am going to change my set up from 11/12/13/15/17/19/21/24/28 to 14/15/16/17/19/21/23/25/28.

I am sure pro's and top club cyclists need the 11 and 12 teeth cogs but not sure why the rest of us would have them.
With a triple or compact chainset I can see this is a different matter, but with you standardish 39/52 double how often would 75% of cyclists use them?
Perhaps I am getting a little over involved for my level or ability but really just want to get the maximum from the effort I put in.
Any thoughts on my musings would be welcome.

 

[lulubel]

Unless you're that bothered about only having single tooth gaps between most of your gears (and it doesn't bother me - I have an 11 - 34 cassette), I don't see the point of it really. If you don't want to use the highest gears, you don't have to.

I've used my biggest gear of 50x11 a number of times on long, straight, gentle descents because it gets quite boring (and can also get cold) just sitting there freewheeling for that length of time.

 

[Fasta Asloth]

FWIW, i recently changed my 8 speed 11-28 to a 12-25, since having a jump of 3 or 4T (28-24-21....) was too much for my riding style and local terrain, now max difference is 2T and is more suited for me on the roads that I most frequent... I love pedalling fast down the 'hills' around here so quite often use a 48/12 gear. Go with what suits you for current and future needs....

 

[MattHB]

Interesting thread.. I'm finding the ratio spacing on my 28-11 a pain in the bum as I have a very narrow preferred cadence range that feels oh'so comfy. I've been considering a 11-25 to flatten them out a bit.

 

[GrasB]

But what have you done with the chainring ranges? This leaves you with an effective overlap lap gears as mostly duplicates rather than offset gears & if you want to keep your chain line then your overlap gears goes from 3 to 1. You'd be much better taking a nice 11-23 cassette & using a compact crank set with a 33/46 chainrings to give you a nicer spread of tight ratios in a slightly larger gearing range.

 

[simmi]

But what have you done with the chainring ranges? This leaves you with an effective overlap lap gears as mostly duplicates rather than offset gears & if you want to keep your chain line then your overlap gears goes from 3 to 1. You'd be much better taking a nice 11-23 cassette & using a compact crank set with a 33/46 chainrings to give you a nicer spread of tight ratios in a slightly larger gearing range.

I agree with you, if I knew as much when I purchased my bike as I do now I would have gone for a compact crank, seems much better suited to my level, I might still end up going down that route but at the moment it is much cheaper to mess with the cassette.
This only illustrates my point, using the compact crank the 12 tooth cog on the cassette would be very similar to a 14 tooth on a standard crank.
I have checked the ratios for my proposed new cassette and find I get more unique gears than I did with my original 12-23 cassette.
It seems to me the my 39/52 chainrings are bound to give overlap in effect the 39 is 3/4 of 52 so a 15/39 would be identical to a 20/52 or a 12 would be a 16, an 18 a 24 and so on.

 

[Peteaud]

Interesting thread.. I'm finding the ratio spacing on my 28-11 a pain in the bum as I have a very narrow preferred cadence range that feels oh'so comfy. I've been considering a 11-25 to flatten them out a bit.

I went the exact opposite.

Fromm 11-25 to 11-28 and much prefer it as it suits my riding style.

 

[HLaB]

A while back I changed my cassette from a 12-25 to a 11-25, I've now changed to an 11-26; I quite like not spinning out and having the gears for sprints but also having gears to fall back on.

 

[GrasB]

I agree with you, if I knew as much when I purchased my bike as I do now I would have gone for a compact crank, seems much better suited to my level, I might still end up going down that route but at the moment it is much cheaper to mess with the cassette.
This only illustrates my point, using the compact crank the 12 tooth cog on the cassette would be very similar to a 14 tooth on a standard crank.
I have checked the ratios for my proposed new cassette and find I get more unique gears than I did with my original 12-23 cassette.
It seems to me the my 39/52 chainrings are bound to give overlap in effect the 39 is 3/4 of 52 so a 15/39 would be identical to a 20/52 or a 12 would be a 16, an 18 a 24 and so on.

Take a look at your proposed setup then compare it to a more typical compact setup in a visual manner. It's not just about the top & bottom but what's in the middle. I think that hole in the higher 70" range on your setup is going to cause issues. the 60-80" gear range for cyclists who are averaging somewhere between 15 & 20mph is a critical area to keep nice & tight.

 

[simmi]

Take a look at your proposed setup then compare it to a more typical compact setup in a visual manner. It's not just about the top & bottom but what's in the middle. I think that hole in the higher 70" range on your setup is going to cause issues. the 60-80" gear range for cyclists who are averaging somewhere between 15 & 20mph is a critical area to keep nice & tight.

Cheers GrasB, I love the Mike sherman gear calculator.
Going to have hours of fun with this!
You are right again the point where I go from 1 tooth to 2 teeth jumps is always going to be my biggest gap, would love to have an 18T aswell but would mean I would have to drop out the 28T or have bigger gaps elsewhere.
I will have a play and see what I can come up with.
I wanted to keep the 28T if I could because hills are definitely my week point.

 

[simmi]

For some reason most of the compact cranks on ebay are not 170mm
My current crank is 170 would I notice a difference with a 172.5 or 175
I am 5ft 11" with a 32" inside leg.
Would 5mm be that noticeable?

 

[GrasB]

You'll see a downward shift in your cadence (your foot speed will stay about the same). But basically you'll adapt fairly quickly.
As for cassettes, a custom 10sp cassette I've been using & really like is this: 11, 12, 13, 14, 15, 16, 18, 21, 25, 30. Note what's happening with the bottom end of the cassette, increasing the ratio gap progressively like that down the low end doesn't seem to be much of a problem I find.

 

[simmi]

You'll see a downward shift in your cadence (your foot speed will stay about the same). But basically you'll adapt fairly quickly.
As for cassettes, a custom 10sp cassette I've been using & really like is this: 11, 12, 13, 14, 15, 16, 18, 21, 25, 30. Note what's happening with the bottom end of the cassette, increasing the ratio gap progressively like that down the low end doesn't seem to be much of a problem I find.

Do you find you use the 11 and 12 though, would think from my point of view better to have a 17 and 19 instead so you have more options in the areas you are using most, or am I missing something?

 

[GrasB]

Do you find you use the 11 and 12 though, would think from my point of view better to have a 17 and 19 instead so you have more options in the areas you are using most, or am I missing something?

Several 100w for a starters & my nominal cadence is around 100-125rpm. Oh yeah this is my Alpine weapon of choice when combined with 36/52 compact. You'll tend to find me hanging around the 13, 14 & 15t sprockets on bottom chainring for normal riding on the flat +/-2% gradient. In all honesty I can quite happily kick through a 53/11 in a meaningful around Cambridge on the steeper descents, but they're short so worth putting loads of power in & then reaping the benefits on the next incline or flat section.

 

[cyberknight]

Interesting stuff, since coming back to cycling i have always rode compact chainsets and i have never had a problem keeping up based on gears , i always run out of endurance before i run out of gears .
For 20 mph i am pushing 50 x 17 on a 12-25 cassette and i only ever use the x13 and x 12 over 30 mph on descents or if were have the hammer down on a club run.
my other bike has an 11-28 that a changed from an 11-32 as i never used the easiest gears and in fact i cant say i have ever used the 28 yet ...... its in reserve for when my legs die.