Thoughts on new crank/cassette ratios please.

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scook94

Veteran
Location
Stirling
I'm in the process of upgrading components on my bike and am now turning to the cranks and cassette.

I'm currently running 50/34 and 12/25 but would like more at either end, especially for long downhill runs as I find I'm spinning out too easily.

My favoured route would be to go to 52/36 and 11/28, which will give me much more top end and a wee bit more for those steeper climbs. I've been on the Sheldon Brown gear chart page but, to be honest, all those numbers don't really mean much to me at this stage.

I appreciate that this will be way different to what I have just now but would appreciate any thoughts/comments you may have.

TIA.
 

eldudino

Bike Fluffer
Location
Stirling
Go 53-39, 11-23 and get bigger thigh muscles instead! ;)

By the way, I'll be going compact I think - it's the only option!
 
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scook94

scook94

Veteran
Location
Stirling
eldudino said:
Go 53-39, 11-23 and get bigger thigh muscles instead! ;)

By the way, I'll be going compact I think - it's the only option!

Unless you have a chat with Craig!? When are you planning on telling Cycle Chat your news anyway?
 
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scook94

scook94

Veteran
Location
Stirling
accountantpete said:
The 11/28 will leave big gaps in the gearing so you won't get a smooth transition if that is important.

This is my concern, and until I actually try it I won't really know for sure!
 

PpPete

Legendary Member
Location
Chandler's Ford
I find this Excel sheet more helpful than Sheldon.

Make a local copy and highlight the rows (sprockets) & columns(chainwheels) that apply to your current set up.

The numbers on the intersections are the "gear inches" - which is a just a number, it's derivation is pretty irrelevant.

Have a think about which ones you use most, because you'll want the same or similar in your new set up.

Then think about where you want to be as far as new "top" & "bottom" gears.

Finally think about the gear changes themselves. Are you going to be making lots of double changes? Do you mind doing that?
 

jimboalee

New Member
Location
Solihull
Firstly, what bike is it? How heavy is it?

Secondly, how fast do you cruise when you're out for 100 km?

How fast do you climb hills? Speed vs gradient please.

Have you any idea of the power you can produce just below your lactate threshold?

What cadence do you prefer? Is it what you would pedal at your cruising speed on the 100 km ride?
 

PpPete

Legendary Member
Location
Chandler's Ford
scook94 said:
This is my concern, and until I actually try it I won't really know for sure!


I went through process above.... but when I thought about the gaps (and what I found acceptable/unacceptable gap on a 7 sp hack) I realised there was no standard cassette that did what I wanted. Ended up buying 2 cassettes and butchering them to combine different sprockets to get all the right ratios.
 

PJ79LIZARD

Über Member
Location
WEST MIDLANDS
I have 50/34 and 11/28 cassette. It's fine for not spinning out so much on decents and the 28t is good for big climbs when your legs have had it. But what annoys me is when i'm in 34 front 11 back it jump on the cassette. I know the chain is at a severe angle but on my other bike 53/39 11/30 on cassette i can use every gear no probs. So i'm thinking about putting a 12/25 cassette on my compact and see if i still have the same jumping problem or if the extra tooth helps. What do you lot think?
 

PpPete

Legendary Member
Location
Chandler's Ford
PJ79LIZARD said:
when i'm in 34 front 11 back it jump on the cassette. I know the chain is at a severe angle

So don't run it like that - you'll wear your chain much faster. You can get the same ratio with 50 front / 16 back - which will be much kinder on your components
 
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scook94

scook94

Veteran
Location
Stirling
jimboalee said:
Firstly, what bike is it? How heavy is it?

Secondly, how fast do you cruise when you're out for 100 km?

How fast do you climb hills? Speed vs gradient please.

Have you any idea of the power you can produce just below your lactate threshold?

What cadence do you prefer? Is it what you would pedal at your cruising speed on the 100 km ride?

Jimbo, as usual you're way too technical for me! the bike is going to be based round a new Ti frame, so hopefully it'll be nice and light, lighter than my current steel frame anyway.

I'm not great at climbing, but I'm making good progress at improving. I don't really want to jeopardise that too much by having too big a granny ring, but on the other hand I'll (at some point) want to really start doing some serious climbs.

I'm currently doing 45 mile rides over hilly and undulating terrain so there's not much cruising to be done.

I'm thinking that if the proposed set up is going to be too different I'll stick to 50/34 on the front and maybe go with 11-26. Perhaps sticking with what I know up front will make it easier to get the cassette that would suit me?
 

PJ79LIZARD

Über Member
Location
WEST MIDLANDS
ok thats fair enough! I didn't realise that that would be the same. I've heard people say on here that one ratio is the same as another, but i've never understood how it is calculated. I'll take that onboard porky. Thanks for your reply.
 
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scook94

scook94

Veteran
Location
Stirling
PJ79LIZARD said:
I have 50/34 and 11/28 cassette. It's fine for not spinning out so much on decents and the 28t is good for big climbs when your legs have had it. But what annoys me is when i'm in 34 front 11 back it jump on the cassette. I know the chain is at a severe angle but on my other bike 53/39 11/30 on cassette i can use every gear no probs. So i'm thinking about putting a 12/25 cassette on my compact and see if i still have the same jumping problem or if the extra tooth helps. What do you lot think?

I find I get a lot of rub at the moment if I use 34/12 but to me that's just an indication that I should be on the 50 up front.
 
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