Gear ratios

[Chris Armstrong]

I am a technonumpty. Could anyone with the knowhow advise me whether a 30 front and 23 rear cassette would have a (lot) lower gear ratio than a 39/28 set up. I feel I might find out that it's a daft question but it is a serious one, and any advice appreciated.

 

[JohnB]

Chris Armstrong wrote:
>
> I am a technonumpty. Could anyone with the knowhow advise me whether a
> 30 front and 23 rear cassette would have a (lot) lower gear ratio than
> a 39/28 set up. I feel I might find out that it's a daft question but
> it is a serious one, and any advice appreciated.

No it would not be a *lot* lower.
Assuming 700c wheels you would have gears of 34.9 inches compared to
37.3 inches.
That would not be noticeable unless you were really straining up a 1in6 incline.

Best place to check gear ratios is of course Sheldon:

http://www.sheldonbrown.com/gears/

HTH

John B

 

[Simon Brooke]

in message <[email protected]>,
Chris Armstrong
('[email protected]') wrote:

>
> I am a technonumpty. Could anyone with the knowhow advise me whether a
> 30 front and 23 rear cassette would have a (lot) lower gear ratio than
> a 39/28 set up. I feel I might find out that it's a daft question but
> it is a serious one, and any advice appreciated.

There's not a lot in it. 30/23 = 1.30 (equivalent to an ordinary with a
35" wheel); 39/28 = 1.39 (equivalent to an ordinary with a 37" wheel).
So you get a slightly lower bottom gear with a 30/23.

--
[email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/
;; We don't just borrow words; on occasion, English has pursued other
;; languages down alleyways to beat them unconscious and riffle their
;; pockets for new vocabulary -- James D. Nicoll

 

[Pete Biggs]

Chris Armstrong wrote:
> I am a technonumpty. Could anyone with the knowhow advise me whether a
> 30 front and 23 rear cassette would have a (lot) lower gear ratio than
> a 39/28 set up.

I'll put it in a way that I hope you might be able to relate more to (or
imagine better) from experience with a 39 tooth chainring..........

30/23 would be almost the same as 39/30, which on a typical road bike
would only feel like "half a gear" or so lower than 39/28. Bear in mind
that difference between sprockets naturally increases at the "low" end --
eg. 32T is usually the next sprocket in a cassette after 28T.

I reckon you'd either need to use a cassette that goes up to at least 25
or 26T, and/or an inner chainring of 28T to make switching to a triple
chainset worthwhile in this case if having lower bottoms gear was the main
goal.

Swapping the stock granny ring for a 28T or even a 26T is a good move
anyway, in my experience. Sheldon Brown also recommends this and calls
30T inners "silly". 30 tooths are nice for slick shifting but otherwise I
agree.

~PB

 

[Tim Hall]

On Fri, 22 Apr 2005 06:23:27 +1000, Chris Armstrong
<[email protected]> wrote:

>
>I am a technonumpty. Could anyone with the knowhow advise me whether a
>30 front and 23 rear cassette would have a (lot) lower gear ratio than
>a 39/28 set up. I feel I might find out that it's a daft question but
>it is a serious one, and any advice appreciated.

Take the front sprocket and divide by the rear sprocket. Thus 30/23 =
1.304 and 39/28 = 1.39

So 30/23 is lower than 39/28. Gear ratios are often measured in gear
inches (which relates to the diameter of the front wheel of a "penny
farthing" or "Ordinary"). To calculate gear inches take the diameter
of the wheel x front sprocket/rear sprocket.

So for a nominal 27 inch wheel

27 x 30/23 = 35

27 x 39/28 = 37


So 30/23 is a bit lower than 39/28.


Tim

 

[davek]

Pete Biggs wrote:
> Swapping the stock granny ring for a 28T or even a 26T is a good move
> anyway, in my experience. Sheldon Brown also recommends this and
calls
> 30T inners "silly". 30 tooths are nice for slick shifting but
otherwise I
> agree.

I /think/ I disagree, though it's not clear cut...

I have a 52-42-30 chainset and 14-25 9spd cassette, which gives me a
bottom gear of 31.5".

Changing the granny ring to a 28 would give me a bottom gear of 29.4"
while a 26 would give me a bottom gear of 27.3", neither of which is
significantly lower - certainly not enough to persuade me to part with
the cash for a new granny ring.

On top of that, I would probably have to buy a new rear mech with an
"extra long" cage to cope with the difference between the large and
small chainrings (the "long" cage tiagra rear mech I currently have
struggles to cope as it is - I realise now that I should have got a MTB
mech), and I would probably want to swap that middle chainring for a 40
as well, just to keep the spacing between chainrings reasonably even.

So, there may be benefits to a smaller granny ring, but in my case I
don't believe they would outweigh the cost of conversion. On the other
hand, if I were the OP, doing the conversion from scratch, I would look
into getting the chainset with chainrings of my choice, rather than the
off-the-shelf selection, and maybe I would go for the 26T granny.

d.

 

[Pete Biggs]

davek wrote:
> Pete Biggs wrote:
>> Swapping the stock granny ring for a 28T or even a 26T is a good move
>> anyway, in my experience. Sheldon Brown also recommends this and
>> calls 30T inners "silly". 30 tooths are nice for slick shifting but
>> otherwise I agree.
>
> I /think/ I disagree, though it's not clear cut...
>
> I have a 52-42-30 chainset and 14-25 9spd cassette, which gives me a
> bottom gear of 31.5".
>
> Changing the granny ring to a 28 would give me a bottom gear of 29.4"
> while a 26 would give me a bottom gear of 27.3", neither of which is
> significantly lower - certainly not enough to persuade me to part with
> the cash for a new granny ring.

Those differences /are/ significant if your bottom gear is just a bit too
high -- just high enough to make you struggle up some hills. I have no
desire to go back to 30T myself. I do agree switching from an existing 30
to a 28 will only make a small difference but still that can be worthwhile
if you're desperate for /some/ help, any help!, and would find 26T
impractical for whatever reasons. The cost can be offset by selling the
original 30T ring if it's in new or excellent condition.

(But I would recommend being brave and trying a 26 first).

Of course the cassette could be changed instead but there are serious
downsides besides cost. There's almost no disadvantage in changing from
30 to 28 apart from the financial cost. Derailleurs will usually cope
fine........

> On top of that, I would probably have to buy a new rear mech with an
> "extra long" cage to cope with the difference between the large and
> small chainrings (the "long" cage tiagra rear mech I currently have
> struggles to cope as it is - I realise now that I should have got a
> MTB mech),

A standard Shimano road triple (and Campag medium) rear mech should cope
with 26-42-52 + 14-25 (and even wider ranges) as long as you avoided using
the smallest 3 or 4 rear sprockets from the inner chainring, which is no
big loss. Having the chain as short as possible for the big-big is the
key. I suspect you could remove a link or two from your chain right now
for a start.

> and I would probably want to swap that middle chainring
> for a 40 as well, just to keep the spacing between chainrings
> reasonably even.

Very fair point (and it's nice to have to have a 40 or 39 middle anyway
when crusing speeds are not super-high).

> So, there may be benefits to a smaller granny ring, but in my case I
> don't believe they would outweigh the cost of conversion.

It's only money ;-)

> On the other
> hand, if I were the OP, doing the conversion from scratch, I would
> look into getting the chainset with chainrings of my choice, rather
> than the off-the-shelf selection, and maybe I would go for the 26T
> granny.

~PB

 

[davek]

Pete Biggs wrote:
> Those differences /are/ significant if your bottom gear is just a bit
too
> high -- just high enough to make you struggle up some hills.

Yeah, maybe. I suppose it depends on the individual cyclist - speaking
for myself, the hills I couldn't get up on a 30*25 gear are few and far
between.

> A standard Shimano road triple (and Campag medium) rear mech should
cope
> with 26-42-52 + 14-25 (and even wider ranges) as long as you avoided
using
> the smallest 3 or 4 rear sprockets from the inner chainring, which is
no
> big loss. Having the chain as short as possible for the big-big is
the
> key. I suspect you could remove a link or two from your chain right
now
> for a start.

Unfortunately, the chain is already too short for the big-big
combination - and it is also too long for the small-small combination,
but since I would never use those gears in practice, I don't let it
worry me. I'm fairly convinced that a longer cage mech would be the
ideal solution - unless I've somehow got the whole thing set up
wrongly.

d.

 

[MSA]

Pete Biggs wrote:
> davek wrote:
>
>>Pete Biggs wrote:

>>On the other
>>hand, if I were the OP, doing the conversion from scratch, I would
>>look into getting the chainset with chainrings of my choice, rather
>>than the off-the-shelf selection, and maybe I would go for the 26T
>>granny.
>
>
> ~PB
>
>


Out of interest, is it possible to buy individual Campag 9/10 rings? I
seem remember seeing individual cogs hanging on a wall in a shop in
France last year...are they available 'over ere'?

--
Mark
_____________________________________________

Deja Moo - The feeling that you've heard this bull before

 

[Pete Biggs]

davek wrote:
> Pete Biggs wrote:
>> Those differences /are/ significant if your bottom gear is just a
>> bit too high -- just high enough to make you struggle up some hills.
>
> Yeah, maybe. I suppose it depends on the individual cyclist - speaking
> for myself, the hills I couldn't get up on a 30*25 gear are few and
> far between.

Ok, but it's not just about what's possible but what's possible in
comfort. But yes, it's very much a personal-preference thing.

>> A standard Shimano road triple (and Campag medium) rear mech should
>> cope with 26-42-52 + 14-25 (and even wider ranges) as long as you
>> avoided using the smallest 3 or 4 rear sprockets from the inner
>> chainring, which is no big loss. Having the chain as short as
>> possible for the big-big is the key. I suspect you could remove a
>> link or two from your chain right now for a start.
>
> Unfortunately, the chain is already too short for the big-big
> combination - and it is also too long for the small-small combination,
> but since I would never use those gears in practice, I don't let it
> worry me.

I would worry about accidentally trying to select big-big one day, as can
happen when knackered + distracted. Could cause serious damange.

> I'm fairly convinced that a longer cage mech would be the
> ideal solution - unless I've somehow got the whole thing set up
> wrongly.

I bet there's something wrong somewhere. A longer cage may well help but
it shouldn't be necessary. People use even wider ranges than you without
needing an MTB mech.

~PB

 

[Pete Biggs]

MSA wrote:
> Out of interest, is it possible to buy individual Campag 9/10 rings?
> I seem remember seeing individual cogs hanging on a wall in a shop in
> France last year...are they available 'over ere'?

Sometimes, but they're flippin expensive. Parker International have a
few, eg. Record/Chorus 2003 52T @ £53.95. Also look out for them (at
more reasonable prices) on eBay. But I've never seen Campag rings smaller
than 30T, or of any unusual sizes, really.

~PB, happy to use TA rings instead.

 

[MSA]

Pete Biggs wrote:
> MSA wrote:
>
>>Out of interest, is it possible to buy individual Campag 9/10 rings?
>>I seem remember seeing individual cogs hanging on a wall in a shop in
>>France last year...are they available 'over ere'?
>
>
> Sometimes, but they're flippin expensive. Parker International have a
> few, eg. Record/Chorus 2003 52T @ £53.95. Also look out for them (at
> more reasonable prices) on eBay. But I've never seen Campag rings smaller
> than 30T, or of any unusual sizes, really.
>
> ~PB, happy to use TA rings instead.
>
>


Oops, didn't make myself clear, I meant rear cogs - cassette.

Unless they do a 52t rear....that'll do the trick


PS: Ordered the Open Pro's today...with Chorus hubs, thanks for the
advice PB.

--
Mark
_____________________________________________

Deja Moo - The feeling that you've heard this bull before

 

[Pete Biggs]

MSA wrote:

> Oops, didn't make myself clear, I meant rear cogs - cassette.

Ohh!

Guess: Individual sprockets could possibly be ordered from the main UK
Campag distributor (Italian Cycle Products or whatever they're called
now), but they're bound to be pricey.

New complete Veloce cassettes aren't very expensive, and not all
higher-model sprockets can be separated anyway as the larger ones come in
pairs & threes on carriers.

Alternatively, there's always Marchisio stuff to build custom cassettes
and then replace sprockets individually: http://anysystem.de

......I s'pose all that's a long way of saying "no"

cheers
~PB

 

[davek]

Pete Biggs wrote:
> I bet there's something wrong somewhere.

I'm sure you're right, but I'm jiggered if I know what it is!

d.

 

[Arthur Clune]

Pete Biggs <pwrinkledgrape{remove_fruit}@biggs.tc> wrote:
: davek wrote:
:>
:> Unfortunately, the chain is already too short for the big-big
:> combination - and it is also too long for the small-small combination,

: I would worry about accidentally trying to select big-big one day, as can
: happen when knackered + distracted. Could cause serious damange.

I'm with Pete on this. I've seen a rider left walking home after wrapping
the rear mech, chain and most of the hanger round the rear wheel, all
caused by trying to engage big-big on a too-short chain while powering
out of the saddle.

Personally, I find myself in big-big frequently. When you are going so
hard your vision is bluring, finesse tends to slip Also, there are
times in racing when you need to hang onto the big ring to avoid a front
shift.

--
Arthur Clune PGP/GPG Key: http://www.clune.org/pubkey.txt
Don't get me wrong, perl is an OK operating system, but it lacks a
lightweight scripting language -- Walter Dnes

 

[JohnB]

Arthur Clune wrote:
>
> Pete Biggs <pwrinkledgrape{remove_fruit}@biggs.tc> wrote:
> : davek wrote:
> :>
> :> Unfortunately, the chain is already too short for the big-big
> :> combination - and it is also too long for the small-small combination,
>
> : I would worry about accidentally trying to select big-big one day, as can
> : happen when knackered + distracted. Could cause serious damange.
>
> I'm with Pete on this. I've seen a rider left walking home after wrapping
> the rear mech, chain and most of the hanger round the rear wheel, all
> caused by trying to engage big-big on a too-short chain while powering
> out of the saddle.

Went out on a hack to a training session yesterday and I'd forgotten I'd
shortened the chain by a few links some months ago after it broke.
With a strong tailwind I went into the big ring, then when the hill came
I started changing down.
Yes, it happened, just as you say - well almost. Everything jammed and
the chain broke another link :-(

Thankfully I didn't have to walk home as the Alien came to the rescue
and I'm now a couple of more links short.

I MUST order a new chain on Monday.

John B

 

[Dave Larrington]

Pete Biggs wrote:

> A standard Shimano road triple (and Campag medium) rear mech should
> cope with 26-42-52 + 14-25 (and even wider ranges) as long as you
> avoided using the smallest 3 or 4 rear sprockets from the inner
> chainring, which is no big loss. Having the chain as short as
> possible for the big-big is the key. I suspect you could remove a
> link or two from your chain right now for a start.
>

IIRC TWFKAML's Kingcycle used to have 30-40-50 and 12-28 with a long-cage
105.

--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
Every establishment needs an opposition.