gear question



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I

Ian

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have just been given a mountain bike by a friend and have been cycling to work. it's quite a flat
journey but i find i am constantly on the big wheel of the front mech.

i calculated the ratio and with a max ratio of 3:1 i need to change it to get up from 74"
towards 90"+.

i'm thinking if the smallest hub on the rear mech had less teeth this would do it - currently has
14. does anyone know if it is possible to change just one sprocket to achieve this or does more
need changing.

any advice appreciated.

Ian
 
S

Sheldon Brown

Guest
Someone wrote:

> have just been given a mountain bike by a friend and have been cycling to work. it's quite a flat
> journey but i find i am constantly on the big wheel of the front mech.
>
> i calculated the ratio and with a max ratio of 3:1 i need to change it to get up from 74"
> towards 90"+.
>
> i'm thinking if the smallest hub on the rear mech had less teeth this would do it - currently has
> 14. does anyone know if it is possible to change just one sprocket to achieve this or does more
> need changing.

Your bike has an old-fashioned thread-on freewheel, which rather limits the options.

Replacing just a single rear sprockets is not practical, but a whole freewheel cluster of 6 or 7
sprockets is not all that expensive, typically about US$20.

The smallest size commonly available in thread-on freewheels is 13 teeth, but there is one Shimano
7-speed model that goes from 11-34.

See: http://sheldonbrown.com/harris/freewheels.html

Depending on the specific hardware on your bike, it might be better to go to bigger chainrings in
front instead.

Sheldon "Gears" Brown +------------------------------------------+
| Genius is one per cent inspiration and | ninety-nine per cent perspiration. |
|. --Thomas Edison |
+------------------------------------------+ Harris Cyclery, West Newton, Massachusetts Phone 617-244-
9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com
 
Z

Zog The Undenia

Guest
Sheldon Brown wrote:

> Someone wrote:
>
>> have just been given a mountain bike by a friend and have been cycling to work. it's quite a flat
>> journey but i find i am constantly on the big wheel of the front mech.
>>
>> i calculated the ratio and with a max ratio of 3:1 i need to change it to get up from 74"
>> towards 90"+.
>>
>> i'm thinking if the smallest hub on the rear mech had less teeth this would do it - currently has
>> 14. does anyone know if it is possible to change just one sprocket to achieve this or does more
>> need changing.
>
>
> Your bike has an old-fashioned thread-on freewheel, which rather limits the options.
>
> Replacing just a single rear sprockets is not practical, but a whole freewheel cluster of 6 or 7
> sprockets is not all that expensive, typically about US$20.
>
> The smallest size commonly available in thread-on freewheels is 13 teeth, but there is one Shimano
> 7-speed model that goes from 11-34.
>
> See: http://sheldonbrown.com/harris/freewheels.html
>
> Depending on the specific hardware on your bike, it might be better to go to bigger chainrings in
> front instead.

Or learn to pedal faster ;-) 42 x 14 is a pretty impressive cruising gear if you pedal at 100rpm
(that's 23mph on 26" wheels)

Spin, don't push.
 
T

Tcmedara

Guest
Sheldon Brown <[email protected]> wrote: (snip OP).
>
> Your bike has an old-fashioned thread-on freewheel, which rather limits the options.
>
I'll probably feel stupid when I see the answer, but here goes.....I re-read the OP several times,
but remain confused. Excuse my ignorance, but how do you know it's a thread-on freewheel rather than
a cassette?

Humbly,

Tom
 

meb

New Member
Aug 21, 2003
1,219
0
36
Originally posted by Zog The Undenia
Sheldon Brown wrote:

> Someone wrote:
>
>> have just been given a mountain bike by a friend and have been cycling to work. it's quite a flat
>> journey but i find i am constantly on the big wheel of the front mech.
>>
>> i calculated the ratio and with a max ratio of 3:1 i need to change it to get up from 74"
>> towards 90"+.
>>
>> i'm thinking if the smallest hub on the rear mech had less teeth this would do it - currently has
>> 14. does anyone know if it is possible to change just one sprocket to achieve this or does more
>> need changing.
>
>
> Your bike has an old-fashioned thread-on freewheel, which rather limits the options.
>
> Replacing just a single rear sprockets is not practical, but a whole freewheel cluster of 6 or 7
> sprockets is not all that expensive, typically about US$20.
>
> The smallest size commonly available in thread-on freewheels is 13 teeth, but there is one Shimano
> 7-speed model that goes from 11-34.
>
> See: http://sheldonbrown.com/harris/freewheels.html
>
> Depending on the specific hardware on your bike, it might be better to go to bigger chainrings in
> front instead.

Or learn to pedal faster ;-) 42 x 14 is a pretty impressive cruising gear if you pedal at 100rpm
(that's 23mph on 26" wheels)

Spin, don't push.

74g.i. is 40T, 42T is 78g.i..
 
S

Sheldon Brown

Guest
tcmedara wrote:

> Sheldon Brown <[email protected]> wrote: (snip OP).
>
>>Your bike has an old-fashioned thread-on freewheel, which rather limits the options.
>>
>
> I'll probably feel stupid when I see the answer, but here goes.....I re-read the OP several times,
> but remain confused. Excuse my ignorance, but how do you know it's a thread-on freewheel rather
> than a cassette?

Onaccounta his top sprocket is a 14.

While 14-top cassettese exist, they're very, very rare, probably not more than one in 100,000.

14-top freewheels are very common on cheap bikes, and many of the bottom of the line bikes mate
them with cranksets that are inappropriate for such a low top gear. I surmise this is the situation
of the O.P.

Sheldon "Inferences" Brown +-----------------------------------------------------+
| Life is the art of drawing sufficient conclusions | from insufficient premises. --Samuel Butler |
+-----------------------------------------------------+ Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com
 
S

Smmb

Guest
"Sheldon Brown" <[email protected]> a écrit dans le message de :
news:[email protected]...
> tcmedara wrote: how do
> > you know it's a thread-on freewheel rather than a cassette?
>
> Onaccounta his top sprocket is a 14.
>
> While 14-top cassettese exist, they're very, very rare, probably not more than one in 100,000.

I see a great number of Miche cassettes - we Europeans just can't master those 11 and 12 tooth
starters like you tough guys. Not to mention, that 16 is a common starter for juniors, which we have
plenty of. Bad idea to hurt young limbs, just to display chest hairs (if any) ...
--

Bonne route,

Sandy Paris FR
 
S

Sheldon Brown

Guest
I wrote:

>>While 14-top cassettese exist, they're very, very rare, probably not more than one in 100,000.

Quel'qu'un inconnu a =E9crit:

> I see a great number of Miche cassettes - we Europeans just can't maste=
r
> those 11 and 12 tooth starters like you tough guys. Not to mention, that 16 is a common starter
> for juniors, which we have plenty of. Bad idea to hurt young limbs, just to display chest hairs (=
if
> any) ...

I'd guess you're speaking of _racing_ style bikes. I was speaking of=20 the general bicycle
population, and, in particular cheap mountain style=20 bikes, such as the one the original poster
had been given.

The 11 tooth sprockets have nothing to do with toughness or chest hair.=20
They're part of the misguided "microdrive" system where the drivetrain =

is shrunken. They are commonly used with chainrings up to 42 teeth, or=20 sometimes 44.

The resulting top gear is not particularly high at all, for example,=20
42/11, with 38-559 (26 x 1.5) tires gives a top gain ratio* of only 7.1. (that's 7.6 meters,
95 inches.)

I think you'll agree that's not an unreasonably high gear for a bike=20 with three chainrings.
Indeed, many people, myself included, would find =

it quite unsatisfactory if there were hills to be descended.

Sheldon "Doesn't Like To Coast" Brown

*Gain ratio is a new system for measuring bicycle gearing. It is explained in detail on my Web site
at: http://sheldonbrown.com/gain.html

+----------------------------------------------------------+
| And what are all these mysteries to me, | Whose life is full of indices and surds? | x^2 +
| 7x + 53 |
| =3D 11/3 --Lewis Carroll |
+----------------------------------------------------------+ Harris Cyclery, West Newton,
Massachusetts Phone 617-244-9772 FAX 617-244-1041 http://harriscyclery.com Hard-to-find parts
shipped Worldwide http://captainbike.com http://sheldonbrown.com
 
T

Tcmedara

Guest
Sheldon Brown <[email protected]> wrote:
>
(snip)
>
> Onaccounta his top sprocket is a 14.
>
> While 14-top cassettese exist, they're very, very rare, probably not more than one in 100,000.
>
> 14-top freewheels are very common on cheap bikes, and many of the bottom of the line bikes mate
> them with cranksets that are inappropriate for such a low top gear. I surmise this is the
> situation of the O.P.

Okay, I don't feel all that stupid now. In retrospect, it seems obvious, as I don't recall ever
seeing a cassette that tops out at 14 (with due regard to our Euro-racing brethren). As basic as
that sounds, I wouldn't have suspected.

Thanks fer the skoolin'

Tom
 
D

David Kerber

Guest
In article <[email protected]>, [email protected] says...

...

> The resulting top gear is not particularly high at all, for example,
> 42/11, with 38-559 (26 x 1.5) tires gives a top gain ratio* of only 7.1. (that's 7.6 meters, 95
> inches.)
>
> I think you'll agree that's not an unreasonably high gear for a bike with three chainrings.
> Indeed, many people, myself included, would find it quite unsatisfactory if there were hills to be
> descended.

Indeed. I use my 52x11 top gear lots more than I do my 30x32 granny. Actually, that should say
"did"; I swapped the 11-32 cassette for an 11- 23 for around-town riding, and I use the 30x23
occasionally, probably about the same as the 52x11.

>
> Sheldon "Doesn't Like To Coast" Brown

Me, neither.

....

--
Dave Kerber Fight spam: remove the ns_ from the return address before replying!

REAL programmers write self-modifying code.
 
I

Ian

Guest
thanks for all the help folks, much appreciated. have seen the shimano 11-32 on www.wiggle.co.uk for
about £14.99

is it an easy job to fit the new one on?
 
R

Rick Onanian

Guest
On 29 Jan 2004 02:43:49 -0800, [email protected] (ian) wrote:
>thanks for all the help folks, much appreciated. have seen the shimano 11-32 on www.wiggle.co.uk
>for about £14.99
>
>is it an easy job to fit the new one on?

Yes, but removing the old one requires a special tool. The new one just screws on by hand.
--
Rick Onanian
 
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