Basic gear question - Cycling Mob: Road Cycling, Mountain Biking and More

07-17-2004, 10:33 AM

This is a real basic question, hopefully not a target for petdowns from
know-italls but here it is.

On a bike with many speeds, three chainrings, it is not mechanically good to
cross chain.
Do you have the same ratios with cross chaining?
I mean obviously you work your way in for low gears and out for high gears.

Do the ratios cover crosschaining, or is it that much different depending on
the crank gear you use?

No reason to cross chain is there?

Someone asked me, that's what I told them, just so they wouldn't crosschain,
but what do you guys say?

Thanx

07-17-2004, 10:52 AM

On 17 Jul 2004 17:33:32 GMT, [Only registered and activated users can see links. ] (Fx199) wrote:

>This is a real basic question, hopefully not a target for petdowns from
>know-italls but here it is.
>
>
>On a bike with many speeds, three chainrings, it is not mechanically good to
>cross chain.
>Do you have the same ratios with cross chaining?
>I mean obviously you work your way in for low gears and out for high gears.
>
>Do the ratios cover crosschaining, or is it that much different depending on
>the crank gear you use?
>
>No reason to cross chain is there?
>
>Someone asked me, that's what I told them, just so they wouldn't crosschain,
>but what do you guys say?
>
>Thanx

It will depend on the chainring sizes and the back gear sizes, but you
are pretty well correct. There is usually some significant overlap.
For example, I have one bike with 48/38/28 up front and 12-25/9 speed
in back. Away from the two extremes- small/large or large/small- I
will have the same gearing on two adjacent chainrings if I move the
rear up or down three cogs.

If you go to this gear calculator-

[Only registered and activated users can see links. ]

you can enter various combinations of chainrings and gears. The
resulting chart will show you the overlaps, etc.

07-17-2004, 10:52 AM

On 17 Jul 2004 17:33:32 GMT, [Only registered and activated users can see links. ] (Fx199) wrote:

>This is a real basic question, hopefully not a target for petdowns from
>know-italls but here it is.
>
>
>On a bike with many speeds, three chainrings, it is not mechanically good to
>cross chain.
>Do you have the same ratios with cross chaining?
>I mean obviously you work your way in for low gears and out for high gears.
>
>Do the ratios cover crosschaining, or is it that much different depending on
>the crank gear you use?
>
>No reason to cross chain is there?
>
>Someone asked me, that's what I told them, just so they wouldn't crosschain,
>but what do you guys say?
>
>Thanx

It will depend on the chainring sizes and the back gear sizes, but you
are pretty well correct. There is usually some significant overlap.
For example, I have one bike with 48/38/28 up front and 12-25/9 speed
in back. Away from the two extremes- small/large or large/small- I
will have the same gearing on two adjacent chainrings if I move the
rear up or down three cogs.

If you go to this gear calculator-

[Only registered and activated users can see links. ]

you can enter various combinations of chainrings and gears. The
resulting chart will show you the overlaps, etc.

07-17-2004, 10:52 AM

On 17 Jul 2004 17:33:32 GMT, [Only registered and activated users can see links. ] (Fx199) wrote:

>This is a real basic question, hopefully not a target for petdowns from
>know-italls but here it is.
>
>
>On a bike with many speeds, three chainrings, it is not mechanically good to
>cross chain.
>Do you have the same ratios with cross chaining?
>I mean obviously you work your way in for low gears and out for high gears.
>
>Do the ratios cover crosschaining, or is it that much different depending on
>the crank gear you use?
>
>No reason to cross chain is there?
>
>Someone asked me, that's what I told them, just so they wouldn't crosschain,
>but what do you guys say?
>
>Thanx

It will depend on the chainring sizes and the back gear sizes, but you
are pretty well correct. There is usually some significant overlap.
For example, I have one bike with 48/38/28 up front and 12-25/9 speed
in back. Away from the two extremes- small/large or large/small- I
will have the same gearing on two adjacent chainrings if I move the
rear up or down three cogs.

If you go to this gear calculator-

[Only registered and activated users can see links. ]

you can enter various combinations of chainrings and gears. The
resulting chart will show you the overlaps, etc.

07-17-2004, 10:52 AM

On 17 Jul 2004 17:33:32 GMT, [Only registered and activated users can see links. ] (Fx199) wrote:

>This is a real basic question, hopefully not a target for petdowns from
>know-italls but here it is.
>
>
>On a bike with many speeds, three chainrings, it is not mechanically good to
>cross chain.
>Do you have the same ratios with cross chaining?
>I mean obviously you work your way in for low gears and out for high gears.
>
>Do the ratios cover crosschaining, or is it that much different depending on
>the crank gear you use?
>
>No reason to cross chain is there?
>
>Someone asked me, that's what I told them, just so they wouldn't crosschain,
>but what do you guys say?
>
>Thanx

It will depend on the chainring sizes and the back gear sizes, but you
are pretty well correct. There is usually some significant overlap.
For example, I have one bike with 48/38/28 up front and 12-25/9 speed
in back. Away from the two extremes- small/large or large/small- I
will have the same gearing on two adjacent chainrings if I move the
rear up or down three cogs.

If you go to this gear calculator-

[Only registered and activated users can see links. ]

you can enter various combinations of chainrings and gears. The
resulting chart will show you the overlaps, etc.

07-17-2004, 10:52 AM

On 17 Jul 2004 17:33:32 GMT, [Only registered and activated users can see links. ] (Fx199) wrote:

>This is a real basic question, hopefully not a target for petdowns from
>know-italls but here it is.
>
>
>On a bike with many speeds, three chainrings, it is not mechanically good to
>cross chain.
>Do you have the same ratios with cross chaining?
>I mean obviously you work your way in for low gears and out for high gears.
>
>Do the ratios cover crosschaining, or is it that much different depending on
>the crank gear you use?
>
>No reason to cross chain is there?
>
>Someone asked me, that's what I told them, just so they wouldn't crosschain,
>but what do you guys say?
>
>Thanx

It will depend on the chainring sizes and the back gear sizes, but you
are pretty well correct. There is usually some significant overlap.
For example, I have one bike with 48/38/28 up front and 12-25/9 speed
in back. Away from the two extremes- small/large or large/small- I
will have the same gearing on two adjacent chainrings if I move the
rear up or down three cogs.

If you go to this gear calculator-

[Only registered and activated users can see links. ]

you can enter various combinations of chainrings and gears. The
resulting chart will show you the overlaps, etc.

07-17-2004, 11:48 AM

In article <[Only registered and activated users can see links. ].com>,
[Only registered and activated users can see links. ] (Fx199) wrote:

> This is a real basic question, hopefully not a target for petdowns from
> know-italls but here it is.
>
>
> On a bike with many speeds, three chainrings, it is not mechanically good to
> cross chain.
> Do you have the same ratios with cross chaining?
> I mean obviously you work your way in for low gears and out for high gears.
>
> Do the ratios cover crosschaining, or is it that much different depending on
> the crank gear you use?

It really depends on the gearing. A very typical road double (52-39)
with some mess of gears like 12-25 will probably have substantial
overlap, such that the middle gears will all be the same, and yes, if
you are tempted to use the 39-12, you'll get about the same ratio on the
52-14.

I think on my race bike (52-39, 13-26 8-speed) I figure that
downshifting on the front is about the same as picking up two gears on
the rear, ratio-wise. So that means I can find equivalent ratios to any
of the middle four cogs on either front ring (albeit some with wretched
cross-ups like the above-mentioned 39-12), but the two highest and two
lowest ratios are only available on the big and small rings.

A triple changes things very little, except that it is often a very
steep drop from the middle ring, so there is less overlap. But don't use
that as an excuse to try the 26-14. Bad ratio.

You can figure this out very precisely (which I am not doing above) for
your own setup by using Sheldon Brown's excellent gear calculator:

[Only registered and activated users can see links. ]

> No reason to cross chain is there?

In general no. Sometimes, it is momentarily more convenient to get to a
gear without an alpine (both front and rear together) shift, so in race
situations I sometimes find myself in the big ring and the second
biggest cog.

> Someone asked me, that's what I told them, just so they wouldn't crosschain,
> but what do you guys say?

Don't crosschain. The ratios, even if unique, are effectively
meaningless, and it's less efficient and hard on the drivetrain (mainly
the chain, though in marginal circumstances you can bend a derailleur).

--
Ryan Cousineau, [Only registered and activated users can see links. ] [Only registered and activated users can see links. ]
President, Fabrizio Mazzoleni Fan Club

07-17-2004, 11:48 AM

In article <[Only registered and activated users can see links. ].com>,
[Only registered and activated users can see links. ] (Fx199) wrote:

> This is a real basic question, hopefully not a target for petdowns from
> know-italls but here it is.
>
>
> On a bike with many speeds, three chainrings, it is not mechanically good to
> cross chain.
> Do you have the same ratios with cross chaining?
> I mean obviously you work your way in for low gears and out for high gears.
>
> Do the ratios cover crosschaining, or is it that much different depending on
> the crank gear you use?

It really depends on the gearing. A very typical road double (52-39)
with some mess of gears like 12-25 will probably have substantial
overlap, such that the middle gears will all be the same, and yes, if
you are tempted to use the 39-12, you'll get about the same ratio on the
52-14.

I think on my race bike (52-39, 13-26 8-speed) I figure that
downshifting on the front is about the same as picking up two gears on
the rear, ratio-wise. So that means I can find equivalent ratios to any
of the middle four cogs on either front ring (albeit some with wretched
cross-ups like the above-mentioned 39-12), but the two highest and two
lowest ratios are only available on the big and small rings.

A triple changes things very little, except that it is often a very
steep drop from the middle ring, so there is less overlap. But don't use
that as an excuse to try the 26-14. Bad ratio.

You can figure this out very precisely (which I am not doing above) for
your own setup by using Sheldon Brown's excellent gear calculator:

[Only registered and activated users can see links. ]

> No reason to cross chain is there?

In general no. Sometimes, it is momentarily more convenient to get to a
gear without an alpine (both front and rear together) shift, so in race
situations I sometimes find myself in the big ring and the second
biggest cog.

> Someone asked me, that's what I told them, just so they wouldn't crosschain,
> but what do you guys say?

Don't crosschain. The ratios, even if unique, are effectively
meaningless, and it's less efficient and hard on the drivetrain (mainly
the chain, though in marginal circumstances you can bend a derailleur).

--
Ryan Cousineau, [Only registered and activated users can see links. ] [Only registered and activated users can see links. ]
President, Fabrizio Mazzoleni Fan Club

07-17-2004, 11:48 AM

In article <[Only registered and activated users can see links. ].com>,
[Only registered and activated users can see links. ] (Fx199) wrote:

> This is a real basic question, hopefully not a target for petdowns from
> know-italls but here it is.
>
>
> On a bike with many speeds, three chainrings, it is not mechanically good to
> cross chain.
> Do you have the same ratios with cross chaining?
> I mean obviously you work your way in for low gears and out for high gears.
>
> Do the ratios cover crosschaining, or is it that much different depending on
> the crank gear you use?

It really depends on the gearing. A very typical road double (52-39)
with some mess of gears like 12-25 will probably have substantial
overlap, such that the middle gears will all be the same, and yes, if
you are tempted to use the 39-12, you'll get about the same ratio on the
52-14.

I think on my race bike (52-39, 13-26 8-speed) I figure that
downshifting on the front is about the same as picking up two gears on
the rear, ratio-wise. So that means I can find equivalent ratios to any
of the middle four cogs on either front ring (albeit some with wretched
cross-ups like the above-mentioned 39-12), but the two highest and two
lowest ratios are only available on the big and small rings.

A triple changes things very little, except that it is often a very
steep drop from the middle ring, so there is less overlap. But don't use
that as an excuse to try the 26-14. Bad ratio.

You can figure this out very precisely (which I am not doing above) for
your own setup by using Sheldon Brown's excellent gear calculator:

[Only registered and activated users can see links. ]

> No reason to cross chain is there?

In general no. Sometimes, it is momentarily more convenient to get to a
gear without an alpine (both front and rear together) shift, so in race
situations I sometimes find myself in the big ring and the second
biggest cog.

> Someone asked me, that's what I told them, just so they wouldn't crosschain,
> but what do you guys say?

Don't crosschain. The ratios, even if unique, are effectively
meaningless, and it's less efficient and hard on the drivetrain (mainly
the chain, though in marginal circumstances you can bend a derailleur).

--
Ryan Cousineau, [Only registered and activated users can see links. ] [Only registered and activated users can see links. ]
President, Fabrizio Mazzoleni Fan Club

07-17-2004, 11:48 AM

In article <[Only registered and activated users can see links. ].com>,
[Only registered and activated users can see links. ] (Fx199) wrote:

> This is a real basic question, hopefully not a target for petdowns from
> know-italls but here it is.
>
>
> On a bike with many speeds, three chainrings, it is not mechanically good to
> cross chain.
> Do you have the same ratios with cross chaining?
> I mean obviously you work your way in for low gears and out for high gears.
>
> Do the ratios cover crosschaining, or is it that much different depending on
> the crank gear you use?

It really depends on the gearing. A very typical road double (52-39)
with some mess of gears like 12-25 will probably have substantial
overlap, such that the middle gears will all be the same, and yes, if
you are tempted to use the 39-12, you'll get about the same ratio on the
52-14.

I think on my race bike (52-39, 13-26 8-speed) I figure that
downshifting on the front is about the same as picking up two gears on
the rear, ratio-wise. So that means I can find equivalent ratios to any
of the middle four cogs on either front ring (albeit some with wretched
cross-ups like the above-mentioned 39-12), but the two highest and two
lowest ratios are only available on the big and small rings.

A triple changes things very little, except that it is often a very
steep drop from the middle ring, so there is less overlap. But don't use
that as an excuse to try the 26-14. Bad ratio.

You can figure this out very precisely (which I am not doing above) for
your own setup by using Sheldon Brown's excellent gear calculator:

[Only registered and activated users can see links. ]

> No reason to cross chain is there?

In general no. Sometimes, it is momentarily more convenient to get to a
gear without an alpine (both front and rear together) shift, so in race
situations I sometimes find myself in the big ring and the second
biggest cog.

> Someone asked me, that's what I told them, just so they wouldn't crosschain,
> but what do you guys say?

Don't crosschain. The ratios, even if unique, are effectively
meaningless, and it's less efficient and hard on the drivetrain (mainly
the chain, though in marginal circumstances you can bend a derailleur).

--
Ryan Cousineau, [Only registered and activated users can see links. ] [Only registered and activated users can see links. ]
President, Fabrizio Mazzoleni Fan Club