Front derailleur clamp size

bill burroughs said:

I am shopping for a front derailleur for a recumbent bike I am
building. I will be using a 34 mm diameter tube for the derailleur
mount. Will a 1 1/4" fit or do I need to go to 1 3/8"?

1 3/8" is 3.49mm, so that would be the size you need.

--

David L. Johnson

__o | Arguing with an engineer is like mud wrestling with a pig... You
_`\(,_ | soon find out the pig likes it!
(_)/ (_) |

bill burroughs said:

I am shopping for a front derailleur for a recumbent bike I am
building. I will be using a 34 mm diameter tube for the derailleur
mount. Will a 1 1/4" fit or do I need to go to 1 3/8"?

Either use a 1 3/8 with a wrapped shim, or braze on a lug for the der.

Quoted message said:

What are the limits to the tube sizes for those clamp sizes?

Not as much as the difference between 1.25 in. and 34mm. Cheap ders
with stamped steel clamp bands can sometimes be fudged in place on a
tube that's not terribly close to the right dimension, but a good der
with a die-cast or forged clamp is not going to gracefully adapt to a
too-large tube beyond perhaps .25mm or so.
--
Typoes are a feature, not a bug.
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In article <[email hidden]>,

bill burroughs said:

I am shopping for a front derailleur for a recumbent bike I am
building. I will be using a 34 mm diameter tube for the derailleur
mount. Will a 1 1/4" fit or do I need to go to 1 3/8"?

What are the limits to the tube sizes for those clamp sizes?

Thanks!

34 mm = 1 1/3 inch. Clamps are specified in mm, so forget about the
inch measurement.

--
Ted Bennett
Portland, OR

In article <[email hidden]>,

David L. Johnson said:

bill burroughs said:

I am shopping for a front derailleur for a recumbent bike I am
building. I will be using a 34 mm diameter tube for the derailleur
mount. Will a 1 1/4" fit or do I need to go to 1 3/8"?

1 3/8" is 3.49mm, so that would be the size you need.

You got the decimal one place off. It's 34.9mm.

--
Ted Bennett
Portland, OR

An observation: If you're using a conventional threaded BB, you can
also use the Shimano E-type front der which has a bracket that clamps
in place between the BB flange and the BB shell, eliminating the whole
tube clamp issue.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Quoted message said:

In article <[email hidden]>,

bill burroughs said:

I am shopping for a front derailleur for a recumbent bike I am
building. I will be using a 34 mm diameter tube for the derailleur
mount. Will a 1 1/4" fit or do I need to go to 1 3/8"?

What are the limits to the tube sizes for those clamp sizes?

Ted said:

34 mm = 1 1/3 inch. Clamps are specified in mm, so forget about the
inch measurement.

Sort of.

Most bicycle tubing's still 1-1/8"=28.6mm, 1-1/4=31.8,
1-3/8=34.8. Adding to the confusion, our industry slang now
truncates to a "31 clamp" or a "34 clamp". Of late some
clamps themselves are marked simply "31 or "34".

In the case of the OP's FDer, I wonder if that tube is 34mm
or 1.375 inches? It won't matter for a front changer, the
clamp design can easily span either.

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Quoted message said:

Quoted message said:

bill burroughs said:

I am shopping for a front derailleur for a recumbent bike I am
building. I will be using a 34 mm diameter tube for the derailleur
mount. Will a 1 1/4" fit or do I need to go to 1 3/8"?

Quoted message said:

In article <[email hidden]>,

David L. Johnson said:

1 3/8" is 3.49mm, so that would be the size you need.

Ted said:

You got the decimal one place off. It's 34.9mm.

Yes, but only in reality.

Campagnolo says 32 and 35, Shimano labels 31.8 and 31.9.
(not 3.49 at any rate!)
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Quoted message said:

Quoted message said:

I am shopping for a front derailleur for a recumbent bike I am
building. I will be using a 34 mm diameter tube for the derailleur
mount. Will a 1 1/4" fit or do I need to go to 1 3/8"?

Either use a 1 3/8 with a wrapped shim, or braze on a lug for the der.

Braze-on is out. The tubing is CF. Maybe I could epoxy a mount for a
braze-on derailleur...

Thanks!

Werehatrack said:

An observation: If you're using a conventional threaded BB, you can
also use the Shimano E-type front der which has a bracket that clamps
in place between the BB flange and the BB shell, eliminating the whole
tube clamp issue.

I've seen those and they always say "requires [censored] part no. Shimano BB"
Unfortunately, I already have an integrated BB/crankset that uses
externally mounted bearings so I don't think I can make that type FD
work.

I'll look for a 34.x clamp size FD.

Thanks!

"David L. Johnson" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

bill burroughs said:

I am shopping for a front derailleur for a recumbent bike I am
building. I will be using a 34 mm diameter tube for the derailleur
mount. Will a 1 1/4" fit or do I need to go to 1 3/8"?

1 3/8" is 3.49mm, so that would be the size you need.

--

David L. Johnson

__o | Arguing with an engineer is like mud wrestling with a pig...

You

Quoted message said:

_`\(,_ | soon find out the pig likes it!
(_)/ (_) |

The last time I checked 1 3/8" = 34.925mm.
-tom