Seatpost terminology: "12-Degree Clamp" ?

I've got two Thompson posts.

The straight one says "0-Degree" on the clamp

The setback says "12-Degree" on the clamp.

I thought the meaning of each was pretty obvious until a framebuilder sent me
a spec that included the phrase: "Requires a center mount post with 12 deg
clamp."


Called them on the phone...and I *think* they said "Yes, this is a straight post
(i.e. no setback) but Thompson shipped their posts with two different kinds of
clamp. Old ones were zero-degree and newer ones are 12-degree."

But I still think I'm not getting it. Eyeballing the clamps on the two posts I
have, I can detect no diff except for what's printed on them.
--
PeteCresswell

On Sat, 24 Apr 2004 00:16:16 GMT, "(Pete Cresswell)" wrote:

I've got two Thompson posts.

The straight one says "0-Degree" on the clamp

The setback says "12-Degree" on the clamp.

I thought the meaning of each was pretty obvious until a framebuilder sent me
a spec that included the phrase: "Requires a center mount post with 12 deg
clamp."


Called them on the phone...and I *think* they said "Yes, this is a straight post
(i.e. no setback) but Thompson shipped their posts with two different kinds of
clamp. Old ones were zero-degree and newer ones are 12-degree."

But I still think I'm not getting it. Eyeballing the clamps on the two posts I
have, I can detect no diff except for what's printed on them.

From http://www.lhthomson.com/SP12X.html :

"Thomson now offers only 12° Seat Clamps on all new seat posts. This
has been the case since April, 2002. Thomson also offers 12° clamps as
replacement clamps that will fit any Thomson Seat Post ever sold. The
12° clamps are direct replacements for the 0° clamps in every way.

The 0° clamps are good in every way and should not be replaced unless
you need the one thing the 0° cannot do that the 12° can. That is, the
12° clamp can bring the nose of the saddle down 12° more than the 0°
clamp. As rear suspension was developed and became more popular the
seat tube was laid back so much on bicycle frames that the 0° clamps
would not allow the nose of the seat to be adjusted down enough.

The 12° clamp has "FRONT" printed on one end. In the vast majority of
cases the word "FRONT" should be placed toward the front of the bike.
But, if the front of your seat will not come up high enough, it is
perfectly acceptable and safe to install the clamp with the word
"FRONT" toward the back. This will allow the front of the seat to be
raised much higher.

Set back seat posts may be mounted with the offset backward or
forward. The 12° clamp may be mounted with the word "FRONT" facing
forward or backward. Mount the seat post and clamp in the direction
that fits your riding style.

Bicycles with seat tube angles of 70° and above (70° thru 90°) work
well with 0° clamps. Bicycles with seat tube angles less than 70° (63°
thru 70°) require the 12° clamps. The customer has had the option to
buy either 12° or 0° clamp for about five years. But, not since April,
2002. There may be some seat posts with 0° clamps in the supply chain.
If you require the 12° clamps, you should request your bike store
supply a seat post with 12° clamps. If you have a seat post with 0°
clamps and want to use it on a bicycle with a seat tube angle less
than 70°, you may purchase a replacement set of 12° clamp for your
Thomson Seat Post.

If you order 0° or 12° seat posts from an old price list you will only
get a 12° seat post from the factory. The new price list only shows
one model for each size. It will come with the 12° clamps from the
factory. Remember a 12° seat post clamp will do everything and more
than a 0° seat post clamp will. A 0° clamp will do everything a 12°
clamp will do except bring the front of the seat down enough on
bicycles with laid back seat tubes (less than 70°).

TO TELL THE DIFFERENCE IN 0° AND 12° TOP CLAMPS: Look at the clamp
from the side. 0° clamps have the seat rail groove parallel with the
top of the clamp. The 12° top clamps have the seat rail grooves
sloping at a distinct 12° angle in relation to the top of the clamp.
Also, see sketches on intruction sheet. Instruction sheet is available
on web site. (www.lhthomson.com) "

On Sat, 24 Apr 2004 00:16:16 GMT, "(Pete Cresswell)" wrote:

I've got two Thompson posts.

The straight one says "0-Degree" on the clamp

The setback says "12-Degree" on the clamp.

I thought the meaning of each was pretty obvious until a framebuilder sent me
a spec that included the phrase: "Requires a center mount post with 12 deg
clamp."


Called them on the phone...and I *think* they said "Yes, this is a straight post
(i.e. no setback) but Thompson shipped their posts with two different kinds of
clamp. Old ones were zero-degree and newer ones are 12-degree."

But I still think I'm not getting it. Eyeballing the clamps on the two posts I
have, I can detect no diff except for what's printed on them.

From http://www.lhthomson.com/SP12X.html :

"Thomson now offers only 12° Seat Clamps on all new seat posts. This
has been the case since April, 2002. Thomson also offers 12° clamps as
replacement clamps that will fit any Thomson Seat Post ever sold. The
12° clamps are direct replacements for the 0° clamps in every way.

The 0° clamps are good in every way and should not be replaced unless
you need the one thing the 0° cannot do that the 12° can. That is, the
12° clamp can bring the nose of the saddle down 12° more than the 0°
clamp. As rear suspension was developed and became more popular the
seat tube was laid back so much on bicycle frames that the 0° clamps
would not allow the nose of the seat to be adjusted down enough.

The 12° clamp has "FRONT" printed on one end. In the vast majority of
cases the word "FRONT" should be placed toward the front of the bike.
But, if the front of your seat will not come up high enough, it is
perfectly acceptable and safe to install the clamp with the word
"FRONT" toward the back. This will allow the front of the seat to be
raised much higher.

Set back seat posts may be mounted with the offset backward or
forward. The 12° clamp may be mounted with the word "FRONT" facing
forward or backward. Mount the seat post and clamp in the direction
that fits your riding style.

Bicycles with seat tube angles of 70° and above (70° thru 90°) work
well with 0° clamps. Bicycles with seat tube angles less than 70° (63°
thru 70°) require the 12° clamps. The customer has had the option to
buy either 12° or 0° clamp for about five years. But, not since April,
2002. There may be some seat posts with 0° clamps in the supply chain.
If you require the 12° clamps, you should request your bike store
supply a seat post with 12° clamps. If you have a seat post with 0°
clamps and want to use it on a bicycle with a seat tube angle less
than 70°, you may purchase a replacement set of 12° clamp for your
Thomson Seat Post.

If you order 0° or 12° seat posts from an old price list you will only
get a 12° seat post from the factory. The new price list only shows
one model for each size. It will come with the 12° clamps from the
factory. Remember a 12° seat post clamp will do everything and more
than a 0° seat post clamp will. A 0° clamp will do everything a 12°
clamp will do except bring the front of the seat down enough on
bicycles with laid back seat tubes (less than 70°).

TO TELL THE DIFFERENCE IN 0° AND 12° TOP CLAMPS: Look at the clamp
from the side. 0° clamps have the seat rail groove parallel with the
top of the clamp. The 12° top clamps have the seat rail grooves
sloping at a distinct 12° angle in relation to the top of the clamp.
Also, see sketches on intruction sheet. Instruction sheet is available
on web site. (www.lhthomson.com) "

RE/
From http://www.lhthomson.com/SP12X.html :

Thanks!....

BTW am I missing something or do the diagrams for their setback
posts (as in http://www.lhthomson.com/seatpostdimsSB.asp?offset=7)
not tell the reader how many inches/mm the clip has been moved back?
--
PeteCresswell

RE/
From http://www.lhthomson.com/SP12X.html :

Thanks!....

BTW am I missing something or do the diagrams for their setback
posts (as in http://www.lhthomson.com/seatpostdimsSB.asp?offset=7)
not tell the reader how many inches/mm the clip has been moved back?
--
PeteCresswell

On Sat, 24 Apr 2004 18:23:48 GMT, "(Pete Cresswell)" wrote:

RE/
From http://www.lhthomson.com/SP12X.html :

Thanks!....

BTW am I missing something or do the diagrams for their setback
posts (as in http://www.lhthomson.com/seatpostdimsSB.asp?offset=7)
not tell the reader how many inches/mm the clip has been moved back?

R sin theta, or roughly 116mm sin 10 degrees = 20mm.

On Sat, 24 Apr 2004 18:23:48 GMT, "(Pete Cresswell)" wrote:

RE/
From http://www.lhthomson.com/SP12X.html :

Thanks!....

BTW am I missing something or do the diagrams for their setback
posts (as in http://www.lhthomson.com/seatpostdimsSB.asp?offset=7)
not tell the reader how many inches/mm the clip has been moved back?

R sin theta, or roughly 116mm sin 10 degrees = 20mm.