Dave,
The Silca framefit pumps are about 1 cm longer than the number stamped on the end without the head and uncompressed, and about 3 cm shorter than the nominal size when compressed. It works out to the approximate space that the pump fits in with a head on it.
The pumps I have seen come in 3 cm increments. A 56 cm should be a bit too long for your bike, so a 53 is what you want. I just tried one on a bike with the same 21" space under the TT that you described and it fit fine. Alas, it is silver, not celeste, so you'll have to keep looking.
There are some differences in the lengths added by pump heads, with the Campy plastic head being the shortest that I have found. However, I would suggest sticking with a plastic head if you are going to hang it from the top tube. The Campy steel head adds enough mass that the pump is more likely to come loose on a really rough road (and we know all about those up here in Vermont). Of course, this is moot if you are going to put a velcro strap around the pump and the top tube (usually people put the head into the seat cluster and the strap about three inches or so ahead of this). The Campy plastic head works best and can still be found cheaply; the Silca head that resembles a Campy steel head works passably well and the other, more common Silca head was designed by the Devil himself and should be graciously presented to those you despise. The Campy steel head is the bset from a functional point of view.
I have found that framefit pumps have a way of wearing at the paint where they hit the frame. A remedy that has worked for me is to cut pieces of flat cork and glue them to the pump and pump head where they rest against the frame, using rim cement. This padding can be applied so that it is almost entirely hidden and has the added benefit of making the pump a bit more secure.
Steve Barner, loving those hated Silca pumps in Bolton, Vermont
> Date: Sat, 27 Nov 2004 21:26:27 -0800
\r?\n> From: <d-gordon@sbcglobal.net>
\r?\n> To: <classicrendezvous@bikelist.org>
\r?\n> Subject: [CR]Silca pump sizing & measurement for frame fit
\r?\n>
\r?\n> I have another question for the experts. Not too comlicated, I =
\r?\n> presume,
\r?\n> but being wrong can be rather inconvenient when trying to order a Silca
\r?\n> frame pump for a restoration job I'm working on. If I had a bunch of =
\r?\n> pumps
\r?\n> to try, no big deal, just squeeze it in the space and see if it fits. =
\r?\n> But
\r?\n> here's the deal I just need to know what length Silca pump to buy for my
\r?\n> Bianchi 58cm frame. I need the horizontal top-tub mount version and the
\r?\n> exact measurement from head-tub brazed-on pump nipple to the resting =
\r?\n> area on
\r?\n> the front of the seat tube is 21", which I calculate as 53.5cm (21" x =
\r?\n> 2.54cm
\r?\n> =3D 53.5cm). This was my calculation. Now, it seems clear that I need =
\r?\n> a pump
\r?\n> than when squeezed in will fit nicely in that space. I am not sure how =
\r?\n> to
\r?\n> measure the Sica pump but I was told it was measured without the head on =
\r?\n> and
\r?\n> from end-to-end without compressing it. Is this correct. Soooo.... =
\r?\n> The
\r?\n> way I calculate it, the amount of compression is abnout equal to the =
\r?\n> length
\r?\n> of the pump head. Therefore I need a pump that measures 53-54cm, =
\r?\n> (without
\r?\n> the head and uncompressed, measured end-to-end). How much variance from
\r?\n> that can I get? I found a guy who has the right (Celeste) color that I
\r?\n> need, but he has a 56cm pump. Will this work? I am guessing that those
\r?\n> pumps will compress at least another 3 cm. I do have a Silca pump here =
\r?\n> in
\r?\n> the wrong color and it measures 19.5" (49.53cm) without the pump head, =
\r?\n> but
\r?\n> it won't fit because its too loose, once I screw the head on it. So I =
\r?\n> know
\r?\n> I need one larger than that. That pump does fit fine along the seat tube
\r?\n> however. =20
\r?\n> I have 2 old Silca pumps here, one with the flat top, and another =
\r?\n> with
\r?\n> the 'frame-fit' contoured head on it. The flat one compresses 4.2cm, =
\r?\n> while
\r?\n> the coutoured model only compresses one inch or 2.54cm. It looks like =
\r?\n> the
\r?\n> 56cm pump will just barely make it, if it compresses like my flat head =
\r?\n> punp,
\r?\n> but not if it compresses like my 'contoured-head' pump. Frustrating. =20
\r?\n> Does anyone on the list have a nice Bianchi (Celeste colored) Silca =
\r?\n> pump
\r?\n> laying around that will fit? It looks to me (from all my calcultions) =
\r?\n> that I
\r?\n> need a 53.5cm - 3cm =3D 50.5cm max, and with compression I have about =
\r?\n> 3cm to
\r?\n> play with, which means I can use a 47-50cm.
\r?\n> Also, the head that I am measuring on my old Silca pump measures 3cm, =
\r?\n> so
\r?\n> I subtract that from the measured frame space to give the uncompressed =
\r?\n> pump
\r?\n> measurement of 50.5cm. Maybe the old metal Campy pump head is a little
\r?\n> shorter, from what I recall. Sorry for all the wordiness, and I think =
\r?\n> I
\r?\n> made it more complicated. It seems kinda crazy considering all I have to =
\r?\n> do
\r?\n> is slip a pump in there, but I could use some help.=20
\r?\n>
\r?\n> Thanks, =20
\r?\n>
\r?\n> -Dave Gordon
\r?\n> Los Angeles