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PAGING C40-Question on C40 fitting.(13 posts)

PAGING C40-Question on C40 fitting.EV2
Nov 15, 2003 7:02 PM
C40,or anyone I would like to ask you regarding fitting for a C40,I'm planning to get one.I'm in between sizes.Size 54 or 55.My height is 5'8 1/4" and inseam of 82.2 cm.I got fitted before and the numbers are 540 TT,53 ST(c-c),74 deg ST and 110mm stem,using a non offset seatpost.I have a long inseam,short upper body and shorter than average femur,but long lower leg.I'm deciding between a 54 or a 55.The 54 has the right TT-540mm but ST is 52(c-c).The 55 has the right ST 53(c-c) but longer TT-544mm.Also I calculated there would be 10mm of spacers in the 55 and 20mm on the 54 under the stem.Which would you think is a better fit?Thanks.
re: PAGING C40-Question on C40 fitting.03Vortex
Nov 16, 2003 3:09 AM
C-40 is the expert and I will leave it to him. He has provided much good advice on fit for all on this site. I just picked up a slightly used C-40 and am roughly your size being 5'9" and inseam essentially the same (32.5in inseam). I have a 55 (C-T which is how Colnago measures)and is what I think you need. I use a 110 stem. The 55 has a 54.3 TT (perhaps its 54.4 as you say). The TT is right where you need to be as well as the ST.

Good luck.
Thanks 03Vortex.....nmEV2
Nov 17, 2003 10:17 PM
not easy...C-40
Nov 16, 2003 4:40 PM
Im always skeptical of anyone's fitting dimensions. A fitting cannot determine your optimum saddle fore-aft position. Most fitters simple use a plumb bob to place the front of your knee in line with the pedal spindle. That's OK to start, but further experimentation is needed to to determine an optimum position. I'd question the recommendation for a 74 STA without an offset seatpost. I use the Colnago offset seatpost with the saddle placed almost as far back as it will go.

You don't mention the stem angle to go with the 20mm of spacers, or the stem length selected for the given TT lengths.

Do you have a saddle height dimension, rather than an inseam to judge the vertical size of the bike?

I can tell you that the top of the bars will be about 88cm above the floor on a 54cm, with a Campy headest (25mm stack height), Ritchey 84 degree stem and no spacers.

My inseam is a longer 83cm, and I'm 1-3/4 inches shorter. My saddle height is about 71cm, using speedplay pedals and Sidi shoes. This gives me a saddle to bar height difference of nearly 9cm.
not easy...-REPLYEV2
Nov 16, 2003 6:29 PM
My saddle height is 72cm from c of bb to top of saddle along the seat tube.I'm also using a speedplay with sidi shoes.I'm going to use my ITM Millenium stem 80 deg,110mm,and a king headset/20mm spacers on a 54 and 10mm on a 55 since it is .9cm longer headtube to get the same bar to floor distance.

Even when using a non offset seatpost my knee is still behind the axle using a plump line.The flite saddle tip is 1cm behind the c of BB.The reasoning for this is that my lower leg is almost as long as my upper leg.These are the numbers on my current bike I tend to duplicate on the C40.

If using that formula inseam x .65,I would be a 55cm-53(c-c)
C40.I see that you would be a 54 (c-c) since you have a 83 inseam,but you are riding a 54,52(c-c) C40?

Does the C40's tend to run larger c-c than the CT's or dream plus since their top tube is almost level with the seat collar and colnago size their frames c of BB to botttom of seat collar.

I would really like your input on which one is a better fit a 54 or a 55?
Nov 17, 2003 1:14 AM
If you are sure that the 72cm saddle height works well, then you either place your saddle on the high side, or your inseam is actually a bit longer than the posted measurement. It's easy to have a 1cm error in an inseam measurement. I use a bike with a horizontal top tube as the measuring tool. I block up the wheels until I get very firm crotch pressure in bare feet and then measure from the floor the top of the top tube.

Based on the 72cm saddle height, the 55cm would be the better choice, unless you're determined to have a of seatpost showing. Performance wise, you won't be able to tell the difference, so it's kind of a toss-up.

You could reduce the spacers to zero on the 55cm with a Ritchey 84 degree stem. I switched from a 55cm to a 54cm two years ago. I was using an ITM Millenium stem amd campy headset with no spacers on the 55cm. The Ritchey WCS stem on the 54cm raised the bar height from 87.5cm to 88cm. I believe that a Chris KIng headset would increase the bar height about .5cm, compared to the campy headset.

All Colnagos should measure very close to the same, c-c. For reference, the standover height on a 54cm is 79cm.

Have you found a seatpost with no offset that comes in a 28.0mm size? Just read a post from someone who used an aluminum shim with an aluminum 27.2mm seatpost in a C-40. Galvanic corrosion has the seatpost stuck in the frame. Something to avoid.
Nov 17, 2003 10:13 PM
Thanks C40.I found a seatpost with a 28.0 diameter with no offset.It is a Thomson Masterpiece.28 x 240mm.It is very lightweight around 145 grms.But it won't be out until the middle of December.Thanks again.
sadde height correctionEV2
Nov 17, 2003 12:08 AM
My saddle height is actually 71.1 cm, not 72 cm. from c of BB to top of saddle along the ST.,using speedplay and sidi shoes.
advice correction...C-40
Nov 17, 2003 1:29 AM
With the 71cm saddle height that you posted, the 54cm would be the better choice. That's one of the reasons that I switched from a 55cm to a 54cm. I lowered my saddle height to 71cm and the 55cm was just a touch large.

You should find the bar height dimensions that I posted useful. I would definitely consider a stem change to reduce the spacers. The Ritchey WCS would be a good choice. I assume that you are trying to achieve a saddle to bar height difference around 7cm. Mine is closer to 9cm using the Ritchey stem and no spacers.
Nov 16, 2003 5:47 PM
Either should work fine assuming that fitting was done properly. Have you put the fitting to the test? What are you riding now and how is it set up? Go larger if you're more into recreational/comfort, and smaller if you lean toward the racing side of things.
Nov 16, 2003 8:06 PM
Yes,I put the fitting to a test since it was done a year ago.It works well for me.My bike is set up now the same as the recommendations it has a 540 TT,74 deg ST,non offset Thomson seatpost, except it is 51 (c-c) and short head tube& a lot of spacers under the stem 42mm using a 80deg 110mm ITM stem.This frame is definetly undersize.I know the colnago tend to run longer head tubes.Should I go with the 54 and be 1 cm ST undersize or go with the 55 and be .4cm TT longer.Does the inseam x .65 rule still valid?for sizing.
Nov 16, 2003 9:52 PM
Assuming we're talking about bikes with horizontal top tubes, head tube length is largely a function of your bb height and seat tube angle and should probably be the last
thing you consider when sizing a bike. Because of threadless setups companies have added some height to the headtube, and people have become obsessed with aesthetics--how many spacers, etc--it really doesn't matter as long as you can get your bars where you want them. One thing you haven't mentioned is wheelbase, which can have a big effect on how "big" a bike feels. I don't know if Colnago published their wheelbase numbers but it would be intersting to compare to this 51cm bike of yours--a longer wheelbase bike will feel more stable at high speed. Anyway, yes, the .65 rule is still valid to get you in the ballpark, for most people anyway. I wouldn't freak out about this too much. I know I'd be happy on a 56 or 57 Merckx, a 57 or 58 Colnago, etc. That .4cm you are talking about is really insignificant. I can vary my stem length as much as 2cm depending on my mood or conditioning--and that's not even taking different bars or STI vs. Ergo into account. My "guess" is that you should go for the 54 if you like the fit on your current bike and the wheelbases are about the same. Anyway, hope this rambling helps a bit.
Thanks gtx....nm.EV2
Nov 17, 2003 10:16 PM