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Frame fitting lesson ...(11 posts)

Frame fitting lesson ...bianchi boy
May 8, 2001 6:51 AM
Well, I finally got smart and had a professional fitting done at a local bike shop. I wish I had done that a long time ago, and recommend it to anyone shopping for a bike -- before you do anything else. Basically, I tried to do this myself (I'm pretty independent minded) 8 months ago and determined from various fit formulas and books that I needed a frame w/seat tube about 54 c-t-c, even though my old Bianchi had a 57 ctc frame that seem to fit me fine (although I was kind of stretched out). I finally ended up buying another used Bianchi measuring 54 ctc seat tube w/ 56 top tube. The new Bianchi felt fine except the bars were lower than I liked, which led to continuing problems with numbness in my fingers from leaning over too much. I have tried various combinations of extra spacers and positive rise stems, but can't raise the bars enough to solve the problem. That leaves me with one more option -- buying a new threadless fork with an uncut steerer tube and stacking up lots of spacers.

Anyway, I got fitted yesterday and the LBS says my new Bianchi is much too small for me. The proper size frame for me -- surprise -- is a 57 ctc seat tube (the same as my old Bianchi) with a shorter top tube, 55 or 56 cm ctc. With the taller frame, it would be much easier to get the bars up high enough for me -- which I would like to be about 1" below my saddle height. The problem with trying to do these fit formulas myself is that I had measured my inseam incorrectly and came up with a number about 2 inches too short.

To make a long story short, it looks like I might not be "bianchi boy" much longer. The frame geometry that seems to fit my dimensions best is a Colnago, so I am exploring my options for a relatively inexpensive new or used Colnago steel frame. This isn't a real problem because I think I can swap all of the components off my new Bianchi, which is full Ultegra, and sell that frame. A full Campy group would be nice but probably outside of my budget right now.

BTW, I rode my old steel Bianchi for several days over the weekend and could not believe how smooth it felt after riding the newer aluminum frame/ carbon fork Bianchi for the past six months. Although the Alloro is smooth riding for an aluminum frame, it can't compare with my old steel frame in terms of comfort. I can ride my old Bianchi over all sorts of bumps and rough pavement and barely feel a thing compared to the Alloro. My next frame will be steel, unless I come across an incredible deal on a ti frame.
DeBernardi ZonaKevin M
May 8, 2001 7:20 AM
Check out the DeBernardi Zona. It has similar geometry to the Colnago Classic.

I just bought one to replace my Bianchi Eros. I wanted something lighter and faster in steel. The price was great (with Columbus Zona tubing) I just got my Kit (Daytona) and am starting to build it up. I can't wait to ride it.
You're right ...bianchi boy
May 8, 2001 10:05 AM
The specs are about the same, except the seat tube angle, which is 74 on the Zona and 73 on the Colnagos. The Zona is a little less expensive ($739 from Chicagoland bikes) but only comes in one color combo (red/yellow) and is TIG welded. Nothing wrong w/ TIG frames, but I like the look of a classic lugged and chromed frame. The Colnago Crystal is $795 at GVH, and the Classic is $930 at my LBS. Both are probably a little heavier than the Zona, but I'm not a weight weenie.
More info...Kevin M
May 8, 2001 2:41 PM
I think the red yellow is the year 2000 model. The 2001 model comes in red/white and blue/silver/white (my choice). I got mine through my LBS from the distributer, Zar International. I realy like the paint job. The fork is Advanced Comp. with Cromoly Steerer.

If you want more info, then check out their "client list" or call them for a local shop who sell it.

http://www.zarintl.com/Framesets/debernardizona.htm
http://www.zarintl.com/clientlist.htm

Good luck in your search.
(I still live my Bianchi Eros).
even with the Colnago...ET
May 8, 2001 7:38 AM
based on your numbers you're a tough fit. First of all, Colnago's c-t goes about .5 cm above the top tube (there is a thread right now on Velonews verifying this as well; if you wait till Doug Sloan measures his bike, you'll be very old :-) PS, Doug--told you so that standover is crucial for many). So subtracting .5 gives a true c-t of top tube. Subtracting another around 1.3 cm gives ctc. The 56 Colnago, with a 54.8 tt, is more like a 53 c-c, and hence way too small. The 57, with a 55.5 tt, is more like a 55.2 ctc. The 58, with a 56.3 tt, is more like a 56.2 ctc. The 59, with a 56.9 tt, is moe like a 57.2 ctc, but now its tt is too long. In additon, Colnago's seat tube angles are generally steeper than those for other bikes, which means that if you fit perfectly on a bike with a gentler angle, your effective top tube on the Colnago will lengthen after you adjust your seat aft to get it back to its natural position. If you have a particular size Colnago in mind, I can plug in some numbers and tell you what the standover would be.

Can you give us some more data? What is your true inseam? Did the fitter say anything about your ideal seat tube angle?
even with the Colnago...AD14
May 8, 2001 9:06 AM
ET has made a perfect assessment. I have a colnago and the seat tube angle does alter effective stem length.
Here's my measurements ...bianchi boy
May 8, 2001 9:54 AM
I am about 5'11" tall. My inseam is about 33" (83.8 cm) in my socks, or 34" (86.4 cm) in my cycling shoes. I sent these numbers to GVH Bikes, and Gary recommended a size 57 cm. My LBS recommends a 58 cm; they measure inseam with your cycling shoes on because you'll always be wearing them while riding. The seat tube angle on my Bianchi Alloro is 74, and the fitter said my setback with pedals and seat was about right the way I had it set up. The seat tube angle on the Colnago is 73/18' for the 57 cm, and 73/11' for the 58 cm. The fitter didn't recommend an ideal angle, but he did say that I would fit better on a relatively short top tube.

GVH says the standover height for the Colnago is 32.4" for the 57 cm. I didn't get the measurement for the 58, but I estimate it would be about 33". Gary says I probably wouldn't notice too much difference between a 57 and 58 because it's just 2/5 of an inch.
Here's the deal...ET
May 8, 2001 11:26 AM
First of all, it's unfortunate the fitter didn't tell you what angle he measured you for and exactly where you ended up on the rails and setback. Without it, you just can't get a custom fit. I've warned many here to check that this appears on the spec sheet or ask before leaving the fitting. Please call him/her up and ask about this before he/she forgets or moves the position on the size cycle. You have a right to call. This is important. While you should be able to figure this out looking at your Bianchi, you then will not get the correct top tube length to go with it. That's what you were supposedly getting fitted for.

The numbers given for the Colnago standover don't seem to jibe. I took off .5 from the sizes to get c-ttt, then took this and multiplied by the sins of the respective STAs and added this to the 26.5 BBH given on Colnago's web site. This gives the following standovers:

size 57: 31.7 (80.6)

size 58: 32.1 (81.5)

size 59: 32.5 (82.5)

Nowhere close to those guy's stats. Published stats on standover are notoriously wrong, and he might be using them. As a check against my own human error, the standover on my 57 c-c Lemond is 82.6 (32.5) (measured independently of me as well, although the catalog is also wrong and way low). The 57 c-c is around 58.3 c-t, so it should come out close to the 59 Colnago, which it does. (All other things being equal, the Lemond standover should be a bit lower due to the 72.5 STA, but it comes out a bit higher because of a slightly larger BBH.) So it checks. And your guy's doesn't. (As another check, Litespeed very explicitly says it measures c-ttt, I've tested their standovers and they exactly match the geometry. Their 59 c-ttt, 73 STA has a standover of 82.7.) So be careful.

I have an inseam (84.2) close to yours. My bike is a 57 c-c. I have around 1.4 inches of clearance in my shoes measured to the tight inseam (which looks less than you might think). I bought what I still feel is the best stock bike for me out there. I'm dead center on my rails with given seat post and 72.5 STA. The seat/handlebar differential is 2.8", with all 4 spacers that came with the bike, but with the stock stem that doesn't angle up much at all. I would not want the standover to be any higher, though. If I were building a custom, I'd probably want it a cm lower. You might be pushing it a drop with a 57 c-c, given your inseam is a drop less than mine. Bikes measuring 58 c-t of tt would give you around the highest I feel you could safely go. Most on this forum seem to go way small. Not sure what that means, though.
PSET
May 8, 2001 11:28 AM
Did the fitter tell you what your ideal seat/handlebar height differential was? He should have. If so, please post.
In defense of the fitter ...bianchi boy
May 8, 2001 12:09 PM
He didn't do a complete fitting. He thought I just wanted to fit my existing Bianchi to see what I could do to make it fit better. I wanted a complete fitting, but he didn't have time, so I am going back next Tuesday for the whole job.

I agree with you about standover heights; the numbers quoted seemed a little high to me. I guess the only way to know for sure would be for some folks to measure their bikes. However, you may be wrong about how Colnago measures their seat-tubes. According to Chicagoland bikes website: "All Colnago frames are measured from the center of the bottom bracket to the top of the seat tube lug." The frame I looked at certainly didn't look like the seat tube projected .5 cm above the top tube. Anyway, it looks like a 57 cm Colnago is roughly equivalent to a 56 cm ctc, and a 58 cm Colnago would be equivalent to a 57 ctc.

As far as the seat to bar difference, we are shooting for a setup that would put my bars about 1" below the saddle. That's higher than a lot of people like it, but I'm 47 and not so flexible anymore. I also like looking at the road ahead without craning my neck too much. Plus, I'm trying to get some of the pressure off my hands. If I find that it is too high, I can always shorten the steerer tube, but can't make it any longer and want to avoid high-rise stem.
then might as well wait...ET
May 8, 2001 12:59 PM
for the complete fitting before deciding on bikes. Wish you would've waited to post until then or said so right off so I would've just waited till then to post comments and calculations, because you may end up eliminating what you think is right for you at this second when you'll have more info next week.

It's possible different Colnagos size a bit differently, but I'd bet not by much; you'll have to post what kind of Colnago you're interested in and see if others respond with measurements. The numbers you gave still don't make sense. Two things: if they indeed size higher than .5 above tt, then the standovers will be even *lower*. Also, there's no way that c-t minus 1 gives c-c. Even if you use the smallest c-t around (top of top tube, which is lower than the definition you gave), there is still typically 1.2-1.5 cm between c-c and c-t. After all, how skinny do you think the top tube is?