# Help with Colnago c-40 sizing.



## jaimemmm (Apr 17, 2007)

I CURRENTLY HAVE A 54CM MERLIN CYRENE. IT FITS ME PERFECT. I AM THINKING OF BUYING A COLNAGO C-40 , 54 CM. I KNOW THAT THE C-40 HAS A HIGH BOTTOM BRACKET. WILL A TRADITIONAL SIZE 54CM. C-40 HP FIT ME OR DO I NEED A SMALLER SIZE. I AM 5'8 AND HAVE A INSEAM OF 30'. :arf: :arf: THANKS


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## cxwrench (Nov 9, 2004)

that should be about right, how do the seat tube able/top tube lengths compare? 

oh...please stop YELLING, we can hear you just fine.


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## Salsa_Lover (Jul 6, 2008)

Colnagos doesn't fit using standard fitting concepts, they fit using the Colnago fitting concept

first read this

http://www.bikesportmichigan.com/reviews/colnago.shtml

and this 

http://redkiteprayer.com/?p=1148

then decide


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## PJ352 (Dec 5, 2007)

According to the Merlin site, there is no 54cm offered in the Cyrene. Is your bike an older model/ custom? If so, do you have the geo chart available?


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## jaimemmm (Apr 17, 2007)

my cyrene is a bought new 2002 cyrene . I know they they don't build a 54 now but they did then. awesome looking measurements . the head tube length is also very nice considering most 53 tubes look very short. a 55 is way to big for me. ahhh, the days when merlin sold a 54.


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## C-40 (Feb 4, 2004)

*No!*

That's the worst bunch of BS ever written. Colnagos are fit to the rider like any other bike.

About the only difference is the steering geometry. They have a relatively slack head tube angle that increased the front-center and wheelbase.


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## C-40 (Feb 4, 2004)

*info...*

Just off hand, I'd say that the 54cm is OK for your torso length, but large for your leg length. 

If you want an accurate answer, you'd need to post the TT length, seat tube angle and head tube length of the Merlin. If the Merlin uses a conventional press fit headset, the head tubes can be compared directly.

I owned a 54cm. If fit me quite well, but I have an 83cm cycling inseam with a 73cm saddle height. If you saddle is a lot lower, then you won't have a lot of seatpost showing.


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## jaimemmm (Apr 17, 2007)

c-40, What is a bunch of b.s. I don't lie. YOU TALKING TO ME? what is a bunch of b.s. I don't know who your talking to. Why so hostile. set me straight and tell me what the b.s. is.


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## Salsa_Lover (Jul 6, 2008)

according to the links I posted you need one cm smaller than the size you usually ride, and lower handlebars and a longer stem.

I have made the experience, I do have riden several Colnagos and currently I have 3 ( EP, ExtremeC and C40) and I have experienced the bigger-higher-shorter vs smaller-lower-longer combinations and I can say their advice is spot on.

C-40 doesn't seem to agree. I would be interested in knowing on what bases his opinion.


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## C-40 (Feb 4, 2004)

*sorry...*

My comments were directed toward the bike sport michigan article. It is baloney.

You fit a bike based on the contact points that it will provide. You need to have the correct head tube length and the proper reach. The actual frame size number means nothing.

I've owned two C-40 frames and found no reason to buy a smaller size than I'd ridden before.

As an example, a 52cm model C-40 would have nearly identical dimensions to a current LOOK 585 in a 51cm size. You could buy a 54cm and get an 18mm taller head tube, but the reach only increases by about 5mm.


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## C-40 (Feb 4, 2004)

*no*

Your fit is not determined by the bike. Handlebars height should meet the rider's needs. The same goes for reach, it should meet the rider's needs and the reach on Colnago frames is not particularly short, requiring a longer stem.


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## paredown (Oct 18, 2006)

Although I like a more traditional fitting than C-40 (less drop from seat to bar) 'cause I'm old skool, I have noticed no particular difference between 'nagos and any other bike

*except*

Colnagos (like a lot of Italian bikes) market their traditional geometry bikes measured c-t-t, unlike the c-t-c of a lot of other manufacturers. It seems I have to argue this point or ask for clarification from every eBay seller out there. For argument's sake a 59cm Colnago (stamped on the BB usually) with traditional tubing/geometry is about a 57 square measured c-t-c. This was true of my 2002 CT-1 that I sold just recently

Also, In the '80s they started using a Freuler style geometry for large frame sizes, extending the seat and head tubes above the top tube. So later Masters/Tecnos with have a 58.5 c-t-c toptube/57 c-t-c seat tube, with ht/st extensions to give you a 60 cm and up nominal size as marked on the BB.

Apart from that, I find little difference in fit--I'm currently riding a Simonetti--derivative Italian (Masi>>Wizard>>Medici>>Simonetti) and a marked "59" is within a mm of the geometry of the "59" CT-1...


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## pmf (Feb 23, 2004)

I have to agree with C-40 on this. There's this school of "geometry experts" out there who will tell you that Colnagos have this wierd geometry that won't fit most people or correspond to most bikes. Over the last 10 years, I've owned a Litespeed Ultimate, Colnago C-40 and Kestrel 200 Sci. All of them were 56 cm bikes, with the same 44 cm bars, 11 cm stems, same saddles and pedals, same components. They all fit me just fine. The bikes ride differently. Hard to say whether one was markedly better, just a bit different. 

Within reason, most of the fine fit adjustments on a bike are made with stem length, saddle height and saddle position. I'm not saying that someone riding a 60 cm bike frame can comfortably fit a 50 cm frame, but a 55 cm frame versus a 54 cm frame isn't all that different (about 1/3 of an inch). If your Merlin is 54 cm and you're happy with it, get the 54 cm Colnago.


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## Salsa_Lover (Jul 6, 2008)

have you all read the redkite blog article ? doesn't it make any sense ?


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## rx-79g (Sep 14, 2010)

C-40 said:


> That's the worst bunch of BS ever written. Colnagos are fit to the rider like any other bike.
> 
> About the only difference is the steering geometry. They have a relatively slack head tube angle that increased the front-center and wheelbase.


Did you read the first article?

The point does not seem to be that your body position is different, as you seem to be implying. The point is that Colnago intends riders to ride a smallish frame with long stem and large setback and they tailor the steering and seat angles to match that intent. Why else would you have a 75 degree seat angle on a road bike?????

I can personally attest to having ridden bikes that "fit" my body, but felt weird because I had to use a long stem to get my position. Colnago appears to have the opposite problem - if you get it sized a little large the steering feels weird because the stem is on the short side.

I don't know if that's true or not (since Colnago doesn't publish steering angles), but C-40 seems to be arguing about something different than the article is explaining, namely: Create your usual position on a size smaller frame.

It would be nice if Colnago put out something about their sizing philosophy so we didn't have only second hand articles about it, and the lack of steering data makes it hard to think out on your own. But the super steep seat angle definitely points to something strange going on. Example:

Let's say you buy your usual correct size frame, based on TT length. The first thing you'll do to fit it is move the seat aft close to 2cm more than some other frame. So you're 53 top tube is now effectively 55cm. You counter this by using a stem that is 2cm shorter than your previous bike, which has an effect on your steering. Depending on the steering angle, this may do two things - make the steering twitchy, and shift more weight off the front wheel and to the rear wheel, which will also make it twitchy.

Moving a size down will give you back an effective TT that is more normal. I would bet that part of the "trick" in sizing Colnagos is adding to the TT what the steep seat angle takes away.

Anyway, this all sounds like a boondoggle. Unless I was dealing with some sort of Colnago expert (and neither posted article sounded like they were written with all that much experience) I'd avoid trying to out-guess their weird geometry. There's plenty of fish in the sea, and most don't make a secret of fit or geometry.


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## rx-79g (Sep 14, 2010)

Salsa_Lover said:


> have you all read the redkite blog article ? doesn't it make any sense ?


I really didn't find the Redkite article very illuminating. All this analysis seems to be about BB drop, and admits he doesn't know what's going on with the steering. He also doesn't address how the steep seat angle longer drop are going to affect wheelbase and weight distribution.


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## paredown (Oct 18, 2006)

The Redkite article makes more sense than the Michigan sports article, but it is directed at trouble shooting people who are experiencing squirrely handling, and Padraig's description of what might be causing the problem is thoughtful and thought-provoking. 

I'd love to have a few EP's and a range of stems to try out various combinations to see if chages are noticeable...

For the bikes in the middle of the range with a 73 deg STA, the issue is likely a non-starter; the 43 deg fork (and resulting trail) seems to me to be fairly typical. 

And Padraig's general description of the fitting process is the same as C-40's in other threads--start with the TT length....


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## rx-79g (Sep 14, 2010)

paredown said:


> The Redkite article makes more sense than the Michigan sports article, but it is directed at trouble shooting people who are experiencing squirrely handling, and Padraig's description of what might be causing the problem is thoughtful and thought-provoking.
> 
> I'd love to have a few EP's and a range of stems to try out various combinations to see if chages are noticeable...
> 
> ...


The redkite article says:


> But is it squirrelly? Based on what I see on paper, my gut says it’s great on fast descents. For anyone not already accustomed to Italian bikes, out of the saddle, this bike is a bit more maneuverable than might be comfortable. I could see how someone might drift off their line on their first few out-of-the-saddle sprints.


So here he seems to be disagreeing that the geo looks at all squirrelly. He goes on to say this:


> I’d expect this bike to seem rather maneuverable out-of-the-saddle, but great on descents, unless, of course, it had a short stem and a high handlebar, and then it would seem squirrelly all day, every day.


Here he's referring to the same problem I am, but hasn't connected it with the fact that if you start with TT length without reference to seat angle, you ARE going to end up with the short stem that he glosses over as an unlikely scenerio.

I guess I was just left hanging by a scholarly analysis of geometry that makes assumptions about head angles and trail, then minimizes their effect, while dismissing the claims of professional reviewers from a magazine thought to rubberstamp all their reviews. The other article at least acknowledges that Colnago geometry is not typical and suggests reasons why and how to address them.

I would be not at all surprised if the Colnago uses a fairly steep head tube angle with a resulting low trail because of the medium rack fork. This was a popular set up for racing in crummy conditions in Europe, because low trail is more stable at lower speeds. But they are vague on descents. A longer stem may help that lack of feel and stability, which takes us back to the first article.


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## C-40 (Feb 4, 2004)

*also no....*



rx-79g said:


> Let's say you buy your usual correct size frame, based on TT length. The first thing you'll do to fit it is move the seat aft close to 2cm more than some other frame. So you're 53 top tube is now effectively 55cm. You counter this by using a stem that is 2cm shorter than your previous bike, which has an effect on your steering. Depending on the steering angle, this may do two things - make the steering twitchy, and shift more weight off the front wheel and to the rear wheel, which will also make it twitchy.
> 
> Moving a size down will give you back an effective TT that is more normal. I would bet that part of the "trick" in sizing Colnagos is adding to the TT what the steep seat angle takes away.
> 
> Anyway, this all sounds like a boondoggle. Unless I was dealing with some sort of Colnago expert (and neither posted article sounded like they were written with all that much experience) I'd avoid trying to out-guess their weird geometry. There's plenty of fish in the sea, and most don't make a secret of fit or geometry.


You analysis is not correct. You don't typically have to move the saddle back 2cm and use a shorter stem. If you really think so, then give me a frame example for a proper comparison.

There is nothing weird about the geometry. As I noted, the TT length and STA are both about the same as typical LOOK 585, in the size I ride. 

The big difference is seen in the steering geometry. The HTA is more slack and the F-C is longer. The slack HTA creates a little more steering trail and a little slower steering. For a given rider position, the weight on the front will be a little less.

The geometry makes for totally stable descending, but if you're used to a frame with faster steering, it requires a little more rider input.


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## Salsa_Lover (Jul 6, 2008)

I have been on a 56 traditional almost since I started riding some 10 years ago on a 11cm stem.

I have riden Colnagos on sizes 57,56,55 and 52s. 

I find myself the best on the 56 traditional or 52s ( same virtual dimensions ) on a 12cm stem.

My EP is a 52s, this was my first Colnago. I bought it from a guy with very similar measurements as me, only he is fatter and older. He bought the bike for the looks and set it up with a high handlebars and short stem.

He sold it because he dindn't like the way the bike rode and felt. he sold it to buy an Specialized Roubaix ( if that is a hint )

At that time I was riding a Bianchi 928SL in size 57 that has same virtual dimensions as a 56 traditional on a 11cm stem.

I tried the EP as it was setup and also didn't like it nor found an improvement compared to the Bianchi.

Then I started looking for other Colnagos and tried one in 57 with a 11cm stem with low handlebars and it was good.

Finally I bought my Extreme C on a 56 Freuler ( the frame is like a 54 with a longer head tube ) this Extreme C had the steerer tube cut very short and handlebars are very low, it has a 11cm stem ( Cinelli Ram ) but the TT is 55 cm.

I had put for sale the EP 52s and bought a C-40 in size 55 this one has a 54.5cm TT, the EP 52s has a 55cm virtual TT.

well, I set up the C-40 as close as possible to the Extreme C and experimented with 11, 12 and 13mm stem and high and low handlebars. The bike felt, rode, climbed and descended beautifully, probably the best would be to find a 12.5cm stem though.

So then I went back to the EP, set the bars as low as it was possible and a 12cm stem. ( I think I could go to 13cm and it would be better but helas my handlebars are also Cinelli Rams, maybe i would look for another Cinelli RAM in 12 for the Extreme C ) 

Now the EP was a completely different bike. The handling, feel and ride is much much better than what it was before with the handlebars 2cm higher and 2cm shorter stem.

Needless to say, my Bianchi 928SL feels and handles "big" now, not as agile on and off the saddle as the Colnagos, It is now for sale.

keep in mind the Colnagos head tubes are longer due to the non-integrated headset.

So, I am no expert, but I find those 2 articles I posted make a lot of sense.


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## C-40 (Feb 4, 2004)

*I agree..*



Salsa_Lover said:


> So, I am no expert, but I find those 2 articles I posted make a lot of sense.


That you are no expert. You can predict how any frame should be setup just by looking at the geometry chart, if you understand it. TT lengths cannot be compared directly unless the STA is the same. Correcting for the difference in easy, but if not done, leads to many false conculsions.

The extreme power has exactly the same geometry as a C-40 or C-50. Colnago did not change their geometry for a very long time. 


http://cbikeusa.com/colnago_extreme_power.htm


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## Salsa_Lover (Jul 6, 2008)

C-40 said:


> That you are no expert. * You can predict how any frame should be setup just by looking at the geometry chart,* if you understand it. TT lengths cannot be compared directly unless the STA is the same. Correcting for the difference in easy, but if not done, leads to many false conculsions.
> 
> The extreme power has exactly the same geometry as a C-40 or C-50. Colnago did not change their geometry for a very long time.
> 
> ...


no, 

I can tell you how my 3 Colnagos and 2 Bianchis feel and perform and what found after experimenting with many stem lenghts and handlebar heights combinations


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## C-40 (Feb 4, 2004)

*well....*

We'll just have to disagree. I've owned a lot of top of the line frames, including two C-40 frames. Understanding how to compare them to other frames, I had to do nothing special to make either of them fit. I've used the same 110mm stem length on every frame I've owned for a very long time, because I know how to figure the reach, before I pick the frames size.

I could buy a Colnago today and it would fit just like my LOOK 585 with the same stem length. I'd use exactly the same saddle to bar drop too. A frame should never dictate your fit.


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## B2 (Mar 12, 2002)

I owned a C40 in the past and currently own a C50. I would have to agree with those that say the Colnagos don't require anything out of the ordinary with regard to fitting. Where Colnagos do potentially differ from other frames lies in the data they claim as proprietary and don't publish. Specifically they don't list the fork rake, HTA and BB Drop in their geometry charts. 

My understanding, which I have nothing to substantiate with, is that the BB Drop is generally larger than most; the HTA is significantly less than most; and the rake is 43mm. I read somewhere that the HTA for a 57cm frame is something like 71.8 degrees. If this is true the trail is much larger than other manufacturers.

I sold my C40 a few years ago and since have owned a Serotta Legend Ti and Pinarello Paris Carbon, both with more typical 73 degree HTA's and resulting trail. In the end I decided I liked the slower, stable, descending geometry of the Colnago and bought a C50. Haven't looked back yet. 

Has anyone substantiated the HTA, BB Drop and rake that Colnago uses?


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## C-40 (Feb 4, 2004)

*info...*

All Colnagos use a 43mm fork offset for all sizes. The BB height is listed, so all you really need is the tire radius. A tire radius of 336mm is common for a 700 x 23, so the BB is the common 7cm, just like the majority of other brands.

I also have a listing of the HTAs - they range from 71 to 73.5 degrees.

Here's a link to a chart.

http://weightweenies.starbike.com/forum/viewtopic.php?f=3&t=71073&hilit=colnago+fit


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## B2 (Mar 12, 2002)

Thanks C40. That correlates exactly with the HTA I had written down.

So it seems to me that the only thing truly unusual about Colnago's geometry is the HTA and subsequently the trail.


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## icsloppl (Aug 25, 2009)

C-40 seems to have a significant bee in the bum on this, which is unfortunate. 
In my experience, you certainly don't *have to* change to a different size than what you're using currently. You could get a larger size. The wheels would still turn and you won't fall off.
However, moving to a slightly smaller size than what would normally be considered optimal does seem to provide improved weight distribution, steering accuracy, and overall handling for many owners.


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## rx-79g (Sep 14, 2010)

C-40 said:


> You analysis is not correct. You don't typically have to move the saddle back 2cm and use a shorter stem. If you really think so, then give me a frame example for a proper comparison.
> 
> There is nothing weird about the geometry. As I noted, the TT length and STA are both about the same as typical LOOK 585, in the size I ride.
> 
> ...


Colnago uses seat tube angles running from 75.5 to 73. A more typical range would be something like 74 to 72.5 (from Tom Kellogg's Merlin geometry). (Lemond geometry would be even more off running 73 to 72.) This puts the difference between 1.5cm and 0 depending on size. In the middle of the range the two are very similar, at the edges they depart pretty radically. For smaller sizes this means a stem length that's 15mm shorter on the Colnago. So a 100mm stem user would go to an 85 or a 53cm would go from 110 to 100 stem. So, maybe not a huge issue, but there it is.

What's probably more of an issue, if anything, is using only one fork rake for a range of HT angles from 70.8 to 73.5. In the middle to tall ranges this works out pretty well because 73.5 degree HT go well with 43mm of rake to produce a "neutral" trail of 56mm. Below that it goes from neutral to very high trail. High trail gives pretty quick steering at low speeds and increasing stability (resistant to turning) at high speeds. At the bottom end of 70.8 degrees HTA, the trail is up to 72mm.

So the middle to larger sizes shouldn't act much different than most other road frames. But the smaller sizes are going to combine shorter stems with very twitchy low speed handling and harder to steer at speeds. A longer stem could help with that, which you'd get with a smaller frame size normally. But on the Colnagos below 53 all the same top tube length once you correct for seat angle.

I don't have any recommendations to make. The frames look hard to fit to smaller people to me since the TT lengths don't really vary and the steering is kind of weird. Middle to taller people shouldn't have an issue, and I'll apologize to C-40 for disagreeing with him. For average to tall people there doesn't appear to be much of an issue. Short people should probably just stay away.


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## C-40 (Feb 4, 2004)

*wrong again....*

I don't want to be rude, but you have numerous errors in your post. Do you understand that a frame that has the same reach will use the same stem length?

As a short guy, 5-6.5" tall with long legs (83cm cycling inseam, 73cm saddle height) and a mechanical engineer with 26 years of "serious" riding behind me, I have a different take on this subject.

Comparing any two frames is really quite simple. Since Merlin has been brought up, I looked at their current geometry and found it to be quite ordinary. 

http://www.merlinbike.com/bike.aspx?content=RD-extralight

As an example, take the 51cm size that I ride. The TT length is 53.5 and the STA is 74. 

Let's compare a Colnago, which I already did before. A 52cm has a nearly identical reach, with a 53.1cm TT and 74.5 degree STA. Perhaps I should emphasize here, that having the same reach means that you use the SAME stem length. You keep mentioning short stems, but you are dead wrong. The head tube is 114mm, just what you would expect for a frame that actually measures 50cm c-c (if you bother to read the geometry charts). Add the same 30mm for the headset and you get 144mm. You could also compare a 51cm, but the reach is still about the same, only the head tube is 8mm shorter.

What all this tells you is that there is no problem fitting a Colnago to a short rider and there is also no problem comparing the geometry to a Merlin or any other brand, if you know what you're doing.

Regarding the steering geometry, it is different than many other brands, but that's just what Colnago intends. I rode a C-40 for four seasons. The last was spent riding up and down Colorado mountains at very slow 8-14mph speeds and down at 40+. I never had a problem at slow or high speeds. At high speeds, you just have to keep countersteering (push on the right side of the bars to turn right) or the bike would want to straighten up quickly. It's not necessarily good or bad, just different. All bikes require constant countersteering to keep turning, but those will less trail don't straighten up quite as quick.


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## rx-79g (Sep 14, 2010)

C-40 said:


> I don't want to be rude, but you have numerous errors in your post. Do you understand that a frame that has the same reach will use the same stem length?
> 
> As a short guy, 5-6.5" tall with long legs (83cm cycling inseam, 73cm saddle height) and a mechanical engineer with 26 years of "serious" riding behind me, I have a different take on this subject.
> 
> ...


You seem to be saying the same thing I am, but just from a different starting point. A 53.5 + 74 STA IS the same as a 53 + 74.5 degrees STA. And, off Colnago's charts, a 51.8 + 75.5 STA is also the same - all the top tubes on the Colnagos under 53 are effectively the same for the reasons that you point out. That means a 49 Colnago has the same reach as a 51 Merlin and all 4 Colnago Sizes above it.

All I was getting at is that the shopper has to do math to compare Colnago's to other sizes, instead of just working off TT lengths. The TT length can be used in sizing for many bikes, but Colnagos are an example of why you need to look at the whole chart. AND, if you need a 52 TT, you aren't going to get one with a Colnago, no matter how small you go.

I imagine your reference to HT heights is about the effect on bar height to reach, but that can be varied through lots of different mean - it doesn't have to be built into the frame.


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## cxwrench (Nov 9, 2004)

rx-79g said:


> You seem to be saying the same thing I am, but just from a different starting point. A 53.5 + 74 STA IS the same as a 53 + 74.5 degrees STA. And, off Colnago's charts, a 51.8 + 75.5 STA is also the same - all the top tubes on the Colnagos under 53 are effectively the same for the reasons that you point out. That means a 49 Colnago has the same reach as a 51 Merlin and all 4 Colnago Sizes above it.
> 
> All I was getting at is that the shopper has to do math to compare Colnago's to other sizes, instead of just working off TT lengths. The TT length can be used in sizing for many bikes, but Colnagos are an example of why you need to look at the whole chart. AND, if you need a 52 TT, you aren't going to get one with a Colnago, no matter how small you go.
> 
> I imagine your reference to HT heights is about the effect on bar height to reach, but that can be varied through lots of different mean - it doesn't have to be built into the frame.


might be good for folks to take a look at the way cervelo does things to get their view on things. on an R5 for example, each larger size is 9mm longer in 'reach' and 25mm taller in 'stack'...very consistant, same difference all the way thru the size range. All cervelos have 73° head angles. seems weird 'til you really look at it, then it seems to make more sense. they have changed the head tube angles/fork rakes on the smaller sizes to reduce the toe overlap issues somewhat as well. 
take a look...
http://www.cervelo.com/en_us/bikes/2011/R5/geometry/


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## rx-79g (Sep 14, 2010)

cxwrench said:


> might be good for folks to take a look at the way cervelo does things to get their view on things. on an R5 for example, each larger size is 9mm longer in 'reach' and 25mm taller in 'stack'...very consistant, same difference all the way thru the size range. All cervelos have 73° head angles. seems weird 'til you really look at it, then it seems to make more sense. they have changed the head tube angles/fork rakes on the smaller sizes to reduce the toe overlap issues somewhat as well.
> take a look...
> http://www.cervelo.com/en_us/bikes/2011/R5/geometry/


I know you meant 73 degree seat tube angles. I was going to use Cervelo as an example, but they don't make the 73 thing easy to find.

Cervelo is also interesting in that the odd sounding HTA are actually spot on to produce neutral trail with the typical 50, 45 and 43 fork rakes.

There's really no reason that all production road frames aren't 73 (since average leg proportions don't vary by leg length), but the Merlin geometry is closer to typical "good" geometry built around a particular trail.


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## C-40 (Feb 4, 2004)

*not any more...*

After 5 years of producing goofy geometry frames in the small sizes, Cervelo finally wised up and now have geometry that's about the same as many other brands. The small sizes now use more slack HTAs and all sizes have longer chainstays.

I always warn those who use those reach dimensions, that they can be misinterpreted. You can't compare the reach of two frames if the stack height height is significantly different. If reach values differ by 9mm, but one frame has a 20mm greater stack, the real difference in reach is about 15mm. 

http://www.cervelo.com/en_us/bikes/2011/R3/geometry/

I tend to agree about the STA. An angle of 73 degrees would work for more people than changing to steeper angles in the small size, but using the same 73 degree HTA does not make sense. The idea of using a slack HTA on small sizes and a steeper STA on the larger sizes is compensation for the longer wheelbase on the large frames a long wheelbase frame will turn slower.


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## rx-79g (Sep 14, 2010)

C-40 said:


> After 5 years of producing goofy geometry frames in the small sizes, Cervelo finally wised up and now have geometry that's about the same as many other brands. Teh small sizes now use more slack HTAs and all sizes have longer chainstays.
> 
> I always warn those who use those reach dimensions, that they can be misinterpreted. You can't compare the reach of two frames if the stack height height is significantly different. If reach values differ by 9mm, but one frame has a 20mm greater stack, the real difference in reach is about 15mm.
> 
> http://www.cervelo.com/en_us/bikes/2011/R3/geometry/


How does that work? Higher bar heights effectively shortens reach, not lengthens it.

And if your saddle to bar drop is the same, then the stack height is meaningless.

And Colnago is still using those crazy seat tube angles on the small end:
http://www.colnago.com/bikes/2011/c59-italia


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## C-40 (Feb 4, 2004)

*no..*

You stated: 

"For smaller sizes this means a stem length that's 15mm shorter on the Colnago. So a 100mm stem user would go to an 85 or a 53cm would go from 110 to 100 stem. So, maybe not a huge issue, but there it is."

That is totally wrong. If frames have the same reach, they use the same stem length. You have never provided an example where a Colnago would use a 15mm shorter stem. As I noted, I've used the same 110mm stem on my Colnagos, that I've used on nearly every frame I've owned, so we are not saying the same thing at all.


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## C-40 (Feb 4, 2004)

*more education...*



rx-79g said:


> How does that work? Higher bar heights effectively shortens reach, not lengthens it.
> 
> And if your saddle to bar drop is the same, then the stack height is meaningless.


 A taller stack does shorten the reach, but I only mentioned the reach DIFFERENCE, not what caused it. 

If you compare frames with a different stack height, the reach must be corrected to compensate. The amount is 3mm for each 10mm of stack height. It makes no difference if you add reach to the smaller frame or subtract reach from the larger frame, it's still the same difference.

I always assume the SAME bar height, but that does NOT make the stack height meaningless. If the stack differs by 20mm and the reach difference is 9mm, the true reach difference, at the same stack or bar height is 15mm.

Reach is not some magical concept that allows you to ignore stack height. Reach values can only be compared at ONE stack height.


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## rx-79g (Sep 14, 2010)

C-40 said:


> You stated:
> 
> "For smaller sizes this means a stem length that's 15mm shorter on the Colnago. So a 100mm stem user would go to an 85 or a 53cm would go from 110 to 100 stem. So, maybe not a huge issue, but there it is."
> 
> That is totally wrong. If frames have the same reach, they use the same stem length. You have never provided an example where a Colnago would use a 15mm shorter stem. As I noted, I've used the same 110mm stem on my Colnagos, that I've used on nearly every frame I've owned, so we are not saying the same thing at all.


The example you quoted is not based on reach, but stated top tube length, as I said before. Why TT length and not reach? Because people often go by some number, and reach is not one that anyone has standardized to make comparisons across brands easy.
We used to use seat tube length, then everyone pointed out that doesn't work since TT lengths aren't standard for heights. So now most people use TT length, but you and I know that doesn't work either, but it is what most people look at.

In the case of a frame that has a steep STA, the advice to go down one frame size makes some sense, as the stated TT lengths on Colnagos don't compare well to average frame geometry, which just takes us back to the advice in the first article. As it turns out, the advice probably doesn't work great, but in light of the STAs and funky steering, I can certainly understand what would motivate someone to devise a simple rule.


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## rx-79g (Sep 14, 2010)

C-40 said:


> A taller stack does shorten the reach, but I only mentioned the reach DIFFERENCE, not what caused it.
> 
> If you compare frames with a different stack height, the reach must be corrected to compensate. The amount is 3mm for each 10mm of stack height. It makes no difference if you add reach to the smaller frame or subtract reach from the larger frame, it's still the same difference.
> 
> ...


Stack height, spacer height, stem height are all the same thing because they all happen in the same line. A 140 stack height with no spacers is no different than 120 + 20 in spacers.

Are we talking about two different things, here?


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## C-40 (Feb 4, 2004)

*no...*

I never, EVER compare TT lengths without proper compensation for the seat tube angle. If the STAs are different, a TT length comprison is worhtless.

A traditional definition of reach is TT length minus frame setback. Frame setback is the c-c frame size times the cosine of the STA. That's where the rule of thumb to add 1cm per degree to TT length of a frame with a steeper STA comes from. The exact amount is (cosA-cosB) times the c-c frame size.


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## rx-79g (Sep 14, 2010)

C-40 said:


> I never, EVER compare TT lengths without proper compensation for the seat tube angle. If the STAs are different, a TT length comprison is worhtless.
> 
> A traditional definition of reach is TT length minus frame setback. Frame setback is the c-c frame size times the cosine of the STA. That's where the rule of thumb to add 1cm per degree to TT length of a frame with a steeper STA comes from. The exact amount is (cosA-cosB) times the c-c frame size.


But we're not talking about you. Well, maybe you are, but I've been talking about how consumers pick a frame size.


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## C-40 (Feb 4, 2004)

rx-79g said:


> Stack height, spacer height, stem height are all the same thing because they all happen in the same line. A 140 stack height with no spacers is no different than 120 + 20 in spacers.
> 
> Are we talking about two different things, here?


You finally made a correct statement.

We're talking about the same basic thing, but take a look at a Cervelo geometry drawing. As you noted, reach gets smaller as the stack height increases, so you're making an incorrect comprison if you compare reach at a different stack height.

If a person is trying to decide what frame size to buy, they will have ONE bar height in mind, so a reach comparison must be done at the SAME stack height. It makes no difference it that requires 20mm of spacer on one frame and none on the other, it's a correct comparison. The reach values in the Cervelo geometry chart are at different stack heights and NOT comparable to one another.


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## rx-79g (Sep 14, 2010)

C-40 said:


> You finally made a correct statement.
> 
> We're talking about the same basic thing, but take a look at a Cervelo geometry drawing. As you noted, reach gets smaller as the stack height increases, so you're making an incorrect comprison if you compare reach at a different stack height.
> 
> If a person is trying to decide what frame size to buy, they will have ONE bar height in mind, so a reach comparison must be done at the SAME stack height. It makes no difference it that requires 20mm of spacer on one frame and none on the other, it's a correct comparison. The reach values in the Cervelo geometry chart are at different stack heights and NOT comparable to one another.


You seem to be saying that one needs to apply a formula to correct for reach with dissimilar stack heights. If everyone published "reach" like Cervelo, that would make sense. But Reach is not a published number, so there is no baseline to correct from. If you're going to measure the frame, you can just measure it from a mean stack height, not the top of the headset.

Your objections and arguments seem to be built around a measurement system system that is neither standard nor in popular use. Objecting that you need to make some weird correction to use a measurement that you are doing doesn't make any sense.

As for Cervelo, they are internally consistant because the stack height goes up with frame size, just like a tradition frame gets a longer head tube as the seat tube gets longer. It's their system, no one else has embraced it.

For the record, my point about stack height and reach is simply about how raising the bar effectively makes for less reach because the rider's arms are not horizontal. I was not talking about the runout caused by the head angle.


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## C-40 (Feb 4, 2004)

*more ignorance...*

You're way behind the times. A number of brands now publish reach and stack values, including Cervelo, Trek, and C'dale.

Even brands that don't list the Cervelo standard defintion for reach and stack can be compared by using the traditional defintion of TT length minus setback - it's still reach. It will produce the same result. I explained the 1cm per degree compensation for TT length, but I guess that went over your head.

Just because a brand uses uniform progression in head tube length, does not mean that the reaches can be compared directly. Cervelo no longer uses uniform jumps in head tube length between sizes.

If you want to know the difference in the stem length required on a Cervelo, take the reach difference and add 3mm for each 10mm of stack height. Since you don't seem to understand trigonometry, the reason for this is the cosine of an average 73 degree HTA is .29. That means that the centerline gets closer to the vertical line through the BB center by .29 times the increase in vertical distance. Rounding off to 3mm is close enough.


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## rx-79g (Sep 14, 2010)

C-40 said:


> You're way behind the times. A number of brands now publish reach and stack values, including Cervelo, Trek, and C'dale.
> 
> Even brands that don't list the Cervelo standard defintion for reach and stack can be compared by using the traditional defintion of TT length minus setback - it's still reach. It will produce the same result. I explained the 1cm per degree compensation for TT length, but I guess that went over your head.* I not only understand it, I used it 8 posts ago.*
> Just because a brand uses uniform progression in head tube length, does not mean that the reaches can be compared directly. Cervelo no loger uses uniform jumps in head tube length between sizes.
> ...


What leads you to believe that this discussion warrants you being insulting? 

There are hundreds of road bike brands. Reach is not a standard, even if a few of the biggest brands are using it. Colnago certainly isn't, and I seem to recall this being a thread about Colnagos, not Treks.

Stop lecturing ME about how to understand geometry. I wrote enough about the subject that is should be clear that I get it. We've been talking about the difficulty in fitting Colnagos, remember? My stating that using TT is part of the problem does not mean that I'm guilty of doing it, duder. Just that the general public is not so savvy.

So, it looks like this "conversation" is over, since you can't talk like a grownup.


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## Salsa_Lover (Jul 6, 2008)

tst tst....

Expert conversation ?

All I read is mathematical calculations to fit the same person across different geometries.

That was not my point.

I can get exactly the same fit on a wide range of sizes from 54 to 59, using stems going from 130mm to 90mm and this resulting on higher or lower spacer stacks.

But the thing is the 54cm on a 130mm stem will feel and perform way different to a 59 on a 90mm stem.

I have riden two Bianchi 928SL frames same model but one 55 one 57, fitted exactly the same, one on a 100mm the other on a 120mm stem. They feel and perform different.

I have also riden 2 Colnagos C-40 traditionals one 55 the other 57, also fitted exactly the same. They do also feel and perform different.

same wheels, sames groupsets.

when I say "feel and perform" I am talking about how they ride, climb and descend, on and off the saddle. there is a an appreciable difference even when mathematically the fit is the same.

But the thing is, as the size 55 has a lower head tube, you can go more down than what the 57 allows you to go.

And then you discover that the Colnago smaller frame with a longer stem and lower handlebars but yet same reach, feels and perform even better.

Even the same bike on a 2cm higher and 2cm shorter stem will feel and perfom different to itself on a 2cm lower and 2cm longer stem. I have experienced this.

It is all about weight distribution and your own position in relationship with the bike's geometry.

And this is what those 2 articles I posted are about.

I specially found interesting Padraig's article that explains that this is due to a difference on how traditional italian frames place the BB drop compared to american/taiwanese designs.

This was my point, and not that is possible to calculate the right fit from geometry charts with some arithmetics, or that you can obtain the same fit on 2 frames with different geometry. That we all know.


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## wim (Feb 28, 2005)

rx-79g said:


> Stop lecturing ME about how to understand geometry.


No! He said you don't understand _trigonometry_, not geometry. There's a difference. On the other hand, who cares? Pertinent comment at 0:37 of this clip: http://www.youtube.com/watch?v=VF6JMotbHYM


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## rx-79g (Sep 14, 2010)

wim said:


> No! He said you don't understand _trigonometry_, not geometry. There's a difference. On the other hand, who cares? Pertinent comment at 0:37 of this clip: http://www.youtube.com/watch?v=VF6JMotbHYM


I was referring to several things he posted at me - the math slap being one. Your point?


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## pmf (Feb 23, 2004)

Salsa_Lover said:



> tst tst....
> 
> Expert conversation ?
> 
> ...


Good points, but WTF is stambecco and why do I want to use that bear for target practice?


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## Salsa_Lover (Jul 6, 2008)

pmf said:


> Good points, but WTF is stambecco and why do I want to use that bear for target practice?


a "Stambecco" is in Italian an Ibex or in german an Steinbock or "Rock Goat" the goats that live on the high mountains of the Trentino/Graubunden.

It was selected as the mascot for the 2009 Giro d'Italia, his name is ""Girbecco" as an hommage to the Climbers.

I am not as a good climber as an Stambecco, but at least I smell like one


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## pmf (Feb 23, 2004)

Salsa_Lover said:


> a "Stambecco" is in Italian an Ibex or in german an Steinbock or "Rock Goat" the goats that live on the high mountains of the Trentino/Graubunden.
> 
> It was selected as the mascot for the 2009 Giro d'Italia, his name is ""Girbecco" as an hommage to the Climbers.
> 
> I am not as a good climber as an Stambecco, but at least I smell like one


Interesting. My father had a big party when I was a kid that included two roasted goats. It still sticks in my mind, but not in a good day.

The bear should stay well away from my uzi.


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