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Thread: Frame Geometry

  1. #1
    Senior Member Timmi's Avatar
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    Frame Geometry

    I am trying to re-create the feel of my second racing bike I had a very long time ago and lost in a crash.
    Never had anything as nimble and well behaved since. It was an italian-made Cambio Rino (from before they started making the knock-offs in Canada). This one was optimized for criteriums.

    Does anyone have any internet links, to a primer or framebuilder data on frame geometry?
    More specifically, covering the head tube angle and trail?
    Ideally, also as relating to wheelbase and center of gravity height?
    But just the info on racing, versus track, criterium, frame geometry would be great.

    I can't find my Framebuilder's book by Talbot in all of my boxes... HELP!
    Last edited by Timmi; 10-15-08 at 11:21 AM.

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    Decrepit Member Scooper's Avatar
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    Two excellent articles on HTA, fork rake, and trail are on Dave Moulton's blog HERE and HERE.

    The Waterford website has the geometries for their different lines (road, touring/commuting, cyclocross, track/fixed gear, etc.).

    http://waterfordbikes.com/

    Along the left margin near the top of the page (Products, Restorations, Dealers, etc.), run your cursor over "Products", then "Road", then "Road Race/Crit", then click on "R-22/2200 Road Racing". The 22-Series Race Frame page will come up. Go to the right side of the page and click on "Sample Geometries".

    You can repeat this for every technology and geometry frame Waterford builds.
    - Stan

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    Senior Member Timmi's Avatar
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    Thank you for that.

    Unfortunately, the blog is for beginners, and the website demonstrates that this is just another manufacturer adopting angles around 73 degrees (give or take a half) as published in Cinelli's landmark 1972 cycling bible on frame geometry and training. Back then the roads were pretty bad, and the geometry was a compromise between road shock absorbing and handling.

    I was looking for something a little more exhaustive.
    Last edited by Timmi; 06-23-09 at 10:41 PM.

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    Senior Member Nessism's Avatar
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    Most all standard racing frames built in the last several decades have head tube angles between 72 - 74 degrees. Fork rake works with the HTA to determine trail - which ranges from 5 - 7 cm. This range has been determined imperially and has held up to the test of time.

    Chain stay length has a small effect on weight balance on the bike, and bottom bracket drop has a small effect on center of gravity placement. Again, common range for frames is quite tight because it just plain works.

    One small Nessism I'll though out is somewhat controversial; I contend that a bike with a low bottom bracket will steer faster than one with a higher BB. The low BB lowers the center of gravity and moves said CG closer to the roll axis of the bike - thus making it easier to turn and lean.

    Enjoy your research.
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    Senior Member Timmi's Avatar
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    Well, the higher bottom bracket height is for the only purpose of being able to pedal through the turns... the tight ones, without scraping your pedals on the ground, and at the very least start to pedal sooner coming out of it. (All my pedals from my racing days are deeply scarred despited the higher BB). The higher BB does affect maneuverability, but relatively little impact... certainly nothing to the amplitude of good versus bad geometry on the rest of the bike. I've noticed that a bike with extremely short chainstays (like, I mean, you can't put on anything fatter than a 25C tire!) does handle better, but this is more apparent at lower speeds, in tight criterium turns, and on track racing on a tight track (in Montreal we had a 333m velodrome with a 49 degree inclination in the banks)... like combined with the right geometry it'll turn on a dime effortlessly when just sitting on it moving forward slowly, but this of course becomes diluted with speed. My road bike was extremely nimble, yet, surprisingly, at 60+mph spinning in top gear on a downhill I don't remember ever getting speed wobbles, yet in the criteriums, it could outmaneuver any Marinoni or other bike in the pack. That's why I miss it so much.


    Quote Originally Posted by Nessism View Post
    Most all standard racing frames built in the last several decades have head tube angles between 72 - 74 degrees. Fork rake works with the HTA to determine trail - which ranges from 5 - 7 cm. This range has been determined imperially and has held up to the test of time.

    Chain stay length has a small effect on weight balance on the bike, and bottom bracket drop has a small effect on center of gravity placement. Again, common range for frames is quite tight because it just plain works.

    One small Nessism I'll though out is somewhat controversial; I contend that a bike with a low bottom bracket will steer faster than one with a higher BB. The low BB lowers the center of gravity and moves said CG closer to the roll axis of the bike - thus making it easier to turn and lean.

    Enjoy your research.

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    Maybe you were just younger back then! Is there any chance of finding a copy of the bike itself? Or info on it's geometry?

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    Senior Member Road Fan's Avatar
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    Quote Originally Posted by tigrrrtamer View Post
    I am trying to re-create the feel of my second racing bike I had a very long time ago and lost in a crash.
    Never had anything as nimble and well behaved since. <

    Does anyone have any internet links, to a primer or framebuilder data on frame geometry? More specifically, covering the head tube angle and trail?
    Ideally, also as relating to wheelbase and center of gravity height?

    But just the info on racing, versus track, criterium, frame geometry would be great.

    I can't find my Framebuilder's book by Talbot in all of my boxes... HELP!
    I have my copy of Talbot, but I'm having trouble seeing what questions you have that you need answered. Are you looking to understand the meaning of trail and how it depends on HTA, or in how to choose values for trail and HTA, in order to get a specific result from a bike design?

    There are a lot of frame geometries on line. Do you need links? What kind of bike do you want the geometry for?

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    Senior Member Timmi's Avatar
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    Yes I would love links, thank you.
    I haven't looked at my Talbot book in about 20 years, so I'm not even sure it would have what I want in it.
    The bike I had was really short... ultra short chainstays, the feet overlapped with the front wheel, it handled amazingly in slow and fast situations... quite different from your standard steering geometry.
    I want someting extremely nimble, but stable on th edownhlls as well... looking for some examples... something tried and tested. Track might not be appropriate for this. I have a track bike with an aggressive geometry from the same maker, and it handles quite differently from the frame I crashed and no longer have.

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    Industry Maven Thylacine's Avatar
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    Quote Originally Posted by Nessism View Post
    One small Nessism I'll though out is somewhat controversial; I contend that a bike with a low bottom bracket will steer faster than one with a higher BB. The low BB lowers the center of gravity and moves said CG closer to the roll axis of the bike - thus making it easier to turn and lean.

    Enjoy your research.
    I don't think that's controversial at all. Most directional changes are made (initiated) via weight shifts, so if your CG is lower, you have a much shorter 'pendulum' which means less movement is required to create the same lean angle.
    Have you earned your stripes? <<click here / Questions about custom frames? Chat me! - warwickg71 (AIM/iChat) ThylacineCycles (Skype)

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    Senior Member Road Fan's Avatar
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    Quote Originally Posted by tigrrrtamer View Post
    Yes I would love links, thank you.
    I haven't looked at my Talbot book in about 20 years, so I'm not even sure it would have what I want in it.
    The bike I had was really short... ultra short chainstays, the feet overlapped with the front wheel, it handled amazingly in slow and fast situations... quite different from your standard steering geometry.
    I want someting extremely nimble, but stable on th edownhlls as well... looking for some examples... something tried and tested. Track might not be appropriate for this. I have a track bike with an aggressive geometry from the same maker, and it handles quite differently from the frame I crashed and no longer have.

    I was thinking of what are you looking for, and then I could send you just a few links.

    How does this strike you: the numbers for my 53 cm California Masi, an odd, tight, short road bike (these are approximate, my notebook is at home):

    ST 51.5 cm c-c
    TT 52 cm c-c
    STA 75 degrees
    HTA 73 degrees
    chainstey 39.5 cm
    BB drop 7.5 cm
    700c tubulars
    has toe overlap

    Or are you more interested in teh general science of frame design and customization?

    Road Fan

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    Senior Member Nessism's Avatar
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    Quote Originally Posted by Thylacine View Post
    I don't think that's controversial at all. Most directional changes are made (initiated) via weight shifts, so if your CG is lower, you have a much shorter 'pendulum' which means less movement is required to create the same lean angle.
    Seems obvious to me, and obviously you, but the old urban legend that a low bottom bracket "adds stability" is what a lot of people believe.

    One of my favorite experiments to make my point is to tell people to take a yard stick and balance it with their palm underneath. After they get the hang of it, I tell them to try the same thing with a 12" ruler; the yard stick is much easier to balance because the CG if further away from the pivot point. This same thing applies to bikes; a high CG is more stable, but harder to turn. Truth be known though, the total range of effective BB heights on bikes is quite narrow so as to make this discussion somewhat unimportant. Interesting internet banter but not overly significant in the real world.
    Last edited by Nessism; 08-11-08 at 08:24 PM.
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    Senior Member Road Fan's Avatar
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    Quote Originally Posted by Nessism View Post
    Seems obvious to me, and obviously you, but the old urban legend that a low bottom bracket "adds stability" is what a lot of people believe.

    One of my favorite experiments to make my point is to tell people to take a yard stick and balance it with their palm underneath. After they get the hang of it, I tell them to try the same thing with a 12" ruler; the yard stick is much easier to balance because the CG if further away from the pivot point. This same thing applies to bikes; a high CG is more stable, but harder to turn. Truth be known though, the total range of effective BB heights on bikes is quite narrow so as to make this discussion somewhat unimportant. Interesting internet banter but not overly significant in the real world.
    A real confusion point, Nessism! The design with quicker response (low CG) is percieved as more stable!

    Personally I think I can feel those differences between my high CG bike, a Woodrup, and the lower CG one, a Mondonico, but I also can't say that CG is the only cause of that handling difference!

  13. #13
    Senior Member Timmi's Avatar
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    center of gravity

    Quote Originally Posted by Nessism View Post
    Seems obvious to me, and obviously you, but the old urban legend that a low bottom bracket "adds stability" is what a lot of people believe.

    One of my favorite experiments to make my point is to tell people to take a yard stick and balance it with their palm underneath. After they get the hang of it, I tell them to try the same thing with a 12" ruler; the yard stick is much easier to balance because the CG if further away from the pivot point. This same thing applies to bikes; a high CG is more stable, but harder to turn. Truth be known though, the total range of effective BB heights on bikes is quite narrow so as to make this discussion somewhat unimportant. Interesting internet banter but not overly significant in the real world.

    We must be careful when making such interpretations.
    A stick (or any other object for that matter), is no harder to balance no matter what the length (height). It is harder to balance for a HUMAN. What I am saying, is that when you take into account our neuro-motricity responses, fine motor movements and larger motor movements in relation to reflexes (in delay and amplitude), a stick at a certain length is easier to balance, merely because it is easier to move our hand around several inches at a time than it is millimeters at a time.

    However, when you are steering the handlebars, we are no longer concerned with fine motor movements such as in trying to balance a pencil or ruler - the movements are slower and more controlled (unless you feel like flying over your handlebars). We must think of the effect on lateral movement of the contact patch under the bicycle in relation to the vertical CG. What is the sideways deviation off a straight course of the front wheel's contact patch in relation to the CG height? And how fast and by how much do we need to move our arms to turn the handlebars. If you have deviation data, and divide it by the CG height, you can derive a probable percentage difference between two BB heights. I don't have that data, so this is all I'll say for now. But I suspect that what we are looking at is more like comparing two yardsticks in slightly different lengths, and definitely nothing of the amplitude of what was suggested. And yes, in this case, steering geometry definitely plays a very large factor.

    Still haven't found my "dream geometry" btw. LOL ;-)

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    Quote Originally Posted by tigrrrtamer View Post
    We must be careful when making such interpretations.
    A stick (or any other object for that matter), is no harder to balance no matter what the length (height). It is harder to balance for a HUMAN. What I am saying, is that when you take into account our neuro-motricity responses, fine motor movements and larger motor movements in relation to reflexes (in delay and amplitude), a stick at a certain length is easier to balance, merely because it is easier to move our hand around several inches at a time than it is millimeters at a time.

    However, when you are steering the handlebars, we are no longer concerned with fine motor movements such as in trying to balance a pencil or ruler - the movements are slower and more controlled (unless you feel like flying over your handlebars). We must think of the effect on lateral movement of the contact patch under the bicycle in relation to the vertical CG. What is the sideways deviation off a straight course of the front wheel's contact patch in relation to the CG height? And how fast and by how much do we need to move our arms to turn the handlebars. If you have deviation data, and divide it by the CG height, you can derive a probable percentage difference between two BB heights. I don't have that data, so this is all I'll say for now. But I suspect that what we are looking at is more like comparing two yardsticks in slightly different lengths, and definitely nothing of the amplitude of what was suggested. And yes, in this case, steering geometry definitely plays a very large factor.

    Still haven't found my "dream geometry" btw. LOL ;-)
    As a controller, the human mind and body are not fast, from an engineer's point of view. A longer vertical stick takes longer to tilt to the point where you can't regain control than a short stick does. That's basically why we find it harder to control. Neuro-muscular certainly factors into this.

    I agree for a bike, steering geometry affects the available leverage to control the bike.

    Is all this in any way addressing the original question?

    Road Fan

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    Senior Member Timmi's Avatar
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    Quote Originally Posted by Road Fan View Post
    As a controller, the human mind and body are not fast, from an engineer's point of view. A longer vertical stick takes longer to tilt to the point where you can't regain control than a short stick does. That's basically why we find it harder to control. Neuro-muscular certainly factors into this.

    I agree for a bike, steering geometry affects the available leverage to control the bike.

    Is all this in any way addressing the original question?

    Road Fan
    Yes, I couldn't have said it any better (as you can witness by the length of my post that this is a reply to).

    I just hate it when people come up with the example of a long stik versus short stick... I couldn't let it go!

    And NO, it obviously doesn't bring us any closer to the original question! ROTFL

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    Senior Member Road Fan's Avatar
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    Quote Originally Posted by tigrrrtamer View Post
    And NO, it obviously doesn't bring us any closer to the original question! ROTFL
    Okay then, I really do have the same question: WHAT IS CRITERIUM GEOMETRY, AND DOES ANYONE HAVE MEASUREMENTS OF AN EXAMPLE?

    BTW, I had a mid-60s Italian bike back in the early '70s, and would dearly like to recreat that one's geometry. Problem is, I don't know the numbers, so I can't really talk turkey with a frame builder!

    road fan

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    Quote Originally Posted by tigrrrtamer View Post
    I am trying to re-create the feel of my second racing bike I had a very long time ago and lost in a crash.
    Never had anything as nimble and well behaved since.
    What model and size bike? I had a Trek 770 in 54cm and it was a crit warrior. Short 41cm chainstays, 38" wheelbase, 74.5-degree head-tube, etc. It cornered telepathically!

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    Senior Member Timmi's Avatar
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    It was a Cambio Rino, imported directly from Italy BEFORE Joe Gardin had a fake "master framebuilder" start making knockoffs in Toronto on these shores. (I was on the racing team of Centre du Vélo that was the first Montreal importer of these bikes, and this was my ride. The owner imported the first roster of these bikes from Italy pending their manufacture here, after which the quality and consistency degraded significantly).

    I believe it may have been a 56cm or 60cm frame - I'm 6ft2. A bit of researching will tell you that the chainstays were extremely short, top tube was as well as my feet had plenty of overlap with the front wheel (and it was fine that way - you get used to it). The bike itself, with Cambio Rino components and sew-ups weighed in at around 18 lbs.

    I have an old photograph, but can't really take measurements firectly from it, because of distortion from viewing anngle of camera lens, angle of bike (lean, direction), distance from lens unknown, height off ground of camera unknown, etc. Just too many variables to try to calculate corrections in the picture to arrive at a measurement.

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    Senior Member Road Fan's Avatar
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    Quote Originally Posted by tigrrrtamer View Post
    It was a Cambio Rino, imported directly from Italy BEFORE Joe Gardin had a fake "master framebuilder" start making knockoffs in Toronto on these shores. (I was on the racing team of Centre du Vélo that was the first Montreal importer of these bikes, and this was my ride. The owner imported the first roster of these bikes from Italy pending their manufacture here, after which the quality and consistency degraded significantly).

    I believe it may have been a 56cm or 60cm frame - I'm 6ft2. A bit of researching will tell you that the chainstays were extremely short, top tube was as well as my feet had plenty of overlap with the front wheel (and it was fine that way - you get used to it). The bike itself, with Cambio Rino components and sew-ups weighed in at around 18 lbs.

    I have an old photograph, but can't really take measurements firectly from it, because of distortion from viewing anngle of camera lens, angle of bike (lean, direction), distance from lens unknown, height off ground of camera unknown, etc. Just too many variables to try to calculate corrections in the picture to arrive at a measurement.
    I'm not familiar with this bike, but I'd suggest taking your question to the Classic Rendezvous site. There are some there who collect bikes of this vintage, and might know where one can be had, or a decent picture you could scale measurements off of.

    Road Fan

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    Advice #1 - Copy an Eddy Merckx frame, believe me, he has been obsessed with this subject!

    Advice # 2 - You can go to bicyclequarterly.com and purchase the issues that deal with geometry

    Advice # 3 - As suggested earlier, you can peruse the internet for geometry of manufactured bikes and attempt test rides at the relevant stores.

    Advice # 4 - Ride your friend's bikes, then decide. It worked for me, but that was before clipless pedals.

    Bad Advice # 1- You can copy my preference for a sporty bike in the 56-60 cm range, 73 head angle, 5 cm trail, 41.5 cm chainstay, 8 cm BB drop. But what do I know?

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    Decrepit Member Scooper's Avatar
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    Here's a Cambio Rino (Gardin Team) on Velospace.

    EDIT - Using a Gerber Variable Scale and goniometer on the photo, I got the following angles and dimensions. The photo is in pretty decent profile to get fairly accurate measurements. Scaling was off the Open Pro rims which have a 622mm BSD. There is a little vertical distortion, so I used vertical rim measurement for vertical dimensions and horizontal rim measurement for horizontal dimensions.

    HTA=77° (steep! -double checked)
    STA=74°
    Wheelbase=940mm
    Seat tube (C-C)=56cm
    Top tube (C-C)=54cm
    Chainstay=400mm
    BB Drop=60mm

    YIKES! I plugged in the measurements I took off of the photo into BikeCAD. My guess is it would be very responsive and fun to ride, but could be tiring on longer rides. It sure looks like fun.

    The photo appears to have been taken from the rear quarter as the front rim measured slightly smaller than the rear rim. This causes me to question the top tube length measurement; the bike may have a slightly longer top tube than the measurement I took off the Velospace photo. Because of this foreshortening, I tried to extrapolate the top tube length from the difference in sizes of the front and rear rims. Based on that, I'm inclined to think the frame is close to 56cm square, which also makes the wheelbase a little longer.

    Here's the revised drawing that I suspect is pretty close to the geometry of the bike in the Velospace photo.



    Last edited by Scooper; 09-19-08 at 03:57 PM. Reason: Revised BikeCAD image
    - Stan

  22. #22
    Senior Member Timmi's Avatar
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    Cinelli, 1972

    Crock, thanks for your suggestions. I'm posting this reply to everyone here who is kind enough to read and/or to post some replies on this topic.

    in 1972, Cino Cinelli published what was considered "THE" cycling bible. It covered everything about racing bicycles, from parts, frame geometry, to training and ergonomics, after exhaustive studies on the topic. Many books have been published since, and all seem to be a watered down version of this landmark book.

    In those days, one of the considerations were the roads of the time: potholed, cracks, cobblestones.

    Angles of the quadrilateral that any bike above the size of a 20" frame is, were 73 degrees for the head angle and same for the seat angle. He said he'd go "steeper", to 74 degrees, if the roads in europe were better. (before any of you try to correct me, that it is a main "triangle", think again. angles do affect vibration absorption because that head tube, although short, is a 4th side to the geometrical shape!)

    My main frustration with a local builder, Marinoni with his bad character and myopic stubborness, and with many others, is that they were still building bikes with Paris-Roubaix frame geometry for north-american roads that have never seen cobblestone roads and with a cycling industry too young to have ever had cyclocross sections on a road race course.

    The Eddy Merckx frames were no exception. They pretty much adhered to the Cinelli standards, as they did provide for a nice handling racing bike. What I find sad, is that if you look at almost all road racing bicycle specifications on the respective builders' websites, they all use the same old Cinelli standards - mainly because it worked, and continues to work for all racers.

    But I do remember riding criteriums, and thinking what wusses they were all to not go faster in the corners, because my bike was able to take so much more than theirs'... way beyond the limits of the other racers' bikes! And I also remember that my Cambio Rino road bike was far better behaved and handling than my Cambio Rino track bike (which I use as a single speed since Montreal decided to convert our beautiful velodrome into an indoor zoo they call a biodome). What was so remarkable, was the handling, maneuverability, yet very stable behavior of the bike.

    I was part of the Cambio Rino racing team, as I already posted somewhere, that imported these into Canada from Italy. The year after, Giuseppe "Joe" Gardin started to make knock-offs in Toronto, which had no consistency and no quality control, first under the Cambio Rino name and the year after under the Gardin name after he started having troubles and reprimands from Italy. I was lucky to have one of the rare ones imported from Italy before they started making inconsistent quality with totally random angles here on these shores. I know, because I saw them in the showroom every day... the whole line. I mean no offense to the owner of the Gardin, honestly! It was a sad reality.

    I've received my carbon fiber cloth, and my resin epoxy has cleared customs on friday, and I'll be making some recumbents now... but I think this will always remain a back-burner project for me.

  23. #23
    Senior Member Timmi's Avatar
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    Taking measurements off of photographs

    Scooper, thanks so very much for the efforts in taking those measurements.
    I don't know what a "Gerber Variable Scale and goniometer" are, LOL, but I need to point out a couple problems with this.

    I myself have an old photograph of me and my Cambio Rino, somewhere in old boxes.

    The problem here, is that in any photo, the center of it will be precise, and as you move towards the edges, EVERYTHING is off, more and more, on a gradual scale. We don't know if it was taken with a 35mm, 40mm, 30mm, zoom lens, etc, nor the effects of distortion... to better understand what I am saying, just think of "fish-eye" lenses (you know the pics where you see a person or a dog, and their nose seems extremely inflated and huge, and items around are tiny and tinier as you approach the edges - this is an extremely wide-angle lens that best displays the way items, dimensions and even angles get distorted in photographs, even on the more "normal" lenses.

    In your photograph, I'M assuming the image was cropped, or the bike was at an angle to the camera, because the rear wheel seems larger in it. This will distort all of the angles in the photograph.

    There is a possibility of "straightening" it, if you know where the original centre point to the photo was... but we don't, because it may have been cropped, with more taken off on one side than the other. If it wasn't cropped, we could figure out the angle of the bike to the camera by looking at the chainring which is most in the centre of the pic. We can even extrapolate it's diameter by counting the number of teeth. But because we don't know the focal length of the lens, nor if it was cropped, this would have limited usefulness.

    I have one of these BTW, and this is a track bike (as mentioned in my post of a few minutes ago), and does not at all have the same handling as the road bike of the same manufacturer. Also, a Cambio Rino or Gardin made in Toronto is not the same as a Cambio Rino made in Italy.

    Once again, Scooper, I am moved that you made such efforts, and I thank you, but it's the wrong bike.

  24. #24
    Senior Member Timmi's Avatar
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    Criterium geometry particularities (reply to Road Fan)

    Road Fan, I was going through this thread and noticed that I had overlooked a couple posts.
    You asked about what "criterium" frame geometry is. You seem to have a rather small frame size (53cm=20"), and this is borderline closest to the smallest one can go before having to extend the top tube because otherwise the downtube would intersect with it... I'm not confident my answer will apply to the smaller frame sizes, but I can comment on more "average" frames such as the more common 22"-24" range:

    Criterium bikes are designed for smooth to average roads/pavement, fast turning with hard acceleration coming out corners.

    3 areas of frame design have been optimized for the criterium type of riding:
    1. more "aggressive" angles - steeper head and seat tube angles
    2. shortest wheelbase possible: shorter chainstays, so that the rear tire almost touches the seat tube (2-6 millimetre clearance), approximate length 39cm. Shorter top tube, with a longer stem to compensate depending on a particular rider's reach (this was good for me as I am longer in the legs as compared to the average a man) - but careful, a shorter top tube also brings the front wheel closer under the rider and increases risks of flying over the handlebars during emergency braking)
    3. some will also have a slightly higher bottom bracket, to allow for pedaling through some of the tight corners at speed


    I believe that my Cambio Rino had a criterium geometry. It was a brazed steel frame, made of a mix of Columbus SL and Columbus SP with semi-sloping cast Columbus fork crown. 18.x lbs back in the mid 80's was rather remarkable for $800 back then! ($1800 Colnagos and other pro bikes with their campy super-record components weighed in at 21 lbs at the time - no $10k bikes back then... $2k was pretty much the upper limit in those days when there were only millionaires, no billionaires on this earth... how things have changed). Despite the criterium geometry, I went on 100-150 km rides daily with it (60-100 miles).

    Take note that when talking ergonomics, I am more or less a believer in importance of seat tube angle for rider positioning, because you can adjust the seat's fore-aft position to change the effective angle. From an ergonomics standpoint, what the seat tube angle DOES in the quadrilateral (YES, quadrilateral with the head tube of any bike 22" fame size and up being the 4th side) is affect dampening of road surface caused vibration and effective perceived comfort of the bike, and from a geometry point of view (and this is more important) as to how close you can bring in the back wheel (thus your chainstay length and ultimately the minimum wheelbase you can attain). But my point of view is that it's not so important for rider positioning, because you can get seatposts with a different offset and you can adjust your seat's position too.
    Last edited by Timmi; 09-22-08 at 08:44 AM.

  25. #25
    Industry Maven Thylacine's Avatar
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    Quote Originally Posted by tigrrrtamer View Post
    But my point of view is that it's not so important for rider positioning, because you can get seatposts with a different offset and you can adjust your seat's position too.
    Wish I could agree with that, but we've had guys come to us that cannot fit on any road frame with a 73 degree STA because there isn't a seatpost on the planet with enough setback.

    Also, there's no such thing as 'criterium' geometry. Nobody has a bike specifically designed just for racing crits because any old road bike does the job just fine. Companies tried to push the idea back in the 80's as a marketing exercise, but nobody bought it.
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