|Frame size question 54cm (c-t) or 52cm (c-t)||ericrob|
Dec 25, 2003 11:44 PM
|Ok here's my dilemma: I know my recommended frame size c-t is 53cm, but I 'm looking at a frame that comes in 52 or 54. if I go with 52cm I'll need to run a 140mm stem for my recommended reach or a 120mm stem on the 54cm frame. Standover clearance is about 2" on the 52cm and 1" on the 54cm. I know the 52cm will be more responsive but I don't want it to be too twitchy. So what would you do go with the 52cm or the 54cm frame? and why? Thanks for your time.|
Dec 26, 2003 7:30 AM
|most american and asian frames have handling designed around 11cm stem, so you'd be better off with 54cm and shorter stem. Italian frames /Colnago, Merckx, etc/ designed around 13-14cm stem, at least used to.|
Dec 26, 2003 7:48 AM
|Frames are not designed around a specific stem length. Don't know how people come to this conclusion. I have a Colnago and I've used stems of 100-120mm in length, depending on my saddle fore/aft position. I could never use a stem as long as a 130.
The poster mentions "recommended reach". Recommendations are usually worthless. What's relevant is the reach that works for the rider, not what some fit program came up with. The other thing I can't believe is that there would be a 20mm difference in reach between these two frames. If you want accurate advice, post the brand and model or the TT length and seat tube angle for an accurate analysis.
One thing that has been overlooked is handlebar height. The smaller frame may handle fine, but you should know BEFORE you buy it, what amount of steering tube spacers and stem rise will be required to get the bars up to the proper height. This can be calculated if the head tube length and type of headset are known. If you can handle an 8-10cm drop from the saddle to the bars, the smaller frame probably won't be a problem, but if you can only handle 5cm, then the larger frame would probably be the better choice. If you know your saddle height, measured from the center of the bottom bracket to the top of the saddle, along the center of the seat tube, an appropriate frame size is simple to calculate.
Another misconception is the idea that the smaller frame will be too quick or twitchy. A good frame builder will modify the steering geoemtry to avoid this problem.
|Myth? not really||cyclopathic|
Dec 26, 2003 8:48 AM
|the difference in euro vs american/asian geometry based on difference in avg body proportions: euros have in avg longer legs and shorter torso.
Second, americans tend to be more top-heavy, and euro pro riders don't have much of the upper body. "Euro" geometry uses shorter TT and longer stem to create "ballanced" ride and compensate for lack of weight on front wheel.
It is well documented fact that Eddy and Colnago liked and designed frames around slacker angles longer stem. It doesn't mean you can't use shorter or longer stems, it just you're likely to sucrifice handling. At least what frame builder intended as is a good start.
Pers I love 9cm stems, and judging by my last wipe out on ice /both wheels slid under in corner/ my weight is pretty centered over the bike.
From original post guy seems to have shorter instem and longer torso/arms, he'd be better off with longer top tube. Besides, most american companies design frames with 11cm stem in mind.
|I might believe it, except...||C-40|
Dec 26, 2003 9:43 AM
|Colnagos have seat tube angles of 74-75 degrees in sizes up to 55cm. Not what I'd call "slack". The head tube angle is slack in the smaller sizes, creating a long front-center and slow steering.
In sizes 55 and smaller, Colnago TTs are actually longer than some U.S. brands.
In the larger sizes the seat tube angle is the same as many U.S. brands and but the TT lengths do tend to get shorter. The head tube angle tightens up and the front-center is not particularly long.
For a given rider to use a longer stem, he would have to move his position foward and ignore KOP just for the sake of weight balance. A long stem by itself makes little difference in weight balance.
|4 what it's worth...||6was9|
Dec 26, 2003 1:05 PM
|there is this article regarding Colnago stem length...
I am not sure how much credence I'd give to what this guy has to say or the Trialtir guy he mentions though. Whether it's a myth or not, for one, I am, somehow, aware of this notion of using longer stem for Colnago. May be someone could post something from more reliable source to confirm this.
Dec 26, 2003 2:04 PM
|This is one of the funniest articles I've read on the subjest. I won't take the time right now to point out all the fallacies in this article, but the first is comparing two bikes made of entirely different materials and drawing the conclusion that a 1cm smaller frame made a huge difference in performance. The TT length of the smaller 52cm frame is actually about 2mm LONGER than the 53cm frame, with the rider in the same position relative to the BB, yet the rider chose a longer stem. To do this he would either have to tolerate a lot longer reach or move his position forward, ignoring the knee to crank relationship. How often have you heard of someone not being able to ge the bars low enough? The guy must have a 10-12cm drop from the saddle to the bars - far more than most folks can tolerate.
Then there's the baloney about a lower center of gravity and how it improved his climbing. More baloney.
I've switched from a 55cm C-40 to a 54cm and the difference was almost imperceptible. The TT length only differs by 3mm, so the same stem length may be used on either one. The head tube on the 54cm is 1cm shorter, so I switched from an 80 degree stem to an 84 to get the bars up to the same height.
|re: Frame size question 54cm (c-t) or 52cm (c-t)||Arnold Zefal|
Dec 26, 2003 8:24 AM
|I would get the 54 with the proper top tube length. To me top tube length is what makes the bike feel right. Standover is not that big a concern on a road bike, 1" is fine IMO. And as stated before the larger frame will allow better bar placement without lots of spacers or radical stems.|
|Another vote for the 54.||dzrider|
Dec 26, 2003 8:40 AM
|It reads like you have long arms relative to your overall height. I do also and find that with longer stems than the 120mm-125mm that I'm used to my body weight is farther forward than feels comfortable to me for good handling. I also agree with the poster who wrote that a smaller frame would be unlikely to feel twitchy, exactly the opposite of the feeling I get with longer stems, and that 1" standover height is plenty on a road bike.
Do keep in mind that the point of all these tiny little measurements is to predict as well as possible what will work. In bike fit, as in most things, humans are able to confound the best possible predictions.
Dec 26, 2003 9:58 AM
|but try to buy the 53 in another brand. knowing you are in the wrong size may become an obsession.|| |