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Trend towards longer top tubes(12 posts)

Trend towards longer top tubesDaveG
Mar 11, 2001 1:39 PM
It appears to me that many more bike manufacturers are going towards the longer-is-better trend in top tube length. While I haven't done that much experimenting, I am currently a member of the short top-tube/long-stem club. Many bikes out there now have top tubes >2cmm longer than what I'm riding now (59 c-c ST with 57.5 top tube). I understand the benefits of a stretched out profile, but what is the advantage of a longer top tube vs. using a longer stem? For folks who have switched to bikes with long top tubes, did you shorten your stem or just get used to it?
re: Trend towards longer top tubesLBS guy(Andrew)
Mar 11, 2001 3:31 PM
The longer top tube and shorter stem will give you better control on the bike, better turning and handling, ussually people have a shorter stem so not to be too streched out, this will benefit climbing, sprinting, descents, the only time it wont really help you out is when your on the trainer
re: Trend towards longer top tubesColnagoFE
Mar 12, 2001 11:13 AM
well if you're like me you can use a short TT and relatively short stem (110). colnago geometry works for me. those long TT bikes are just too long. all depends on your body proportions. get a bike that fits you with a "normal" stem.
re: Trend towards longer top tubessteveq
Mar 11, 2001 3:54 PM
in addition to the control issue mentioned above i think it's a matter of personal preference. for those of us (like me) with shorter legs and longer torsos a longish top tube will give my upper body the room it needs. i can then fine tune my position with the appropriate stem length/height. one of the reasons that kept me away from a c-40 was the short top tube. i woulda had to get a 140cm stem to get it to fit right and that would compromise handling. sq
Longer compared to what?Dog
Mar 12, 2001 12:10 PM
For me, I choose a bike based upon top tube length, largely, rather than seat tube height. The top tube seems to be a much more critical dimension, the other being seat tube angle. I always have had lots of seatpost showing with top tubes that are anywhere close to correct; seat tube length is nearly irrelevant.

Another advantage of picking by top tube length is that the companies seem to specify them fairly uniformly, center to center. You see all sorts of crazy specs on seat tube length.

Complicating things, however, are sloping tt frames. There, you need to see the 'virtual' length, that is, what the length of the tt would be if drawn parallel to the ground from the head tube to the seat post. What will really skew the numbers is looking at the lengths of a sloping frames seat tube and top tube - tt's are definitely getting longer with respect to seat tubes.

So, the real question may be, are seat tubes getting shorter compared to top tube length? We know they are for sloping tt frames, but maybe even so for standard (parallel to the ground tt) frames.

Doug
Longer compared to what?DaveG
Mar 12, 2001 2:54 PM
Doug, I understand your comment about relative top tube lengths and sloping seat tubes. But, it still seems to me that the industry trend is towards longer top tubes overall. Would you disagree with that? I don't completely agree that seat tube length is totally irrelevant as you can create an excessive seat-stem difference if you aren't careful. Sure you can toss on lots of spacers (if its threadless) and a steep rise stem, but at best it looks goofy and at worst might affect handling. I'm sure you didn't mean something that radical. I guess was question really was: are longer top tubes merely a trend or does it offer significant advantages?
I agree; seat tube length is not nearly irrelelvantET
Mar 13, 2001 4:26 AM
I would speculate that the reason Doug thinks so is because he is at the extreme regarding seat/handlebar height difference: if I recall, his handlebar is an incredible 4-5 inches lower than his seat, whether due to great flexibilty, body proportions, experience, being a natural, or whatever. So for him, he doesn't care whether he has 1.5 inches or 4 inches of standover clearance (which itself is a function of seat tube length and angle, I might add), because he can just use less spacers. For almost everyone else, though, it matters a lot, because, as you said, one will have to resort to goofy steep rise stems and/or more spacers than recommended.

As an example, on my 2001 Lemond Zurich, with the max of all 4 cm of spacers left on just as it came in the showroom (I don't know enough to change it right now, it feels good, and Lemonds are already stretched), the seat/handlebar height difference is already 2 inches (this for the zero-looking, i.e. parallel-to-the-ground stem), and yet my standover clearance is only around 1.5". Just think what adding another inch or two of standover (by getting a bike with a smaller seat tube) would do to the seat/handlebar height differential. And you can't add any more spacers.

I say seat tube is important for most, it just so happens not for Doug Sloan. And too many people, even on this forum, have tried to be like Lance (or Doug Sloan!), and their not understanding the seat tube sizing games associated with bikes like OCLV and Bianchi and being told to just measure for the top tube cause them to end up with bikes for which they can't legitimately or at least ungoofily (is that a word?) build up the stem, then regret their purchase, sometimes not having even figured out what went wrong. Be careful out there--and ignore all advice from Doug Sloan. :-) Hey Doug, just kidding.
The original questionDog
Mar 13, 2001 5:39 AM
OK, maybe I have a little too much of an egocentric view on this. :-) Not only do I ride one of the reputedly shorter top tube bikes now (Colnago), but in my frame size, nearly all bikes are close to "square" (same length tt and st). The Colnago actually has a slightly longer tt than st in the 54, according to my measurements, and is nearly the same as my Bianchi's, within 1/2 cm.

I checked, and my 1980 Bianchi is nearly "square", too. But, one or two bikes don't make a good sample.

In any event, the original question was whether there is a [i]trend[/i] towards longer top tubes. To know that, we'd have to know what the proportions were several years ago, and then know the proportions of a good sample of today's bikes. Not sure we've examined that. As I have proven, judgments based upon small samples aren't valid.

So, I think it may take some research to answer the question, rather than some general observations.

Nonetheless, it does appear that we presently enjoy the luxury of having literally hundreds of bike manufacturers from which to choose, including custom made, with many having widely varying geometries. So, I'd think there is hardly an excuse for not finding one that fits, even if there is a trend in any particular direction.

Doug
more warningsET
Mar 13, 2001 7:28 AM
If you're egocentric, you're forgiven; if true, it's only because you assume everyone rides as good as you, and even if so, offering helpful advice to all shows what you're made of.

Some important warnings:

Before doing the research on whether top tubes are lengthening, one has to decide what one means by longer TTs. In particular, do you mean for a fixed seat tube angle, or regardless of seat tube angle? So for example, if one needs a 72.5 degree seat tube angle to be on the middle of the rails and gets on a bike with a 74 degree seat tube angle, he will have to push the seat way back (around 1.7 cm), effectively lengthening the top tube. So this is important, e.g. companies might be switching to steeper seat tube angles rather than longer TTs but the effective result could be the same.

Furthermore, one has to decide if he is looking at a particular size or not, because some companies have different philosophies than others as the sizes get bigger, e.g. some keep steep seat tube angles even in higher sizes, but most slacken off a lot; some are mainstream at the lower sizes and then have longer top tubes at the higher sizes compared to other companies.

Finally, one must measure the frames by the same standard (e.g. true c-c or c-t of top tube, but absolutely not c-t of seat tube or lug, since that can be totally arbitrary) to put things on a level playing field. And connected with this, Doug, one thing I won't let you get away with is saying simply that your bikes are (close to) square (ST = TT): You have to say what definition of seat tube you're using for this to be meaningful. This is IMPORTANT! Confusion abounds and is reaching hilarious proportions. As one amazing example, Bulltek claims Ciocc sizes c-t (it doesn't say of what), and its competitor Cbike claims it sizes c-c of seat tube lug (is that a completely unique measure?). As another example, my 57 c-c Lemond is almost square (57.5 TT) measuring c-c, but is nowhere close when measuring c-t of top tube (58.3) or seat tube (lug)—the last probably well over 59. So better not to say it's square without telling us how you're measuring. I keep trying to tell everyone that a Trek frame size 56 (which has a 56 TT, so it's square!) is actually something like a 53 c-c and 54 c-t of top tube, so nowhere close to square by these more standard measurements, so those unaware (and without your ability to handle a dramatic seat/handlebar height difference) will have trouble with their stem and reach on OCLV by basing their sizing on TT alone, all because Trek sizes its seat tubes almost arbitrarily to the top of the universe and much higher than most, so in reality the seat tube is rather small for the corresponding top tube.

Yes, I agree, it's nice we have so many choices. It's also nice to be aware what those choices are.
how to measure?Dog
Mar 13, 2001 9:24 AM
Is c-c the best way to measure, as far as consistency and fairness is concerned? I'll measure mine tonight. I think both Bianchi and Colnago measure center of bb to top of top tube, right? Based upon that, they are 'square.' Based upon anything short of that for the seat tube measurement, they have 'long' top tubes, contrary to the myth of the Colnago 'short' top tube, at least in my size. Chicagoland website states: "All Colnago Frames are measured Center of Bottom Bracket to the Top of the Seat Tube Lug." (http://www.cbike.com/colnago.htm) That's not the very top of the seat tube, but it's higher than the top of the top tube. Since the measurements for a 54 are spec'd at 54/54, then the top tube is relatively long, right? This is a little goofy, though, as each bike model will have different types of "lugs" for the seat tube, making the measurements different for every bike frame model. This is not true, of course, if they are not stating what they really mean - they may really mean top of seat tube, period. ??? (scratching head) For smaller or larger frames, things change in either direction quite a bit.

Research will be very difficult, though, as there is no accurate and standard way to convert c-t measurements to c-c without actually measuring. Plus, the published info, even if reported clearly, may not be accurate.

I don't think there is any hope of resolving this. Too many variables.

Doug
measurementsET
Mar 13, 2001 10:43 AM
FYI: I believe both Bianchi and Colnago measure (unfortunately) to some top of seat tube, an expression which apparently can be used to mean anything—end of set tube, lug, clamp--higher than top of tt. From the posters here, it seems that Colnago's extends less above the tt than many others, so it's closer to c-t of tt than other c-t of st bikes.

Everyone agrees that measuring to the top of seat tube is the worst and least informative way. However, there can be legitimate opinion as to whether c-c or c-t of tt is better: the first gives the true center lines of the frame; the second effectively gives the standover, which is useful for proper clearance and stem and handlebar reach calculations, reasons I prefer this measure.

It is not as hopeless as you make it sound. First of all, there are some rules of thumb in going from c-c to c-ttt and back: the c-c is typically around 1.3 cm less than c-t for steel, and more like 1.6 less for oversized aluminum. As I've said before, give me one of standover or c-ttt and I'll produce the other (with STA and BBH), because a little HS geometry will convince you that STH – BBH = (STcttt) x sin(STA). Of course, it seems to be more the rule that companies (include Bianchi in this group) publish false standovers if they publish them at all. A notable exception is Litespeed (check them out at Bulltek and look at the geometry). They say in as clear terms as you could ask that they measure c-t of tt. So plugging in e.g. data for its size 57 (57 STcttt, BBH = 26.6, STA = 73 degs) in to the formula above and out pops 81.1 for the STH, exactly as published!

Many other companies do say clearly that they measure c-c, so we know it for them and can use the rule of thumb to get c-ttt, standover, etc. So it's not all hopeless. All we need to do is to look more carefully at those companies doing the top of seat tube thingy. Asking the people on this board to do measurements helps clear the air once and for all, as we did for Trek.

If you decide to measure, please measure everything: STH, BBH, standover, c of BB to t of tt, c-c, c-ttt, c-t of seat tube that matches the given frame sizes, etc. It helps as a double check. (Warning: measuring c-ttt is difficult to do as it's hard to eyeball the exact intersection, given that the ST is slanting away. It helps to have someone (a wife?!?) hold a credit card horizontally along the top of tt over the ST when you measure this. Thanks.

RE: the Colnago myth of shorter tts, sorry, but it's not a myth, at least not when you move up to larger sizes than you take (there you go being egocentric again :-)). I'll talk more about that after you post the stats.

One last point: your Bianchi has a sloping tt, doesn't it? Just forget it, then! :-)
Colnago apparently bucks the trend ...bianchi boy
Mar 12, 2001 7:07 PM
I've never seen such short top tubes as on Colnagos. I don't know how people ride them because, for me, to get the correct top tube length I would need a seat tube about 2-3 cm too long for my legs. I am long-waisted, though, but their proportions still seem off to me.