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Definitive Bike Fit. Frames to small? TTs too long?(16 posts)

Definitive Bike Fit. Frames to small? TTs too long?Spunout
Mar 7, 2003 7:19 AM
[rant]

With the advent of the threadless stem and Lemond geometry in the bike world, there is suddenly a glut of long TT bikes with very low head tubes/stack heights (especially with integrated, low profile headsets).

The loss of threaded headsets and stems results in the handlebars of today's bikes are at least 1cm lower, more in many cases. Add to this, Trek/Lemond.. TT length, and people are fitting in to smaller frames to fit the top tube, which have lower head tube lengths.

Some frame makers are working hard to counter-act this: Pergoretti with the extended headtube (and Rivendell, Kellog, etc.). Colnago with the big-stack headset. Serotta's Ti headcup spacer (ultimate proof that everyone's bikes are made wrong). Riser Stems (shudder).

For example, I ride a 55cm Lemond. TT is 56.5 so I use a bit shorter stem and hike the seatpost waaay up. Looking at Colnagos(I rode a 56 in high school), I could ride a 57 (almost 58) with a similar TT and have no difference, except my handlebars will be 2cm higher. More comfortable, no spacers, and I can still stand over the top tube. Maybe compact geometry have a purpose(shudder), if only they made them shorter with more sizes?

C-40 is going to jump all over this, for sure. I just envision the top tube being lifted 1-2cm on today's bikes without affecting anything but the seat cluster and head tube height.

Everyone thinks Italian frames have TTs that are too short, but that is because most look to purchase the frame too small! Who on this board suggested that bikes should be fit by top-tube first? I am thinking that they may have been right, in today's era.

[/rant]

Peace rules,

Michael.
Top Tube AND Head Tube.MR_GRUMPY
Mar 7, 2003 7:36 AM
Since I started to look for a new frame in this era of threadless headsets, I discovered that the old idea of getting a frame as small as you can fit on, is out the window. For myself, I can't stand the look of two or three CM of spacers. Because of this, I had to find a frame with, not only the correct size TT, but also the correct size head tube. It took a lot of looking, but I finally found one, and bought it.
For me, things would be a lot easier if threadless headsets were never introduced on road bikes.
Top Tube AND Head Tube.Live Steam
Mar 7, 2003 7:55 AM
I personally don't like "the look" of spacers exceeding 2cm on a threadless headset either. However why didn't/don't we feel the same about that much and more being employed when a quill stem is used? Afterall the steerer tube extending up beyond the headset crown and covered by spacers is equivallent to the quill on a threaded stem that may be sticking up beyong the crown more than just a few CM.
Yes, head tube height is needed...Spunout
Mar 7, 2003 7:56 AM
Such as this CCKMP, even without an integrated headset.
my sentiments exactlytarwheel
Mar 7, 2003 8:03 AM
One of the major bike manufacturers is going to get smart (I hope) one of these days and start selling frames, like Pegorettis, with extended head tubes and shorter top tubes. I don't even bother looking at most of the mainline US frames anymore -- the geometry is all wrong for me. It seems like the only way to buy a new US-made bike these days without a long top tube and huge drop from the seat to saddle is to order a custom frame. I nearly ordered a custom last fall for that reason, until happening upon one of the last remaining Merckx frames with a threaded fork. Serotta seems to be building a good business over this issue, which is remarkable considering the price of their frames.
Opposite observationFez
Mar 7, 2003 8:38 AM
Someone posts a nice bike with 2-3cm of spacers under the stem and the "Spacer Police" has a lot of comments on that. Some detractors say its ugly, others say the integrity of the steer tube is compromised (usually only relevant with 1" all carbon steerers). If you have high spacer needs, just simply get an aluminum steerer - it will still weigh less than comparable threaded setup.

On the other hand, someone posts an equally nice bike with a quill stem raised up high (more than 2-3cm of exposed quill) and no one criticizes it as being ugly because there is no "Quill Police."

I actually think threadless systems give more flexibility as far as setup. Although the headset has a marginally lower stack height, there are more stem angles to choose from. And the common 80 degree threadless angle (vs 73 for quill) offsets the reduced stack height by approx 1 cm.
Your lemond situationFez
Mar 7, 2003 9:11 AM
I think I recall seeing your Lemond. Its very nice looking.

But in response to your rant, the Lemond top tube is not as long as it appears.

First of all, the Lemond frame sizes are center to center, so on that alone, you would have to upsize the comparison frame if that frame measures center to top.

Second of all, the Lemond geometry has slightly slacker seat tube angles, so the saddle position would have to be adjusted to maintain a comparable KOPS distance with a comparison frame. The Lemond top tube may not be as long after you adjust.

Maybe you should first check your saddle fore/aft position. Do you have a setback post? Is your current position correct for you on the Lemond? If it is too far back, get a straight post and then you could easily go to a larger frame and the top tube may not be too long.

Good luck.
Your lemond situationSpunout
Mar 7, 2003 9:18 AM
Well, I am KOPS and all that. C-T means nothing these days, the Lemond is 55x56.5 from the centres. Traditional geometry looks to be around 56 square, sometimes shorter TT (56x55.5) on some Italians.
ItaliansFez
Mar 7, 2003 9:33 AM
Maybe Lemond isn't the greatest frame geometry for you.

But remember to look at the seat angle of the Italian frames. When I was looking at Colnagos, I seemed to remember steeper seat angles to go with those "shorter" top tubes.
yes steeper.Frith
Mar 7, 2003 9:45 AM
Not sure how you would have a shorter top tube (given a particular seat tube height) without a steeper seat tube...I suppose head tube angle plays in there somehow but to a much lesser extent.
I fit by Top Tube first...biknben
Mar 7, 2003 9:13 AM
I ride a 56cm Top Tube. When I'm brousing frame specs that's the first thing I look at.

I'm all legs, no torsoe. Well not that bad, but my legs are longer than average for my height. Combine that with the current trend in frame geometry and I end up with this:

Seat post nearly at the limit and a high stem.

The stem police love my other bike with the threadless riser stem. It fits like a glove though.

Does anyone make a frame with 56 TT and a 59 ST?
Gios is close, also Merckxtarwheel
Mar 7, 2003 9:25 AM
I ride Gios for that reason. A 59 (c-t) Gios has a 56.5 top tube, a 58 has a 55.5 top. All Gios have steep seat tube angles (74), though, so they fit a little longer than they might appear looking at dimensions alone. Eddy Merckx frames have some of the shortest effective top tubes. Nominally they run longer than the Gios, have Merckx have much slacker seat tube angles (72.5) so that effectively shortens the fits across the top. If I recall correctly, I believe a 59 (c-c) Merckx has a top tube about 57.5, which is pretty short considering the 72.5 seat angle.
correction, re: Merckxtarwheel
Mar 7, 2003 9:36 AM
A 59 (c-c) Merckx has a 57.8 top tube and 72 seat tube angle. So it would effectively fit even shorter than the Gios if you maintain the same knee over pedal position. A 58 Merckx has a 57.3 top and seat tube angle slightly higher than 72. You can subtract about 1 cm in top tube length for each degree slacker the seat tube angle. So, compared to the Gios, a 59 Merckx would fit like it had a 55.8 top tube, and a 58 Merckx would fit about like a 55.3 top. When you consider that the Merckx are sized center-center, and Gios center-top, the Merckx clearly has the shorter effective top tube for a given size.
I fit by Top Tube first...russw19
Mar 7, 2003 9:38 AM
I always look at top tube fit first. I have been fitting people that way in the shop I work at for a while now too. With mountain bike seatposts, you can make sure someone has proper standover and still has enough post in the frame. But the top tube is another story.
My solution to the threadless steerer and not wanting to put a ton of spacers in is simply to look at a few companies that offer stems closer to 90 degrees. Which when you put it in your frame would rise by 15 or so degrees. You don't have to do that far, but with my Pinarello, the top tube is fine, but the steerer was already cut when I got it, so I was limited with only having the ability to put one 1cm spacer in. It wouldn't have gotten me high enough. So I bought a Deda Newton 86 degree stem. It put it so that the nose of the saddle to top of the bar difference on my bike was just over 2 inches and right where I wanted it. And the rise of the stem is subtle enough that it doesn't look stupid, unlike if you flip a stem that has a negative 16 rise. Which after you put it on your frame upside down gives a silly looking plus 25 degree or so rise depending on your head angle. If I were to flip my stem it would have a plus 17 rise. It is a plus 13 the other way once you factor in the head angle. But more importantly, it puts my bar in the proper location in respects to my saddle on my bike, so that I am comfortable. I will take a picture of it this weekend and post it for anyone who wants to see what I am talking about.

Russ
mostly correct....C-40
Mar 7, 2003 9:49 AM
Comparing Lemond's current geometry to Colnago's in identical sizes (55cm Lemond and 57cm Colnago), the seat tube angles are both the same, so TT lengths can be compared directly. The Lemond TT, at 56.5cm is .9cm longer that Colnago's 55.6. Just means you use a 1cm shorter stem on the Lemond.

The head tubes on Lemond frames are unusually short. I don't know why they would do this in todays world of threadless stems. The head tube is only 133mm, compared to Colnagos' 151mm. One of the forst things that I look at when considering a new frame is the head tube length. If I liked the frame really well, but the head tube was too short, I wouldn't be opposed to using an 84 degree stem flipped to 96 degrees to get another 2cm of rise. It's still a better way to go than using 2cm of spacers.

It's important to know what dimensions you need for a good fit. I know exatcly what I need and if a brand won't fit without doing something too ugly, I won't even consider it. It's not just the TT length that you must consider. If you place your saddle a long way back due to long femurs or just personal preference, then it's likely that most brands will have top tube that are too long, unless the STA is 72.5 degrees or less. If that's the case, the geometry of most LOOK frames would fit you better.

With my 54cm Colnago I have the saddle at a modest 17cm above the top tube with a 100 or 110mm stem and an 84 degree Ritchey WCS stem with no spacers. This results in a 9cm drop from the saddle to the top of the bars and a very comfortable fit.
..whew!...Spunout
Mar 7, 2003 10:12 AM
So, most people have the issue of bars too low. Nobody has a problem with bars too high, we don't buy frames that large.

I agree with the head-tube height, the Lemond is short. In a Colnago, I could even ride a 58(c-t) which measures 56x56.3. For a Look, even their 55(c-c) has a 151mm head tube, also 18mm higher than the Lemond.

Enough for now, I've still got to make do with what I have. I'll double check KOPS, my knees don't hit my elbows when I'm in the drops, and I'll keep on my core exercises. I am able to do 40 minute tempo intervals in the drops, so I'm not that bad!

Thanks,

M.