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Sloping top tubes - What's the deal??(15 posts)

Sloping top tubes - What's the deal??DWridesGT
Jun 4, 2002 10:02 PM
I have noticed the big trend in sloping top tubes, (Specialized, Giant, Schwinn, etc..) and the claim that it makes the frame weigh less and feel stiffer. Does the two inches of top tube really weight all that much on a standard straight frame?? Where does all this supposed weight savings come from? How about the need for an 18 inch seat post, that's gotta add some weight to it. Anyways, how do these sloping tubed bikes ride? Can you REALLY feel a difference, does the sloping tube bother anyone? I've heard some people just can't get used to the idea of it. What do you guys think.....

DW
re: Sloping top tubes - What's the deal??weiwentg
Jun 5, 2002 4:55 AM
the rear and main triangles are smaller with compact frames, which makes them stiffer. since they're smaller, they're lighter. yes, this probably does translate to a lighter bike + seatpost: would you rather have shorter main tubes, or a shorter seatpost? probably the latter.
the other big thing is that a manufacturer can now produce bikes in 3 or 4 sizes, as there is more standover clearance and a wider range of people can fit on each size. the savings does get passed on to the consumer: look at Giant. don't look at Litespeed's Ghisallo. :p
the sloping top tube doesn't bother me. however, all the bikes I've had are compacts; this is because I'm short, and have relatively short legs. I simply cannot fit on almost any regular frame.
re: Sloping top tubes - What's the deal??brider
Jun 5, 2002 5:35 AM
It makes a big difference in FRAME weight. However, you do get a slightly lighter package -- while the seat post is longer, that's traded off with shorter seat tube and seatstays. The smaller triangles make for a stiffer frame (I have a softride, which does the same thing in the rear triangle). You get some relief from the stiffer frame in that the longer seat post can flex more, making for a little less road vibration transmitting through to your tush.
re: Sloping top tubes - What's the deal??sticky
Jun 5, 2002 6:06 AM
You get a stiffer lighter frame for sure. As other posters have said rear triangle and main triangle are stiffer. However, overall bike weight is actually slightly more because you need a longer seatpost, and the thickness of the seatpost is way more than the thickness of the seat tube. see interesting link.

ps. i'm not selling cannondales nor am I saying a compact geom. bike is bad - I think they look pretty good and may get one myself. A stiffer more responsive frame for racing is better imho.
Many people say net effect is weight gain...elviento
Jun 5, 2002 6:46 AM
I don't think that's true. Here is why:

1. seattube is shorter, seatpost MAY be longer. But seatstays and toptube are also shorter on a compact frame.

2. Not everyone needs a longer seatpost. My Dura Ace post works well on a compact frame (31 inseam).

3. Even if you need a longer post, XTR post is only 15 grams heavier than Dura Ace. Those so called comparisons of the two designs typically do two things to mislead you into thinking the extra weight of a longer post outweighs the weight savings of the frame: a), compare a 20cm road post with a 35/40cm MTB post, while compact frame usually only need 5-8cm more post; b), use examples with different clamp designs so that the so called extra weight may come from a heavier clamp rather than the shaft.

The overall weight savings of a compact frame probably isn't much, but if a frame is a bit stiffer and allows for more clearance with no performance or weight penalty, I can't see why it shouldn't be the trend, aesthetic objection aside.

Some blame this design for the lacks of sizes by Giant, but I think it's just that Giant is lazy. Specialized offers over 10 sizes in the compact design. So does many Euro manufacturers.
Many people say net effect is weight gain...weiwentg
Jun 5, 2002 9:40 AM
> but I think it's just that Giant is lazy.

I wouldn't be so sure. the MSRP on the E5 team frameset (the one available in red/white or zebra stripes) is $1600 or so. I can get a TCR or OCR Elite frameset from the LBS for around $900 (caveat, not sure if that's MSRP or not). and the frames are probably around the same quality (never had the luck to ride an E5, though).
Well, what percentage of the price differenceelviento
Jun 5, 2002 11:38 AM
... should be attributed to Giant's lack of sizes? I suspect not much. Making fewer sizes probably does save some money but I don't think as much as $700. A taiwan made bike is almost certainly much cheaper than a US made one regardless of sizes offered.

Besides, my ultimate question is, what's the benefit of Giant TCR if they don't have my size?
This is from the Serotta websits.Len J
Jun 5, 2002 6:22 AM
• Compact Geometry

Is this the latest fashion statement from the Euro crowd a trend that has practical advantages?

The answer is, both. Contrary to marketing hype, Compact Design doesn't save a lot of weight or make the drive-train extra stiff. However, it does allow for a higher handlebar position while maintaining adequate stand-over height. You will need a longer seat post, so make sure you choose one that will support your weight when fully extended. We believe Compact Design will have a place in the future. All 2002 models are available in standard or compact geometry.

len
re: Sloping top tubes - What's the deal??SnowBlind
Jun 5, 2002 7:31 AM
For the most part, it is so sizing is 3 to 5 sizes for everybody. Bike stores end up with less stock, manufactures are make fewer types of frames. You know, the economy of scale BS.
For the (male) rider it means more room for the boys, but that is about it.
re: Sloping top tubes - What's the deal??legs
Jun 5, 2002 7:33 AM
I don't notice a difference between my compact frame and my standard frame when i am riding in the saddle.. but i do notice a difference out of the saddle.. it feels to me as if my compact frame accelerates much more intensely when i am out of the saddle (especially whilst climbing)... its an amazing sensation... and i dont know how to explain it...
re: Sloping top tubes - What's the deal??MP
Jun 5, 2002 8:39 AM
I agree with legs. My Litespeed Siena weighs about the same as a Tuscany, but it accelerates faster and climbs easier. Also, compacts will have a slightly lower center of gravity which probably explains the nice cornering they do.
hmmm ....laffeaux
Jun 5, 2002 10:44 AM
Do you really thing that lowering a a few grams an inch or so makes a bike handle that much differently? WIth that reasoning, the amount of water in your water bottle also drastically changes the handling characteristics.

I ride a compact frame (Bontrager), but my guess is that the compact design offers minimal changes over a non-compact design. Other than lowered inventory costs due to the often resuced number of frame sizes required to fit riders, which can pass a price reduction to consumers, there's not enough difference to matter.
hmmm ....legs
Jun 5, 2002 4:49 PM
its funny because intellectually i don't know how to justify my experience..
and i have been riding roadbikes for many years..
and even though there are many reasons for compact frames (from marketing and manufacturing to lower bb's)..my merlin xl compact is noticeably different in handling out of the saddle... and i attribute this difference to the compact frame...
so yes.. a few millimeters here and there can make a big difference...(i am not saying that one is better than the other..).. but i am supersensitive to what i am riding...
re: Sloping top tubes - What's the deal??Gary
Jun 5, 2002 1:03 PM
When I asked a trustworthy local bike shop manager about them, he said is simply a marketing driven push since it allows shops to carry fewer frame sizes. If I recall, mtb used to come in 1" incremental sizes but most have gone t to s-m-l-xl presumably for the very same reason.

Gary
re: Sloping top tubes - What's the deal??laffeaux
Jun 5, 2002 1:57 PM
The best reason for moving to s-m-l sizing is that consumers quit comparing sizes inaccurately. In the world of MTBing a 18" frame means little. An 18" frame with a radically sloping top tube will not fit the same person that an 18" non-sloping top tube bike would fit. Since there's no standard slope, the seat tube length measurement is obsolete as a reliable way of measuring frame size. A new method to measure bikes was needed. I personally would have picked top tube length, but s-m-l works okay. Understanding that two "large" bikes are different sizes, seems to be much easier to understand than two 18" bikes are different sizes.