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sloping top tube question

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sloping top tube question

Old 11-01-06, 01:36 PM
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coleadam
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sloping top tube question

what is the advantage/disadvantage of a sloping top tube? I'm in the market for a new frame (spring time) something intermediate and i see a lot of newer bikes w/ sloping top tubes. It looks a little weird but i've never road a bike with a sloping top tube. any input would be helpful. thanks

if anyone has frame recomendations in the $300 range that would be cool.
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Old 11-01-06, 01:45 PM
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Originally Posted by coleadam
what is the advantage/disadvantage of a sloping top tube? I'm in the market for a new frame (spring time) something intermediate and i see a lot of newer bikes w/ sloping top tubes. It looks a little weird but i've never road a bike with a sloping top tube. any input would be helpful. thanks

if anyone has frame recomendations in the $300 range that would be cool.
The sloping tube compacts the frame, shortening your reach to the bars and positions you in a more upright/comfortable riding position.
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Old 11-01-06, 01:50 PM
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In most cases, sloping frames do nothing more than give you some additional standover room. They're nice in that they can make it easier to fit someone whose legs are a bit short for their overall body confirmation. They don't change riding position, they're not stiffer and they don't save (much) weight. Just another way of building a frame.
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Old 11-01-06, 01:51 PM
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The sloping top tube reduces weight, increases stiffness, reduces the quantity of sizes required thus reducing manufacturing and inventory costs resulting in greater corporate margins and a faster bike.

I am on record for dising them because they do not have room for the bottles and I prefer the look of a traditional frame.
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Old 11-01-06, 03:08 PM
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ok so we have some coflicting info here i'm not that concerned about the weight issue a few grams isn't going to change much. My friend has a sloping top tube 59cm but his saddle is like 8 or more inches out of the seat tube it looks weird. i don't know i guess i'll just have to ride them but both of my bikes now have a non-sloping tube and i think it looks better and i ride comfortable. i was just curious...
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Old 11-01-06, 03:17 PM
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Aside from the argumentative advantages -vs- disadvantages...when shopping for sloping roadie, pay attention to the "effective/virtual length" of the T-T. This is perhaps the most important aspect of the geometry IMO.
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Old 11-01-06, 03:20 PM
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Originally Posted by FormerBMX'er
Aside from the argumentative advantages -vs- disadvantages...when shopping for sloping roadie, pay attention to the "effective/virtual length" of the T-T. This is perhaps the most important aspect of the geometry IMO.
ok good to know. see this is the answer i was looking for something useful.
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Old 11-01-06, 03:48 PM
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Originally Posted by plainsdrifter
The sloping tube compacts the frame, shortening your reach to the bars and positions you in a more upright/comfortable riding position.
This is simply wrong. A shorter top tube shortens your reach to the bar, whether it slopes or not.

A "compact" frame with a sloping top tube can be made with varying length top tubes, and can be made to favor an upright or an agressive position by changing a number of other dimensions, (not the least of which would be the length of the head tube.)

For example Giant TCR's and Giant OCR's both use sloping top tubes. Yet one is designed for a more relaxed set up, and the other is raced by Jan Uhllrich.
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Old 11-01-06, 03:49 PM
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Head tube length on sloping bikes is critical, while it pretty much goes without saying that you're going to want a bike that has the same effective TT length as the bike you're riding.

Make sure that the HTL is such that you can get your bars up or down where you want them. The most compact bike I own has a very long HT and that is somewhat compensated for by the fact that it has an integrated headset. But where I might use 5-10mm of spacers on a traditional frame, I use none on this in order to get my bars 10cm below the saddle. You need to watch out for this.

Aside from the minor differences in design, yes - they do look different. But I'll be very surprised to hear that there is a significant difference in ride that cannot be attributed to something else, like tires, saddle, wheels, etc.
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Old 11-01-06, 03:49 PM
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Girls' bikes.
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Old 11-01-06, 03:51 PM
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Oh Al, time to move forward into the 1990s.
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Old 11-01-06, 03:52 PM
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one thing is for certain...they are becoming more and more common. i still like the tradional geometry myself, and always will.
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Old 11-01-06, 03:53 PM
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Compact frame stiffness is somewhat negated when you're riding on 3 feet of seatpost.
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Old 11-01-06, 03:57 PM
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Originally Posted by hiromian
...reduces the quantity of sizes required thus reducing manufacturing and inventory costs resulting in greater corporate margins...
This is the real reason many more bikes are being made with compact geometry. If there were any competitive advantage (speed, weight…) then all pro riders would be using this type of frame. In fact, pro teams have relationships with manufacturers that have compact and traditional geometry bikes.

With a mix of seat position, stem length and angle there is no real difference between a well fitted standard or compact geometry bike.
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Old 11-01-06, 03:59 PM
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just a different design
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Old 11-01-06, 04:03 PM
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Originally Posted by merlinextraligh
This is simply wrong. A shorter top tube shortens your reach to the bar, whether it slopes or not.

A "compact" frame with a sloping top tube can be made with varying length top tubes, and can be made to favor an upright or an agressive position by changing a number of other dimensions, (not the least of which would be the length of the head tube.)

For example Giant TCR's and Giant OCR's both use sloping top tubes. Yet one is designed for a more relaxed set up, and the other is raced by Jan Uhllrich.
Stand corrected. Just testing ya Merlin.
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Old 11-01-06, 04:13 PM
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Originally Posted by blue_nose
This is the real reason many more bikes are being made with compact geometry. If there were any competitive advantage (speed, weight…) then all pro riders would be using this type of frame. In fact, pro teams have relationships with manufacturers that have compact and traditional geometry bikes.

With a mix of seat position, stem length and angle there is no real difference between a well fitted standard or compact geometry bike.
As an illustration, you can take two different bike manufactures with similar bikes. I use these two bikes as illustration only, but are representative of the size differences for frames with standard and compact geometry.

The Trek 5000 has traditional geometry comes in 7 sizes:
50, 52, 54, 56, 58, 60, 62cm

In contrast, the Giant OCR2 has compact geometry and comes in 5 sizes:
XS, S, M, L, XL

In realty, you can fit the same broad population with the range of bikes sizes from both manufacturers. Thus, Giant can save some production and inventory costs by manufacturing 5 frame sinstead of 7.

I personally like the look of traditional geometry, but that is just a personal preference.
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Old 11-01-06, 04:23 PM
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The sloping top-tube is a byproduct of a design to satisfy specific criteria. However, different manufacturers are trying to address different criteria. One may use a sloping top-tube simply to increase standover. Another may use it because in their specific design, the sloping top-tube provides for a more rigid rear triangle. Another may use it because they believe it saves some weight. Another may use it because they think it will make the bike look better. There is no one definitive positive or negative that can be said about all bikes with sloping top-tubes. You have to take into account thye rest of the frame design/geometry.
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Old 11-01-06, 05:59 PM
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Originally Posted by The Fixer
Compact frame stiffness is somewhat negated when you're riding on 3 feet of seatpost.
True but that's not where it counts. The BB and HT need to be ridged in relationship with the rear wheel. The seat tube is not part of that picture.
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Old 11-01-06, 06:22 PM
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I agree with Ernesto Colnago who says its all about marketing. I suppose the frame might be stiffer as it is smaller but then you have way more seat post hanging out. I personally I prefer the look of standard geometry. Plus it seems like you have more sizing options with standard geometry frames.
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Old 11-01-06, 06:26 PM
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Old 11-01-06, 06:50 PM
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Originally Posted by hiromian
The sloping top tube reduces weight, increases stiffness, reduces the quantity of sizes required thus reducing manufacturing and inventory costs resulting in greater corporate margins and a faster bike.

I am on record for dising them because they do not have room for the bottles and I prefer the look of a traditional frame.
What kind of bottles do you use that won't fit? I use two big bottles on my Giant + a road morph pump on the seat tube and no problems.
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Old 11-01-06, 07:02 PM
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Originally Posted by OCRider2000
I agree with Ernesto Colnago who says its all about marketing. I suppose the frame might be stiffer as it is smaller but then you have way more seat post hanging out. I personally I prefer the look of standard geometry. Plus it seems like you have more sizing options with standard geometry frames.
I would say part of it is the short legs/long torso fit. and the rest of it is just marketing. The whole stiffness/weight reduction thing is splitting hairs at best.
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Old 11-01-06, 07:03 PM
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ok i think i got it, just based on looks i don't like the design maybe b/c i already have 2 standard desined frames. I'll just take a few sloping bikes out for a spin and see how they feel. thanks for all the input
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Old 11-01-06, 07:06 PM
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I've always been a traditionalist, and thought that compact frames just didn't look right. But its growing on me. To my taste, the TCR Advanced Team I have on order looks pretty slick. Perhaps its the integrated seat post that pulls the look together

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