# Traditional vs Sloping geometry, in concrete



## Salsa_Lover (Jul 6, 2008)

I have been searching for this subject in the forum, 

found many threads discussing different aspects like


standover/reach
simpler manufacturing processes
esthetical considerations
what is subjectively perceived to be "right"

However what I haven't found is in concrete what is the difference for the rider.

If you hypotetically would have to chose between a bike with traditional geometry and another equivalent bike with slopping geometry, both the same model ( say a Colnago C-50 traditional vs a C-50 sloping ) both fitted exactly the same, same reach, same crank-to-saddle, same saddle-to-handlebars, same seatback etc etc 

What do you win or lose when you chose one over the other ?


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## Hank Stamper (Sep 9, 2009)

Basically, nothing.

Unless you have a weird body so have standover considerations or need a saddle lower than traditional Geo will allow the only difference is visual in my opinion.

Maybe a very slight weight reduction from the sloping. But you'd have more seat post so that's probably just about cancelled out.

I have one of each. One bike is better than the other but that has nothing to do with sloping vs traditional that I can detect.


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## brblue (Jan 28, 2003)

+1

By using the sloping geometry, they just introduced new numbering charts, making room for even more size numbering, and measuring methods, generating just more chaos.

Weight:
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+ What you win is an effective top tube that is shorter thus lighter, since it's alomst perpendicular to head and seat tube

- What you lose is a short light seatpost in favor of a longer one (which is probably a few grams heavier)

Fit:
---
+ You have a lower top tube so normally small people can still stand / both feet on the ground without risking any injury 

- Because of that, people who use a large saddle to bar drop, thus needing a long seatpost with classic geometry frames, will need an even longer one with a sloping geometry.

+ The lower top tube allows some people to pedal "knees in" without hitting their top tube with the knees.. might be helpful for someone


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## majura (Apr 21, 2007)

What they said. There's recently been a move by manufactures away from compact frames, including the company that brought it to mass market - Giant.

What you find on most production bikes now is basically a form of semi-compact.


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## T K (Feb 11, 2009)

Sloping top tube supposidly creates a smaller rear triangle resulting in a stiffer bike, and a longer seat post resulting in a more comfortable bike. That's what they say.
I definatly believe the seat post part.


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## Salsa_Lover (Jul 6, 2008)

more comfortable even if the fit is exactly the same? 

why is that ? leverage of the seatpost that gives you some "play" on the saddle ?


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## PJ352 (Dec 5, 2007)

In the example you cite, there's little to gain or lose choosing compact or traditional geo, but for someone proportioned short legs/ long torso, compact geo offers the option of going to a slightly larger frame, and with it they gain the advantages of shorter standover/ longer reach that their proportions require. 

Think of them as the opposite of WSD bikes (sorta).


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## PJ352 (Dec 5, 2007)

Salsa_Lover said:


> more comfortable even if the fit is exactly the same?
> 
> why is that ? leverage of the seatpost that gives you some "play" on the saddle ?


If you're traversing smooth roads, comfort would likely be the same, but over some rougher sections, by design a bike with sloping TT and CF post (w/ more exposed as was mentioned) does have the inherent ability to flex more than say, a seat tube.  

I'm not saying I buy into this without question, but IME the setup described does offer a level of 'buffering' to the rider. As always, YMMV.


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## FatTireFred (Jan 31, 2005)

I seem to recall cyclingnews/Huang doing that test a few yrs back


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## icsloppl (Aug 25, 2009)

What do you win or lose when you chose one over the other ?


IMO advantages of compact/sloping - 

Torsional stiffness - the main and rear triangles are smaller.
The overall center of gravity is lower.
The frame can be lighter for the same level of stiffness as less material is used.
The lowered position of the top tube in relation to the rider's legs can be an advantage while climbing and sprinting.


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## SystemShock (Jun 14, 2008)

We can get all 'science-y' about it, but we're generally talking about small differences, except for a few oddball fit scenarios.

I mean, 'lower center of gravity'? Really? How much does the top tube weigh in relation to the entire bike? Much less, the rider? 

And of course the 'lighter' part gets largely cancelled out by the need for a longer seatpost. No free lunch an' all that. 

It really comes down to aesthetics for the majority of ppl, I strongly suspect... some love the way a traditional level top-tube frame _looks_, and some prefer the compact frame look.

But this isn't unusual... I bet even seasoned riders buy on the basis of, say, frame color, more than they'll admit to. :wink5:
.


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## danl1 (Jul 23, 2005)

icsloppl said:


> What do you win or lose when you chose one over the other ?
> IMO advantages of compact/sloping -
> Torsional stiffness - the main and rear triangles are smaller.


Not exactly true. It is correct to say that the frame object itself is stiffer, but that hardly matters. The contact points are still in the same relative position, and moving triangulated support away from them makes the bike (as a whole) less stiff.



> The overall center of gravity is lower.


Possibly, but also possibly not. To get the same stiffness as a larger triangle, the longer seatpost cantilever will need to be stiffer, and because of the smaller diameter relative to the frame tubes, disproportionately heavier. Probably a wash to net negative in reality, but by such a small amount as not to matter either way.



> The frame can be lighter for the same level of stiffness as less material is used.


Frame? yes. Entire bike? no. See first point.



> The lowered position of the top tube in relation to the rider's legs can be an advantage while climbing and sprinting.


Actually, not. If the intent here is that it lets the bike sway more from side to side, that's a really bad idea. Having a level top tube to teach decent form would get much more of the available power to the road, rather than wasting it flailing the bike about. 


But it's all angels on the head of a pin. The only advantage is that it appeals aesthetically to former mtb'ers and bmx'ers, where most of the initial road riding market comes from.

That is, other than the 'true' advantage: It allows more people to have both proper fit and psychologically comfortable standover. Previously, a lot of bikes had goofy front-end setups with lots of spacers and high/long stems, a result of getting a too-small frame (to accommodate standover,) or goofy bar-saddle drops that meant the bar drops couldn't be properly used. (see also: compact bars.)

Before that, folks rode the proper-size bike, without regard to whether or not there was suitable standover: It was understood not to matter for anyone but tandem captains and fully-loaded touring bikes.


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## Hank Stamper (Sep 9, 2009)

icsloppl said:


> What do you win or lose when you chose one over the other ?
> 
> 
> IMO advantages of compact/sloping -
> ...


okay, if we ran that though the MIT lab you'd probably be right but realistically:

-Traditional geo can't provide all the stiffness we need?
-Not unless the bottom bracket/pedals are lower. A couple grams a few CMs lower on the frame is meaninless compared to body weight....which is on the saddle and bars at the same height with either geo.
-okay, a little lighter......maybe.
-Who's ever bumped a knee on the top tube? I suppose it might help someone but it's a stretch.


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## danl1 (Jul 23, 2005)

SystemShock said:


> But this isn't unusual... I bet even seasoned riders buy on the basis of, say, frame color, more than they'll admit to. :wink5:.


I freely admit that titanium grey is the only acceptable color for my bike.


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## Sablotny (Aug 15, 2002)

I like to think of how it'd be if sloping geometry frames were around first. All the retrogrouches would be up in arms because something new and different came along. 

"Just because the horizon is level doesn't mean our top tubes have to be!" 

"There's no reason to make three tubes longer just to get a shorter seatpost! Its a scam by the seatpost manufacturers trying to make fewer lengths available!"

"There's no reason to make a frame a few grams heavier just for the sake of being different!"


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## laffeaux (Dec 12, 2001)

Salsa_Lover said:


> However what I haven't found is in concrete what is the difference for the rider.


That's because there is no difference to the rider. Unless you need the extra stand over of a compact frame, pick the frame that you think looks best (assuming identical fits)

I personally think that a very minor slope (1-3 degrees) looks best.


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## ukbloke (Sep 1, 2007)

Compact frames are largely a marketing gimmick, backed up by a smattering of pseudo-science, designed to sell more bikes. The bike industry continually comes up with these innovations to obsolete last year's bikes so that they can sell this year's bikes. They do it with components, colors, materials, controls, wheels, anything they can think of, to get a unique selling point for the coming year's bike range. And then most other manufacturers follow suit to level the playing field. And when they run out of new ideas they just reuse the old ideas and flip back to traditional designs.

Welcome to the bike industry!


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## laffeaux (Dec 12, 2001)

ukbloke said:


> Compact frames are largely a marketing gimmick, backed up by a smattering of pseudo-science, designed to sell more bikes. The bike industry continually comes up with these innovations to obsolete last year's bikes so that they can sell this year's bikes. They do it with components, colors, materials, controls, wheels, anything they can think of, to get a unique selling point for the coming year's bike range. And then most other manufacturers follow suit to level the playing field. And when they run out of new ideas they just reuse the old ideas and flip back to traditional designs.
> 
> Welcome to the bike industry!


Welcome to the consumer economy. Companies need to sell things, even if people don't need to buy things. It's what the US economy depends on. Ain't it wonderful?


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## sbindra (Oct 18, 2004)

ukbloke said:


> Compact frames are largely a marketing gimmick, backed up by a smattering of pseudo-science, designed to sell more bikes. The bike industry continually comes up with these innovations to obsolete last year's bikes so that they can sell this year's bikes. They do it with components, colors, materials, controls, wheels, anything they can think of, to get a unique selling point for the coming year's bike range. And then most other manufacturers follow suit to level the playing field. And when they run out of new ideas they just reuse the old ideas and flip back to traditional designs.
> 
> Welcome to the bike industry!


I don't think there's anything gimmick about it. Sloping geometry is a manufacturing efficiency. Giant manufacturers 6 sizes. Those 6 sizes fit the same range of riders as 9 or 10 sizes of traditional geometry. Larger production run, cheaper; fewer sizes for the retailer to stock while still having inventory on hand to fit anyone coming through the door, cheaper; less overstock sold at discounts of odd sizes, cheaper.


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## the_gormandizer (May 12, 2006)

Here's something no-one else brought up. For the right size frame, how much seatpost is showing? If not at least 4 inches, then a sloping top tube is advantageous. Why 4 inches? Because that's how much is needed for a Park Tools bike stand. It's so liberating to not have to extend your seatpost just to put the bike in the repair stand!


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## ukbloke (Sep 1, 2007)

sbindra said:


> I don't think there's anything gimmick about it. Sloping geometry is a manufacturing efficiency. Giant manufacturers 6 sizes. Those 6 sizes fit the same range of riders as 9 or 10 sizes of traditional geometry. Larger production run, cheaper; fewer sizes for the retailer to stock while still having inventory on hand to fit anyone coming through the door, cheaper; less overstock sold at discounts of odd sizes, cheaper.


What's the value to the customer in manufacturing efficiency? I don't see much cost saving being passed along. Marketing certainly doesn't promote manufacturing efficiency and cost saving to the end customer as the rationale for compact frames.

Maybe "gimmick" isn't quite the perfect world.


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## slamy (Mar 15, 2004)

sbindra said:


> I don't think there's anything gimmick about it. Sloping geometry is a manufacturing efficiency. Giant manufacturers 6 sizes. Those 6 sizes fit the same range of riders as 9 or 10 sizes of traditional geometry. Larger production run, cheaper; fewer sizes for the retailer to stock while still having inventory on hand to fit anyone coming through the door, cheaper; less overstock sold at discounts of odd sizes, cheaper.



Funny, sounds cheaper: but the frames certainly have not gotten cheaper to buy. I agree, it helps the manufacturers and the shops by only having to carry about 4-5 different sizes. I'm not sure that it makes the new production(sloping) of the product better. But I'm a traditional guy and refuse to ride sloping.


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## MerlinAma (Oct 11, 2005)

icsloppl said:


> ..............The lowered position of the top tube in relation to the rider's legs can be an advantage while climbing and sprinting.


I've found it to be a big help in descending on roads with switchbacks/corners. I get a much better feeling of keeping the bike under me. With a traditional frame, I feel like my body has to lean more and it is harder to keep my weight on the outside pedal.


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## SystemShock (Jun 14, 2008)

Sablotny said:


> I like to think of how it'd be if sloping geometry frames were around first.


Wasn't it first, though, kinda sorta?

The Rover Safety:


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## SystemShock (Jun 14, 2008)

danl1 said:


> I freely admit that titanium grey is the only acceptable color for my bike.


Show-off. :wink5:
.


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## Richard (Feb 17, 2006)

I have one "slightly" sloping top tube bike (my concession to a modern "race bike") and 4 lugged steels with level top tubes. I'll be dam*ed if I can tell the difference.

On the other hand, being the fitter in our shop, I've seen the advantage of sloping (not compact) top tubes for men with short legs and long torsos/arms. Getting 'em on a bike with the proper "effective" top tube length is just plain easier.


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## jamesau (Apr 22, 2002)

Tom Kellogg of Spectrum / Merlin offers his view on compact vs. traditional here:
http://www.spectrum-cycles.com/616.htm


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## Salsa_Lover (Jul 6, 2008)

Interesting article.

So in a nutshell the sloping geometry compared to the traditional all else equal feels the same as traditional while seated with just a little weight difference ( 4 ounces lighter ).

But the big difference is when climbing or sprinting off the saddle, where the sloping geometry ( due to the different center of gravity ) makes it feel much more agile, light and responsive.

So it suits better climber and sprinters you'd say ?


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## tuccillo (Feb 22, 2010)

Basicly the same as the golf, skiing, sailing, etc. industry



ukbloke said:


> Compact frames are largely a marketing gimmick, backed up by a smattering of pseudo-science, designed to sell more bikes. The bike industry continually comes up with these innovations to obsolete last year's bikes so that they can sell this year's bikes. They do it with components, colors, materials, controls, wheels, anything they can think of, to get a unique selling point for the coming year's bike range. And then most other manufacturers follow suit to level the playing field. And when they run out of new ideas they just reuse the old ideas and flip back to traditional designs.
> 
> Welcome to the bike industry!


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## C-40 (Feb 4, 2004)

*thoughts...*

I've owned conventional and sloping frames at the same time and alternated riding them on long mountain climbs, but I never noticed the difference that Kellogg claims to have.

I have found that all of my sloping frames seemed to ride little smoother, but with carbon construction, you don't really know how much of that is due to the sloping geometry and how much is due to other differences in the carbon layup. I've owned two Colnago C-40 frames and a LOOK KG381 that were all conventional carbon. I now own a sloping KG461 and two sloping 585s. I prefer the sloping TT frames.

I think that the short answer is that there is no disadvantage to the sloping TT frames.


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## laffeaux (Dec 12, 2001)

I'm not buying the 4oz lighter frame made the bike feel 3 lbs. lighter argument (as Kellogg stated). A traditional frame will use a 250mm seat post. A frame with a 17 degree slope (as Kellogg used) will need at least a 350mm post, and maybe longer. According to Thomson's web site, for a 27.2mm "Elite" post:
- 250mm = 201g
- 330mm = 241g
- 410mm = 289g

The seat post adds back at a minimum 40g and maybe as much as 88g (about 3 ounces). So the claim is that by lowering the frame weight 1-3 oz, and dropping the center of gravity slightly, these huge effects are felt? If that's true, any rider that does a climb with a filled-water bottle and then does the same climb with a half-filled water bottle will feel an exponential effect, since the water bottle has the same, but much greater, effect as the change in the frame configuration.


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## TTCC (Feb 27, 2010)

I think the benefits come on the very small and large frame sizes. On very small frames it allows the headtube to be a bit taller to make a cleaner junction of the TT, HT and DT with the common oversized tubing that is used without affecting stand over.

On the very large frames it could be useful to keep the triangle as small as possible to retain rigidity. On the mid-range sizes, it is more than likely for the look.


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## sokudo (Dec 22, 2007)

MerlinAma said:


> it is harder to keep my weight on the outside pedal.


Why do you need to keep your weight on the outside pedal?
Jobst Brand has a paper discussing descending techniques and weight distribution. The only reason to keep your inner foot up is to avoid hitting the pavement with it in a tight turn. Forces at a patch where the tire contacts the road are the same, IIRC.


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## sonic_W (Sep 2, 2008)

if you have a steel, ti, or aluminum frame, and a carbon seatpost, the compact frame will have more seatpost sticking out, providing more carbon dampening. any carbon post will do, but a compact frame would just have more carbon exposed.


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## danl1 (Jul 23, 2005)

sokudo said:


> Why do you need to keep your weight on the outside pedal?
> Jobst Brand has a paper discussing descending techniques and weight distribution. The only reason to keep your inner foot up is to avoid hitting the pavement with it in a tight turn. Forces at a patch where the tire contacts the road are the same, IIRC.


True enough, as far as it goes. Unfortunately, Jobst spends too much time in _Gedankenexperiment_ and too little out on the road.

Weighting the outside pedal doesn't change the center of gravity, but it does change the way it is connected to the bike: the "hinge" in the system moves from the saddle down to the pedal, and the motion damper from the pedal to the saddle. This lets the bike be more responsive, making it easier to carve the lines. 

Where pavement is broken, the lower pivot point allows the bike to regain contact faster.


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## MerlinAma (Oct 11, 2005)

sokudo said:


> .....Jobst Brand has a paper...


Jobst has no credibility with me. Sorry.
Weighting the outside pedal may make no difference in tire contact patch but that isn't the purpose in the first place.


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## sokudo (Dec 22, 2007)

MerlinAma said:


> Jobst has no credibility with me. Sorry.
> Weighting the outside pedal may make no difference in tire contact patch but that isn't the purpose in the first place.


Re Jobst - fair enough. But what is the purpose?


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## sokudo (Dec 22, 2007)

danl1 said:


> True enough, as far as it goes. Unfortunately, Jobst spends too much time in _Gedankenexperiment_ and too little out on the road.
> 
> Weighting the outside pedal doesn't change the center of gravity, but it does change the way it is connected to the bike: the "hinge" in the system moves from the saddle down to the pedal, and the motion damper from the pedal to the saddle. This lets the bike be more responsive, making it easier to carve the lines.
> 
> Where pavement is broken, the lower pivot point allows the bike to regain contact faster.


Jobst recommends descending with feet parallel to the ground (in 3-9 position), and the weight on feet, not on the saddle. So the riders weight is hanging on a bottom bracket, same way as with the foot down. But the system is stable, a rider does not have to move feet back and forth going through serial turns, and, to increase a stability of the system, may keep both knees pressed to the top tube.


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## MerlinAma (Oct 11, 2005)

sokudo said:


> Re Jobst - fair enough. But what is the purpose?


danl1 explained it as well as I can. By weighting the outside pedal, you are putting your body in a better position to steer and make adjustments.
I've always thought that was the way Davis Phinney taught descending, but that's from reading, not actually going to his school.
I know I feel much more secure doing it that way.


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## C-40 (Feb 4, 2004)

*thoughts...*

I've doing 10-mile mountain descents 3-5 times a week for the last 7 seasons. I find absolutely no need to weight my outer foot while cornering. Some of my descents have a series of S turns that really don't allow weighting the foot for any significant time.

What can be proven is that if you weight the pedal the weight on the front wheel increases. That might be an improvment for some riders, but it depends on your bike's weight balance to start with. I like to see 42-45% of the weight on the front wheel with the riding in an aggressive corner position. Mine is about 45%, so I don't need more weight on the front wheel from weighting the pedal.


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## DrD (Feb 5, 2000)

slamy said:


> Funny, sounds cheaper: but the frames certainly have not gotten cheaper to buy.


Might not be cheaper to buy in a "retail price reduction" point of view, more that it allows the manufacturers to reclaim some profit and slows future price increases...


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## sokudo (Dec 22, 2007)

Here is Descending by Jobst Brand I'm talking about.
http://www.sheldonbrown.com/brandt/descending.html


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## C-40 (Feb 4, 2004)

*thoughts...*

Seems like a well written article, like most of Brandt's writings. He's a little short on the importance of countersteering, or more specifically the need to apply a constant countersteering pressure to maintain a turn. Bikes require so little pressure compared to a motorcycle that many people don't even realize that they are doing it, but if they didn't the bike would never turn.

Where some arguments start is about the direction the tire is pointed. It doesn't matter. All you need to know is that the bike will quit leaning and go straight if countersteering pressure is not applied. All motorcycle riders know this, it's the first thing you learn. Push on the right side of the bars to initiate a right turn. If you're not leaning and turning sharply enough, push harder. Quit pushing and the motorcycle will straighten up.

Some cyclists will argue that once a bike is leaned over it will keep turning all by itself, which is wrong. It's most evident to cyclist in a hairpin turn. If you've got a bike like a Colnago with a lot of steering trail, you have to keep applying pressure on the bars or it will straighten up in a hurry. It's the same for any bike, but more obvious with a lot of trail.


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## MerlinAma (Oct 11, 2005)

sokudo said:


> Here is Descending by Jobst Brand I'm talking about.
> http://www.sheldonbrown.com/brandt/descending.html


From the article:
"Outside Pedal Down
It is often said that putting the outside pedal down in a curve improves cornering. Although most experienced riders do this,............."

So he confirms that's what experienced riders do. Really his explanation as to why they do it is a moot point, although I'll agree it doesn't have to do with traction.


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## sokudo (Dec 22, 2007)

MerlinAma said:


> From the article:
> "Outside Pedal Down
> It is often said that putting the outside pedal down in a curve improves cornering. Although most experienced riders do this,............."
> 
> So he confirms that's what experienced riders do. Really his explanation as to why they do it is a moot point, although I'll agree it doesn't have to do with traction.


They had not learned better. Tradition is often not the best guide. It is a defense, of sorts, though.


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## a_avery007 (Jul 1, 2008)

simply clearance for me...
i ride a traditional 54cm frame but need the standover or my thighs will hit the top tube seat tube intersection...

and for cross it is just easier to dismount in a hurry..


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