memebag

Also heavier bikes are faster downhill. Do it backwards.

Maelochs

Why would longer chains stays affect wheel rotation? Not a smart-mouthed question, i just don't see any relationship. Longer chain stays will stretch the wheelbase and slow the handling, bit shouldn't affect acceleration or speed.

I second @memebag here---weight gives you extra momentum on the downhill, and you can carry an extra mph or two into the start of the flat.

Use your tech. Look at the speeds at various parts of the run on several runs on each bike, and see where the speed difference is gained.

I can't believe that hasn't occurred to you already.

athrowawaynic

Possible, of course. All of this was late season last year when I discovered how nice the retroroadie rides on semidecent tires.

I'm itching for the spring for more observation, but that's at least a couple months down the road.

I know the anecdote doesn't make a strong case. I guess it just feels like, having more weight pressed down on the rear wheel transmits more of the power my puny legs generate. (You can tell I'm mostly layman because of the lack of proper use of terminology.)

Maelochs

Shorter chain stays could actually put your weight more to the rear which would increase rear traction ... but since we aren't talking the kind of torque which can break loose the tires and spin them (by Any rider) this isn't really an issue.

Lots of different issues could be affecting performance .... pretty much the same rtiding position but the rest of the frame geometry is exactly the same? Doubt it. Same wheels? more bearing drag?

I have no idea, but ... UI think pretty much every difference would be marginal except two, aero and weight.

Aero makes a difference above 18 mph (I have heard) and increases geometrically, so it makes a lot more difference the faster you go. However, unless your riding position is drastically different between the two bikes, I wouldn't expect a really big difference.

Weight, now ... on the downhill weight is free speed, so a heavier bike will let you hit a higher top speed for the same effort. once you hit the flat, you have to work harder to maintain that speed (aero) but even as you slow, you are still riding faster than you ever get going on the lighter bike.--and weight means very little once it is moving, particularly on a short burst, so you will never go more slowly on the heavier bike, but you will go more quickly.

If the geometry and riding position id much different between the two bikes, you might also be getting as little more power from one or the other ... but the weight makes the most sense to me. Add a couple-few mph on the downhill section and hold it for the first few hundred yards of the flat and there you are.

athrowawaynic

I could test overall weight by adding some weight to the bike.

Yeah, not to the point of breaking traction (so, it's unlike a rear wing on an F1). Someone brought this up the last time I asked.

What about the effect of weight on the tire? I assume rubber doesn't stretch uniformly. More weight on the rear could mean a higher effective pressure (if that's a thing)?

Maelochs

Interesting ... science in action. You should video the whole thing and put it on the Internet---seriously.

I assumed that you were running Strava or RideWithGPS .... either of which would give you readouts of your measured speed at each part of the run. If you are running either app (both free, by the way) you wouldn't need to do much testing ... you could just compare different runs on different bikes and look at where the speed was higher.

But ... the idea of weighing the bikes and adding weight intrigues me.

caveat---beyond a certain mass i would imagine that your ability in the initial acceleration would be impeded---i had assumed you were talking a flying start, and that would be the best way ... hit the start of each segment at the same speed and then go as hard as possible.

Easiest way would be to weight the two bikes and then ballast the lighter one---wear a knapsack or a couple full water bottles or something.

it would make an interesting video .... trying different tests, determining howo much different factors impacted speed at which point in the run.

Kontact 

It could be the 4 pounds difference, but that's easy to test with some full waterbottles.

More likely some difference in your bars, shifters, reach, etc cause you to sit less aero on one bike.

The frame or wheels could somehow be less efficiently transmitting your pedaling energy, but this doesn't seem real likely either.


Or, the combination.

Voodoo76

The impact of chainstay length is rider weight distribution. Great example, a modern TT frame has very short stays and a long front center. To accommodate the rider sitting much further foreword w/o putting too much weight on the front wheel. My Slice has stays almost 10mm shorter than the CAAD10 I ride on the road. They are shorter than my Track bike. And it is by no means a quick handling frame.

athrowawaynic

Handling, sure. How does it compare for straight-line acceleration? (That's what I'm curious about. I assume overall speed is better because of aero.)

Voodoo76

Good question, I don't quantify acceleration rate directly. One comparison I have with a number, peak on my Track or Road bike is 150W or so greater than my TT bike. I think that is a fit issue not necessarily a geometry issue. The base bar on the TT bike is not in as advantageous a position for a full gas standing start or acceleration. No reason to mess with it, suits the purpose and is wandering a ways from the Endurance vs Race geometry topic.

wphamilton

Do you think that it's possible that the reason that the longer wheelbase bike gets to speed more slowly is due to a difference in handling? I am imagining a counter-steering happening less quickly and scrubbing off a tiny portion of speed against the pavement, maybe every pedal stroke.

99Klein 

I'm far more comfortable bent over and stretched out, than sitting up. 100 miles.... is that a 4 hour ride or a 7 hour ride? I'll take me "race" geometry for a 100+ miller anytime, but I have friends who prefer the more straight up position. It's more individual then people realize. I get a sore back in a hurry on my "endurance" bike I ride on gravel. What I wouldn't give to drop the handlebars 2 or 3 inches.

dddd

I take the term "Endurance" more literally than most, assuming that the rider will be "enduring" a longer ride, more time in the saddle.

The implication of longer ride time/distance/elevation is that the rider will not be pedaling as forcefully on average than while riding a shorter, more-sporting event.

One implication of a lower pedaling intensity is that there is less torque affecting the rider's fore/aft balance atop the bottom bracket, so less force holding the rider's weight upward against the pull of gravity. The resulting shift in balance puts more weight on the rider's hands, which can make the rider's hands, arms and shoulders very uncomfortable over longer ride distances.

The rider's neck muscles also suffer on longer rides from holding the weight of the head upward.

So Endurance geometry firstly alters the rider's position to address these potential discomforts, by facilitating a more-rearward saddle position with less forward/downward reach to the bars.

In summary, a combination of relaxing the seattube angle and/or shortening the toptube reduces the forward reach to the bars, while a taller headtube allows the bars to move upward. Both changes thus in concert with the rider's body rotating rearward about the bottom bracket toward a balance point that favors a lower pedaling intensity.

The same geometry features that make a good Endurance bike also make a good bike for less-seasoned riders, for older riders, and for off-season riding. Serious and fit racers have less need for an endurance bike up to a point of much greater distance/elevation for the same reason, that they can maintain a high level of pedaling intensity over a much longer ride.

Lower tire pressure and lower gearing also help the rider endure longer rides, as does a more-relaxed steering geometry, so these are also part of the "Endurance" theme with clearance provided for wider tires that can be run safely at lower pressure.

Oh, and make my endurance bike lightweight, no discs please!

Photos below may serve to illustrate Endurance vs. Race rider positioning (where's the rider?!), though here it is more in the fitting setup than in terms of actual frame geometry because these two bikes actually have similar frame angles. Note Endurance bike's softer saddle and much lower gearing.

Maelochs

They used to be called "touring bikes."

Exactly what you say---longer rides, the legs don't support as much weight, the butt does. The hands shouldn't---so ........

Kontact 

That's all okey-dokey, but you don't need special frame geometry to slide your seat back and raise your bars - especially since modern racers have tall head tubes.

dddd

Touring bikes without the long chainstays, and preferably lighter for today's popular and more-sporting Fondo-type events.
These endurance bikes thus do a pretty good job of substituting for a race bike actually, as long as they aren't burdened with excess weight as might be further imposed by disc brakes, battery shifting (or the 2kg wheelset on my Colnago).


I used a Trek 720 touring bike for most of my riding when I lived on the east coast and did most of my riding by myself at an easy pace.

dddd

I think that Orbea may have been almost ahead of their time and would agree with you.

The bikes I pictured really have just one geometrical difference, and that is the headtube length.
And I only had to move the race bike's saddle forward and fitted a longer stem to be better suited to higher-intensity riding.

The Orbea is a 2004 and the Colnago is a 2016, both bikes have relatively steep seattube angles for an endurance bike at 73.5 degrees, both have 72.5-degree headtube angles and both have 55.5cm toptube length.
And that is purely by coincidence, since both were just opportunistic used-bike buys from extremely motivated sellers.


Most race bikes do have at least a steeper headtube angle than endurance bikes it has to be said, and setting them up with a shorter stem will make the steering quicker yet, not the best on long rides over varied conditions.
And contrarily, putting a longer stem on an endurance bike may not jibe well with the relaxed headtube angle while riding off of the saddle.

dddd

I had the same problem with an admittedly sorta too-large Scott CR1 that I used for a while.

The lowest stem that I could readily find was called "variable angle" (by means of an eccentric shim), and by appearance atop this bike's 73-degree headtube looks like it achieves all of a -17 degree rise.

Kontact 

You aren't going to find "endurance bikes" with relaxed seat tube angles for a different position. No one is selling that fit philosophy in the endurance market. That's a rando thing.

dddd

Interesting that his heavier old steel bike is faster on a course that I assume involves an out-of-saddle effort.
The modern gravel bike may have an issue with flexing chainstays due to compromises toward large tire clearances. Lateral flex in back will hold back a sprint effort.
With the rider off of the saddle, suddenly there are large lateral forces at the bottom bracket due to the rider leaning the bike side to side under maximal effort. Longer chainstays here could be a big part of the problem, in that the chainstay length is the lever that converts lateral force at the bb into torque that gets resolved into lateral force at the front wheel's contact patch. Such force at the front wheel tries to push the steering back and forth which the rider must then control. With a wide enough handlebar controlling a short enough stem this may require no additional effort on the rider's part, but the added forces fed into the front tire will cause increased flex in the front end of the bike and would cause increased frictional losses in the front tire as well.

Jan Heine recently tested a "gravel" type bike with what he considered to likely be a flex issue in the chainstays that impeded the rider's acceleration efforts, and here the added loadings of athrowawaynic's gravel bike's longer chainstays being fed into the front half of the bike could only increase the degree that pedaling force is being softened by overall flex.

dddd

Yep, the Orbea has a 73.5-degree seattube angle and so does the Colnago.


Often a shorter toptube is used in lieu of any relaxing of the seattube angle, which has the exact same effect on reach and with the only overall difference perhaps being what style (zero or offset) of seatpost that the rider ends up selecting or that the bike comes with.


So the only obvious difference between the Orbea Orca and the Colnago CX-Zero would seem to be the headtube length.
But, since this Colnago in this particular "52s" frame size is generally considered to be the same fit as their standard (vs. compact) 56cm frame, it's 55.5cm TT is rather short for a 56cm frame. The Orbea (a Pro Tour racing bike) is a 55cm frame with same angles and same 55.5cm toptube length.

HTupolev

Depending on the era being referenced by "used to", that might be in line with what Maelochs was saying. Some of those 1970s sport tourers were pretty close to what endurance road bikes are today.

Like, I've got one of these. Chainstays aren't crazy short, but full-length fenders are a pretty tight fit. Granny gear of about 32 inches, very similar to what you get with the 34-28 on a lot of endurance road bikes now. It's a couple pounds heavier than the similar-tier racing bikes of its model year, but those were running tubulars and had comparatively extremely narrow gearing.

dddd

I rode a very similar Fuji S12-S-LTD back in the early 80's that had just the sort of sprightly-but-stable ride that I thought was awesome. Even the wheels and tires they spec'd on it were a contemporary and just-right 25mm (labeled as 28mm or 1-1/8" or some such) mounted to decently-wide rims. Geometry was 73x73. They really had the formula down, and of course those bikes take bigger tires easily and had plenty-low gearing.


I sold my Fuji just one day after buying (half-price sale day) a Trek 720 and a Cannondale R400 in 1986. Neither of those bikes would prove as well rounded as the Fuji, but each was specialized in it's purpose, I always had a second/spare bike from then on, and my days of comparing different geometries and gearing strategies had begun.

RoadLight

Hi mrblue,

Race vs Endurance Geometry
Like raria, I'm surprised by the variety of the response you're receiving. There are two geometries here (the position of the cyclist's body and the layout of the frame) and raria hit the nail on the head: it's all about aerodynamics. The single biggest resistance to a cyclist going fast is wind resistance as the cyclist pushes themself and their bike through the air. The only exception is when climbing a very steep hill or mountain when the total weight takes over as the source of greatest resistance.

When racing a bicycle on most road courses, the wind resistance will be so high that it will dwarf all others (like rolling resistance and drivetrain resistance). That's why a heavier aerodynamic bike is faster than a lighter non-aero bike.

A "race geometry" is the one where the cyclist assumes a body position with the least wind resistance that they can hold for the length of the race while still being able to deliver their maximum power to the pedals. In order to achieve this, they will often select a road bike frame that is a little smaller. For example, a cyclist that normally fits a 58 cm frame will often choose a 56 mm frame. They will position their body on the bike so their back is parallel to the road and their head does not stick up, resulting in the need for their handlebars to be lower and farther forward (farther away from the seat).

The race geometry will not produce the most comfortable position. The cyclist is sacrificing comfort for decreased drag so they can go faster with less effort. It takes years of experience to dial in the optimal position. And it often takes years of experience to adapt to a full "aero" position. Some well-funded pro teams do extensive wind resistance tests to "dial in" the geometry for each cyclist on their team. The goal is to get the cyclist into the most aerodynamic position possible, within the UCI rules, without reducing the cyclists power at the pedals and without making it too dangerous or uncomfortable to the cyclist. The biggest danger is not being able to tilt your head back adequately to see down the road. The biggest discomfort is the neck, shoulders and back.

When riding in a time trial, the cyclist can safely be pushed into a more aggressive aerodynamic position than for general road racing because they will be riding solo or with their team only and will not need the visibility required to safely travel in a peloton. Plus, UCI rules permit aerobars to be used during time trials which, by resting the upper body weight on the forearm pads, helps make an aero position more comfortable. In fact, with properly fit aerobars, the only source of discomfort is usually the neck. But this can vary greatly, depending on the individual cyclist.

Other factors also contribute to a bicycle's "race geometry" that are not influenced by aerodynamics or the cyclist's body position and they are secondary in nature. For example, most pro cyclists desire fast maneuverability in a race. To provide this, the "trail" of the fork is shortened. This gives the bike a "twitchy" feel where seemingly tiny movements of the handlebar result in large changes in direction.

And, as others have noted, the wheelbase, bottom bracket shell height, etc, also influence a frame's race geometry but these are, in my opinion, subjects that delve deeper than I can here.

An "endurance geometry" is a tradeoff of both the cyclist body position and frame layout in favor of comfort so that the cyclist can endure a longer time on the bike without the aid of aerobars. Keeping wind resistance to a minimum is still important, but the cyclist will be on the bike longer than most road races so the cyclist's body position must be relaxed a little with head and shoulders higher than the hips so as to reduce discomfort. The cyclist may be pushing well into exhaustion and may not be able to maintain their balance as well. For this reason, a longer fork "trail" will be used to add more stability.

The endurance geometry is better for amateur cyclists who have not trained for a race geometry and will usually find the latter uncomfortable. But this idea is misleading because an endurance geometry puts more weight on the lower back, hips and hands. If the amateur is able to use aerobars on a regular basis, they will often discover that a race geometry is more comfortable because they can rest their upper body on their forearms -- not their hands.


Sloping top tubes
Dial back the clock to the time when steel-frame bikes dominated road racing and most manufacturers chose to use a horizontal top tube because it increased the size of the triangle formed by the top tube, down tube and seat tube, producing a frame with less unwanted flexibility. Back then, the easiest way to determine if a frame was the correct size was to test its stand-over height. If your crotch cleared the top tube by an inch or so when you straddled the bike with both feet flat on the ground (in your cycling shoes), it was a good fit. (Not entirely, but I'm trying to simplify.)

The problem with those frame designs is the top tube was very high and always in the way (unless you sized down like a pro cyclist). I still have my classic 1985 Fuji road bike with its quad-butted steel frame and horizontal top tube. I can't count the number of times that I "racked" myself hitting the top tube unexpectedly. ;-(

Improvements in frame construction methods and, to a lesser extend, materials, enabled bike frame manufacturers to achieve a good, if not superior, ride with a sloping top tube. This eliminated (mostly) the pain of landing on your top tube and generally increased ease of use of the bike. It also made it easier to fit a bike to a cyclist because a frame with a sloped top tube usually offers a wider range of seat height adjustment and the stand-over height no longer presents a primary impediment to fit. As far as I'm aware, a sloping top tube doesn't have anything to do with "race" vs "endurance" geometry. It's a general improvement that works well with either geometry.


Compact geometry
To me "compact geometry" either means: A pro cyclist choosing an undersized bike frame in order to decrease drag and weight. Or, a type of crankset with a smaller BCD (usually 110 mm) designed for slightly smaller chainrings. I think "compact crankset" is the more common phrase used.

But there is a third possibility that comes to mind: Some aero bike frame designs shorten the wheelbase in a couple of ways. The seat tube is curved and the seat and chain stays are shortened in order to move the rear wheel closer to the bottom bracket. This often involves lowering the seat stays as well. The down tube is curved (or has a curved cutout) to enable the front wheel to tuck in closer. The goal is to reduce drag, making the bike frame, fork and wheels more aerodynamic.

Therefore, it's hard to know what "compact geometry" is referring to without seeing the context in which the phrase is used. However, I don't think that a "compact geometry" relates to a "race geometry" even though they may have very similar goals (reduced drag).

Kind regards, RoadLight

Kontact 

There is nothing about a "race geometry" frame that forces or even strongly encourages an aero position. Many high end race frames have tall head tubes and racers struggle to get into a low position.

Endurance frames also don't have short top tubes. Those variation are normal among racing bikes.



There is way too much theoretical made up stuff in this thread. The philosophy of "endurance" does not mean that the frame geometry numbers are anything other than what you see when you look at a geometry chart, neither of the above notions are found in geometry charts.


So can we please stick to reality?