Other factors being equal, what noticable performance/handling differences, if any, would there be between a conventional frame-- which I know and whose appearance I prefer-- and its compact cousin?

My experience has been that conventional frames are a bit more stable. Not sure why.

But those experiences were on two different bikes, so surely there were many other factors at play beside the top tube design.

(I guess this was a useless post!)

There is some thought that the triangles being smaller on a compact frame will create a stiffer frame that is capable of absorbing more rider input power without flexing. This doesn't necessarily result in a comfortable frame. Modern CF frames work more toward allowing some vertical compliance for comfort while retaining lateral stiffness.

My own opinion is that compact frames allow some more virtual top tube length without increasing standover height. While this may be good for riders such a Tom Bombadil and myself with relatively short legs and long torso's I'm not sure if the population in general will benefit.

I think that the top tube is just one of many variables that have and influence on performance, ride characteristics, handling, etc. There is also frame material, dimensions (including angles), shape and thickness of various tubes, etc. I think it is the combination of all these things that make a total package. Looking at just the top tube angle is not a good way to determine performance or handling.

They can also be designed to allow for a somewhat more upright riding position, depending upon if they raise the headtube as part of the compact design.

There are many variants of compact frames.

As a general rule, they also have a wider range of fit than a traditional frame. This is one of the factors driving the broad adoptance of them. This wider range enables a manufacturer to make say 6 or 7 different sized frames instead of 8 or 9, saving manufacturing, warehousing, and even end-of-season clearance expenses (as you have fewer odd-sized frames to get rid of).

I ride Compact frames and a sloping top tube frame. The smaller triangle is supposed to impart a better pedal response to the rear wheel, make for a more responsive bike and make for more road feel to get back to the rider. Don't know if it does- but as a short legged rider- I find I can get a better fit on either frame than the other one. There is no difference to me on feel- response or transmission of road shock back to the rider. I ride a 46.5 compact frame and a 51 sloping tube. Top tube is 1/4" difference between the two, I can get the same saddle and bar height on the two and they don't feel any different to sit on.

What I have noticed though is that I never bounce my knees off the top tube on the compact- which I do on the sloping tube occasionally. Only happens on corners and where I try to correct steering in the corners- but it has happened. Side whack on the joint as I try to change weight and position.

To me- the look of a compact is natural. It seems right and if I were asked the difference between the two- I don't think I could find one. Now as to the frames where the top tube slopes down at the front- weird!!!

The key is "noticeable" differences in "performance/handling" -- the short answer, imho, is "none". As it happens, I prefer the look of compact frames, but that's by the by. An elite-level pro rider might - MIGHT - notice the alleged advantage in stiffness that some companies promote, but I can't see how most of us could. Other than that, what difference could there be, all else being equal? Fit at the contact points, and essential frame geometry (s/a, h/a, rake, trail) have no correlation to a sloping or conventional top tube.

Tom B wrote:

"As a general rule, they also have a wider range of fit than a traditional frame."

I was always under the impression that the complete opposite is true, that compact frames offer fewer fit options, as most manufacturers make fewer sizes as compared to the olden days with standard frames coming in many more sizes.

Everything I've ever read has stated that the frame makers make up for fewer frame sizes - the oft told quote is sizes in S, M, Lg and XL, by allowing for longer or shorter seat posts and stem lengths. Seat post length matters for nothing in terms of whether it's a long post with a short seat tube on a compact, or shorter post on a traditional frame, as long as the seat is at the right position.

Stem length is not as easy to get correct, as anything under 90 or over 120 or so, adversely affects the handling of the bike. Thus it's possible to NOT be able to get a good fit with so few frame sizes and trying to make up for it with an incorrect stem length. It's easier with a compact that comes in too few sizes, to find yourself between sizes, with no good options.

"This is one of the factors driving the broad adoptance of them."

Cart before the horse. What's driving acceptance is simply there are fewer and fewer standard geometry frames being made. No choice, no problem - I'll buy a compact.

"This wider range enables a manufacturer to make say 6 or 7 different sized frames instead of 8 or 9, saving manufacturing, warehousing, and even end-of-season clearance expenses (as you have fewer odd-sized frames to get rid of)."

Provided the manufacturer makes 6 or 7 sizes in compact. I don't know, as I don't follow the market the way I used too, but are the manufacturers now offering more sizes ?.

Here's a quicky sample of some compact manufacturers

Specialized Tarmac S-Works DA - 6 sizes.
Trek Madone 5.2 - 7 sizes
Giant TCR - 6 sizes
Fuji assorted road- 6 sizes
Cannondale assorted road- 8 sizes (nice choices)
Look 585 - 5 sizes

Some traditional sizes:

Waterford competition series - 11 sizes
Serrotta - all custom
Independent Fabrications - custom
Habenaro Ti. - 8 sizes
Surly Pacer - 9 sizes

One thing that came out, is it's the smaller companies that make traditional and many offer fewer sizes, eliminating the very small and very large sizes. Too bad.

So in general, most manufacturers have gone compact, not for any particular advantages to the consumer in terms of fit, but all to save money as well as to stay competitive. Seemingly the compact frames ARE now offered in more sizes then the oft lamented S,M,L, XL. That's a good thing.

Steve B.

As a second observation, I believe that we have just come out of a period where bicycle manufacturers were much more involved with MTB design than Road bike design. I suspect that the frame designers may have been letting knowledge gained in this design phase to leak over into the new generation of road frames. It may be that if you check, you will find that companies with a larger MTB base are more prone to compact road frames and more traditional road companies have stuck with more traditional road designs.

Now that CF is on its way to being the designers tool of choice all bets for future frame design are off. A designer using a cad system to design for flex direction and amplitude may well opt for custom tube angles.

As to whether or not the average rider will notice the difference..........read the reviews and posts here when people are comparison riding and you can tell that they notice. A pro may be able to articulate exactly what the difference is but you do the average rider a disservice if you think that they don't notice ride and stiffness differences. As BSLeVan points out, there are many more variations then just frame design but when comparing apples to apples frame design still matters.

Quote: As to whether or not the average rider will notice the difference..........read the reviews and posts here when people are comparison riding and you can tell that they notice. A pro may be able to articulate exactly what the difference is but you do the average rider a disservice if you think that they don't notice ride and stiffness differences. As BSLeVan points out, there are many more variations then just frame design but when comparing apples to apples frame design still matters.[/QUOTE]

Weeeell, perhaps, but at the risk of repetition, I'll say again: in what would these alleged differences inhere? Note that I'm responding specifically to the OP's original question: what noticeable performance/handling differences could be discerned as between compact and conventional frames. I simply don't understand what these could be. Differences in 'stiffness' there certainly are, as between frames, but those are typically attributable to materials/materials manipulation/basic frame geometry; again, I don't see where/how a sloping or not t/t on a road bike creates a 'difference' in this respect. Same goes for vibration absorption. Others claim differences in 'vertical compliance', but where would this come from on a more-or-less conventional diamond frame, compact or conventional? True, lateral twist (quite possible, just like a traditional barn door construction) can be perceived as 'vertical compliance', but typically diamond frames don't have such a quality (just like a barn door). Even if such a quality could be 'built in' through materials manipulation, surely it would be swamped by choice of tire, pressure, saddle/rails, even the choice of riding shorts! Vibration damping is an entirely different matter, but that's primarily down to materials, not basic geometry, I should have thought.

Steve,

It is true that bike companies are offering fewer fit options, which we both stated in our posts, but this is due to a compact geometry frame having more flexibility to fit a wider range of riders.

Now whether riders are able to get as precise a fit, well, that's another question. The manufacturers contend that you can, but that doesn't mean such a claim is true.

Taking up your example, even if a stem is limited to a range of 90-120mm to maintain handling, that should still enable nearly all riders to obtain a proper fit from a range of 6 to 7 sizes instead of say 8 or 9 traditional frame sizes.

Let's look at an example:

The Trek Madone 5.2 is available in 7 sizes, 50-62cm. Let's look at the 54 vs 56 bikes. Standover is significantly lower than a traditional frame, at 74.2 & 76.6. Thus shorter-legged riders can clear the top tube. The effective top tube lengths are 53.8 and 55.7. This difference is easily within the overlap of using a stem from 90-120mm.

Let's say the stock stem is 120 (I'm sure it is close to this). This would enable the rider of the 54 to have a top tube range from 50.8 to 53.8, on the 56 it would be 52.7 to 55.7. So there is overlap. The same is true for the next model up, the next model down and so forth.

Most riders will be able to find a compact geometry frame in a size that will fit their standover, leg length, and top tube needs and do it from a shorter list of sizes.

Furthermore, shorter-legged riders will find that they can find better fits in a compact frame than anything short of a custom made traditional bike.

Ironically the same can also be true for longer-legged riders with shorter upper torsos/arms. On a traditional bike, if they buy to fit their legs, then the top tubes are too long. If they buy to fit their arm length, they have to jack up their seat posts into the sky, and the stems, creating a rather odd bike. Whereas a compact frame with a raised headset will require less modifications.

For one of normal proportions, a traditional bike line of 9 sizes would probably enable you to find a stock bike that needs fewer fit adjustments.

Here are links that support the claim that compact geometry enables a better fit:
https://www.fezzari.com/technical.htm
https://www.siskiyoucyclery.com/road/allez.html (gets their argument from Specialized)
https://gunnarbikes.com/newsletters/11-24-05.htm

Tom,

What I could not articulate well, was that I started out thinking that compact offered too few options, when the reality as my (very basic) research showed, as well as your own information, is that it's not so much that compact offers better fit choices, it's that having enough different frame sizes allows better fit options, and it matters not whether the frame is compact or traditional, as long as there are closer differences between the sizes, then was once typical - and as is common in mt. bikes, of 4 sizes - Small, Medium, Large and X-Large. Clearly all the manufacturers I looked at offered better then 4 sizes and that makes all the difference for avg. riders. The key is to have approx. (and as minimum) 2cm differences in effective TT length in order to avoid stems that are too long or too short and that's what has developed. S/M/L/XL didn't offer that.

I personally feel that stand-over height on a road bike is not a particularly useful or necessary thing. The avg. rider tends to un-clip, lean to one side and put a foot down - which they have to do in order to put a foot on the pavement in any case. Being able to stand over the bike while the bike is dead upright is not something most people need to worry about. Mt. bikes are another story and you don't want to be slamming the soft spots on a TT. Moot point in any case as in a lot of cases with full suspension, the suspension design drives the TT design.

So my take is that there is no advantage to compact, but there is nothing lost either. Preference as to look is up to the consumer.

Steve B.

On that standover height- I am one of the riders that has his saddle set so that if I unclip- I cannot touch the ground whilst still sitting on the saddle. The only part of a bike that will allow me to gain the 2" to enable me to touch the ground would be a lower bottom bracket height. Obviously I have a bike that fits so have yet to have a bike- whether compact or normal- Where if I were to get off the saddle- I would have a problem with the top tube getting in the way. Now on the stem length to alter the fit on a compact frame- I use stem lengths from 80 mm to 120. On the tandem- I occasionally go as pilot and I can ride the bike with the stem as set up for the pilot with a 120- or if it is a long ride with me as pilot- I fit the 80 mm. I may be a craop pilot- but the stem length does not affect the steering ability of the bike. Does effect the fit though- hence the change for a long ride. And on the OCR that I have- It came with am 80mm stem and I have changed it to a 110- but with a steeper rise.

When I come to a stop- I keep one foot clipped in. Normally I would just lean the bike whilst seated to touch the ground-but occasionally it is off the saddle slide forward and keep the bike upright and foot on the ground.

It makes no difference to me if the bike is conventional or compact. I just make certain I get the right size in the first place.

Can't find it now, but Kellogg had some observations on two identical frames, except one compact and one not. No difference in the saddle, but the compact being very lively and quick out of the saddle. That aligns with my experience. Compact looks funny riding along normally, but I'm used to it. Out of the saddle, especially up hill, it's a rocket.

I have a Trek 5200 54cm, and a new Madone 5.5, 56cm. I guess the 5.5 would be considered a "compact frame" since it has the up-sloping top tube. I can't tell any difference between the ride of the two that I would attribute to the frame style. This is the first 56cm frame I've had (I'm 5'8") but it really fits well.

I always thought a smaller triangle is sturdier/stiffer/stronger than a larger triangle. If we forget compact v regualr frames for a sec and compare 2 regular frames, one 50cm, one 58cm, I would say the smaller one is stiffer.

Now we can apply this analogy to a compact frame, a 58cm compact frame and 58cm regular frame, I'd say the smaller triangle (compact frame) is stronger.

As an aside, I too prefer the look of a regular frame (see my post "My ugly Allez" but I'm now getting more accustomed to compact frame designs.

The 2 biggest reasons (performance) that compact frames are used by racers are the "smaller triangles are stronger/stiffer, and the compact frame uses less material than a traditional frame and is thus a lighter frame.

Beyond that there are all sorts of rationals for fit, comfort and manufacturing cost. One can go back and study the history of Giant Bicycles development of the compact frame for some of these.

Whether a stiffer frame is of any benefit to us has been debated for years. Most of us, especially those of us over 50, would benefit from a more forgiving frame, especially on rough roads.
I think the whole stiffer is better thing is over rated. Fit and comfort are the most important.
The racers, the top pros at least, ride what the sponsor gives them.
Whether one design is stiffer than another just by the position of the top tube on the seat tube is questionable, as well. The absolute stiffest, most bone jarring, teeth rattling bike I have ridden is my Tesch s-22. This is a steel, conventional, 64 cm frame with short wheelbase and steep angles. Why anyone would want anything stiffer than that bike is beyond me. It makes my Cannondale feel like a Cadillac. The Cannondale CAAD5 however, makes the Gunnar feel soft and cushy, but the Gunnar has a sloping top tube. I once had a Landshark made from Tange Prestige tubing in size 63cm conventional. This was the softest riding road bike I've had and was so whippy, I knew it would break if I kept riding it. Surprisingly, I could climb on it as well as I have on anything else, even though when I stood up on it the bottom bracket would sway from side to side as if it was broken.
The racers, the top pros at least, ride what the sponsor gives them.

I disagree with the bit about compact frames having a wider range of fit. Much has been written about how compact frames save manufacturers money because, as Tom notes, they produce fewer sizes. For example, the Specialized compact frames I've ridden (Sirrus and Sequoia) were available only in S-M-L-XL, while other traditional frames are typically manufactured in 2-cm increments.

I sold the two compact frame bikes I owned because they were so uncomfortable. The cockpit on those bikes was so small I felt as though I were pressed into a sardine can, even though the height was right for me. Maybe one result of that is that I have a new love for retro frames--straight top-tube frames made of steel. Yes, I am building up a Specialized Roubaix, which has a sloping top tube--not sure if it qualifies as compact or not--and I'll see how that works out fit-wise when it's complete.

I'll add that my LBS worked with me to try to get my compact frames to fit better, moving the seat, changing out the stem for angle and length, nothing really helped. I'll venture to say that *most* people on this board wouldn't feel lick of difference in *performance* between a compact and a traditional frame but would absolutely feel a fit that is right, or off.

Only if your seat post is stiffer than your frame tubes.

I think most pro racers praise a stiffer frame for when they are out of the saddle sprinting. The length of the seat tube may be moot under those circumstances.

I bring up the racers because the OP asked about performance features of the compact vs the traditional. I suppose you could list comfort and ride quality as a performance feature but that was not the way I took the question.


Quote from Giant's literature (Giant is recognized as the modern era developer of the compact road frame) " Giant’s Compact Road design is arguably one of the most important developments to hit the peloton since Lycra. So significant is the design that the Union Cyclist International (UCI) was forced to change their rules regarding frame configuration. And bike makers, from the most respected European custom builders to the largest companies in the world, have adopted the design.

By sloping the top tube downward toward the rear of the bike, two very important characteristics were achieved. First, the frame became stiffer for improved acceleration and more solid cornering. Second, the bike got lighter."

I think most pro racers prefer to ride on the bikes provided by their teams.

Check out cervelo.com web site about this. Cervelo does not use the word "compact" but rather sloping top tube. There is a distinction here and Cervelo gladly tells it.

The stiffness comes from miximizing flex in the bottom bracket and rear.

I guess it depends on how you ride, but I don't apply much lateral force (or fore and aft force for that matter) at the saddle. When in good form I don't even put much weight on the saddle, so I don't see where short seat tube length with a long post is likely to be negatively affecting apparent frame stiffness. The forces that make the frame flex are at the bottom bracket and (especially for standing climbing) at the head tube.

I like my compact frame just fine. I find it comfortable and think that I can tell that it is stiffer at least when loaded touring. I admit that since I don't have two otherwise identical frames I can't be positive whether or not I really can feel the difference.