sloping/compact geo vs standard...any pros/cons?

[canali]

just was wondering as i see some manufacturers offering both styles and it seems the bikes of yesterday were not compact.
(Desalvo for instance http://www.desalvocycles.com/)

what are the pros/cons of such?

[Ken Robb]

check Spectrum Bike site for Tom Kellogg's thoughts.

[dekindy]

Styling or a way to lower standover height. Cervelo used to have a technical paper on their website that listed the design advantages for each but for all practical purposes both configurations can deliver the desired frame characteristics.

[Gummee]

Compact = more crotchetal clearance for those of us built like gorillas.

Otherwise? Looks and maybe slightly less weight once you figure in a long seatpost.

M

[dave thompson]

I've had both level top tube and sloping top tube (compact) bikes. IMO it boils down to style and fit. My last three customs were slopers, I like the looks. Having the ability to upslope the top tube allows me to fit both my inseam and handlebar location much more easily.

In extreme cases, Tom Kellogg's Spectrum compacts come to mind, compacts can be very different than their level brethren.

[oldpotatoe]

just was wondering as i see some manufacturers offering both styles and it seems the bikes of yesterday were not compact.
(Desalvo for instance http://www.desalvocycles.com/)

what are the pros/cons of such?

Sloping is essential for headtube/standover/fit considerations only. If not, it really does nothing for the performance of the frame.

[jlwdm]

When I met with Tom Kellogg for my Spectrum one of the questions was do you rock the bike side to side when you ride out of the saddle. I do so I have a 5 degree slope. Although it is still a 62.5cm frame - actual.

Jeff

[kramnnim]

Would the flexing/cushioning of a more extended seatpost be something to consider?

[ultraman6970]

The rear triangle is stiffer in a sloping machine because the triangle is smaller. In the front triangle I'm not that sure because i dont have a sloping machine built with the same tubing than my steel bike but I guess it should be stiffer compared with a regular geometry bike. Besides it should weight tad less too.

[FlashUNC]

I think sloping top tubes look horrible. Though understand if its needed for a fit issue.

I tend to think all the weight/stiffness arguments are marketing gloss to cover the fact the big manufacturers can cut down the number of different frame sizes they produce.

[coelacant]

Give it a few years for the sloping look to sink in. In my case it took over 10. In addition to all previous postings, you'd save at least a couple of ounces, if built with steel, with the top tube, seat tube and seat stays all shorter. Go sloper if you prefer modern, level if classic, or, have both.

C

[firerescuefin]

I think sloping top tubes look horrible.


I really like the look (compact frames), but came from MTBing. I think out of the saddle a compact "feels" a little snappier, but I wouldn't sell you on one because it performs better.....really comes down to what "floats your boat"

[happycampyer]

Until recently I had what is pretty close to a perfect A/B comparison of standard vs. sloping geometry—a VaMoots SL and Compact SL in the same size. Pre-2010, the VaMoots and the Compact had the exact same geometry, the only difference being the slope of the toptube.

The Compact frame was marginally lighter, but you couldn't tell the difference with the bikes fully built. The Compact may have been stiffer when measured in a laboratory, but on the road I couldn't detect any difference in stiffness.

I agree that a really steep slope feels different when you swing it side to side—the stock RSL I test rode had a very unique feel, like the weight of the bike was very low, for lack of a better description. My custom RSL has less slope (6º vs. 10º for the stock frame), and doesn't have quite the same feel. I'm fine with that since I prefer the aesthetics of the frame with less slope.

[shankldu]

sloping all the way lower ctr of gravity stiffer better aceleration, racier looking.











just was wondering as i see some manufacturers offering both styles and it seems the bikes of yesterday were not compact.
(Desalvo for instance http://www.desalvocycles.com/)

what are the pros/cons of such?

[Ken Robb]

opinions are like elbows: everybody has a couple. :)

[fogrider]

I have 4 bikes with classic geometry and 3 with compact. they are all made with different materials so I can't really do a direct comparison. while the classic geometry frames ride and handle well, one of the classic geometry and two of the compacts are the best. the compacts might have more to do with the builder since they are both by the same builder. the serotta (classic) and rock lobster (compact).

[FlashUNC]

I really like the look (compact frames), but came from MTBing. I think out of the saddle a compact "feels" a little snappier, but I wouldn't sell you on one because it performs better.....really comes down to what "floats your boat"


Totally agree. And given sales these days, it seems I'm in the minority of retro grouches who prefer a more traditional geo.

[Bob Ross]

it seems I'm in the minority of retro grouches who prefer a more traditional geo.

Just so you don't feel alone: I too prefer the aesthetics of a traditional, level toptube. If all other things were equal, I'd have a level toptube on all my bikes.

But when Carl Strong built my most recent bike he gave me 2 or 3 compelling reasons to go with a sloping toptube...unfortunately, I can't remember what any of them were!

[rePhil]

i remember Carl calling one morning saying he was getting ready to weld my bike and wanted to make sure there were no last minute concerns / questions. Talk about customer service!
He suggested a slight slope, I listened,and he delivered a really nice frame.


Just so you don't feel alone: I too prefer the aesthetics of a traditional, level toptube. If all other things were equal, I'd have a level toptube on all my bikes.

But when Carl Strong built my most recent bike he gave me 2 or 3 compelling reasons to go with a sloping toptube...unfortunately, I can't remember what any of them were!

[christian]

Well, there's the fact that sloping geo road bikes look horrible. And don't allow you to rest with your thigh on the top tube.

[ultraman6970]

Not all bikes look bad, my BMC looks nice... speedwagens looks terrific. All depends of the geometry of the frame.

The main problem with many brands is that they built the front tube as big as a truck and then the bike really look bad, like for example some specialized frames, the riders look like riding a super ugly flat bar.

[happycampyer]

stiffer better aceleration<snip>

I would agree lighter, but stiffer and better acceleration is marketing. The Pinarello Dogma isn't exactly a noodle, and Lance Armstrong won seven Tours on a bike with a level top tube. The problem is, it's hard to build a stiff, sub 1,000-gram frame (let alone an 800-gram or sub 800-gram frame) with a level top tube.

Ask Bob Parlee or Tom Rodi at Parlee whether the Z2 or Z3 is stiffer, and they will explain that they can make either one a stiff as anyone could possible want—it's just that, for any given stiffness, the Z3 will be slightly lighter. Iirc, according to Moots, the difference between the VaMoots SL and the Compact SL that I mentioned earlier was .3lbs in size 55. The Compact had more standover clearance and appealed to a different aesthetic, but to say that it was noticeably stiffer or accelerated better than the VaMoots would be a stretch imo.

[Ken Robb]

and then you add the weight of the extra-long seat post and how much difference in weight remains?

[happycampyer]

and then you add the weight of the extra-long seat post and how much difference in weight remains?
Egggsactly. But Cervélo, Scott et al. aren't in the business of selling seatposts... A longer seatpost probably doesn't make up the full difference, but the grand scheme of things the weight difference is inconsequential. If only the bikes came with white lunch bags filled with EPO, then they'd accelerate better. :)

[RPS]

and then you add the weight of the extra-long seat post and how much difference in weight remains?
A compact saves “about” an inch from top tube, and maybe about 2 to 3 inches from each seatstay. I’d guess that you are correct that the longer seatpost weighs as much as what you’d remove from seat tube; maybe even more.

Net you save a little mostly by shortening the seatstays. But in reality there is little to preclude a builder from shortening the seatstays without sloping the top tube. Granted that doesn’t look traditional either – kind of combining a little of both.

If reducing a little weight was your main goal then lowering the seatstays down the seat tube should reduce weight about as much. You’d end up with a traditional main triangle and a compact rear triangle. Picture below is an example of a middle ground. Lots of time trial bikes do it too, not just to lower weight but to make seatstays more aerodynamic. Obviously if done right (i.e. – to a greater degree) it can be used to provide rear passive suspension but not with seatstay geometry shown on this picture or that typically used on many time trial bikes. Unfortunately a few inches below the top tube doesn't do much in that regard.

[TAW]

This topic was largely debated a few years back, so this is not new information. My main beef with (non-custom) sloping top tube bikes (and I have one) is the limited sizing options. With a Colnago, for example, I can choose from 3 different sizes depending on how I would like it set up, what type of stem/bars and seatpost I would like, and how aggressive I would like to be. With my Specialized, I have basically one size that will fit me, and my choice of components is much more limited.

[CunegoFan]

This topic was largely debated a few years back, so this is not new information. My main beef with (non-custom) sloping top tube bikes (and I have one) is the limited sizing options. With a Colnago, for example, I can choose from 3 different sizes depending on how I would like it set up, what type of stem/bars and seatpost I would like, and how aggressive I would like to be. With my Specialized, I have basically one size that will fit me, and my choice of components is much more limited.

My main beef is that compact frames are a cost saving measure for manufacturers and bike shops that is disguised by marketing dubious performance benefits. If it was just low or mid priced bikes I could understand, but when I see high priced steeds, custom ones even, with compact geometry I think of buying a Ferrari and asking for the leather to be replaced with naugahyde.

[rePhil]

IMO there is a big difference between a frame with 4, 5 or 6 degrees and a true compact.

[EDS]

This topic was largely debated a few years back, so this is not new information. My main beef with (non-custom) sloping top tube bikes (and I have one) is the limited sizing options. With a Colnago, for example, I can choose from 3 different sizes depending on how I would like it set up, what type of stem/bars and seatpost I would like, and how aggressive I would like to be. With my Specialized, I have basically one size that will fit me, and my choice of components is much more limited.

I guess if you have to ride a specialized then limited sizing options is an issue, but with so many choices/manufacturers I think it is easy to find a production frame that fits.

[dana_e]

for small frames and short folks the sloping is nice since you can get enough post to clamp the work stand to.

that is the case for me

although all my rides are non-slopers

[EDS]

My main beef is that compact frames are a cost saving measure for manufacturers and bike shops that is disguised by marketing dubious performance benefits. If it was just low or mid priced bikes I could understand, but when I see high priced steeds, custom ones even, with compact geometry I think of buying a Ferrari and asking for the leather to be replaced with naugahyde.

Really?

Aren't you just saying that you prefer the look of a level top tube? Nothing wrong with that if it floats your boat. Nothing wrong with someone liking a sloping top tube either. As long as the bike fits properly it is a win.

[forrestw]

My main beef is that compact frames are a cost saving measure for manufacturers and bike shops that is disguised by marketing dubious performance benefits. If it was just low or mid priced bikes I could understand, but when I see high priced steeds, custom ones even, with compact geometry I think of buying a Ferrari and asking for the leather to be replaced with naugahyde.
Huh?

The only reason I think a bike ever needed a horizontal TT would have been that lugs were only built that way. Once welding became the primary way of building frames the door was open to a wider array of geometries. Today there's at least one lug maker selling lugs with sloping TT angles so that's no longer a limitation either.

As others said above, other things being equal, a compact frame geometry offers stiffer, lighter and with a longer head tube (stiffer) while still offering workable stand-over.

I like the look of a traditional horizontal TT better, same as I like the look of old style quill stems but neither is a better design solution to producing the best possible bike.

[mister]

When I met with Tom Kellogg for my Spectrum one of the questions was do you rock the bike side to side when you ride out of the saddle. I do so I have a 5 degree slope. Although it is still a 62.5cm frame - actual.

Jeff

you sure he wasn't thinking about the bottom bracket height when he asked that question?

[palincss]

As others said above, other things being equal, a compact frame geometry offers stiffer, lighter and with a longer head tube (stiffer) while still offering workable stand-over.


I don't see why an irregular shape like a typical compact frame should be any stiffer than a level top tube. I would think it would be significantly less stiff, considering the level top tube is closer to a triangle while the compact is an irregular polygon. As for the compact being lighter, perhaps so without a seat post, but I think seat tubing weighs less than seat post material, and you're trading the former for more of the latter as you go compact.

No argument that you get more stand-over, and without a doubt there's a group that prefers the aesthetic -- perhaps it looks more like the MTBs and BMX bikes those users came up with -- but all in all, I think the primary advantage to compact frames is that manufacturers can stock fewer sizes to cover the full range. And I don't see them passing any of that on to the consumer.

[firerescuefin]

I don't see why an irregular shape like a typical compact frame should be any stiffer than a level top tube. I would think it would be significantly less stiff, considering the level top tube is closer to a triangle while the compact is an irregular polygon. As for the compact being lighter, perhaps so without a seat post, but I think seat tubing weighs less than seat post material, and you're trading the former for more of the latter as you go compact.

No argument that you get more stand-over, and without a doubt there's a group that prefers the aesthetic -- perhaps it looks more like the MTBs and BMX bikes those users came up with -- but all in all, I think the primary advantage to compact frames is that manufacturers can stock fewer sizes to cover the full range. And I don't see them passing any of that on to the consumer.


Curious if you have ever ridden/owned a compact frame or are just theorizing.

[palincss]

Curious if you have ever ridden/owned a compact frame or are just theorizing.

Never.

[firerescuefin]

http://www.spectrum-cycles.com/616.htm

COMPACT FRAMES

Compact frames are developing a sizable following in the cycling community. As a compact frame owner myself, I appreciate the nimble liveliness afforded by the design. Like all bicycles, the handling characteristics of compacts starts with the geometry so let's take a look.

In designing the our first compact prototype back in mid '98, we wanted to discover what if any the real world differences there would be between traditional and compact frame designs. Our first compact frame (still my favorite frame) was an exact replica of my then current titanium frame in materials and geometry save for the sloping top tube. I designed it with a severe (17 degree) slope to ensure that any differences would be as obvious as possible. We had assumed that the new frame would be somewhat stiffer and lighter. It was lighter (about 4 ounces) but it was not appreciatively stiffer. Although we were able to measure a slight increase in stiffness, it was too slight to feel. The big change came when I stood to accelerate or climb. As I stood up, the bike appeared to loose three pounds. The inertia of the bike as I rocked it back and fourth was reduced so much that I felt as though I was on a twelve-pound bike. Interestingly, when seated, a compact frame feels exactly like a traditional design. The compact design has no effect on handling beyond the increases responsiveness during climbing and accelerating.

When considering a compact frame, take the time to check out the angles, the virtual tube lengths and how these consideration affect handling. If you need some advice give us a call.

[bikemoore]

IMO, the larger the frame size, the worse sloping top-tubes look. They look good on small frames because it eliminates the visual impression that the frame is too small for the full size wheels. But I think they look really bad on larger bikes: makes the long head tube seem even longer in relation to everything else. Since I ride a 62 and do not experience any issues with either stand-over clearance or the need for a taller head tube, I stay away from ugly sloping top tubes. But I were shorter, I'd probably think they look OK.

[jlwdm]

IMO, the larger the frame size, the worse sloping top-tubes look. They look good on small frames because it eliminates the visual impression that the frame is too small for the full size wheels. But I think they look really bad on larger bikes: makes the long head tube seem even longer in relation to everything else. Since I ride a 62 and do not experience any issues with either stand-over clearance or the need for a taller head tube, I stay away from ugly sloping top tubes. But I were shorter, I'd probably think they look OK.

I have a 62.5 actual with 1 degree of slope that you would not notice. Also a 61 actual with 4 degrees of slope that most people don't notice the slope.

Jeff

[RPS]

I don't see why an irregular shape like a typical compact frame should be any stiffer than a level top tube. I would think it would be significantly less stiff, considering the level top tube is closer to a triangle while the compact is an irregular polygon.
I’m not advocating for compact in any way, but if one assumes that the greatest pedaling efforts (both forces and torque) are applied while rider is out of the saddle for sprinting or climbing, then there is little doubt (I’d say none) that having the top tube higher than a line that runs straight between the head tube and rear wheel axle will be as stiff (everything else being the same). When out of the saddle only the BBKT, head tube, and rear axle play a role in frame loads, so making the main triangle larger towards the saddle just makes it more flexible IMO. The more compact the triangles (again, everything else being equal – same tube OD and WT) the stiffer they should be laterally and torsionally.

Whether being marginally stiffer is advantageous or not is a different matter, but I don’t see how if one started out with a compact frame as a point of reference, that raising the top tube to level wouldn’t add some incremental flex.

Seated pedaling is different matter and more complicated because the saddle resist lateral loads created by rider, so differences should be much less. Also IMO riders don’t normally exert as much force on frame while seated, so if they are going to notice flex it’s more likely while standing.

[Grant McLean]

http://www.spectrum-cycles.com/616.htm

COMPACT FRAMES

Compact frames are developing a sizable following in the cycling community. As a compact frame owner myself, I appreciate the nimble liveliness afforded by the design. Like all bicycles, the handling characteristics of compacts starts with the geometry so let's take a look.

In designing the our first compact prototype back in mid '98, we wanted to discover what if any the real world differences there would be between traditional and compact frame designs. Our first compact frame (still my favorite frame) was an exact replica of my then current titanium frame in materials and geometry save for the sloping top tube. I designed it with a severe (17 degree) slope to ensure that any differences would be as obvious as possible. We had assumed that the new frame would be somewhat stiffer and lighter. It was lighter (about 4 ounces) but it was not appreciatively stiffer. Although we were able to measure a slight increase in stiffness, it was too slight to feel. The big change came when I stood to accelerate or climb. As I stood up, the bike appeared to loose three pounds. The inertia of the bike as I rocked it back and fourth was reduced so much that I felt as though I was on a twelve-pound bike. Interestingly, when seated, a compact frame feels exactly like a traditional design. The compact design has no effect on handling beyond the increases responsiveness during climbing and accelerating.

When considering a compact frame, take the time to check out the angles, the virtual tube lengths and how these consideration affect handling. If you need some advice give us a call.


With respect to Tom... i have a couple of issues with this, and think some
of it dated.

I really think it's useless to talk about "sloping", when you're really talking
about a frame with a specific seat tube length. Nobody believes the angle
of the top tube has an effect on the ride. Is Tom really saying that bikes
with shorter seat tubes ride better? If that's the case, he's just saying
small bikes ride with more responsiveness, which is logical because they're
tubes will be stiffer. Modern wheels are a good example of how very small
changes to stiffness are very noticeable in ride quality.

But that brings us to the fact that most modern frames are really stiff, much
more so than a few years ago. I've often head the claim that sloping the
top tube "lowers the centre of gravity" or some such claim based of the
argument of the location of mass. This excludes the reality that the saddle
and post combo used would have far more effect, or the use of a seat bag
or not.

A frame with a 50cm seat tube, for example, rides the same regardless of
the angle of the top tube. Once you start changing the
lengths of the tubes you're comparing different frames, and can't isolate
the single criteria for the change in ride qualities.

Bottom line, fitting and designing great frames is an exercise in understanding proportionality.


-g

[RPS]

But that brings us to the fact that most modern frames are really stiff, much
more so than a few years ago. I've often head the claim that sloping the
top tube "lowers the centre of gravity" or some such claim based of the
argument of the location of mass. This excludes the reality that the saddle
and post combo used would have far more effect, or the use of a seat bag
or not.
+1

Effective inertia to resist rocking is easy enough to calculate, but in my opinion not worth the effort. For 15 pounds to feel like 12 there has to be more involved than lowering the top tube along with seatstays and rear brake a little (even allowing for the 4-ounce weight reduction).

From a standpoint of reducing the effective moment of inertia as it affects rocking, most of us could do far more by removing a typical saddle bag that can easily weigh a pound or two when loaded. And while we may be able to feel the difference, it isn’t going to make us faster anyway as long as we carry the weight somewhere on the bike.