stapfam

Some of us have short legs and to fit a frame- I either go too small and fit a longer bar stem or get a bike that fits. One Thing I have found from mountain biking is that a small Triangle is more rigid. Transfers pedal power to the back wheel more efficiently and the rear triangle does not flex as much.(Smaller front triangle- Tighter rear one.) Less flex does mean less power loss. When I went to a road bike this year- I naturally went to a Compact frame. I tried one of my mates Non-Compact on a ride and It did not feel right. He is the same size and the bike fitted but I did not feel part of the bike

95RPM

My eye has difficulty accepting the sloping top tube. To me, it just yields an ugly geometry.

My mind sees the resulting reduced 'double-diamond' frame as less rigid. Imaging shrinking that already reduced double-diamond into its most extreme form -- a single tube connecting the handlebar, bb and rear axle. My conjecture is that such a structure would be less resistant to the torque of pedaling, not more so. Then, add the effect of the longer seatpost. Though these effects may not be at all noticeable while riding, why bother with them unless they grant you some size or straddling advantage, which some people do claim. For most of us, the sloping top tube frame is of no advantage, in my opinion.

msheron

My thought...........hmmmmmmmmmmm, personal preference!

DM4

I believe they were called Mixtie (sp) frames. The idea was that you could ride while wearing skirt...or a kilt

Bekologist

For a lot of us used to "a fistful of seatpost", compact frames are blasphemous. I avoid 'compact' frames because I'm a dyed in the wool curmudgeon.


compact geometry became popular as a way to fit more people on less bike sizes and was market driven, not performance driven IMO. Its easier to get a bike buyer on a bike that fits. easier for the bike shop business model of low paid, seasonal help without a lot of bike fit knowledge. Also easier on bike shops to keep the correct bike sizes in stock when there are four frame sizes versus 10.

AND, an uber long seatpost makes a bike look suspiciously undersized and weak, even if the bike is actually sized "correctly".



If you like them, go for it, but there isn't anything magical about compact geometry - its a convienence in marketing tool, rather than a brilliant advance in bike frame engineering.

baj32161

This is the best post I have read in here in a very long time

Retro Grouch 

Good point!

Since bike thieves don't actually buy bikes it expands the market because the victems have to pay for replacements for their stolen bikes. Quick releases also expand the replacement wheel and saddle market by making theft more convenient. Can you think of anything else we should be doing to increase this theft replacement business?

pigmode

Some sloping TT frames look pretty sharp, and I like their look. OTOH, a horizontal TT is the best for sitting on while waiting for long traffic lights at busy intersections.

FarHorizon

With all due respect, Bekologist, I must disagree with you (and the majority of other posts on this thread). Yes, there is a manufacturing advantage in having to stock fewer frame sizes, but that isn't the main reason for compact frame geometry (AKA sloping-top-tube bikes).

The sloped frame allows riders to be fit to the bike without needing to go to a custom frame. In my case, for example, my legs are short in relation to my torso & arms. If I get a conventional frame that will fit my leg length, then my fit is all messed up because I need such a ridiculously long stem. On the other hand, using compact frame geometry, I can get the top-tube length that I need for proper fit while still having safe stand-over height on the top tube.

If compact geometry wasn't available, I'd need to get a custom frame with a REALLY long top-tube in relation to the seat tube length. For the hundreds (thousands?) of "non-standard-shape" riders like me, compact geometry is the only practical solution to getting a production frame that really fits.

If you don't like the looks or the feel of compact geometry, fine. There's no issue with anyone's taste. Don't dismiss compact geometry as a marketing ploy or a fad of the year, though. Compact geometry is here to stay for good, practical reasons. HAPPY NEW YEAR!

Bekologist

like I said, it means manufacturers need to make less frame sizes that will fit more people "off the shelf".

market driven design, not performance driven.

dekindy

Here is what Cervelo says about the subject in the engineering section of their website.

Answer - Traditional, sloping & compact frames
A sloping frame is a frame that has the toptube higher and the headtube than at the seattube, as opposed to a traditional frame that has a horizontal toptube. It really doesn't change anything important in the geometry, the headtube, bottom bracket and saddle, the only points you connect with on a bike, are still in the same spot.

There are however some small differences between sloping and traditional frames that can be exploited in design. If you have two frames that are made identically except for the sloping vs. horizontal toptube, then the following can be observed:

1) slightly higher bottom bracket stiffness for the sloping frame
2) slightly higher torsional stiffness for the horizontal toptube frame
3) slightly lighter frame with the sloping toptube
4) slightly lighter seatpost with the horizontal toptube frame
5) slightly more seatpost compliance with the sloping frame.

Issues 3 and 4 are a wash, and for us at Cervélo the choice between sloping and horizontal depends on what combination we are looking for out of 1, 2 and 5. For our Road bikes, which have plenty of bb and torsional stiffness anyway, we go with a sloping toptube (or a dropped toptube on the tri bikes which has the same effect) to get a bit more seatpost compliance.

Compact geometry is the use of a sloping toptube to convince people you only need to make 3-4 sizes. As is obvious from the above, nothing changes in the way a bike fits when you make the toptube sloping. So if you need six sizes in a traditional geometry, then you still need six if it is sloping. Henceforth we're not big believers in compact geometry. But the terms compact and sloping are really used interchangeably by many people, so make sure you understand what they mean.

C_Heath

I would ride a Tarmac if not for the sloping top tube. I just dont get it either.

cs1

+1

I like my road bikes to have a TT and seat tube equal. The seat and bars are always level. "a fistful of seatpost" is just fine also. Just depends on what you are used to. Us Retrogrouches can't seem to warm up to compact geometry and frames made out of recycled pop cans and plastic.

Tim

DM4

+1. Giddyup.

EuroJosh

Where are all of you getting this "fewer sizes" idea? I work in a shop that sells Giants, the company that's responsible for compact geo. They come in sizes XXXS, XXS, XS, S, M, ML (on TCRs), L, XL. That is the same number of sizes that our brand that uses traditional geometry makes. The bottom line is that compact fits some people better and vice versa. OTOH I do not find them (compacts) pretty for even a second.

Bekologist

Trek's compact road bikes (Pilots) use just six sizes, and there's a size jump from a 58 to a 63.

I never before realized just two bike sizes would fit a lot of people over 5'8" tall.

jpearl

As a dyed-in-the-wool ol' skooler, I will always be partial to the look of a straight top tube. The sloping top tube found its way onto the road bike in the early 90s, along with many of the other technological innovations from the MTB scene which at the time was growing, maturing, and finding its own unique technology that none-the-less appealed to the roadies.

One benefit to the sloping top tube is that it helps with sizing for those who fall in between the standard sizes offered by manufacturers. For example, the Specialized Langster can be had in an interval of 2 cm sizing. As somebody who would need a 55 cm Langster, the 56 cm gave me the standover height and top tube length I needed, while the 54 cm provided a bike that was too small and too compact.

Ideally, a sloping top tube provides a frame that is indeed lighter and stiffer. Yes, it does make the bike appear to have a huge front end and a low rear end, certainlly not as sleek looking as a bike with a straight top tube, but none of that really matters when you're actually on the bike, peering just past your handlebars and front wheel to the road or trail rushing at you.

JanMM

My Novara Big Buzz has a compact frame and handles very nicely, thank you.

michaelalanjone

Hey, we're not all tall and skinny triathletes! I am 5'6", and I have been riding uncomfortable bikes for 30 or so years. I am not rich like you, so I can't afford a custom made bike.

My 2003 Giant OCR-1 is the best fitting bike I have ever ridden, and I love it. I will always buy a sloping top tube from now on. My mountain bike also has a sloping top tube, which saves the 'boys' from abuse.

rule

I got out on a ride this morning on my Madone SL 5.9 and was thinking the same thing DM4. I love the feeling of being down out of the wind and balanced forward over the bike. It is a much more comfortable riding position for me by a long shot. I am reminded of this every time that I take this bike out. Like anything else though, I guess it depends upon what you are comparing it against in terms of your other bikes. Definitely works for me.

HAMMER MAN

all of my bikes have been traditional top tube
I recently purchased/custom made Serotta CDA which has and I requested a 3 degree sloping top tube.
After 30 years of road riding I cannot tell the difference between a traditional and a sloping when it comes to riding and performance. Seems about equal all the way around.

slowandsteady

It may be mostly marketing hype(isn't everything), but it works for the vertically challenged. Let's face it, compact geometry is no more unnatural than so called traditional geometry. It is all just a bunch of metal tubes welded together, nothing inherently natural or normal about it.

If they came out with sloping top tubes first(a gazillion years ago) then revolutinized cycling with a level top tube people would be complaining that it just doesn't look right. Buying something solely because it is new and popular makes about as much sense as not buying something because it is new and popular. Get what fits and suits your needs....the rest is just fluff.

UmneyDurak

Are you talking about compact frames? Bottom line it allows companies to reduce number of frame sizes they offer. So instead of 50,52,54,56,58,60,etc its S,M,L. Not a big fan of them either.

2manybikes

I like my bikes that have compact frames, because they do what I want. I think that makes them look good.

I like my bikes with horizontal top tubes because they do something that I want, so that makes them look good too.

I like my antique curved bar (cantilever) Schwinn frames. I like my ladies frame beater bike. I like the frame on the 39 year old trike too. It works.

I buy a bike depending on what the bike was designed to do and how well it does it, who cares where the top tube is unless there is some kind of a problem like clearance? I like a sloping tube on an mtb for the clearance.
But I never notice a problem or even a difference when riding my mtb with a horizontal top tube compared to the one with a sloping top tube. I never even though about it until now. I love both bikes, don't make me pick one or the other, that's silly.

Roody

Exactly. It's basically whatever you're used to. I admit, the first time I rode a compact frame, it did take me a while to get used to....about 5 minutes. And now, it takes me about another 5 minutes to reorient to a level tube. Damn! I wasted 10 minutes of my life.